Headers and a Four-Barrel Carburetor on a Jeep 225 V-6?

[Stefan L]

I was just about to slap a set of fender well headers on my 66 cj 6 with a 225 and it seems I have heard quite a few folks say they prefer the stock manifolds. I intended to move up to a 4 barrel intake and Holley 390 at the same time. What is everyone's opinion on this matter?

[Moses Ludel]

Hi, Stefan...Thanks for joining the forums!

I have a range of concerns around headers and the Jeep/Buick 225 engine's particular needs.  Also important is the safety of your vehicle's occupants.  Your desire to improve the performance of your Jeep CJ-6 is fully understandable.  I'd like to begin with the positives around adding headers, a performance 4-barrel intake manifold and a four-barrel carburetor:  

1) The 225 Buick/Dauntless V-6 engine will perform better with headers, as the stock 225 exhaust manifold design is highly restrictive.  More directly, a flipped over cast iron exhaust manifold at one bank was Kaiser/Jeep's hasty way of fitting the 225 V-6 into an F-head four-cylinder engine bay.  

2) Headers, if tuned properly and not just designed to fit okay and look good, can offer less restriction and better exhaust scavenging.  Seek out performance (preferably dynamometer chart) results for the headers.  Headers can be a distinct boost in power output, typically in the mid-range to high rpm range.  Headers generally do not make much, if any, performance difference at lower engine speeds unless the OE exhaust system is badly engineered.  We know the stock exhaust layout is marginal.

3)  A Buick 225 V-6 in the earliest CJ chassis looks like a conversion engine.  Jeep Corporation was struggling to fit the package into the F-head four-cylinder engine bay.  On your '66 model, a set of headers will look good and inevitably perform better than the stock exhaust system.

4)  The four-barrel intake manifold distributes fuel more uniformly than the stock Rochester 2-barrel (2GC type) intake.  Cylinders receive a more uniform air-fuel charge with a four-barrel manifold, although a V-6 engine does better with a two-barrel carburetor than a V-8 engine does.  (The worst case for uneven fuel distribution is the Jeep inline sixes with either one-barrel or two barrel carburetion.)  A dual-plane versus open plenum intake manifold is another question we can discuss. 

I do have several concerns and biases related to modifying your odd-fire 225 Dauntless V-6:

1)  Carbureted engines require warming the intake manifold as quickly as possible to facilitate proper combustion of air/fuel when the engine is cold.  It is desirable to warm the intake manifold when the engine first starts and begins to warm up.  Once a stock 225 V-6 engine is warm, the intake manifold is also warm and no longer needs an auxiliary source of heat (in this case exhaust back-pressure flow) across the intake manifold.  The heat riser opens, which dramatically reduces the exhaust flow across the intake manifold.

Note: Your planned aftermarket intake manifold for the Holley 390 may not have an exhaust crossover passage to warm the base of the carburetor.  This leads to incomplete combustion when the engine is cold.  The passage in the stock iron manifold is the typical head-to-head cast port that runs beneath the plenum.  On a bright note, aluminum dissipates heat rapidly, and the aftermarket manifold would warm up quickly once the engine block, heads and coolant begin to warm.

2)  You may have a hand choke on your Jeep's carburetor.  If, however, you have a heat stove or bimetallic spring choke, you need heat across the intake manifold and at the choke's heat source.  On the Buick 225 V-6 and other period engines, a heat riser valve is used to create exhaust back-pressure and flow hot exhaust through the crossover passageway beneath the intake manifold.  When you install headers, the headers' collectors are usually too far from the engine to efficiently operate a bimetallic spring heat riser valve.  Stubby headers might be close enough for a heat riser.  

Note:  One remedy would be a vacuum operated heat riser like later emissions carbureted engines use. the signal coming by way of a thermal vacuum switch (TVS) threaded into a cooling port on the heads or intake manifold's coolant passage.  Without a heat riser, like with most header systems, there will be no hot exhaust passing across the intake manifold when the engine is cold—which also means that there will be insufficient heat to operate a bimetallic spring choke.  At the least, you would have to live with a balky engine when cold and during the engine warm up phase.

3) If you have a pristine '66 CJ-6 and want the body to remain stock, make sure the headers do not require fender/well cutting or extreme modifications.  Fender well exit headers have been popular and require sheet metal modifications that you may not be willing to make.  At least know the fitment requirements before starting the project.  Make your judgment call.

