Basically Stock CJ-7 - UPDATE

Kreep · Jan 26, 2022

Time for an update, I've been making slow steady progress...

The exhaust system is complete. The headers are pretty long which should boost low end torque, the length from exhaust valve to collector is 41.6" for the shortest, 46" for the longest and the rest are 45.25". The length of the secondaries ranges from 24" to 29".

Anyone familiar with CJ's will notice that the collector runs right through the space normally occupied by the mechanical clutch linkage and clutch fork. :flipoff2:

Kreep · Jan 26, 2022

So, the plan is to convert to a hydraulic clutch. Ebay yielded a pedal assembly at a reasonable price. I was able to swap just the clutch pedal which was a relief. I was not looking forward to pulling the cage so I could pull the dash just to swap pedal assemblies.

First pic shows the factory blank in the firewall. It fits the Wilwood master perfectly, a few minutes with a step bit, drill two holes and ta da!

The second pic is from inside under the dash. The hydraulic pedal assembly had this cool bracket that mounts to the end of the shaft. I believe the purpose is to stiffen the firewall so it doesn't oil can. The top hole matched one of the Wilwood mounts but I had to clearance it a bit for the rubber boot. The lower hole was not even close, plus the bracket was hitting the fuse box. So I bent it a bit and punched a third hole in the firewall.

Kreep · Feb 23, 2022

Spoiler alert: this engine build does not end well. But as they say, it's about the journey just as much as the destination...

Stats on short block:
Bored to 4.185" with a torque plate
.10 over mains (1-4 .0019" clearance and .0025 for #5)
Internally balanced
Molnar AH6000LLB8-A rods
6.0" long
2.1" big end
.927" little end
RaceTec Pistons
AutoTec 4032 Forging A4119F
1.295" Compression Height
-7.5 CC Dish
504 grams
Wrist pins .927" diameter x 2.7" long x .180 wall
Total Seal MS0690 065 rings
1/16" Gapless AP Steel top ring
1/16" Napier 2nd ring
3/16" High Tension oil control ring
King Bearings
AM-Series Main Bearings MB5518AM 010
BB-Series Cam Bearings CS526BB
XP-Series pMax Black Rod Bearings CR-807XPN
ARP Main Studs 135-5402
Rollmaster Red Series Timing Chain

Block prep:
I'm using "BJ Builds an AMC" as a guide. I re-drilled the main bearing oil feeds with a long 5/16" bit. Yes, the holes did not go all the way through. I installed a plug in the driver's side oil galley with a 0.200" hole, reduced the four rear camshaft bearings oil supply holes to 0.150 and did the lifter valley drain mods.

Here is my setup for measuring thrust end play, I got .0045

Kreep · Feb 23, 2022

Here it is getting ready to fit the rings. I used the torque plate per Total Seal's instructions. I checked, it does make a difference, the gap closes a little without the torque plate.

Kreep · Feb 23, 2022

Let's take a minute and talk about pistons. Keeping the heat in the combustion chamber helps the engine run cooler and increases cylinder pressure thus producing more torque - especially at lower RPMs. Initially I thought about going with hyper-eutectic pistons due to the lower thermal conductivity. But the trade off of increased brittleness wasn't worth it. I also considered thermal coatings but doubt they have much effect given how thin the insulating coating is. Since I don't plan on any power adders I don't need the full tilt 2618 forged pistons.

So forged 4032 alloy seemed like a good compromise. I got lucky by asking the machinist to go easy on the bore. It turns out RaceTec has forged blanks for my 4.185" bore, $600 for a set of 8 machined to my specs. These are in their lower performance AutoTec line, note the equal sized valve reliefs.

Kreep · Feb 23, 2022

So, the reason I post build logs is to 1) share tech, 2) get answers to my questions, and perhaps most importantly to share my mistakes so others don't make them. Here is my first one on this project. Gapless rings have a very thin lower ring. Everything went fine on cylinders #1-7, but on #8 I guess I got tired and didn't get the end of this ring tucked into the groove all the way. I'm using a tapered ring compressor and this thin ring bent and bit into the piston. Not the end of the world, $75 and 10 days later I had another piston...

