Any risk in 4.6 stroker 4.0? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-13-2000, 05:55 PM Thread Starter
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Any risk in 4.6 stroker 4.0?

My block has been diagnosed with a bad ring or piston hole. My plug (#4) has oil all over it, and the cylinder holds NO compression in a leak down test at TDC compression stroke. The pressure pushed into the crank has caused all sorts of leaks in lower engine as well as additional pressure in valve cover.

I don't know if this was ready to go and the additional pressure from the 4.0 head and MPI caused the weak link to go, but in any case, I need to rebuild/replace short block. This highlights the advantage of doing the whole thing at once instead of relying on the short block's worthiness (It is a fairly recent rebuilt engine that show 150 +/- 4psi compression in all cylinders

A Jeep dealer mechanic races a late model comanche truck off road and has built a over bored stroker 4.0s resulting in 4.6 displacement (this is what he races his truck with). He can build me one (out of his home shop) for around $1,000. We would use the head I just finished along with my new MPI kit and replace the block with a .030 over bored 4.0 block using the 4.2 crank for longer stroke using new pistons/rods. I have read that this is a pretty good set-up.

Providing he can give me a written warranty, does anyone see any inherent problems with this set-up?

TIA, and in the mean time I have a straight 5 that leaks like the devil.




-raymo
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post #2 of (permalink) Old 12-13-2000, 06:02 PM
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Re: Any risk in 4.6 stroker 4.0?

Don't know about the worthyness, but I have some info you might like. For some more $ you could really stroke it to about 5.0L, maybe 5.1L(if my math is right). If you can use a 4.2 then using a 4.7 stroker kit would be nice(I think Hesco makes it, and last I checked Rosser had 2 in stock). That would be something to see a 5.1L FI I6.




Jason

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post #3 of (permalink) Old 12-14-2000, 01:41 AM Thread Starter
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Re: Any risk in 4.6 stroker 4.0?

Any other comments?

-raymo
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post #4 of (permalink) Old 12-14-2000, 07:14 AM
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Re: Any risk in 4.6 stroker 4.0?

There is no replacement for cubic inches. And the longer the stroke the better. IMHO for off road low end grunt.

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post #5 of (permalink) Old 12-14-2000, 08:16 AM
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Re: Any risk in 4.6 stroker 4.0?

I have two of these engines, and they are very reliable and sound. I could only recomment two things. One: Make sure that you balance the engine, that means the harmonic balancer, flywheel, and pressure plate. Should run about another $100.

second: Why is there a hole in number 4? make sure that your injector is good on that cylinder, and that there is no major vacuum leaks arount that area of the intake. You don't want your new engine doing the same thing.

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post #6 of (permalink) Old 12-14-2000, 10:30 AM
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Re: Any risk in 4.6 stroker 4.0?

Jason,
if I'm not mistaken, Hesco's kit uses the crank from the 4.2.


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post #7 of (permalink) Old 12-14-2000, 12:37 PM Thread Starter
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Re: Any risk in 4.6 stroker 4.0?

dorfs,

I don't know what has caused the ring to go bad. You mention an intake leak? Is that a common cause of rings going bad? The old intake manifold gasket was leaking between the 5 & 6 cylinders and that was 1 of about 20 reasons I went to the 4.0 head/mpi. However, when I completed the 4.0 head/mpi set up, it ran really strong. The performance loss happened all at once. So, if anything, the rings had been weakened, but were still funtioning when the upgrade was completed.

To your second point....yes, it seems like it will have to be balanced since parts from several sources will be used.



-raymo
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post #8 of (permalink) Old 12-14-2000, 12:51 PM
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Re: Any risk in 4.6 stroker 4.0?

This was a stroker kit for a 258, that Rosser had. I think that when I talked with Todd Rosser he said that the company that made it was discontinuing it. He had 2 in stock, one for him and one to sell. But he has a V8 in his CJ, so unless he has anothere product there should be one there.

This kit stroked a 4.2L to 4.7L. That should be about .5L. Aren't there only 2 ways too gain c.i.? 1-stroking with a larger crank and 2-boring(only if you have to). I could be wrong. Im sure that you could use diffent pistons, shorter connecting rods or something, but I am not an engine wiz. Just leave that to someone else.




Jason

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post #9 of (permalink) Old 12-14-2000, 07:55 PM
 
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Re: Any risk in 4.6 stroker 4.0?

I am suprised no one has posted this link yet.....
http://bc4x4.com/tech/bryce/stroker/stroker.asp
Bob in Ma

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post #10 of (permalink) Old 12-14-2000, 08:27 PM Thread Starter
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Re: Any risk in 4.6 stroker 4.0?

Maybe I should have mentioned that I have been reading that (drooling is probably fair to say as well) as a point of reference. It seems like there are people doing it, but not as many as have done the 4.0 head on the 258 motor. I would just like to know of any potential problems ahead of time.

The guy who will build it is a Certified Jeep Mechanic. I like the idea that this is the engine that he uses to race with. He really seems to know his stuff.





-raymo
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