4) In the day, headers were often accompanied by side exit exhausts and short mufflers.  Not sure where you plan to go here.  I can only say that side exit pipes on a Jeep CJ (81" wheelbase vintage CJ-5 or even the 20" longer wheelbase CJ-6) are a very bad idea.  I always run exhaust pipes to the rear of the vehicle, emulating the stock approach, either with a single, larger diameter exhaust pipe or with dual exhausts of the right diameter each.  Carefully fitted, you can get dual exhausts beneath your CJ-6.  It takes a competent muffler shop and a lot of precise bends to avoid the chassis, axle, brake and other components!  An experienced shop can determine the right size exhaust tubing and muffler inlet/outlet sizes.

5) Side exit dual exhausts or open headers can make vehicle occupants sick. Crawling on rocks or idling, with typically rich fuel mixtures roiling up from the tub sides, will flood the cabin with toxic and noxious fumes.  While an open top would seem like the worst situation, a cloth top or hard top can lead to accumulation of fumes and lethal (i.e., odorless CO) gas mixtures.  If you jet that 390 CFM Holley four-barrel for sea level, I guarantee that by 2500 feet elevation it will be running rich, and the condition will worsen proportionately as the altitude increases.  This overly rich air/fuel mixture, whether you find it acceptable or not, needs to exit the rear of your Jeep.

This may seem like a blunt view of headers or the Holley square-bore carburetor design.  In fairness, headers and a Holley 390 square-bore, four-barrel carburetor with aftermarket manifold have been a chosen path for many Jeep 225 V-6 owners.  If you're satisfied with this approach, I understand.

My personal carburetion choice, however, would be either a Carter AFB (genuine Carter from a specific OE engine application, I can offer particular AFB model numbers) or a Quadrajet from a small displacement GM engine as close to 225 cubic inches as possible.  

Note:  The altitude hypersensitivity of "high performance" 4100 square bore 4-barrel series carburetors and even the universal 2300 series two-barrel Holley carburetors is a consideration here.  Objectively, manufacturers like International Harvester and Ford did have success with properly tuned and equipped OE versions of both the 2300 series two-barrel and 4100 series square-bore four-barrel carburetors.  As for the off-the-shelf aftermarket "universal" Holley carburetors, unless you have Holley tuning experience and know Holley jetting, power valve requirements, accelerator pump and float tricks, you might be much happier with a blueprinted OE Carter AFB or small GM-application Rochester Qjet carburetor.  

Many would suggest that your best bet is a TBI (Throttle Body Injection) conversion.  This is a highly beneficial option, however, cost could be an issue.  TBI/EFI does not require a heat riser and would respond nicely to headers...We can discuss various ways that OE or aftermarket TBI could be retrofitted. 

I'd like to know more details about your engine, its overall condition, the Holley carburetor (part number) that you have in mind, and the type of headers you have considered.  Also, what is your current ignition distributor type and firing voltage?  Camshaft profile?  Compression ratio (stock or otherwise)?

Do you need a 390 CFM four-barrel carburetor?  The 2G and 2GC Rochester two-barrel series is highly reliable, these are predictable carburetors.  They were found in a wide variety of applications.  In the late 'sixties, I rebuilt large 2GC units that fueled standard compression 389 Pontiac V-8s and other big GM cars equipped with base engines.  I have rebuilt and tuned tri-power systems that benefited from 2G and 2GC carburetion.  From the mid-'fifties onward, the standard compression small-block Chevrolet V-8 truck and passenger car versions, units similar to your 2G or 2GC, were popular.  Your carburetor is easy to service and will deliver excellent performance in return.

I unearthed these figures courtesy of Doug Roe's classic work, Rochester Carburetors (HP Books, page 108) for approximate CFM flow on various 2G series carburetors.  We could look into your carburetor's dimensions and weigh what you currently have in flow rate:

1-1/4" flange, 1-7/16" bore x 1-3/32" venturi = 278 CFM

1-1/2" Flange carbs each have 1-11/16" bores:

1-3/16" venturi = 352 CFM

1-1/4" venturi = 381 CFM

1-5/16" venturi = 423 CFM

1-3/8" venturi = 435 CFM

All ratings @ 3.0 in HG

It would be great to see our vintage Jeep CJ 225 V-6 forum members jump into this discussion!  Please share your experiences with Stefan...