Kreep · Feb 23, 2022

With that little snafu out of the way the bottom end is together. I'm using a crank scraper from Ishihara-Johnson.

Kreep · Feb 23, 2022

Originally I was all hot on a roller cam that would have good low end torque but breath well enough to give a wide power band, but after reading up on The AMC Forum, American Motors Discussion Forums I came to the conclusion that a hydraulic flat tappet was a better choice. Roller lifters are heavy, and require stiffer springs. Plus you get into bushing the lifter bores and then need to do the oil bypass line...

Instead I'm trying to keep the valve train light with the idea that it will still spin up even with an RV style cam. I did go with Topline Hylift-Johnson lifters (its confusing since there are two claims to the name). I went with a Bullet cam. They make some nice grinds that take advantage of the larger .904 AMC lifter bore. Here are the specs:

Topline Hylift-Johnson Lifters, A-2330S (Slow bleed, Type II endurance material)

Bullet Cam
AMC 267/270-14HC
Intake HC267/320
214 @.050”
.3200” lobe lift, .544” with 1.7 rocker
267 duration @.006”
Exhaust HC270/335
226 @.050”
.3350” lobe lift, .570” with 1.7 rocker
270 duration @.006”
114 lobe separation
110 intake centerline

This cam was recommended by John at RBJ Racing - they should probably name this grind after him

Bullet recommended something with a little more duration, probably to keep the cranking pressure and dynamic compression ratio down. Hopefully I'll be OK with E-85. Using the cam spreadsheet from the AMC board I'm looking at a dynamic compression ratio of 9.18 and a cranking pressure of 235.

Kreep · Feb 23, 2022

I think Rollmaster has solved the AMC distributor oiling problem. They machine a recess so that no matter where oil comes out of the camshaft it feeds the path to the chain and distributor gear. They also incorporate a thrust bearing that goes against the block.

Stop for finding top dead center...

Setup for degreeing the cam. I had to advance it 4 degrees to get the #1 intake lobe center at 110 degrees per Bullet's instructions.

Kreep · Feb 23, 2022

Lesson #2 on the engine is timing covers, AMC elected to put the oil pump in the timing cover. The oil pump bores were all scored from debris when the pickup dropped onto the sludge at the bottom of the pan. So I got a fancy nickel plated cover and HRC gears from Bulltear. Knowing what I know now I would have kept the OEM cover and just run the HRC gears which have cool little pressure relief vanes cut into them. These aftermarket covers just aren't right.

Here is my setup for checking oil pump end clearance. Lots of back and forth getting the clearances right, porting oil passages and gnashing of teeth.

Kreep · Feb 24, 2022

A good set of heads is the foundation for making power. I elected to keep the iron heads with bridged rockers that came on my 1975 engine. Edelbrock makes aluminum heads that can flow more and have a more modern combustion chamber but I've had bad luck warping aluminum heads on iron blocks.

John at RBJ Racing reworked the 502-2 heads. He installed beehive springs and valves with 8mm stems help keep valvetrain weight down. I'll also be doing LS rocker arm swap that he pioneered to further minimize weight over the valve. A street port and 2.055" intake and 1.650" exhaust valves help move air.

More details:
Combustion chambers ended up at 65 cc's
Ferrea exhaust valves - F6270 24º Tulip Super Flo
Ferrea intake valves - F6234 12º Super Flo. Radius Groove

COVID-19 messed up the supply chain, so instead of the PAC KS21 beehive spring kit we settled for Liberty Performance LRV-9937 springs. Ended up with 140# spring pressure at 1.78" installed height and 307# at .570" of lift.

