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Stuart_Snow

4.2 L first time start-up after re-build.

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After doing a long and careful re-build on my 77 CJ7 4.2 engine I expected it to spring to life. So far I'm only getting spitting and coughing through the carb but it did fire once for a second which gives me hope. I'll quickly run through the vitals here:

Fuel system: New gas tank and lines. I have verified that it is pumping fuel to the carb. The carb is a re-build Carter YF 1 barrel. It was dirty and needed a new accelerator pump  but in good shape otherwise. I used a kit from Mikes Carbs and did it my self which was pretty straight forward. I have spent a fair amount of time messing with the carb on my CJ-3b so I was familiar with it. It does appear that fuel is making down the intake but when I pump the throttle I'm not seeing anything from the accelerator pump so its coming back off to diagnose that. 

Ignition: Its a DUI HEI unit, I installed it per instructions and set it up to fire the #1 cylinder at TDC.  I verified it is working with my timing light. Using my remote starter switch I can see the timing mark and I'm able to run it up and down the the advance markings by rotating the distributor while I crank from 0 degress to 12 or more all it does is spit out the carb.  DUI recommends 12 degrees static as a starting point for racing or off road which may be a bit much for me until I get past emissions. I currently have it at 6 but have tried the whole range. My factory settings only call for 3 degrees +/-2 @500 Rpm . I'm guessing this is due to smog regulations of the day. Anyway I've demonstrated that the ignition is working and I can set the advance up and down with no results.

Valve train: I spent a lot of IMG_1556.thumb.JPG.687acf5eb011beca6131be7a4b1f63e5.JPGIMG_1556.thumb.JPG.687acf5eb011beca6131be7a4b1f63e5.JPGsetting this engine up and do not anticipate valve-train problems unless the springs are tired or something is sticking. I ran through all cylinders in firing order with a cheap press on gauge and got  100 psi or more on all. I do have an aircraft style differential compression tester which I intend to use once I modify it to fit auto plug threads. I did a thorough priming of this engine and verified the lifters were pumped up and oil was making it to all the rockers.

So I have a flame throwing ignition system and an anemic carb. I understand that spitting can be a symptom of a lean condition but I assumed that was for an engine that isIMG_1549.JPG.2f4910055f666ef0a38b6eddcab84cee.JPG already running.

I'll report back when I trouble shoot the carb and verify my compression is good when and where its supposed to be. No back firing  but lots of spitting and coughing up the carb. I have kept the air cleaner on to keep flames out of my face.

 

 

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Stuart...See my comments below...Moses

13 hours ago, Stuart_Snow said:

After doing a long and careful re-build on my 77 CJ7 4.2 engine I expected it to spring to life. So far I'm only getting spitting and coughing through the carb but it did fire once for a second which gives me hope. I'll quickly run through the vitals here:

Fuel system: New gas tank and lines. I have verified that it is pumping fuel to the carb. The carb is a re-build Carter YF 1 barrel. It was dirty and needed a new accelerator pump  but in good shape otherwise. I used a kit from Mikes Carbs and did it my self which was pretty straight forward. I have spent a fair amount of time messing with the carb on my CJ-3b so I was familiar with it. It does appear that fuel is making down the intake but when I pump the throttle I'm not seeing anything from the accelerator pump so its coming back off to diagnose that. 

Does sound like the accelerator pump...Look for the checkball that keeps fuel in the plunger bowl.  Verify that the carburetor bowl is full, float working properly at the right height.  Fuel filter looks new.  Check the fuel pump pressure at the carburetor side of the fuel filter.  Fuel volume is important, too.  Is the fuel tank and pickup (if there is one on your tank pickup) clean?  Note the fuel flow rate and pump pressure.

Ignition: Its a DUI HEI unit, I installed it per instructions and set it up to fire the #1 cylinder at TDC.  I verified it is working with my timing light. Using my remote starter switch I can see the timing mark and I'm able to run it up and down the the advance markings by rotating the distributor while I crank from 0 degress to 12 or more all it does is spit out the carb.  DUI recommends 12 degrees static as a starting point for racing or off road which may be a bit much for me until I get past emissions. I currently have it at 6 but have tried the whole range. My factory settings only call for 3 degrees +/-2 @500 Rpm . I'm guessing this is due to smog regulations of the day. Anyway I've demonstrated that the ignition is working and I can set the advance up and down with no results.

