Jump to content
Stuart_Snow

4.2L Re-build 77 CJ-7 Project

Recommended Posts

I have begun the rebuilding of the 4.2 engine from my 77 CJ-7 barn find project. My local NAPA store in Buckeye, AZ has a reputable engine shop attached and run by an family friend of my wife. Its good to have friends with years of experience to help. I opted for NAPA's deluxe master  rebuild kit which is a good value when you get it all at once.

IMG_E0509.thumb.JPG.d952e82391471dbdcf9adc0a0b051595.JPG

I was pleased with how clean the hot tank process got my dirty block and sheet metal. I had given up on scrubbing and even the pressure washer didn't work well. After taking measurements it was decided to go with the .030 re-bore.  My sharp eyed engine man noticed that the oil bypass valve retainer had damage to the shoulder that fits into the block for alignment. I think I understand how this valve works and felt this damage would compromise the integrity of the valve. I am  not sure how the damage occurred other than  forces applied during removal or installation. Luckily there is a good bit of info about the valve in my Jeep CJ re-builders manual by Moses Ludel.

IMG_0511.thumb.JPG.292108afc363bf7a00b393ef2775742b.JPG

A trip to my local AMC junk yard did not yield one. I'm not sure if this part is still stocked anywhere. I decided to see what I could do with my MIG welder and I think I succeed but I would still use a new or salvage one if I can find it.

IMG_0513.thumb.JPG.1cca7784feae473a75dd43380c8dadaa.JPG

Next I installed the nice brass plugs that come with the kit and the oil passage plugs. The new cam is standard OEM grind and fit nicely into the new bearings installed by my shop. I'm not sure exactly what holds the cam in place on this 77 vintage engine. Chain? Lifters? Distributor? All three? My engine does not have the spring and Pin thing on the timing cover that Ive heard about on later engines. My jeep project had signs of good regular care by one owner. My crankshaft was still within specs for a polish only and standard bearings. 

IMG_0515.thumb.JPG.72e0c11c722febdf105733d6cf4ea2df.JPG

IMG_0516.thumb.JPG.ddc78ec287a7e90be5eac392aa7cf16f.JPG

The crankshaft is now installed after verifying still in specs on oil clearance with plasti-gauge.

IMG_0518.thumb.JPG.4295415f8b33a9f8f6da8af1565df05b.JPG

Share this post


Link to post
Share on other sites

Nice work, Stuart...Did you polish the crankshaft?  Looks good...No regrind and balance?  Inline sixes are very tolerant of balance, OEM cranks and flywheels generally do not create an issue.  I usually grind 0.010"/0.010" undersize and balance the reciprocating parts.  Match weighting helps, too.  Not sure if any of this is in your plan...

I'll look through my OEM Mopar parts for the 4.2L projects.  I may have a valve retainer.  The original part number is J3173225.  The number may have been updated later by Mopar.

Moses

Share this post


Link to post
Share on other sites

Moses,

No regrind. Just a polish. I cant afford to get too carried away, hopefully I'll be ok. My 77 jeep factory shop manual showed up today, lots of good info in there. I got the timing chain on today. I fumbled around with that quite a bit but got it clocked correctly. I have wondered if Mopar has a stock of the older jeep parts like the valve retainer. Ill have to check.

Stuart

 

 

 

Share this post


Link to post
Share on other sites

Stuart...I'll look for a retainer in my boxes of NOS Mopar parts and get back...I am doubtful that Mopar has any interest in this part (J3173225) or AMC era engines.  Unlike us, they focus on new models and late technology...This part is officially discontinued, though I found a package of four (NOS) at eBay by running the part number.  That particular ad is in Spanish.

I will let you know if my boxes of parts include a retainer...

Moses

Share this post


Link to post
Share on other sites

Stuart...I messaged a note your way...Found a J3173225 Retainer, brand new in the original Mopar bag...I have two (2)...See my message.  Pleased that you're working with a '77 factory service manual, that's first generation information..Moses

20180628_170634[1].jpg

Share this post


Link to post
Share on other sites

I'm sending the Retainer your way, Stuart...The 4.2L/258 engine looks good, always easier to install the main seal with the block upside down.  Nice attention to detail!

