Max overbore? - Team Camaro Tech
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post #1 of 11 (permalink) Old Sep 7th, 02, 01:04 AM Thread Starter
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I have a 302 for a 68 Z/28 that I am considering reinstalling, but it has been bored .06, that has got to be pushing it I would think. It ran fine when my dad pullled it for a 355. He put a supercharger on it and didn't want to use the 302. I have aquirred the car due to his passing and I may put some of the car closer to original.
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post #2 of 11 (permalink) Old Sep 7th, 02, 03:33 AM
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Some blocks will be fine at .060 but not all. If it works, don't fix it.

I would be thrilled to have such a car as yours by the way. My dad had a few classics over the years but he never kept any of them. I realy wish he had because I have lots of fond memories of those times.

-Mark.
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post #3 of 11 (permalink) Old Sep 7th, 02, 07:02 AM
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The older blocks are often OK to go .060 but its a good idea to have them sonic checked before you bore them beyond .040. If the engine has already been done and its at .060, I wouldn't worry at all about it and would just leave it alone as long as it runs.

Sometimes you can even redo a block that's already .060 by using a looser fitting piston and doing a light hone on the walls. I just did this on my block after breaking a piston. My old KB's were a tight fitting piston and my new SRP's need a little more room - so we just honed them out another .002" to achieve the recommended SRP spec.

You could also have the block sleeved too if you have a numbers matching block that's all used up. Nothing at all wrong with a sleeved block if is done by a competent machinist.

Keep in mind though that 302 pistons are hard if not impossible to find - so don't throw any used ones out!


[This message has been edited by Eric68 (edited 09-07-2002).]

[This message has been edited by Eric68 (edited 09-07-2002).]
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post #4 of 11 (permalink) Old Sep 7th, 02, 08:41 AM
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i have a 307 block that i bored .125 over to accept the 4" 350 piston. replaced the crank w/ a 350 crank and placed well over 70 k miles trouble free. It never let me down.
i think i was lucky there was no voids deep in the walls, and the older block walls were more than thick enough to allow it.
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post #5 of 11 (permalink) Old Sep 7th, 02, 09:21 AM
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Eric, Ross Pistons makes NHRA stock replacement pistons for "290HP 67-69" 302's. They are forged. They cost $647, so i agree with Eric dont can the ones you have unless they dont fit!
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post #6 of 11 (permalink) Old Sep 7th, 02, 09:57 AM Thread Starter
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Unfortunatly one of the pistons has a chunk out of it down to the first ring so I'll need new ones. It's not disassembled so I havent checked the bores. Sleeving is an idea though.
thanks for the information!

Doug
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post #7 of 11 (permalink) Old Sep 7th, 02, 06:49 PM
 
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dude dont change that car

------------------
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post #8 of 11 (permalink) Old Sep 8th, 02, 07:06 PM
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blown,
I've done as Eric has with a light honing. I've even used my ridge reamer prior to honing if there was a light ridge to cut it down first. But bores have to be true and good to begin with.

I hope you'll find the piston you need. I just sold a set of +.020 302s that were brand new. I've also had .040 and.030 sets. I've never run across a .060 set, but I know someone will have them, for the right price I'm sure.

Good Luck,
Dave
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post #9 of 11 (permalink) Old Sep 8th, 02, 07:12 PM
 
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I agonized over stroker pistons for my 496 for several days b/c I'm a tight-a--!!

I was going ta use stock forged and deck and such stuff but after it was all said and done with, the peace of mind I got after buying my ROSS pistons made up for all the hassle, (and cost), I was putting myself through!!! pdq67



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post #10 of 11 (permalink) Old Sep 8th, 02, 09:02 PM
 
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If pistons for the 302 are so expensive

I've got an intresting idea how about getting a set of long rods without the pin machined then set them up so you can use 350 pistons. You could have the benifits of longer than stock rods and a cheap source for pistons
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post #11 of 11 (permalink) Old Sep 9th, 02, 04:03 PM
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You know, the cost of a set of custom pistons is not all that far out of line when you are building a stout engine. $400 for a set of off the shelf vs maybe $700 for a set of custom made slugs ain't all that bad. No sense whining about it for an extra $300 in the whole car/engine. Everything else is easy and even the cranks are not that bad when compared to another forged factory piece.

-Mark.
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