John did really nice work on the ports. Here are the flow rates:

Lift Intake Exhaust
0.1 69.5 57.7
0.2 141.2 109.6
0.3 203.0 148.8
0.4 249.9 163.3
0.5 266.7 166.7
0.6 272.2 173.0
0.7 275.9 181.7
0.8 276.5 183.3
0.9 281.0 181.2

Kreep · Feb 24, 2022

One of AMC heads quirks is that if you hold them down with studs the nuts interfere with your headers. So your choice is to (A) use factory bolts or to (B) cut down the studs on a lathe, skip the washer and clearance the header. I decided to try something new and spot faced the shoulder 0.27" to countersink the head stud washer and nut. You can see it pretty clear in this picture. I didn't want the studs to interfere with the headers and seemed to me there was plenty of meat there. John was not a fan and pointed out "there's water in there" as witness the tendency of the heads to crack and leak in this corner. He used an epoxy sealer as insurance and so far it's been fine.

Here you can see the end result, the washer and nut are recessed enough for the header flange to clear with minimal clearancing. Note the nut/washer to the right is standing proud on the factory surface. Also, ARP makes a thinner washer or you could skip the washer so you wouldn't have to cut so deep into the head. Personally, I feel having a washer improves clamping consistency.

Kreep · Feb 24, 2022

I used Cometic .040 MLS gaskets to get good quench with the zero deck pistons.
Here is the parts list for the ARP studs:
18 - AR4.750
4 - AR3.250
6 - AR3.000
3 - 300-8336 12-Point Nuts (5/8" socket), set of 10
3 - 200-8534 Washer w/o Chamfer, .120" thick, 1/2" Inside Diameter, set of 10

Kreep · Feb 24, 2022

Time for some cool tech! How does LS rockers on an old piece of AMC iron sound?

As I said before, I'm running a conventional hydraulic cam and trying to keep the valve train light without breaking the bank. The LS rocker swap pioneered by John at RBJ Racing ( jcisworthy on this board) fits this theme perfectly. I pulled a set from a local junkyard for pocket change and began mocking things up to measure pushrod length. First step is to install checking springs and cut the rocker stands into four sections:

Next up, determine socket head screw length. Note John skimmed the mounting bosses when he was working on the heads. I measured 1.875 inches from the shoulder to the bottom of the threads, so a 1.75" screw should prevent bottoming while torqueing the rockers down.

Kreep · Feb 24, 2022

The final step before measuring for pushrods is checking rocker geometry. So I set the exhaust valve half way through it's lift and... Houston we have a problem. Rocker contact is too close to the exhaust side of the valve stem. Also, I believe that the gap at the trunnion should be even at half lift. I estimated that the pivot point is 0.90 above the mounting boss. At this point I pulled out the original AMC bridge and rockers and estimated the pivot point is 0.63" above the mounting boss. It helps that we went with the 8mm valves, which are about 4.9" tall vs stock at 4.8", but I wish I had gone with John's original suggestion of using valves from a 455 Pontiac which are available in 5.1" and 5.2" heights. My guess is that 5.2" version would be perfect.

Here is the witness mark, looks like about 0.1" from the center.

Kreep · Feb 24, 2022

There are several ways to correct the rocker geometry. I decided to shorten the pedestals. Time to break out the heavy machinery! I suspect that the trunnions are 19mm, the closest endmill I have is 3/4" (19.05mm). I removed 0.105" from the pedestal which allows the bottom of the rocker to just barely clear the pedestal rail.

Here is the new geometry with the valve closed. I installed a stock AMC pushrod for grins and there is 0.004" clearance. Since the base circle on my cam is smaller than a stocker, it seems we are in the ballpark on geometry (unless my brain has failed me again).

At 1/3 lift (0.190"):

At 1/2 lift (0.285"):

And close to full lift (0.57"). This dial indicator didn't have enough travel so I'm probably off a couple of hundredths here...

Here is the wipe pattern. It's still a little closer to the exhaust side of the stem. Also, I'm not crazy about how wide the pattern is, right at 0.200" but I'm not sure anything can be done about that.