Moses

Share this post


Link to post
Share on other sites

The long hot summer is over and I'm finally able to get some things done and update progress. The new by-bass valve retainer has been installed. Thank You Moses!  Pistons tapped int place with no trouble. I had some trouble with the front timing cover spacing clearing the cam gear retainer bolt. My solution was to glue two timing cover gaskets together which gave me the clearance need to to keep the cam gear retainer bolt from grinding against to timing cover. The replacement harmonic balancer did not want go on without ridiculous amounts of force so I backed it off several times and finally had to remove and lightly polish the mating surfaces. It went on normally after that. I used the 4 piece oil pan gasket and spent a lot of time making sure I had potential leak area well sealed. The oil pan is now on so we will see how that works. At some point I realized that my water pump pulley was missing from this project. I thought this was no problem until I learned how hard they are to find for a two groove early 4.2 engine. Mine is a 77.  I brought one home from our local AMC jeep salvage yard which turned out to be from an 87 YJ. This is a problem since apparently the later 4.2 engines used a pulley and water pump combination with a shallower offset which causes the belt to not align properly on my 77 engine. I briefly considered using a later model water pump that doesn't stick out so far but didn't know what other problems that would introduce. I finally found a salvage one on E-bay from Southwest off road in New Mexico. This part seem to be the right fit from a 76-86 4.2 engine so I am back in business.

Piston install.JPG

oil pan gasket.JPG

water pump pulleys.JPG

Share this post


Link to post
Share on other sites

Nice work, Stuart, appreciating the cooler weather here, too.  The electric bill with my Haier portable air conditioner running in my shop leaped up $75 per month during our similarly hot summer.  Worth it, at least I was able to continue using the shop.  Glad you're getting relief and able to pursue the 4.2L engine build.  See my comments below:

22 hours ago, Stuart_Snow said:

The long hot summer is over and I'm finally able to get some things done and update progress. The new by-bass valve retainer has been installed. Thank You Moses!  Pistons tapped int place with no trouble. I had some trouble with the front timing cover spacing clearing the cam gear retainer bolt. My solution was to glue two timing cover gaskets together which gave me the clearance need to to keep the cam gear retainer bolt from grinding against to timing cover.

I'm sure you confirmed that the sprockets and chain align vertically.  Was the timing gear hub thicker?  The cam sprocket washer looks like normal thickness...The cam sprocket appears to ride flush.  Correct?  If everything else is okay, a thicker gasket stack shouldn't create any issues.  1981-up Mopar catalogs show the "pin kit" that consists of the camshaft bolt with a hollow recess for a tensioner spring and a pin that rides against the timing cover.  This arrangement only works for engines that use a timing cover designed for the pin and spring tension...Your earlier '77 4.2L/258 setup should not require the spring-and-pin nor a bolt with the recess for the spring and pin. 

For later 4.2L sixes, this 1981-86 parts illustration shows cluster #13 off to the left.  Zoom-in for detail:

image.png

The replacement harmonic balancer did not want go on without ridiculous amounts of force so I backed it off several times and finally had to remove and lightly polish the mating surfaces. It went on normally after that. I used the 4 piece oil pan gasket and spent a lot of time making sure I had potential leak area well sealed. The oil pan is now on so we will see how that works.

Smart move on polishing the damper hub and crank snout.  4-piece pan gaskets are a real chore to install with the engine in the chassis, it's much easier on an engine stand with the block upside down!  Results are always better on the stand.

At some point I realized that my water pump pulley was missing from this project. I thought this was no problem until I learned how hard they are to find for a two groove early 4.2 engine. Mine is a 77.  I brought one home from our local AMC jeep salvage yard which turned out to be from an 87 YJ. This is a problem since apparently the later 4.2 engines used a pulley and water pump combination with a shallower offset which causes the belt to not align properly on my 77 engine. I briefly considered using a later model water pump that doesn't stick out so far but didn't know what other problems that would introduce. I finally found a salvage one on E-bay from Southwest off road in New Mexico. This part seem to be the right fit from a 76-86 4.2 engine so I am back in business.