Moses

Edited March 10, 2016 by Moses Ludel

[bryanb]

I swapped a 225 into my 59 cj5. I went with a set of Sanderson headers, sort of a block hugger style, only because my stock manifolds were junk. My brother did the same swap, on same year jeep and stuck with manifolds. I think his drivers side manifold was from a commando or something, it actually points to the back. There is zero difference between the two performance wise. Mine is louder for sure.  I'm certain his manifolds will outlast my headers. I went with raw steel finsh and painted them myself with high temp header paint, about a hundred coats, wich is all gone replaced by nice looking rust. We both considered doing a holly 390 with a offenhauser intake, but it was going to be pretty expensive. That was what stopped us. Also Rochester 2gc carbs are literally everywhere..easy to work on and cheap too.

[Stefan L]

Thank you Moses for the in depth reply. Let me tell you what I am looking to gain and perhaps you can make some suggestions. I have a 66 cj6 that currently is bone stock with a buick 225. I have been parts collecting for the past year and plan on getting the build started this summer. As a novelty, I would really like to keep the major components of this jeep as jeep factory items so I have a th400 and dana 20 from a commando, a postal rear end and a narrow track dana 30 front end waiting on the shop floor to be swapped in.  I am looking to make a weekend beach/camping family vehicle out of her and want to build the motor to get myself up in the 175-180HP range without getting exotic with it. I am not one to do burnouts or punch the gas un-necessarily but would like to keep up with highway traffic and have enough on ramp power to merge without scaring my wife. I would like to be able to tow a small trailer with her on occasion as well. Honestly 80% of my driving will be on road and I was trying to get the performance I was looking for through induction and exhaust. I wouldn't mind gaining some power through a cam upgrade as well but i haven't gotten that far in my plans to know what is available our how it would compliment my potential set up.  I plan on running a mild lift with either 32 or 33 inch tires and 4.10 gears. The motor that is in the jeep now has the stock ingnition but I have a spare motor that has an HEI set up that I was planning on using. I live in North Central Florida where everything is flat and we probably never get above 750ft of elevation. I wouldn't mind a TBI system, what is out there? Perhaps I am barking up the wrong tree? Maybe I should be trying to build that power internally? Let me know what you think! 

[Moses Ludel]

Stefan L...This is helpful, thanks for clarifying your Jeep CJ-6 equipment and goals.  Here is my take on each of your points:

4 minutes ago, Stefan L said:

As a novelty, I would really like to keep the major components of this jeep as jeep factory items so I have a th400 and dana 20 from a commando, a postal rear end and a narrow track dana 30 front end waiting on the shop floor to be swapped in.

I'm on board with preserving a pristine CJ-6 body and frame.  Your proposed changes should not have a large impact on the chassis if done properly.  Good plan, does the narrow track 30 have disc brakes?  The postal rear end should have decent size drum brakes, the combination would work.  Ditching the OEM brakes is wise for your family's safety and modernizing the vehicle's handling.

6 minutes ago, Stefan L said:

I am looking to make a weekend beach/camping family vehicle out of her and want to build the motor to get myself up in the 175-180HP range without getting exotic with it. I am not one to do burnouts or punch the gas un-necessarily but would like to keep up with highway traffic and have enough on ramp power to merge without scaring my wife. I would like to be able to tow a small trailer with her on occasion as well. Honestly 80% of my driving will be on road and I was trying to get the performance I was looking for through induction and exhaust. I wouldn't mind gaining some power through a cam upgrade as well but i haven't gotten that far in my plans to know what is available our how it would compliment my potential set up.  

Understood that this is a family, multipurpose vehicle.  Drivability is a key issue, you have good plans, and the 101" wheelbase does help with handling.  A Saginaw power steering conversion with one-piece tie rod (see Advance Adapters) would surely be a consideration if you still have the Ross TL steering gear...Engine wise, with the gearing and tire diameter proposed, and without overdrive in the THM400 transmission, I would build the engine for strong low-end and mid-range power.  For me, this translates as an RV camshaft or a grind with very mild duration increase and an emphasis on more valve lift than stock for bottom end power.  You need to move this vehicle along, and especially for light trailer toting, higher rpm power is not the goal. 

For a multipurpose 4x4, my camshaft mantra for decades has been the CompCams 252 grind or equivalent.  Fortunately, this grind is still available for the 225 Buick V-6.  Here are details at Summit Racing, you may find more at the CompCams' site:  http://www.summitracing.com/parts/cca-cl63-234-4/overview/make/buick.  If your engine is in top condition, you can change the camshaft and lifters in the chassis, add a Cloyes timing sprocket and chain kit and Melling's high volume oil pump kit, additional gains while you're at it.  If you are interested in judging the engine's condition, follow the cylinder leak down testing I describe in the General Repairs forum and elsewhere at these forums.