Six degrees is plenty if your vacuum advance is working properly.  Make sure your vacuum advance hose goes to a ported vacuum source, not a manifold source.  Disconnect and tape off the vacuum advance hose when verifying the base spark timing...If the vacuum advance hose routes through a thermal vacuum switch, check the switch and advance vacuum as you tip-in the throttle.  For the vacuum advance to work, the engine must be warm when there is a thermal vacuum switch in the hose circuit.

Check the spark output at the plugs.  You should have a real zap with the DUI.

Valve train: I spent a lot of IMG_1556.thumb.JPG.687acf5eb011beca6131be7a4b1f63e5.JPGIMG_1556.thumb.JPG.687acf5eb011beca6131be7a4b1f63e5.JPGsetting this engine up and do not anticipate valve-train problems unless the springs are tired or something is sticking. I ran through all cylinders in firing order with a cheap press on gauge and got  100 psi or more on all. I do have an aircraft style differential compression tester which I intend to use once I modify it to fit auto plug threads. I did a thorough priming of this engine and verified the lifters were pumped up and oil was making it to all the rockers.

Priming was done with the pushrods and rocker arms installed, right?  You want to make sure the lifter plungers are not overextended.  They will bleed down as the crankshaft rotates, so they should be normalized by now.  (Depending upon engine design, the concern is valve interference/bending valves if the plungers are hyperextended while cranking the engine.  Unseated valves, even if they do clear the pistons, will cause spitting back through the carburetor.  With no noise, you likely have the valves clearing the pistons.  Also, your compression check indicates that the valves are seating.)  Valve timing is crucial.  I'm sure that you were painstaking when aligning the timing sprockets...Always a concern, though.

So I have a flame throwing ignition system and an anemic carb. I understand that spitting can be a symptom of a lean condition but I assumed that was for an engine that isIMG_1549.JPG.2f4910055f666ef0a38b6eddcab84cee.JPG already running.

I'll report back when I trouble shoot the carb and verify my compression is good when and where its supposed to be. No back firing  but lots of spitting and coughing up the carb. I have kept the air cleaner on to keep flames out of my face.

Though seemingly elementary, re-check the spark wire firing order:  1-5-3-6-2-4.  The distributor rotor rotates clockwise. 

You were painstaking with the assembly, I'm betting the issue is simple...Moses

 

 

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It runs!  I had the distributor setup one gear too late so it was not lined up with the plug terminal exactly. All I was getting was the warm afterglow which was causing my spitting problem. It fires right up now. Turns out indeed my accelerator pump port was also clogged. Carb spray did not clear it so I used one of the welding tip cleaning wires to clear the obstruction.

It idles very smooth. I ran it at about 1600 rpm for about 20 minutes to mate the cam with the lifters. My break in oil is Rotella 15-45 and I used the Lucas break-in additive with ZDDP. It looks good after the break in run and nothing leaking out of the bottom.

I have a slight exhaust leak to deal with at the manifold. It sounds like a beast.  At least now I can work on fine tuning things. 

Thank you Moses for getting me to start thinking and looking at it closer. I'll keep you posted on my break in progress.

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Yea, Stuart!  Sounds like you nailed it...This will be a great engine.  Smart to use Lucas break-in oil with ZDDP.  The camshaft lobes-to-lifter bases represent the highest friction point per square inch in the engine.  Proper break-in will deliver many, many years of quality service! 

Congrats on a job well done...

Moses

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Well its been a long and difficult road to being street legal but I finally made it.  Arizona Emissions testing took 4 tries but It is running just like it rolled off the assembly line in 1977.

The first thing that surprised me is the inspectors totally ignored all my OEM correct emissions gear and just marked n/a or not tested for everything including my evap canister. They only were concerned with the levels coming out of the tail pipe at idle and loaded which is a dyno run at about 35mph.

Gasses tested were HC Hydrocarbons and CO Carbon Monoxide. NOX was not tested. I assume because my jeep is a non-catalyst model with air injection and EGR only.

I passed HC every time with no trouble which told me at least I was getting ignition on all cylinders. 