Your cylinder block bores and new pistons look great!

Piston install.JPG

Damper/pulley clears the timing cover, right?  The cover seal benefits from a fresh location on the damper hub...

oil pan gasket.JPG

Helpful to point out the difference in water pump stickout height, dramatized in your photo/comparison below, Stuart.  Thanks for sharing and helping others avoid this problem.  One of the issues is the later/optional use of serpentine belts that altered the water pump stickout length.  Serpentine belt use began in the late 4.2L CJ era, alternating with V-belt use.  All YJ Wrangler 4.2L engines and 4.0L sixes use a serpentine belt.

water pump pulleys.JPG

 

Share this post


Link to post
Share on other sites
On 10/14/2018 at 12:03 PM, Moses Ludel said:

I'm sure you confirmed that the sprockets and chain align vertically.  Was the timing gear hub thicker? 

This is all I can figure. My vertical alignment is good. I'm glad I test fit the cover or I wouldn't have noticed this problem.

On 10/14/2018 at 12:03 PM, Moses Ludel said:

Damper/pulley clears the timing cover, right?

Yes and I remembered to use sealer on the back  where it mates against the oil slinger. My CJ re-builders guide helped me head off trouble here. I used a longer bolt to pull the ballancer on and the extra threads saved me when the forces got too hard. Lucky thing I decided to back off  and figure out what was wrong.

Share this post


Link to post
Share on other sites

You're wise to respect force limits, Stuart.  Interference always has a cause.  It's possible to split a damper hub at its keyway from too much force.  Also, it is always wise to isolate the applied force to the damper as you did with the long bolt...I prefer using Grade 5 or 8 rod stock and Grade 5 or 8 nuts and washers to pull the damper onto the hub.  The threaded rod stock, threaded into the crankshaft snout first, will not rotate and apply twisting force to the snout threads.  The washer and nut pull the damper onto the crankshaft snout.  Load is on the rod stock threads. 

Footnote:  Never pound a damper onto the crankshaft snout.  The main bear inserts have a set with side thrusts to control crankshaft end float.  Avoid pounding or forcing against this internal bearing surface.

Moses

Share this post


Link to post
Share on other sites

I have made a little more progress in that I have the head  and water pump on the engine. One of the things missing from this project was the head bolts. I was able to find a set of ARP bolts at JEGs that were reasonably priced. The Felpro gasket  was put on dry per its instructions. The old Jeep shop manual says to use "perfect seal" sealer which I believe predates modern gaskets. When in doubt follow the instructions from the manufacturer. 

I followed ARP's instructions for use or their Ultra Torque assembly lube. My shop manual specifies 105 ft lbs. ARP specifies moving up in three equal steps to 100 ft lbs following the shop manual circular tightening sequence. I marked each bolt with a witness mark for the last two steps and didn't see any anomalies in turn radius between bolts. About midway through each pull up to 100 ft lbs I felt a decrease in the amount of force needed to turn the bolts. This caught me off guard and I'm guessing it is the Ultra-torque lube doing its thing to the pre-load. Let me know if this sounds strange.

The old Prestolite distributor is getting  replaced with a DUI HEI unit from Performance Distributors provided by Summit along with a set of their wires. Im looking forward to what this will do for me.

The old BID unit has an electronic module that dates itself with the "Made in Hong Kong" label. I remember seeing that a lot on things as a kid growing up in the 70's but not since the British gave up control I think. 

This beast of an engine is getting pretty heavy on the stand and reminds me of the tractor engines I grew up around in the Midwest. I'm anxious to get it back in the jeep but need to go through the T-18 and spicer 20 first. I recently verified that the T-18 on this 77 jeep has the 6.32:1 first gear which will suit my needs.