With the 252 camshaft or equivalent, you could run a set of headers or simply maintain the stock manifolds and split the exhaust into dual exhausts.  Rear exit tailpipes are a mandatory for wife, children, driver and other living creatures!  Headers, with the concerns I mention, are a consideration, there's certainly some benefit over the stock manifolds.  As for the induction, a dual-plane manifold is essential, I would consider a small AFB (not the Edelbrock equivalent if a stock OEM AFB carburetor is available) or a smaller application Rochester Quadrajet.  The original Rochester 2G or 2GC is a failsafe alternative, there is adequate CFM with a "blueprint rebuild" of the stock carburetor, and the intake manifold is not that bad.  Choice is governed by your budget here.

20 minutes ago, Stefan L said:

I plan on running a mild lift with either 32 or 33 inch tires and 4.10 gears. The motor that is in the jeep now has the stock ignition but I have a spare motor that has an HEI set up that I was planning on using.

Good plans.  Be certain to widen the track width with negative offset, wider wheels.  4" lift, 33x12.5x15 on a maximum 10" wheel with negative rim offset would be the limit.  Make sure you have the fender and frame clearance for the tires and wheels, test a set of wheels and tires at a reputable tire store before spending money here.  You may need a smaller tire, though many run 33" with a 4" or so lift and negative offset wheels.

That Delco-Remy HEI ignition needs to be odd-fire era 1975-77 GM/Buick 231 V-6 type.  If you have a complete 231 odd-fire V-6, that's a possible buildup, though I would opt for the 231 even-fire engine like I address in my Jeep CJ Rebuilder's Manual:  1946-71 (Bentley Publishers).  In the book, I discuss engine details mentioned here as well.

29 minutes ago, Stefan L said:

I live in North Central Florida where everything is flat and we probably never get above 750ft of elevation. I wouldn't mind a TBI system, what is out there? Perhaps I am barking up the wrong tree? Maybe I should be trying to build that power internally? Let me know what you think! 

TBI is always an option.  There were OEM GM 3.8L V-6 engines with TBI in the early 'eighties.  If you're good with electronics and wiring, an OEM boneyard or Craigslist donor might be available.  Another route would be Howell Engineering TBI.  This system is compatible with your standalone ignition and has been popular for Jeep 258 inline six retrofits.  Howell sells various segments of the kit, including the TBI unit and computer (essentially 4.3L GM V-6 pieces) plus a wiring harness interface and correct pressure fuel pump.  Using an adapter, you can mate the TBI unit to your current intake manifold or a 4-barrel manifold, either would work...This is mostly OEM, proven GM parts, and the system would not be overkill for a Buick 225/3.7L V-6, especially with oxygen sensor feedback and electronic fuel metering.  Worth visiting the Howell site.

There are distinct gains with TBI.  On the Jeep 258/4.2L, TBI delivers approximately 50 extra horsepower over stock while using the OEM (i.e., poor flow) intake manifold.  TBI is not altitude sensitive when using O2 sensor and MAP feedback.  TBI would certainly deliver more performance gains than any other modification we're discussing.  Headers would work very well with TBI and offer the kind of exhaust flow you need with EFI.  The O2 sensor bung can be installed on any exhaust system, though it needs to be located at the right point with regard to engine heat and accurate exhaust content readings.

Carburetion is acceptable with your fixed altitude plans, and even the 390 CFM Holley could be made to run well at this narrow range of elevation.  It would come down to cost and your budget.  If it comes down to headers versus a four-barrel intake and carburetor, I would start with the headers and a complete dual exhaust system to the rear of the tub (stock exit locations).  In the event you want more induction after that point, you would have the required exhaust modifications in place.

Moses

 

[Stefan L]

Hello again Moses. I have been working a lot and haven't had a chance to start my Jeep project yet but I do have Any laying around the shop. I thought it be way too big though. I think it is the smaller version, 750 cfm. I agree with that being a much better carb but again will the 225 be able to handle it? Can I jet it way down? Let me know. I am very interested in going that route if possible. Thanks!