Kreep · Feb 24, 2022

Then I went back and spent a little more time comparing how AMC and GM did things. Full disclaimer: some of these measurements are hard to do and I lack the experience and tools to get really precise results, so consider all these measurements suspect. (you've been warned)

First up is locating the rocker. AMC uses the screws to locate the stands, I get about .020" movement depending on if you push it toward the intake or the exhaust side of the head.

GM cast locating tangs in the stands. These clear the boss in the AMC head, so you don't need to remove them. They also drilled one hole smaller, .320" vs .356" for the rest (note arrows). Luckily, I started working with a stand that had two large holes. I get about .050" movement depending on how you push the stand while tightening the screws. I've been pushing the stand away from the valve to try and get the contact pattern to the center of the stem.

Kreep · Feb 24, 2022

I also took a closer look at the rockers.

The AMC rocker is about 2.36" from center of pushrod to center of contact pattern so for a 1.6 ratio I get:
0.908" from pushrod to pivot
1.452" from pivot to valve (Edit: Bulltear says 1.455" so that gives an idea of my accuracy)

The GM rocker is about 2.33" from pushrod to center of contact, so for a 1.7 ratio I get:
0.863" from pushrod to pivot
1.467" from pivot to valve

So ideally the GM stand should be moved .015" away from the valve and I've been moving it .025" away (since there is .050" total play).

Kreep · Feb 24, 2022

While we are comparing rockers, check this out. The AMC pushrod has a .095" hole while the GM rocker has a .065" hole, so you might think that the GM rockers will restrict oil flow to the heads. However, those clever AMC engineers offset the hole in the rocker so that while the lifter is on the base circle (where it spends most of its time) only about 1/3 of the hole in the pushrod is exposed. As lift increases, the hole gets closed up so that the pushrod rides on a cushion of oil while forces are highest. In contrast, the GM rocker has the hole drilled in the center. With the lifter on the base circle I was able to fit a .060" pin through the GM rocker and into the AMC pushrod.

Kreep · Feb 24, 2022

I was not happy with the width of the valve contact pattern so I went back to school and came to the conclusion that correct rocker geometry means that the rocker is 90 degrees to the valve at 1/2 lift. The drawing isn't mine, but shows what I wanted to achieve. The measuring setup is mine.

Edit: A year later I think this is right for roller tips, but I should have been shooting for a smooth rocking motion across the valve stem. In this case the rocker should not reverse and drag back across the stem...

Kreep · Feb 24, 2022

The stock LS stands are about .498" and my first cut was .120 which is as deep as you can go without the bottom of the rocker body rubbing the stand. Correct mid-lift geometry meant I had to cut another .127 on the intake rockers and .139 on the exhaust. This meant I had to hog out the base of the stand to clear the rocker body. At this point I was pretty confident the LS rockers would work and switched from junkyard rockers to new GM rockers and Brian Tooley Racing V2 trunnion bearings

Kreep · Feb 24, 2022

And so I hit the next speed bump. If you look closely at the last picture, you'll see the rocker contact has moved to the intake manifold side of the valve stem. Not good. This is for two reasons. First, as I lowered the pivot point of the rocker, the contact point on the valve stem moved to the heel of the rocker pad. When I started it was on the toe and pushed all the way to the exhaust manifold side of the valve stem. Second, there is about a 10 degree angle between the valve stems and the rocker stud. As you move the rocker pivot point down you also move it away from the valves. Crap.

So, picked up another set of stands. This time I measured a .503" stock height and figured a .181 cut would get me centered over the valve stem. I didn't mess with intake/exhaust specific cuts this time. You will notice I didn't have to hog out the base as much either.

One nice thing about milling the stands is that I was able to use rocker studs. Sadly, the washers and nuts provided were too large so I had to get smaller ones. Here are the part numbers:
Studs ARP 144-7201
Nuts ARP 300-8331
Washers ARP 200-8584

Kreep · Feb 24, 2022

Finished product:

Kreep · Feb 25, 2022

Time to prep the intake manifold. If you run a PCV system on these engines the key to minimizing smoke on high throttle climbs is to stay with the OEM baffle that goes under the intake. Edelbrock did a great job on the manifold for their Pro Flo 4 system and even has little bosses in the casting where the screws go. Here I've transferred the holes with a sharpie.

