4.0 swap? - JeepForum.com

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post #1 of 166 Old 06-15-2015, 11:04 PM Thread Starter
Gausswave
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4.0 swap?

My 4.2 is having some issues. There's enough crank case pressure to blow oil out around the dist, dip stick tube and valve cover. The PCV valve is clear and the baffles have been cleared as well. It has some other issues like over heating at highway speeds despite an all new cooling system( pump, fan clutch and radiator etc...
Through some trading I've aquired a 4.0 from a 97 Cherokee Sport with all the major components. Motor wiring harness, the ECU etc.. The 4.0 has sat for ~ a year. I wanted to do some testing before I spend a bunch of time trying to make it work. I can't run it so there is no way to do a warm test. I hooked up a battery to do some compression testing. Dry testing compression was WAY low(60-75#). Wet I get 175-190 PSI. Well above the 125 to 150 I was hoping for. I verified those #'s with different meters. Leak down is horrid. I'm assuming sitting and being cold this isn't unexpected. I'll do an auditory test later to see where it's leaking. Assessment? Other things to check?


A couple other questions about this I haven't found an answer to yet.
1) The VSS. The usual answer is find the unit from a 91 Wrangler because it has both the electronic and mechanical connections. The 97 has a 3 pin connector. The adapter has only 2 pins. The only solution I can think of is to go with the electronic VSS and find a new speedo. Is there another solution?
2) It came with the automatic transmission so I have a LOT of extra connectors. Can I just remove them? And or will this cause the ECU any issues since I'm going Manual? Yes, I already have a resurfaced flywheel.

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post #2 of 166 Old 06-16-2015, 06:41 AM
Mike Romain
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I think this engine is going to blow oil as bad as the one you have. The rings are shot..... You said you did several tests wet. The first wet test should have freed up any sticky rings, and a sticky ring will only have one cylinder low. All low over several tests, well.... I would find a better donor. I got a 93 from a rust bucket that had been sitting for a couple years and first try on compression was in the 150 psi range dry.
On mine, I wanted to keep the good gas mileage and performance so I kept it carb by putting all the 258 stuff on the 4.0 long block. Runs great and gives a sweet 25 US mpg.

Mike
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post #3 of 166 Old 06-16-2015, 11:12 AM Thread Starter
Gausswave
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Quote:
Originally Posted by Mike Romain View Post
I think this engine is going to blow oil as bad as the one you have. The rings are shot..... You said you did several tests wet. The first wet test should have freed up any sticky rings, and a sticky ring will only have one cylinder low. All low over several tests, well.... I would find a better donor. I got a 93 from a rust bucket that had been sitting for a couple years and first try on compression was in the 150 psi range dry.
On mine, I wanted to keep the good gas mileage and performance so I kept it carb by putting all the 258 stuff on the 4.0 long block. Runs great and gives a sweet 25 US mpg.
Thanks. Not what I wanted to hear but it's close to the same assessment I came up with. When I got the motor it had an automatic trans mission and transfer case. I sold that so I'm at the break even point.
I was considering going the same route you did. The necessary mods to do fuel injection seem to be more points of failure to me. The idea of staying with a carb and no computer has a lot of appeal. Which cam did you use? My 4.2 supposedly has a Clifford cam. It does have the Clifford intake.
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post #4 of 166 Old 06-16-2015, 12:07 PM
Jeepsr4me
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Pulling the pistons and putting in new rings is not that hard.

But I would not give up on that engine yet. How many miles where on that used engine you got?

cause even abused 4.0s can get 200k easy and still be good enough.

All it cost you is a head gasket replacement to pull the head and look at the bores. If they clean, Pull the piston out and check it and change rings. Then take a ball hone and deglaze the walls of the cyl and put back together..
That could give you another 100k..
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post #5 of 166 Old 06-16-2015, 01:08 PM Thread Starter
Gausswave
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Quote:
Originally Posted by Jeepsr4me View Post
Pulling the pistons and putting in new rings is not that hard.

But I would not give up on that engine yet. How many miles where on that used engine you got?

cause even abused 4.0s can get 200k easy and still be good enough.

All it cost you is a head gasket replacement to pull the head and look at the bores. If they clean, Pull the piston out and check it and change rings. Then take a ball hone and deglaze the walls of the cyl and put back together..
That could give you another 100k..
The 4.0 had 125K on it. I'm seriously considering doing that. A mild rebuild so to speak. I'll probably lap the valves as well. I'm reviewing what to look for on the cylinder walls and how to measure them.
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post #6 of 166 Old 06-16-2015, 01:48 PM
Jeepsr4me
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no need in lapping the valves... 125 k... I would pull the head just to swap in a new gasket. Those rings are fine..
cyl walls easy test is to run your finger nail up it to feel for top ridge, and side to side in the bore to feel for groves..
If the surface is SUPER slick then the rings have lost tension and polished the walls..
Ball hone for about a few seconds and new rings...
dont worry about measuring the bore for taper or over bore... That is what you do if rebuilding it completely and even then only a machine shop needs to do ot for next size up pistons to use.
I have a lot of experience with high mile motors and pulling them down.. Unless they were run hot.. most just need a little love and they back to purring..
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post #7 of 166 Old 06-16-2015, 03:00 PM
Mike Romain
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Quote:
Originally Posted by Gausswave View Post