[Moses Ludel]

Stefan L...The 750 CFM would be way too much flow.  The venturi bores are not desirable, and "jetting down" is not practical or likely to produce good results.

300 CFM would be plenty, 350-400 CFM would be more than enough even with the headers.  Think in terms of approximately 1 CFM per cubic inch of engine displacement to spin the engine at 4,000 rpm.  350 CFM would provide 6000-plus rpm capability.

Moses

[ahmichigan]

Thank you all for your good advice in this thread, it has been very helpful.  I would like to share my unique approach that has turned out well for me.

I purchaseed an offy 360 dual port manifold, without a real plan for a carb.

Anyway, I read Moses's comment about a Carter or Quadrajet, and also read a lot about the Quadrajet's being good at off angle without flooding.   Turns out I had an old Quadrajet from an old big block buick electra that my Father in law gave me.  I had never even considered bolting this massive carb to my small v6, but I began to read up on the Quadrajet, and GM took a unique approch to this design really making it a "Variable CFM" carb that could be used in many engines.  The primaries are similar to a normal 2 barrel,  and the secondaries only open as needed, and are metered based on engine vaccume/demand.  After convincing myself it was worth a try, I realized the carb and intake was too tall with the 3/4" thick square bore to quadrajet adapter to fit under the hood of my 2A.  I called Offenhauser, and got there thoughts on reaming the aluminum square bore intake opening to fit a quadrajet.  There was plenty of casting, and I added some epoxy steel in the center to keep the primary and secondary ports 100% separated.  Lots of aluminum chips later I had the big old Quadrajet mounted to the offy dual port.  I tried it out and it of course ran so rich I felt like I was pumping fuel out or my exhaust.  Conveniently my neighbor happened to have an old "Dual Jet" carb that presumably was used for smaller engines.  I switched the primary jets from 73's down to 65's, and the primary rods from 48-B's down to 44C's.   the secondary metering rods I changed from CT's down to CH's.   I really think the small quardajet primaries, combined with the small fast passages of the dual port offy makes the driveability excellent, instant torque, and not flat spots or hesitation.  The secondaries are only there for fun if you really want to step on it, but when they kick in you know they are there!    Again, taking some advice, I kept my manifolds but ran 2.25" dual exhausts all the way to the back, and everything still fits around my Hudson steering box.  :)   

I can say for sure it is a power upgrade, but the best part is the driveability is much better.  

[Moses Ludel]

ahmichigan...Thanks much for sharing your solutions and ultimate satisfaction with the Quadrajet!  This carburetor design remains my all-time production engine favorite for all around use.

For those without the ability to modify a Quadrajet like ahmichigan has done, there is another approach.  There were several Quadrajet applications on smaller displacement engines, and the closer we get to the displacement of the 225 Buick V-6, in this case, the better the carburetor will work for a 225 Buick V-6.

The closest engine of course would be the Buick 231 V-6.  There are late '70s applications of the 231 equipped with a Quadrajet specifically jetted and circuited for this smaller displacement engine.  For a vintage Jeep Dauntless V-6, avoid the feedback carburetors and "ECS" or C-4 units that require an electronic module interface and wiring.  Here are 1978 Buick Century applications (pre-feedback) Quadrajet four-barrel carburetors, and there are many other Buick V-6 examples in the late '70s and well into the 1980s:  #17058240, #17058246 and #17058540.  There should be many 231 and 252 V-6 Quadrajet carburetors still available.  Look for a non-electronic feedback type.  Make sure the carburetor is original by tag/stamping numbers to assure proper jetting and flow.  Any rebuilt (aftermarket) carburetor is suspect; try to find an original, matching numbers carburetor.

For ahmichigan, the workaround was rejetting (jets and metering rods) another Quadrajet application to get air-fuel (A/F) ratios desired.  This can be done and backed up with an exhaust reading for A/F, ideally on a dynamometer.  At bare minimum, a reading of spark plug coloration and tailpipe soot is smart. 

Another approach, popular when I wrote for performance magazines in the eighties and nineties, was the Edelbrock onboard A/F meter.  These affordable kits required installing an oxygen sensor bung on the exhaust header(s).  The meter reads stoichiometric (the ideal 14.7:1 A/F for gasoline) and deviations in both directions from stoichiometric (range includes rich 12:1 to lean 15:1 A/F) under light and heavy throttle loads, various driving conditions and so forth.  This is an affordable, real world and real time A/F readout that uses the vehicle and various loads and throttle positions to simulate a dynamometer.  The Edelbrock device is still available:  https://www.summitracing.com/parts/edl-6593.  The A/F meter serves as a fuel flow and tuning monitor while also enhancing driver awareness.