The CJ-3B in these pictures gets used as a work table too often due to its fenders and hood. I know its a terrible way to treat a jeep. Its engine is the one from the re-build guide at https://www.cj3b.info/Engine/Rebuild.html but that is another story. I'll have to start a thread for this jeep in the vintage section.

 

 

engine with head.JPG

ARP head bolts.JPG

DUI Distributor.JPG

Share this post


Link to post
Share on other sites

Hi, Stuart!  Always pleased to get your updates on the 4.2L engine project...See my comments below...Have a pleasant Holiday Season!

13 hours ago, Stuart_Snow said:

I have made a little more progress in that I have the head  and water pump on the engine. One of the things missing from this project was the head bolts. I was able to find a set of ARP bolts at JEGs that were reasonably priced. The Felpro gasket  was put on dry per its instructions. The old Jeep shop manual says to use "perfect seal" sealer which I believe predates modern gaskets. When in doubt follow the instructions from the manufacturer. 

You'll be fine with the Felpro coating.  This has always been a fail-safe gasket design and material...

I followed ARP's instructions for use or their Ultra Torque assembly lube. My shop manual specifies 105 ft lbs. ARP specifies moving up in three equal steps to 100 ft lbs following the shop manual circular tightening sequence. I marked each bolt with a witness mark for the last two steps and didn't see any anomalies in turn radius between bolts. About midway through each pull up to 100 ft lbs I felt a decrease in the amount of force needed to turn the bolts. This caught me off guard and I'm guessing it is the Ultra-torque lube doing its thing to the pre-load. Let me know if this sounds strange.

Of course we'd be leery of pulling block threads, but if your torque wrench is reliable, that should not be the case halfway through the pull.  I've not tried the Ultra Torque, does it act as a sealer, too?  Any bolts entering water jackets need sealant.  This may apply to the #11 bolt (left/driver's side at the front of the cylinder head) on your 4.2L engine.  Consult with ARP about the torque feel and also whether Ultra Torque will suffice as a sealant for through bolts into water jackets...Loctite 592 Paste has Teflon and is recommended for the later 4.0L engine head bolts.  (Grips like cement over time, too.)  If you need to check seal, remove the #11 bolt and run a piece of mechanic's wire through the threads to see if this enters a water jacket.  Re-torque the bolt after adding sealant to threads. (100 ft.lbs. is plenty for this bolt with sealant.)  Then go through the entire tightening sequence and add a couple of ft.lbs.  You don't need to re-torque a Felpro coated gasket after running the engine.  

 

 

Quote

The old Prestolite distributor is getting  replaced with a DUI HEI unit from Performance Distributors provided by Summit along with a set of their wires. Im looking forward to what this will do for me.

You did yourself a favor by replacing the Prestolite distributor.  The DUI/HEI is a great choice, reliable and even easy to tune (timing curves, etc.).  Should be reliable, which is what you want.

The old BID unit has an electronic module that dates itself with the "Made in Hong Kong" label. I remember seeing that a lot on things as a kid growing up in the 70's but not since the British gave up control I think. 

This beast of an engine is getting pretty heavy on the stand and reminds me of the tractor engines I grew up around in the Midwest. I'm anxious to get it back in the jeep but need to go through the T-18 and spicer 20 first. I recently verified that the T-18 on this 77 jeep has the 6.32:1 first gear which will suit my needs.

Very pleased that you have the 6.32:1 first gear.  The close-ratio version of these T-18s did not have the compound low ratio.  You'll really like this gearing, especially with the taller low range ratio of the Spicer 20 transfer case.

The CJ-3B in these pictures gets used as a work table too often due to its fenders and hood. I know its a terrible way to treat a jeep. Its engine is the one from the re-build guide at https://www.cj3b.info/Engine/Rebuild.html but that is another story. I'll have to start a thread for this jeep in the vintage section.