Thanks. Not what I wanted to hear but it's close to the same assessment I came up with. When I got the motor it had an automatic trans mission and transfer case. I sold that so I'm at the break even point.
I was considering going the same route you did. The necessary mods to do fuel injection seem to be more points of failure to me. The idea of staying with a carb and no computer has a lot of appeal. Which cam did you use? My 4.2 supposedly has a Clifford cam. It does have the Clifford intake.
I just stayed with the stock 4.0 long block. Only took a weekend for the swap. $100.00 for the engine, $50.00 for a fuel pump, $50.00 to mate the 4.0 header to the 258 exhaust, a little tinkering with the intake and the pilot bushing and away I went. 5 years later and it still purrs. Starts first crack of the key in any temperature.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #8 of 166 Old 06-16-2015, 03:54 PM Thread Starter
Gausswave
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Quote:
Originally Posted by Jeepsr4me View Post
no need in lapping the valves... 125 k... I would pull the head just to swap in a new gasket. Those rings are fine..
cyl walls easy test is to run your finger nail up it to feel for top ridge, and side to side in the bore to feel for groves..
If the surface is SUPER slick then the rings have lost tension and polished the walls..
Ball hone for about a few seconds and new rings...
dont worry about measuring the bore for taper or over bore... That is what you do if rebuilding it completely and even then only a machine shop needs to do ot for next size up pistons to use.
I have a lot of experience with high mile motors and pulling them down.. Unless they were run hot.. most just need a little love and they back to purring..
Is it worth hydro testing the valves since I'm pulling the heads any way? Leak down was more or less 99% loss on at least the 4 cylinders I tested.
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post #9 of 166 Old 06-16-2015, 03:59 PM Thread Starter
Gausswave
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Quote:
Originally Posted by Mike Romain View Post
I just stayed with the stock 4.0 long block. Only took a weekend for the swap. $100.00 for the engine, $50.00 for a fuel pump, $50.00 to mate the 4.0 header to the 258 exhaust, a little tinkering with the intake and the pilot bushing and away I went. 5 years later and it still purrs. Starts first crack of the key in any temperature.
Good to hear! If my research is right I won't be able to use my Borola Headers from my 4.2?

I'll need gaskets, Fuel pump, Pilot bearing and may be new headers? I have the stock 4.0 manifold. Its got a crack around the collector. I can weld that.
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post #10 of 166 Old 06-16-2015, 04:13 PM
Jeepsr4me
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Originally Posted by Gausswave View Post
Is it worth hydro testing the valves since I'm pulling the heads any way? Leak down was more or less 99% loss on at least the 4 cylinders I tested.
Lay the cyl head on its side and Pour some rubbing alcohol in the ports
Watch the chambers where you can see the valve heads and see if anything comes out...
Last head I had off I did that to verify the valve was not bent.

Had a piston crack and destroy itself and tossed pieces of it all in the chamber area..

valve did not leak...


But I would not ever worry about it...
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post #11 of 166 Old 06-16-2015, 05:37 PM Thread Starter
Gausswave
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Quote:
Originally Posted by Jeepsr4me View Post
Lay the cyl head on its side and Pour some rubbing alcohol in the ports
Watch the chambers where you can see the valve heads and see if anything comes out...
Last head I had off I did that to verify the valve was not bent.

Had a piston crack and destroy itself and tossed pieces of it all in the chamber area..

valve did not leak...


But I would not ever worry about it...
It cracked from water being left in the chamber?
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post #12 of 166 Old 06-16-2015, 05:41 PM
Jeepsr4me
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not sure how you could read in to what I said and come to that question./..

But no... piston broke before I took engine apart.... that is why I was testing the head...
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post #13 of 166 Old 06-16-2015, 06:26 PM Thread Starter
Gausswave
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Originally Posted by Jeepsr4me View Post
not sure how you could read in to what I said and come to that question./..

But no... piston broke before I took engine apart.... that is why I was testing the head...
Oh OK this is how I got there. I asked about hydro testing. Normally done with water. Usually water in a running engine leads to bad things like bent parts. Your posting style suggested a possibility if a sequence of events. I was thinking water got trapped in the head after a test. Thus the suggestion of using alcohol since it would evaporate long before you actually ran the engine.
OTOH my next question would have been wouldn't the alcohol evaporate fast enough to be a questionable material for this application? All the variants of the hydro test I've seen use water or soapy water to create easily visible bubbles. I just found the alcohol an interesting if not a potentially dangerous choice.
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post #14 of 166 Old 06-16-2015, 07:01 PM
triplej1954
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The engine sounds like it needs new rings, not that hard a job. If you get answers to your questions, I need to know as well (1989 wrangler with a 1997 Cherokee engine and wiring) trying to replace a 2.5 with it.
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post #15 of 166 Old 06-16-2015, 07:11 PM
Jeepsr4me
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No alcohol is exactly what you need to use in a off the block test..

And no it will not evaporate that fast... If the seal is not perfect it will come out fast..
If after a few seconds its not leaking... then its good... very fast test.. and very accurate.
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