Making the most of your AMC 2.5

[Wrench]

Sure thing.

I plan to drop the oil pan / pump to clean and check everything out.

[Wrench]

Dropped the oil pan last night and removed the cam. There were few metal shavings here and there in the pan, and a little sludge at the very bottom. I will be installing a magnetic plug just to help with things.

The cam is definitely not in good condition (distributor drive teeth worn too much), but I dont think there is any way to fix it (sad, the rest of the cam and lifters look PERFECT). The oil pump had one drive finger broken off, which could very well have been what caused the distributor gear to shell out like it did.

New parts are on their way.

I decided to go with a stock cam, which means everything in the engine will be back to stock. Cam selection for this engine just plain SUCKS.

[Lurch]

While you have the oil pan off you should pull a couple rod caps and check the bearings and crank. If there is metal in the pan there is a good chance your crank is damaged.

[Wrench]

Got some info from Clifford Performance that I thought I would share.

The cam he recommends is the "264" grind, gives peak power at 4300 rpm. Cam only is $200 for the 2.5, and you can use stock lifters.
Specs:
-110 LSA
-206 deg @ 0.050
-107 deg intake centerline
-0.474" lift

These specs are not too far off from stock, except for the lift. His recommended springs require different keepers, and machining of seat in the head for clearance. He claims this cam will give more torque and a broader torque curve than any other cam.

He also claims a 50% increase in power if you modify your head and install Chevy 1.94/1.5 valves.

I also found out from Crane Cams that they do custom grinds. You send them a cam and tell them what you want, they will do their best to grind it to your specs if the cam will allow it. I was quoted around $130 for a regrind.

[Wrench]

While you have the oil pan off you should pull a couple rod caps and check the bearings and crank. If there is metal in the pan there is a good chance your crank is damaged.

I pulled ALL the rod and main caps. The crank looks perfect, but the bearings are prematurely worn with what looks similar to cold-start wear. Nothing into the copper, though. The bearings will be replaced.

AFAIK, the oil supply should be filtered before it gets to these parts. Does all that garbage really get past the filter?

BTW, if anyone is wondering what to use next time they need silicone sealant/gasket maker, try "Right Stuff". Just be sure you use it on something you dont plan on pulling back apart ever again...

[Lurch]

AFAIK, the oil supply should be filtered before it gets to these parts. Does all that garbage really get past the filter

You would be surprised how much unfiltered oil actually get circulated in your engine. Anytime you find metal in the oil pan it's a good idea to check out the bearings. My brother had a cam lobe go flat in the 383 stroker in his jeep and it pretty much destroyed the engine.

[Wrench]

Interesting:
I tore the '86 spare engine apart in the last few days. The '84 (in my Jeep) uses a much thicker head gasket (0.070"), while the '86 uses a steel shim gasket (0.020").

[Wrench]

New cam and lifters (stock), oil pump, main/rod bearings, and distributor installed.

I am switching the alternator/brackets and power steering pump/brackets over from the spare '86 engine and eliminating the A/C pump. I like the newer cast brackets much better, and have decided against the OBA idea.

Anyone have a remote power steering reservoir they would donate to the project? The plastic one I had with the '86 setup has a broken return line connection.

[Wrench]

Back in business!!

Got her running last night and cam broken in properly. She seems to run a whole lot better off-idle than the last cam.

[Wrench]

Update:

She seems to be running very good. After switching to the stock cam I was having alot of spark-knock, even when retarding the ignition timing. I switched to NGK BKR7E plugs that made a noticeable reduction in spark-knock, and eliminated it almost completely after switching to Premium pump gas.

[Wrench]

Update:
Just before the Othello mudfest, I decided to experiment by building my own tri-y header. It seemed to run a whole lot smoother with more pull on bottom, but hurt the top-end.

Over the last 2 weeks in preparation for the 4x4 Challenge in Kennewick, I decided to work on the head port profile. Looking at the head and intake, I found that the ports were angled UP at the exit of the intake, and DOWN coming into the head, so the transition was an immediate direction change. I also found that the head opens up, then restricts back down, before opening up to a very square pocket before the valve. I stuffed the ports with a combination of JB Weld, JB Kwik, and JB Stick and totally reprofiled them. Now, there is a gradual taper down in cross-section from about 2" inside the intake all the way to where it opens up just before the valve pocket, using a "D" shape the whole way. I raised the floor of the port about 1/4", and also profile the whole port to where the only bend coming from the intake is just at the valve pocket and has a noticeably larger radius. With this complete port change, the engine was much more responsive, with dramatically cleaner running low-end and midrange, with most the power addition in the middle. Best way to describe it is that it seems to run much more like a fuel injected vehicle now.