Always my favorite, a good friend retired from Mopar and began a Jeep restoration business.  Here is his first project, a frame-off CJ-3B with a new steel tub.  This should inspire, maybe enough to place parts on a work bench:

IMG_20180606_180020094_HDR.jpg

IMG_20180601_173823842.jpgIMG_20180530_183838760_HDR.jpg

Keep up the good work, Stuart, your 4.2L is a work of art!

Moses

 

 

 

 

 

 

Share this post


Link to post
Share on other sites
7 hours ago, Moses Ludel said:

Any bolts entering water jackets need sealant.  This may apply to the #11 bolt (left/driver's side at the front of the cylinder head) on your 4.2L engine.

#11 is the only one that goes in the water jacket from what I can tell. It will need sealer. I don't think the Ultra Torque will suffice as ARP advertises a separate thread sealer.

Share this post


Link to post
Share on other sites

As expected...Loctite 592 is the end-all sealant and found on many late model vehicle uses.  Caution here is that the paste sets up like a brick, and some complain about removal of parts later.  On pinion flanges of axles, this paste prevents oil seepage or wicking out the splines—I've used a HD puller to remove these flanges after years in service.  This has not been an issue with 4.0L Jeep sixes and other cylinder head bolts.  The torque settings are far less than a pinion flange nut.

Traditionally, I have used Permatex Super 300 Form-A-Gasket brush applied sealant.  It works very well on head bolt threads.  Like any other sealant, torque needs to be applied when the sealant is still "wet" and pliant.

Share this post


Link to post
Share on other sites

I checked with ARP tech support on my experience with reduced force midway through the pull up to 100 Lbs on the head bolts. They did not have any concerns as long as I got up to 100 lbs and went slowly which I did.

One of the other parts missing from this project were the push rods. I was able to source some from Melling which were specific to my particular engine configuration. 

The rockers needed a lot of cleanup work but appear to be in good condition otherwise. This engine uses the aluminum rocker bridges. I was skeptical of their use but they have worked for the last 40 years and 118,000 miles.  After verifying my push rods were properly seated down in the lifters I torqued these down very slowly and evenly to the specified 21ft lbs.

Items like the fuel pump,  Spark/EGR  vacuum cto switches, thermostat and housing have been sourced through NAPA-online which I've had good luck with.

 

IMG_1318.JPG

IMG_1320.JPG

Share this post


Link to post
Share on other sites

Hi, Stuart!  Pushrods often get overlooked and can be reused in many cases.  I like to roll the original pushrods on a piece of flat glass to check for straightness.  Ends can wear, a concern of course...Replacing the pushrods as you have done is a fail-safe approach, and Melling remains a high quality engine parts source.  (I always use a Melling replacement oil pump, most often a High Volume design.  OEM Jeep oil pressure runs quite high, so a quality OEM replacement pump by Melling is plenty.) 

Did you check pushrod length to match the valve and lifter height?  How far do the pushrods depress the lifter cups—with each piston at TDC on its compression stroke?  (This is measurable at the pushrod end of the rocker arm with a dial indicator.  From zero valve and pushrod clearance, measure the amount of cup drop into the lifter as you tighten down the rocker bridge.  This amount is lifter preload.)   If you surface the head, reface valves, grind or replace valve seats and/or deck the block, the lifter plunger height—with the lifter base on the heel of the camshaft lobe—is worth checking.  There is some latitude built into the lifter's preload plunger range.

Here is a vlog I did on valve "adjustment" for fixed rocker AMC/Jeep sixes:  https://www.4wdmechanix.com/jeep-232-258-and-4-0l-inline-six-and-2-5l-straight-four-valve-clearances-and-adjustment/

Here's valve lifter adjustment on a typical Jeep six here at the forums:  https://forums.4wdmechanix.com/topic/849-choosing-jeep-40l-and-stroker-six-pushrod-length/

There's a simpler way around all of this:  a pushrod length tester like this CompCams item:  https://www.summitracing.com/parts/cca-7704-1/overview/.  This is the tool for testing your pushrod length needs.  The tool determines the gap between the lifter cup (with lifter plunger fully extended and the camshaft on the heel of its lobe) and the rocker arm cup.  The rocker arm is secured in place for this measurement.  When the tool is adjusted to fill this gap, you add the amount of normal lifter plunger preload to the tool's length.  (Preload can be 0.030"-0.060", I prefer 0.030"-0.040" with a freshened valvetrain.  This would be a useful preload range for a flat tappet hydraulic lifter.)  The gap length plus the desired amount of lifter plunger preload is the pushrod length you need. 