Oddly, Edelbrock made provisions for a small PCV baffle but it wasn't included in my kit. But it's the same one that came with the Performer Air Gap on my 304 which I still had in my leftover parts. So I stuffed some coarse steel wool in the hole and screwed down the plate...

...and covered the whole thing up with the OEM baffle.

Kreep · Feb 25, 2022

Buttoning up the internally balanced bottom end. Ishihara-Johnson scraper, Canton pan, Romac 0289 balancer held on by an ARP 235-2502 bolt (fits 1-1/16" 12-point socket), Milodon pan studs. I hit the damper with clear coat, but wish I had painted it flat black or something so the timing marks are easier to read. The glare from the shiny steel makes it very difficult to read...

Kreep · Feb 25, 2022

Buttoning up the top. Smith Bros. pushrods, 5/16 x .083 with a .040 restriction. Edelbrock Pro Flo 4. Edelbrock high flow water pump. I go lucky on the air cleaner, base is the same as my old GM TBI throttle body. That means you could use any GM TBI cleaner with the Pro Flo...

Kreep · Feb 25, 2022

Here it is ready to go on the engine dyno.

We couldn't get the dyno to cover the whole powerband in one pull, so here are two overlapping pulls. Call it 480 ft-lb at 4,200 rpm and 438 HP at 5,500...

Kreep · Feb 25, 2022

Well, I warned you this wasn't going to end well. The engine failed 20 miles later, three days before we went to Moab...

Crap.

Here she sits waiting for my wife to come rescue me...

Kreep · Feb 25, 2022

Back at my shop I determined that the exhaust lifter on #2 had collapsed and I had a bent valve. I had been as careful and meticulous as I can be putting the engine together. Apparently that isn't careful and meticulous enough.

So I pulled the engine, packaged everything up and sent it to jcisworthy

He pulled it apart and determined the #4 cam bearing had been bored oversize from the factory. I didn't think to check that dimension (who does?) and the machine shop didn't notice the bearing went in too easy. At any rate it rotated 90 degrees on startup, cutting off the oil supply. What followed was a short series of unfortunate events...

So John went through the engine building it his way. Port matching the oil passages, discarding the oil restrictor in the right lifter galley, installing shorter main studs and a roller cam. Oh yeah, he replaced the bent valves too. :flipoff2:

Here's what I got from his notes:
Rod side clearance .017-.022
Mains .0025-.0027
Rods .0022
Lifter to bore .0025
Cam degreed to 107 (dot to dot)
Cam end play .007
Smith Bros 3/8" pushrods with a .040 oil hole, 7.225" long
Springs 144 lbs. @1.75", 330 lbs. open

Gaterman lifters
Bullet roller cam
Intake
216 @.050”
.3600” lobe lift, .612” with 1.7 rocker
Exhaust
224 @.050”
.3600” lobe lift, .612” with 1.7 rocker
112 lobe separation

And here it is on John's dyno, just need to put on the air cleaner and rock and roll:

Best pull was 472 HP at 5,200 rpm and 508 ft-lb at 4,300 rpm (457 HP and 492 ft-lb corrected) with 1.75" long tube headers.

Kreep · Feb 25, 2022

I'd been curious how the headers I built compared to traditional long tube headers. We were only able to get one pull on them late in the day and forgot to turn on the fan so the air was hot and full of smoke from oil burning off the headers but it seems I gain a little in the midrange and give up a little top and bottom end. For comparison this pull is in green with the best pull (black) and one we made right before it (blue). The AFR and timing are the same for all three pulls.

Here's a video of the pull...

Basically Stock CJ-7 - UPDATE

Rock God

Attachments

Rock God

Attachments

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God

Rock God