As a point of interest, the Quadrajet can be a busy carburetor design for staging and tuning.  (If you want to take Quadrajet carburetors seriously, find a copy of Doug Roe's book, Rochester Carburetors, originally published by HP.)  The good news is that the Quadrajet is relatively adaptable, as ahmichigan discovered.  Most aftermarket Holley carburetors are not.  Trying to re-jet, meter block, power valve and change pump stroke on a "universal" Holley 2300 series 500 CFM carburetor can be daunting.  The universal aftermarket 500 CFM carburetor is designed to flow fuel into a Lincoln 430 V-8 or a circle track stock car engine.  The metering block and other circuit features in the main body make this nearly impossible. 

The 300 CFM Holley universal version would be much more suitable.  However, for retrofitting a Holley carburetor onto a 258/4.2L Jeep inline six, I always recommend a stock replacement I-H 266 V-8 two-barrel Holley 2300, manual or automatic choke version.  The typical adaptation uses a Clifford or Offenhauser intake manifold with a two-barrel adapter plate. 

At the end of the day, I prefer a Quadrajet four-barrel over a Holley (two- or four-barrel) or even the reliable Carter AFB for the reasons that ahmichigan and I cite.  The flexibility of a Quadrajet and its adaptability to a wide variety of driving conditions is the hallmark.  Ahmichigan's 225 V-6 serves as a testimonial.

Moses

[ahmichigan]

I really like the idea of the A/F sensor, it’s highly unlikely I got everything just right with some free spare parts!  Lol.  It’s great to have a positive second opinion on this!  Thanks Moses!

[ahmichigan]

Lots to fit under that hood!  But it can be done!😄

[Moses Ludel]

Wow, ahmichigan!  The Quadrajet dwarfs the 225 Buick/Dauntless V-6...Quite an adaption, impressive and one of a kind!  All for the better.

Metering the Q-Jet to flow properly with this small displacement engine was an accomplishment.  Staged properly, as you have done, this is an exceptional carburetor for tolerating altitude.   To test that out, you'll need to travel West:  the Rockies, Sierra Range or Moab!

The Edelbrock A/F meter reads exhaust stream changes in real time, a big plus.  This is so much more efficient than reading spark plugs or even the old stationary tune-up exhaust analyzers.  You get an instantaneous A/F read for a given throttle position, engine load or driving condition. 

Be sure to place the oxygen sensor bung at the appropriate point, as described in the Edelbrock kit.  If cost were not an obstacle, I would suggest a meter for each bank (an O2 sensor in each header with separate meters).  This is a terrific tuning aid;  it would be a great training tool for the Mobil Economy Run.  To maximize fuel efficiency and mileage, the aim is to tune the engine and drive as near stoichiometric A/F (14.7:1 for gasoline) as possible.

Moses

[ahmichigan]

Just went through a month of frustration, but all ended well. Turns out standard quadrajet footprint was larger than that of a standard square bore base plaeau, when modified for a spread bore pattern.  Not sure if anyone will ever try this, but just an FYI if you do.

although the quadrajet was much improved, when it would get hot the gasket would leak because the quadrajet gasket has a 1/2 overhang in the front beyond the offy 4 barrel intake.   I have been sucking air for a month or more, and struggling with why I could not get it it idle down!  I built out the intake with some steel stick, and all is now well.  On top of that, I propped my heat riser into the permanently closed position when it began to rattle.  (Imbarrased to admit) but with those two bugs fixed, and with a fresh new carb and Petronix just added, WOW!  😄. Finally running awesome.  Have to expect the bugs...

[Moses Ludel]

Yes, the spread bore base is in a league of its own!  And risers can be confusing...Glad you worked out the bugs and have that 225 performing well again.

Moses

[ahmichigan]

Just an update since last august

Called a Maine carborator company and asked for a new quadrajet jetted for 225 displacement, and configured for cars not boats.  Quadrajets on GM 4.3 marine engines apparently are very common. 1 week and 350$ later it arrived, bolted it up and haven’t touched it.  Just another source if anyone was curious.   Recent HEI upgrade also added fire the fuel, and complemented this setup well.
 

