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  #1  
Old March 10th, 2019, 17:45
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JMOliver JMOliver is offline
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Building 4.o help

I have a 99 xj, I picked up a 95 block that I want to build.
I noticed that pistons split year from 90ish-95 to 96 up. Why is that? I wanna order pistons bored .030 over but don’t want to order wrong ones, anyone here that can help?
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Old March 11th, 2019, 10:27
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Re: Building 4.o help

Call Russ Pottenger at Bishop-Buehl and get some advice from him. He can also sell you very high quality rebuild kits.

Russ
Bishop-Buehl Racing Engines
531 N. Lyall Avenue
West Covina, California 91790
Work (626) 967-1000
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Email/PayPal: RussBnBracing@yahoo.com
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Old March 11th, 2019, 15:04
RCP Phx RCP Phx is offline
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Re: Building 4.o help

The blocks are the same, only the heads/exhaust/intake is different(if it's a XJ block)
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Old March 12th, 2019, 17:55
JeepNoob JeepNoob is offline
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Re: Building 4.o help

Quote:
Originally Posted by RCP Phx View Post
The blocks are the same, only the heads/exhaust/intake is different(if it's a XJ block)
Wrong!

The pistons are different because pre-'96 4.0's used a slightly longer stroke (3.4375 inches vs. 3.414 inches.) The connecting rods are the same length, however. And the displacement still rounds out 4 liters. To compensate for this and keep deck clearances and what-not the same, the pin location on the pistons is EVER so slightly different between the pre-'96 and '96+ pistons.

If it was me, I'd figure out a way to put that '95 crank into that '99 block (if you've got it.) using pre-'96 style pistons.The '96 and later blocks (ostensibly) had more webbing in the block plus a main-cap girdle. Guys here will claim that that was only done as a noise, vibration, and harshness (NVH), but I still have a hard time believing that that didn't also mean a stronger block. And the longer stroke of the '95 crank should mean a smidge more engine displacement.
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Old March 12th, 2019, 18:04
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Re: Building 4.o help

You know just enough to be dangerous.

That .023" difference in stroke is irrelevant to the already gaping deck clearances and has nothing to do with the Piston change.

And to get a little more stroke you want a 232 crank. Which bolts in with no other changes, no matter if you use early or late pistons.
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Last edited by cal; March 12th, 2019 at 18:08.
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  #6  
Old Today, 04:55
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JMOliver JMOliver is offline
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Building 4.o help

So ordering 96+ pistons will be no problem in a 95 block correct? Just trying to order parts


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  #7  
Old Today, 06:17
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Re: Building 4.o help

Yes.

But seriously, Call Russ and talk to him before ordering. There are a lot of things you can do to get a lot more for the same money, and his parts prices are competitive.
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Old Today, 06:56
RCP Phx RCP Phx is offline
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Re: Building 4.o help

Plus if you play your cards correctly, Russ can raise your compression ratio thru the size of the dish.
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  #9  
Old Today, 07:23
RCP Phx RCP Phx is offline
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Re: Building 4.o help

JM, you need to make sure you have the pistons your going to use before you have the block bored to get the right cyl wall/piston clearances.
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  #10  
Old Today, 07:52
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Scott91370 Scott91370 is offline
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Re: Building 4.o help

This is some good info. I am going to slowly be rebuilding the current engine in my XJ (went to change the rear main seal and found the main bearing on the rear cap totally dry) and was going to be asking some of the same as the OP.

Thanks!
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  #11  
Old Today, 14:24
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JMOliver JMOliver is offline
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Building 4.o help

Absolutely gonna get pistons before any machine work


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  #12  
Old Today, 15:53
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JMOliver JMOliver is offline
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Building 4.o help

Talked to Russ! Thanks so much for the recommendation!


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