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Discussion Starter #1
The stock bore is fine on this motor but I since I'm ordering new pistons and having the block completely redone at the shop I was wondering if I should go oversized or not? Price doesn't matter, it's only $100 more to have it bored. Just wondering if there are any advantages.
 

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Aaron,
The stock bore may look okay, but if it's got any significant mileage on it. the bores have started to taper. The factory did not use a deck plate either when doing the original machining, so it's wasn't made as round as it could have been in the first place.:eek: 2.5's are notorious for piston slap due to longer stroke. The forged pistons require much more piston to wall clearance than the factory cast pistons, so this will have to be compensated for by machining even if you stay with std. bore. Have the pistons and deck plate in hand before the machining starts. this way, the machinist will be able to have the bores correctly fitted to your Venolia's. This to me is a no brainer. IMO, I would overbore .020 for sure. Make sure you get the deck surface resurfaced too, so your new motor's headgasket has a prayer of sealing for the long haul.
 

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Discussion Starter #3
Trust me. I just paid $2500 for a new motor only to have the block crack for some reason. I will NOT cut ANY corners on this new build!!

Thanks for the advice. Any reason to go .040 over? Even more?
 

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Trust me. I just paid $2500 for a new motor only to have the block crack for some reason. I will NOT cut ANY corners on this new build!!

Thanks for the advice. Any reason to go .040 over? Even more?
Definitely not! Leave as much meat in the cylinders as possible. @ .040 over, your motor will be a one hit wonder, and you will need yet another block for your next rebuild.
 

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How and where did the block crack? I've never seen a block crack on one of these motors - especially a common block.
 

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Discussion Starter #6
No idea, but new known good head, 3 headgaskets, and new turbo... still mixing coolant and oil when it gets warm.
 

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NOOOOO Don't tell me this. Makes me scared to build up even a CB now ahhh CRAP were you running unusually high boost or something?
 

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There's no hard evidence that the block was cracked though. Could have been, but its a theory only.
please offer suggestions then. i have been doing this atleast 10 years and my pop is a chryco tech from 1984. i have had a fit with this van. i have replaced heads and headgaskets as aaron stated and the deck surface is in line. no matter what it runs great but keeps mixing.

PLEASE give me some of your insight.


Norm
 

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please offer suggestions then. i have been doing this atleast 10 years and my pop is a chryco tech from 1984. i have had a fit with this van. i have replaced heads and headgaskets as aaron stated and the deck surface is in line. no matter what it runs great but keeps mixing.

PLEASE give me some of your insight.


Norm
Does your turbo have coolant lines hooked up? Could the turbo be the actual culprit with a cracked center section letting the fluids mix? Did you hook up the lines correctly?
 

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Discussion Starter #12
Yes it has both oil and coolant lines, all hooked up. Turbo is NEW and was taken apart and checked before installation!
 

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What about magnafluxing the block? It'll have to be torn all the way down again to find out, and either way, you're stuck with basically starting all over which sucks. Boo on that.

With an assembled engine full of coolant, yank the oil pan off and pressurize the cooling system for 8 hours and inspect what comes dripping out and from where.

Keep in mind that I don't know you guys, I have no idea what exactly is going on because I am not there to see the issue, so I cannot make any kind of sound judgement on the quality of work and / or parts being used. You could very well be dead on and the block could be cracked. I have no idea. Therefore, please don't let me get on anyone's bad side. I just personally know way too many people who have been in a trade a LOT longer than I have and still don't do a good job at it. I bought a '95 Grand Prix (pos) from a neighbor of mine who says he worked for General Motors for 21 years as a mechanic. The car was running rough and making a failed rod bearing-type noise. His diagnosis was that the fuel injector on cylinder #4 was stuck open, causing the rough running and discolored spark plug. He decided not to pursue the project because of the engine noise. Either way, it needed a replacement engine, but his diagnosis was WAY wrong. I hooked my fuel pressure guage up to it (a 20+ year mechanic by trade should have his own, right?) and shut the engine off.. oh look, its holding fuel pressure. Oh look, I can ground the injector wire for that cylinder and the pressure drops. Hey, start it back up once. Oh no, there's an awful lot of exhaust coming out of the oil fill hole.
I bought the car with the bad engine, and replaced the engine because there was obvious piston / ring issues in it, and it would have been cheaper just to get a good junkyard engine than to machine this old one and fix it up. The old engine had a really beat up piston / cylinder. The dead cylinder caused a sudden change in crankshaft speed which caused the really loose timing chain to slap around and make a lower end noise. The rod bearings were all in excellent condition. Transmission died 1500 miles after I got the engine in. (*&###@ Chevy!) Bottom line is that this "mechanic" by trade has very poor diagnosis skills. Perhaps he is stretching the truth regarding his credentials???

There's a woman I work with--AT AN EYEGLASS SHOP--that has been working there 28 years and has a pretty bad case of presbyopia and early cataracts and cannot see anything clearly that is less than 3 feet away. She is in denial and claims to be able to see sufficiently. Thats a bunch of crap and another example. When it comes to working with eyeglass frames, the skill level she has is equivalent to about 1 year. I get red in the head every time she defends herself with "I've been doing this for 28 years...."
 

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:(

I've seen this happen, but not because of anything Chrysler ever did or because of any weakness in the blocks.

The only time I've ever seen blocks crack and mix fluids is when the thread holes for the head bolts aren't thoroughly chased and cleaned when doing the rebuild. The head bolts get installed and the crap in the thread holes sits in the bottom. The torque to yield bolts are then installed and guess what - the torque is reached because the bolt is bottoming out - not actually torqued to the proper torque. Then the extra 1/4 turn is put on it, and POP - the block cracks along the entire side of the thread hole. You can usually clearly see a crack of this nature on the top of the block.

Norm - did you notice any cracks between the head bolt holes and the coolant and/or oil passages when doing any of the head gasket changes? I know it's not something that most people would look for (these blocks are pretty stout), and I only look for it because I helped a novice friend out who had done exactly this when he "rebuilt" his motor and had problems. Ever since then, I make it point to check out this area of the block before doing any kind of rebuild. These cars were known for popping head gaskets back in the day, and many of them had multiple head gasket jobs done to them, and the thread holes almost never get cleaned and chased for your average joe blow head gasket job.

Just my .02 to help you stop pulling you hair out over it....
 
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