 

[Moses Ludel]

Very helpful, ahmichigan!  Closer displacement and each engine is a V-6.  Let us know whether the jetting works.  Did the shop change the 4.3L carburetor's jetting for your smaller 225?  Very curious about the outcome. 

One helpful device would be an O2 monitor on the exhaust stream.  Not cheap but a good way to confirm the jetting and watch the overall behavior of your carburetor in real time.  I used these years ago on carbureted engine buildups and reduced fuel consumption.  You can drive by optimal air/fuel ratios.  Simply install the oxygen sensor bung on the exhaust pipe, according to instructions, and wire it up:

https://www.summitracing.com/parts/edl-6593

Thanks!

Moses

[ahmichigan]

I did ask them to re-jet accordingly for the 225 before sending.  And I’m sure they used a 4.3 carb and just modified it.  I just bolted it up and have had great drivability for 8+ months.   It’s no exact science, but so far so good.  Still considering the mix sensor for fine tuning but overall great results.

[ahmichigan]

https://www.i-5automotive.com/product-category/marine-carburetors/
 

so..  one of the stock marine engines is actually a 2.8.  Very close to 225/3.7L. 

[Moses Ludel]

ahmichigan...Indeed, 3.7L is nearly spot on for the 3.8L OMC engine.  This should work really well!  Glad they jetted accordingly.  You will have a strong performer.  The Q-Jet also allows for decent fuel efficiency—if you stay out of the secondaries!  An optimal choice for a four-barrel, others will benefit from your research.

Considering contemporary carburetor costs, this is actually a good price, too.  Are these 4MVs built from marine engine cores?  The price is outright without a core deposit?

Moses

`

[ahmichigan]

This seemed to be all new, and no core charge asked for.  30 day warrantee, so best to try it out.  Stephan was out of California, knowledgeable and backed up his product in my option.   May be an import carb, but seems to work for me.

 

[Moses Ludel]

Go for it...30-day trial, how can you lose?  Watch your tailpipe coloration.  Check a spark plug(s) after a fairly hard, fully warmed up run.  Look for burn coloration and any signs of rich or lean mixtures. 

Which manifold did you use?  Offenhauser?  Looks like a good fit, is the manifold a single or dual plane design?  For a spread-bore carburetor?

[ahmichigan]

I started with the offy 360 dual plane aluminum intake setup for a normal square bore.  I machined the ports out with a dremmel and added steel stick to some areas to make it have 2 compliantly isolated circuits.  One for primaries and one for secondaries without any crossover.   The carb needed to bolt directly to the manifold only with the 3/16 thick insulating spacer between in order to still Barely fit under my flattie hood without any modification.  Normal driving is all primaries, and the secondaries only open up at higher rpm under load, and they really do add something.  I do think the secret to making this carb work is the dual port segregation.  Small primary ports keep the velocity up.  If I have the carb off any time soon I’ll snap a picture.👍

[Moses Ludel]

Dual plane will deliver better bottom end torque, idle vacuum and idle stability.  Good approach. 

So, the "steel stick" will stay in place?  What is the bonding and temperature range for this?  

[ahmichigan]

The Steel stick bonds well to roughed up aluminum and is rated up to 300 degrees.  Sounded low, but the aluminum intake should not get much hotter than the coolant running through it at 180 to 200 degrees or so.  Used for just re-shaping the ports, it doesn’t see any real stress either.  

[Moses Ludel]

ahmichigan...You want the product to stay put and not slough into the intake stream.  My biggest concern would be a chunk passing through an intake valve and into a cylinder.  Keep an eye on this material.

I'm guessing this is J-B Weld's SteelStik®:  https://www.jbweld.com/product/steelstik-epoxy-putty-stick.  J-B Weld makes good products, they work when consumers stick to the instructions and product properties (PSI rating, bonding characteristics, temperature, etc.).  The PSI rating is on the low side, but as you share, there is no direct pressure beyond manifold vacuum (negative pressure in PSI, roughly 1 in/hg mercury per each 0.49 PSI) and air velocity.  Fuel resistance would be a concern.  The product description indicates that it will bond to aluminum.  You'll have to see how this works. 

I've used J-B Weld products with expected results based on their PSI ratings and specified use.  Frankly, metal-to-metal bonding at the 3,000 or so PSI tensile range can be quite weak.  By comparison, fusion welding (oxy-acetylene, MIG, TIG or stick) would be more like 70,000 PSI (using a common mild steel filler rod like ER70S-6) or brazing rod ranging from 40,000-100,000 PSI.  Realistically, however, you're not bonding two pieces of metal together here.  For shaping, the material only needs to stick to the aluminum.