After the head mods, I decided to recalculate the length figures for my homemade tri-y header, and found that I made it too LONG. I cut several inches off and redesigned my collector and WOW, what a difference. It has the top-end that my old shortie had, but now retains the low-mid power that I initially gained from the tri-Y!

Sorry, I was short on time and didnt take any pics. I am sure I will have the head off some time again soon for more tweaking (she still pings a little on the freeway even on 92 octane). I also didnt get a chance to get her on the dyno yet, but she seemed to have enough to give a few 4.0's a run for their money at the drags!

[iaccocca]

...but she seemed to have enough to give a few 4.0's a run for their money at the drags!

More than a run for their money... Paul walked away from everyone he went up against. (And their money is in his pocket.) Very cool! And here is a guy that was more smiles over the trophy than the $100 in his pocket.

edit: I'm talking about the mud bog, but the 4cyl. held its own in the dirt drags too.

[Wrench]

So.....

in search for more acceleration, I decided to take my spare ('86) flywheel down and have her loose some weight. The machinist turned it down, but left a generous thickness as not to compromise integrity. Before and after scale weights showed a 4 pound weight loss.

Then I pulled the tranny from my jeep, and took the old flywheel off. Surprise, surprise, they are not the same! I am really not sure what year that flywheel and clutch are from, as the tranny is not original (has external clutch slave cylinder and junkyard markings on it).

The old and new ('86 version) clutch pressure plate are not the same, bolt patterns are just a hair off. And the clutch disk on the new one is about 1/2" smaller OD. Hope that doesnt bite me later...

I weighed the flywheel I just removed from the Jeep against the one I just had turned down, and there is a 13 pound difference!! Evidently , the one that was in my Jeep was already about 9 pounds heavier than the '86 version before I even had it lightened!

Can't wait to see how well she pulls now!

[SPR]

Sounds like you're now running a Franken-Clutch. I heard that some old buick racers liked the heavier flywheel for drags. Apperantly, the heavy spinning mass kept the engine turning fast on blast off and they could start in a higher gear. Wrench, do you shift gears during a drag or just spin the hell out of the RPMS?

[bobracing]

I decided to take my spare ('86) flywheel down and have her loose some weight.

I'm sure you know this but:
Just it is understand, this is great for racing, sand, and mud but not good for trails. The extra weight helps over come the stalling affect after hitting a rock or whatever.

[Wrench]

Wrench, do you shift gears during a drag or just spin the hell out of the RPMS?

I found in the 200' drags that I reached the other end faster if I just kept it pinned in 3rd/low rather than upshift to 4th. I was hitting the rev limiter in 3rd just after the finish, and 4th would hold RPM but not accelerate. After my up-shift is where the 6-cylinders would pull away during the dirt drags.

I did find it launched well if I dumped the clutch at 6k off the line. I am sure that heavy flywheel was helping my starts a bit, but I am also sure it's not good on clutch life. I am also surprised it didnt snap anything in the drive train doing that...

I'm sure you know this but:
Just it is understand, this is great for racing, sand, and mud but not good for trails. The extra weight helps over come the stalling affect after hitting a rock or whatever.

That's the plan. I am not a fan of dragging my stuff over rocks, and I prefer good throttle response. With the big flywheel, it really felt sluggish on throttle response. Installing the 4.88 gears with only 33" tires seemed to amplify the heavy-flywheel effect a whole lot (especially in LOW), and I am trying to bring back some response. I am also trying to find better fuel mileage. I am getting around 11mpg right now.

[OldGreen]

I don't know if they still do it or not, but someone used to sell HEAVIER flywheels for the AMC 4-popper because they stall so easily. It will be fun to see how she does!!! Hook it up!

[Wrench]

Pics: old and crusty vs. new hotness





Seemed to work good enough in the mountains, but I will say the heavier flywheel would have been better. I had plenty of power, and rarely ever needed to open the secondaries on the carb.

How I figure it works pretty well:

The biggest issue with going to a lighter flywheel is the snappiness of the acceleration. This is a drawback to the larger engines that have tons of low-end torque already that totally loose traction when you barely tap the throttle. My engine has a very mellow and smooth build of power over a very broad RPM range, and really takes off over 4k rpm. So my "throttle response" can be regulated by my gear selection (low RPM: strong yet smooth power with very forgiving throttle response, high RPM: very snappy response). It still crawls well at idle primarily due to the 33" tire / 4:88 gear combo, and also the engine mods (porting / squish clearance / high compression ratio) that enhanced the low-end power.