CO carbon Monoxide was my problem which is the result of incomplete combustion. My limits I had to beat were 1.5 percent for loaded and 2.0 percent for idle. I failed bad the first try with 3.8 loaded and 6.0 idle. I began to worry I the standard was too high for my carburated jeep.

I installed a beautifully rebuild carb with new bushings from Carburetor Exchange in El monte, CA. I also verified my EGR and air injection were working. This improved my CO numbers a little but I still failed and in fact the HC number got worse but still passed. At this point I was wondering if Howell fuel injection was in my future.

Back to the books I went for more study. I read in a trade article that platinum or iridium plugs can give a slight advantage when trying to pass the CO carbon monoxide test.  Out came my nice Denso copper plugs and in went a platinum set. Then I adjusted the idle mixture per my shop manual.Next I backed the timing off even more than the OEM specified 3 degrees. Acceleration is pretty bad like this but I passed idle with almost no reading at all and just missed loaded by a small fraction of a percent. Since this was still failing I took it to the professional emissions guy down the street who was able to tune the final little bit out and get her to pass. I know he bumped the advance back up because my power is back but he did not divulge his secrets.

I hind sight it may have been smart to start with the Pro shop who can check his tuning with his gear and then go for a guaranteed pass. I was just happy to know that this carburated engine can meet the standard. It has been rewarding to take this engine from a basket case back to original running condition.

I also avoided all the wives tale advice I got from people about pouring alcohol or moth balls in my fuel tank.

I'm ready to take her out to the trail and see how she does. It sure rides better then my CJ-3b.  I also found some rust free doors at F/N jeep in Colorado springs. I now need to adjust my steering gear to take the scare factor out of driving this thing.

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Wow, Stuart, the long and winding road!  Years ago, Arizona required a simple tailpipe reading for emissions and never opened the hood.  That changed, as you hint, to match California and other states where a visual inspection of emissions equipment is a mandatory part of emissions tests.  Maybe there is a model year cutoff for the full inspection test, and if old enough, a vehicle reverts to the older tailpipe reading only method?  Or does this have to do with your zip code?

Pleased that you're on the road.  This must be gratifying.  The high HC/CO readings with your original carburetor could have reflected a unit with the wrong jetting.  You were meticulous in your approach to rebuilding the carburetor, it should have performed to OEM standards.  (The old carburetor may not have been in original form.)  In any case, the El Monte shop's build must have the right jet and metering rod.

Keep us posted on the performance and your driving impressions.  Yes, the CJ-7 is a great improvement over the vintage Jeep CJ3B chassis, worlds apart.  You have a longer wheelbase (94" versus 80") to smooth out the washboard roads plus longer springs to improve ride quality and control. 

I like an aftermarket front spring/shackle reverse on any of the Jeep models through the YJ Wrangler.  Vehicle control and steering improve, and there's less frame impact when climbing over rocks or limbs.  The front axle trails instead of being pushed forward from the anchor (rear) end of the front springs.  Something to consider, not a must.

Where will you be driving off-road at Arizona?  You have a wealth of open country to explore!

Season's Best,

Moses

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Life has been busy and I have finally had a chance to go on a few shakedown runs. There are some BLM areas west of Phoenix that I can access via back roads without getting on the interstate. The jeep wants to move on out when I roll it down the highway with the 3:56 gears. I have had it up to 60 @ 2500 rpm. The steering box is worn and needs adjusting or rebuilding. Also with only the old lap belt I'm ready for a shoulder harness for better safety.  I'm really impressed with how it pulls when accelerating from low rpm.  Driving on the road requires all your attention and there is some body lean in corners. Did later models come with stabilizers?  Off road I really like the option of a low first gear with the T-18 without shifting into low. Shifting the t-case to 4 low or 4 high required some strength. Maybe a twin stick conversion will help this. The trails are mostly old mining roads and decomposed granite which can make hill climbs a challenge. I pushed it up a steep climb for a test. It finally got steep enough that I ran out of traction with the open diffs and at the same time the  carb reached its critical angle of attack and the engine began to buck and snort so I had to abort the climb. I was amazed at the torque the engine makes even at very low rpm. Maybe Howell fuel injection and some lockers are in my future.  I'm researching the aftermarket parts to beef up the common fail points on these jeeps. For now I'm having fun getting to know this jeep after working so hard on it.  I have had it out on a few long trips and made it back with no mechanical issues. Im getting some data on fuel burn which can run from high 12's to 14 mpg. I'm most excited that there are NO LEAKS. This make me very happy and I feel lucky to have this jeep to enjoy. The dog likes it too!