Melling and others offer a variety of pushrod lengths (Melling:  9.594" to 9.7" lengths measured end-to-end of pushrod) that will fit the Jeep 4.2L inline engines.  You can select the right length and part number for your engine's measurements.  Depending upon the camshaft machining and other variables, some take this to the point of varying the pushrod lengths per lifter and valve.   As long as you fall within the acceptable range, you're close enough.  What you want is a lifter plunger that is not fully extended to the retainer and that also has enough range to compensate for normal valvetrain wear.  Valve seat recession will increase the preload, but this should not be a significant amount (thousandths of an inch) over the life of the engine.  Wear takes into account the rocker ratio, we'll spare that discussion.

Footnote:  Do not "fill" or soak the lifters with oil before installation.  (I coat the lifter base, pushrod seat and the lifter bore with engine assembly lube.)  If filled with oil, the lifter plungers will be fully extended during initial cranking.  This will unseat the valves, and depending upon engine design, can even create valve-to-piston crown interference.  It takes quite a few crankshaft revolutions to drop a hyper-extended lifter plunger to normal preload height;  one formula is 4 crankshaft revolutions per 0.001" of plunger drop.  If valves are standing open, this is an issue...I like to assemble the valvetrain completely, to the point you are now, then I prime the oil system.  This fills the lifters "normally" and will establish the correct lifter plunger heights and preload without unseating the valves.  I like to prime the oiling system with #1 piston at TDC on its compression stroke, then I prime three more times at 180-degree turns of the crankshaft/damper.  This allows the lifters to all fill to normal plunger heights before starting the engine.

As for the cast aluminum rocker bridges, they work very nicely.  Their role is to help stabilize lateral forces at the rocker arms.  There are many engines that use rocker pivots like the AMC six but without bridges to resist wobble.  AMC was ahead of it here.  The bridges have minimal load and seldom break.  Failure is usually due to a valve stem or rocker tip with irregular wear.

Your engine is a work of art, Stuart...It should run equally well!

Moses

  

Share this post


Link to post
Share on other sites

Moses,

Thank you.  Your Vlog on push rod measurements is timely. Since my seats and valves were re-ground and not replaced and my head and block surfaces were cleaned up I should look at this measurement before proceeding. I'll look at getting the Comp Cam measurement tool since I have time. The lifters are still dry, I'm glad I waited to prime this thing.

Have a Happy New Year!

Stuart

Share this post


Link to post
Share on other sites

Happy New Year, Stuart...Pleased that you're getting the CompCams tool.  It's easy to use and intuitive.  New Melling and other source pushrods are available at a variety of lengths, which should make the selection process simpler.  Of course, there are also adjustable pushrods, but that's a more costly alternative.  Melling fixed-length pushrods sell individually, so you have the ability to precisely fit individual pushrods.

In the heyday of AMC inline sixes, head work typically meant grinding the original seats and refacing the valves—at least the intakes, new exhaust valves were often installed.  This raised the valve stem heights.  Machinists used a bridge gage to determine the height of the valve stem above the cylinder head deck.  With the head on the bench after seat and valve reconditioning, the gage was fitted squarely over the top of the seated valve's stem.  Valve stem tips were ground individually to correct the stem height. 

The other factor that needed consideration was block decking and cylinder head surfacing.  Either or both processes will lower the cylinder head toward the camshaft, which has the same effect as increasing the length of the pushrods.  The result is too much lifter preload. 