The best J-B Weld product, in my experience, has been the two-part Plastic Bonder "High Strength Structural Adhesive" for bonding plastics.  It's superior to any other plastic bonder or plastic repair product I've used.  Simply put, it actually works if you need to repair or bond plastics.

Moses

[ahmichigan]

I grew up on the coast of Maine and was a boat builder for a time.  I was repeatedly amazed by some of the crazy things epoxy was used for.  I have no idea if there will be any long term fatigue or brittleness or slow reaction to fuel, but I guess I’ll take the risk.  It has been a really interesting progression with this little v6.  When I installed it, it had the original ignition and the 1 barrel that came with the early Buick 225 fireballs.  I then upgraded to the 2 barrel and noticed some fairly minor torque gains as expected.   Then I moved to the 4 barrel intake with the quadrajet and standard ignition.  This had faster pedal response and a bit more torque.  Then I upgraded the exhaust to dual exhaust (all the way to the back) and this just seemed to help in the upper rpm range opening up the secondaries.  Next I swapped in the Correct quadrajet as we talked about seemingly with proper jet sizes, and this probably is saving gas and probably adding some power.  Most recently I changed to the HEI and added voltage and spark plug gap really made everything finally click.  Torque is now instant, and the power just feels effortless.  Super fun!😄  finally at the point where I may just leave it alone!

 

 

 

 

[Moses Ludel]

The manifold and carburetor look impressive!  There were later 252 V-6 versions of the even fire 3.8L series engine that used a Quadrajet, so there's a precedent here.  I'm very pleased to hear how much satisfaction this vintage Jeep has provided.  The 225 is a rugged workhorse and just the right amount of power for the vehicle's size and weight. 

Avoid the scourge of rust on that vintage CJ!  It's a classic and, as you share, super fun 4x4!  

Keep us posted on the four-barrel's performance.  You've got plenty of fuel, spark and a free flowing exhaust system.  Exhaust flow was an issue with the OEM exhaust system.

[ahmichigan]

[ahmichigan]

Will do!

[Moses Ludel]

ahmichigan...You shared your use of Steel Stick on the manifold shaping.  I'm a follower of Goodson.com and its product releases.  I found this interesting and thought of your shaping chore.  Apparently, there is a precedent for these buildup methods, you were on the right track.   Note the 500-degree F rating:

https://goodson.com/products/prk-99-intake-port-reshaping-kit

How's the system working?  Leak-free and delivering the performance you sought?  Having fun with the Jeep this summer?

Moses

[ahmichigan]

Hi Moses, very cool on the Goodson product!  I’ll have to keep that in mind!

I spent all last week on the silver lake sand dunes in Michigan, and my only problem was slowing down at the top!  Couldent be happier with the engine, and I have not touched a thing in months!  I was forced to run an ethanol mix for a few tanks, and did not have any issues with the heat or extreme angles or boil over.  
min sure people were surprised to see those NDT’s claw up the sand. 
love the front and back powrloks. 
I have some fun calculating my best climbing gear in the sand.  Up was the jeep T-18 in 4th (1:1) in low range (2.45) with the Saturn engaged( .75) or not depending on how many people were with me! 4.27 final is a great gear all around I think.  Only down side was if I got stuck and had to backup, the 7.0 reverse gear in low range is painfully slow!Lol.

[Moses Ludel]

Very pleased that the Jeep is doing what you intended it to do...Great fun on the dunes, sounds like a "Yahoo!" 

Have a safe, fun summer and fall...Your research and considerable work has paid off...

Moses

[B Rad]

New to the Jeep family and picked up a '68 CJ5 Willys Overland. Needs a little work. 225 dauntless odd fire, SM 420 4-spd,  Model 20 Spicer transfer case, Saturn overdrive, Dana 44 Jeep Wagoneer axles, 538 gears and Warren hubs. Current issue is that after it warms up, it stalls out. Sit for a few minutes and you can start back up and go another 1/4 mile or so before repeating the issue. A couple of thoughts that may be causing this.... mechanical fuel pump going bad, coil collapsing, distributor issue?? It does have the Rochester 2 jet, single barrel carburetor on with stock manifod.

Thanks in advance for feedback.

[Moses Ludel]

B Rad...See my reply at your topic post...Stefan L is a good contact and resource, too.

Moses