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Stuart...This is just what I envisioned for your end result:  a great venue to enjoy that CJ-7!  The Jeep looks terrific, the terrain does, too...In answer to your questions:

On 2/15/2020 at 7:54 PM, Stuart_Snow said:

Life has been busy and I have finally had a chance to go on a few shakedown runs. There are some BLM areas west of Phoenix that I can access via back roads without getting on the interstate. The jeep wants to move on out when I roll it down the highway with the 3:56 gears. I have had it up to 60 @ 2500 rpm...I'm really impressed with how it pulls when accelerating from low rpm. 

The steering box is worn and needs adjusting or rebuilding...Also with only the old lap belt I'm ready for a shoulder harness for better safety.  Driving on the road requires all your attention and there is some body lean in corners. Did later models come with stabilizers? 

The steering gear looseness would definitely impact your cornering, too.  If this is manual Saginaw ball-and-nut steering, the gear may have significant wear.  If only slight over-center wear, a minor adjustment might work.  Use the factory service manual for this adjustment, and check for the over-center measurement in particular.  This is an easy gear to rebuild or is available as a complete new unit in the aftermarket.  For alignment and steering performance, the gear must be on center with the front wheels pointed straight ahead.

Yes, the later CJs did have a sway bar.  In the late seventies, it was standard on models with the factory molded hardtop and optional otherwise.  You either do not have the optional front sway bar or it was removed.  There are a variety of aftermarket sources (Hellwig and other suppliers) for an add-on front sway bar.  If you don't do hardcore trails that require a great amount of axle articulation, a factory style sway bar works well.  If you have a significant lift kit or are articulating the front axle to extremes, you need a sway bar kit with disconnect links for off-pavement rock crawling.

Off road I really like the option of a low first gear with the T-18 without shifting into low. Shifting the t-case to 4 low or 4 high required some strength. Maybe a twin stick conversion will help this.

The stock Spicer/Dana 20 transfer case can be stiff to shift.  Driving it a bit may help.  An aftermarket twin stick conversion has added shifting features and is an alternative. 

The trails are mostly old mining roads and decomposed granite which can make hill climbs a challenge. I pushed it up a steep climb for a test. It finally got steep enough that I ran out of traction with the open diffs and at the same time the carb reached its critical angle of attack and the engine began to buck and snort so I had to abort the climb.

A traction rear axle would make a world of difference.  I like a manual locker that you can leave in open diff mode when added traction is not necessary or you're driving on an icy off-camber highway or a muddy off-camber trail.  Here, I leave the rear locker in open mode to avoid side slipping.  I prefer the ARB Air Locker, OX and other manual lockers work, too.

I was amazed at the torque the engine makes even at very low rpm. Maybe Howell fuel injection and some lockers are in my future.  I'm researching the aftermarket parts to beef up the common fail points on these jeeps. 

The front shackle frame support at the front springs is a weak point.  AMC punched a hole to clear the frame rivet and made this a weak piece.  A major handling and safety gain is a shackle reverse kit for the front axle/springs.  This places the anchor end at the front of the front springs and allows the axle to trail from the frame, rather than the frame pushing the axle forward from the back end of the front springs (stock mode).   Highway handling can improve dramatically, and the shackle reverse kits are usually a mild 2" over stock lift that can be replicated at the rear of the vehicle with 2" lift springs.  Usually, the shackle reverse kit is part of a chassis lift if you want to go that route, but stock height models can surely benefit if you can find a kit that does not involve a lift.

For now I'm having fun getting to know this jeep after working so hard on it.  I have had it out on a few long trips and made it back with no mechanical issues. Im getting some data on fuel burn which can run from high 12's to 14 mpg. I'm most excited that there are NO LEAKS. This make me very happy and I feel lucky to have this jeep to enjoy. The dog likes it too!

The mileage is somewhat normal for a 258 six, you'll pick it up a bit after engine break-in...As for our dogs, they are right in their element on a Jeep trip!

 

 

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