Note:  Modern machine shops usually match up the valve stem heights when grinding valves and doing seat work.  This makes pushrod fitting easier...Using the CompCams pushrod fitting tool, regardless of the valve seat depth, the valve stem heights, block decking or head surfacing, you can determine the right pushrod length for the desired lifter preload. 

Considering all of this, the best remedy is to fit the pushrods with an adjustable gage like the CompCams tool.  Follow the directions provided with the tool...I'll gladly answer any questions you have during this process...If you could snap a few photos of your pushrod length tests, others will benefit from seeing how quickly you demystify the valve clearance/lifter preload issue for this engine. 

Moses

Share this post


Link to post
Share on other sites

My comp cams tool arrived in short order. It's nice having a Summit warehouse nearby in Nevada. I went to work on the #1 cylinder which I already had setup at TDC.

I adjusted the tool for "zero lash" finger tight only carefully making sure the lifter plungers were not depressed.  Using my new Melling push rods as a reference I found the the exhaust valve measurement was .040 shorter and the intake valve measurement was .050 shorter than my new Melling pushrods.  If I understand you correctly this lifter pre-load of .040 and.050 on these two valves is with-in tolerance but slightly on the high side. I will check the rest and see what I get.

IMG_1337.JPG

IMG_1339.JPG

IMG_1341.JPG

Share this post


Link to post
Share on other sites

Hi, Stuart...Thanks for sharing the CompCams adjustable pushrod tool with Members and Guests!  Below is a listing of the various Melling pushrod lengths.  You may be as close as it gets with the current pushrods, and there is plenty of reserve plunger travel within the lifters.  Would the next available pushrod (shorter) create too little preload?

Here are typical Melling offerings for the pre-4.0L era inline sixes (258/4.2L).  You likely were sold the Melling MPR-301 or MPR-333 pushrods installed, depending upon your cylinder head type.  When selecting pushrods, make sure the ball ends and lubrication method are correct for your engine application:

[MELLING OEM REPLACEMENT PUSH RODS FOR AMC 258/4.2L INLINE SIXES]

MPR-301 9.594” x 5/16 1971-1974 without Rocker Arm Shaft

MRP-332 9.658” x 5/16 1971-1974 with Rocker Arm Shaft (BB ends)

MPR-301 9.594” x 5/16 1975-1976

MPR-301 9.594” x 5/16 1977 w/ Temp Sending Unit in front of engine

MPR-333 9.622” x 5/16 1977 w/ Temp Sending Unit in rear of engine

MPR-333 9.622” x 5/16 1978-1980

MPR-353 9.700” x 5/16 1981-1988

So this is a classic example of valve work and decking/milling.  The plunger preload for a "standard" (1977 4.2L/258 OE replacement length) pushrod has increased, likely due to the head height being lower.  Your cylinder head was surfaced, right?  Block was surfaced/decked, too?  Even the head gasket thickness can impact the lifter preload, then there's always the valve seat depth and valve stem height.  If the original cast seats were cut (no steel inserts installed), this raised the valve stem height and increased valve lifter preload.

This was a smart test, Stuart.  You could have second guessed that there was reasonably close preload, but this approach eliminates that guesswork.  Curious to see whether all of these standard length pushrods will work.

Moses   

Share this post


Link to post
Share on other sites

Moses,

My replacements are the MPR-333 9.622. I re-measured everything and assuming I use these new push-rods this is what my pre-load would be.

1 - .042/.042

2- .042/.052

3- .042/.052

4-.032/.032

5- .042/.032

6-.052/.042

My block deck and head were resurfaced. The reworked head came with this project and I'm not 100% certain if seats were replaced or ground.

I'm glad you had me check this as I was not aware the lifters had limits on pre-load. 

Stuart

 

Share this post


Link to post
Share on other sites

Stuart, you're right where you want to be on #1, #4 and #5 cylinders.  The MPR-301 might be a consideration for the #2, #3 and #6 pushrods that now have 0.052" preload.  That would be a 9.594" pushrod, which would reduce preload by 0.028".  The current three valves with 0.052" preload would have 0.024" preload with the MPR-301 pushrods.   0.024" is just enough preload and would increase slightly with normal valve wear.

