jeep 360 issue

[jeepcj7304]

I was attempting to install a Junkyard TBI setup on my Cj. It has a 360 out of a 1987 J20. The motor was running fine before starting this project. I got it running and it ran pretty good for a few days then on the first hot day we had this summer I had a backfire and never got it to run right again. I pulled the TBI and installed the old carb and pump this week. It was backfiring through the carb and running like crap. I put a vacume gauge on the carb and it would have around 15 PSI until the miss when it would drop. I checked the cylinder pressure and all were around 125 except for the rear passengers I think that is 8. It would go up to 120 and then immediately drop to 0 over and over as it cranked. I pulled the valve cover and there seems to be a little play in all the rockers. really not sure what is exceptable. A mechaninc friend also said that I shouldnt be able to push the pushrod down at all and I would say they go down about 1/4 inch but I was also told this is normal with lifters. I bought this motor used and am not really sure how many miles or the shape of any of the internals. Any help would be great. I talked to you Fuzz at Jeep events before about possibly helping me build a motor if this interests you let me know I dont feel comfortable building the motor myslef and possibly screwing up that much money.

[fuzz401]

we can talk I am on limited resturestions right now

pm me a phone number

[tufcj]

Sounds like it either ate the distributor gear or jumped time. How many miles on it? Has the timing set or distributor been replaced?

Bob
tufcj

[jeepcj7304]

i pulled the dizzy and set the timing twice with no change. the gear looks ok little wear but nothing major. with the loss of pressure on the number 8 cylinder i am assuming a valve issue. not sure of the mileage I was told around 20k but they way it is leaking from the rear main i dont believe it.

[jeepcj7304]

Ok I am deciding no whether to rebuild it or replace it. I dont really feel comfortable doing a rebuild myself. I figure a basic rebuild is gonna run 500-800 in machine work and 600 for a rebuild kit. so that is looking right around 1400. I found these guys on the web.

http://www.hiperformer.com/engines/a...amc_360lb.html

Its gonna cost me about 1900 to the door but it carries a 7yr warranty. So I am not sure where my best option is rihg tnow looking for opinions. Also what would be the best year to look for to get the best heads?

[ironman_gq]

Sounds like you have sticking valves or dead lifters. For heads the early 70's heads have higher compression but dont flow as well the later heads are the dogleg style and flow a lot better.

[tarior]

Sounds like the ol' timing set took a dump.
You should be able to get the crank turned, rings, bearings, gaskets, timing set, and have the heads reconditioned for well under $1000.

I just freshened up a 401, I think I'm into it for about $600, including stuff like break in lube, oil, miscellaneous bolts, valley line and other incidentals. I already had a fresh set of heads on hand, and I did my own assembly.

And don't start getting hung up on which heads to use, just use the ones that were on the motor to begin with. And re-use your old distributor gears and timing cover if at all possible.

[jeepcj7304]

I guess I am thinking of how easy it would be to pull it and drop the new one in in one day. And not have the rebuild time. Plus I would be getting the warranty if it is any good.

[Old Rugged Crosser]

May I give you my thoughts on your problem? It sounds like the issue is isolated to the #8 cylinder. With the compression rapidly dropping off when you rotate it I would say that you have a valve problem. Possibly and more likely a lifter which bleeds off. You say that you get 120 #'s and then it drops to zero. That would indicate a lifter.

May I make another suggestion? If you are cost conscious I would try replacing both lifters on # 8 before I made any other move. you can prime up 2 lifters and install them rotate the engine and check the compression and see if it acts any different. You may cure the problem for the cost of 2 lifters and gaskets. Keep in mind that you can do your experiment without installing the intake manifold. Just make sure all the water is drained.

As for warranties they are only as good as the vendor is honest. Also keep in mind that if you are dealing with a out of town manufacturer in order to have them make any restitution you will have a shipping cost plus your added labor. Believe me they have many loopholes that they can use to void your claim.

Speaking to your desire for minimal down time keep in mind that a long block that you would get from them will still require your time to install many of the parts you presently own to complete that long block. You will save minimal time by buying that long block. Also when you order that long block you have no choice of what heads they will put on it. You will get what you get. The only way around this mess is to have a custom build.

What did you mean when you wrote: about the leaking rear main? Could it be the seal around the pan?

You say that you were told that the motor only has 20k on it. One way to tell is to pull the center main bearing which is the thrust bearing. It should still look relatively new. And if you are not sure take it to a competent mechanic and have him read it. Don't forget to torque it down to a 100 lbs. By taking these steps you can save yourself a lot of money and still have a motor that will have a lot of life left in it.

You have nothing to lose by doing these simple checks and everything to gain such as keeping a lot of money in your pocket.

[tarior]

Well, when the OEM nylon timing gear finally fails, the cam timing ends up being out of whack. Usually on at least one cylinder, there will be some piston to head contact resulting in a bent valve. Said bent valve won't close all the way, and a dead cylinder is the result. It will also run weak and crappy because the cam timing is now way retarded.