To save the hassle, I would stick with the current pushrods (0.052" preload) to assure adequate preload.  You have plenty of lifter plunger travel for the 0.052" preload plus an allowance for normal valve and seat wear over time.  If you're curious, the lifter plunger travel can be easily measured from its fully extended plunger (against the retainer clip) to the fully depressed plunger with no oil in the plunger cavity.  (This should be done with the lifter just out of the box or without priming.)  You're measuring the total travel available.  Subtract the preload amount, and you have the remaining travel.

Make sure you add a zinc engine break-in supplement before running the fresh engine.  Lucas and others make a supplement specifically for this purpose.  Contemporary oils do not have zinc additive, and you need a zinc additive to protect the (flat tappet) camshaft lobe-to-lifter base.  Protect the cam-and-lifters during the break-in period.  Many continue to add a ZDDP additive after break-in.  The biggest concern is the break-in period.

Moses

 

 

Share this post


Link to post
Share on other sites

I have made some more progress. The engine is finally in and I'm slowly going thru the checklist of making sure everything is done. I decided to take time out to rebuild the T-18 transmission and Model 20 transfer case since it was all out and needed cleaning. I will try to make a separate post about that as it all turned out good.  

I had the clutch rebuilt and resurfaced the flywheel and added a new pilot bushing. Everything was torqued to specs and threadlocker was used. I had a little trouble getting her in and had to use a load leveler and extended hoist but its in.  I still need to rebuild the carter carb. In the meantime I'm getting ready to prime it and study my DUI ignition instructions. I used the ARP thread sealer on the #11 head bolt. Just taking my time to make sure I don't forget something like putting the oil in.

IMG_1441.thumb.JPG.d48fa8370d0a08473f766dd54fb9ba02.JPGIMG_1452.thumb.JPG.64e8761c22d81c6447c0a785af0c778c.JPG

Share this post


Link to post
Share on other sites

Really looks nice, Stuart...I like your approach, taking time to not overlook details.  This should be a 200K-plus engine when you finish. 

Once past break-in, my recommendation would be either a synthetic motor oil like Mobil 1 or Chevron's Supreme with ISOSYN formulation.  This is a long stroke engine with lots of piston travel.  Protect those fresh cylinder walls and piston rings, and they will deliver many years of service!

Looking forward to the T18 and Spicer 20 details.  Quite a restoration...The Model 20 AMC rear axle and Dana 30 front each hold up well.

Moses

Share this post


Link to post
Share on other sites

I have a question about spacing between my fan and radiator.  The old radiator was not salvageable and had a thin cross section and the fan used a 1 inch spacer. The new replacement is an aluminum replacement and much thicker. I plan to keep my original fan and using the spacer is not an option. There is now 1-3/16" clearance between the fan and radiator. I don't know what is optimal.  If this jeep had a shroud I don't have it. I guess I can make one or find an aftermarket one.

Share this post


Link to post
Share on other sites

These radiators did use a shroud, Stuart.  It's worth having.  As long as the shroud captures the air flow through the radiator, it will work well.  There are shorter fan spacers available, too.  Maybe a 1/2" spacer would work better?  Fan spacers are available from aftermarket fan manufacturers like Flex-A-Lite. 

Quadratec and others offer a new replacement shroud.  This illustration should be helpful if you're looking for a used shroud:

https://www.quadratec.com/products/51218_100_07.htm?utm_id=go_cmp-1786233520_adg-68197440694_ad-346566180389_pla-713667809956_dev-c_ext-_prd-25868&gclid=CjwKEAjw__fnBRCNpvH8iqy4xl4SJAC4XERP1R-KZjCF1QKdm_qY9195D2k2kM5vzYCvYfdYqcMTWhoCokXw_wcB

Moses

Share this post


Link to post
Share on other sites

×
×
  • Create New...