1985 Chevy Nova pistons.

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BaileySims
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1985 Chevy Nova pistons.

Post by BaileySims »

Ive read somewhere on the site that pistons from the 85 nova will fit our 3ac. Is this accurate?
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jimcrazy
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Re: 1985 Chevy Nova pistons.

Post by jimcrazy »

they should work but gonna have to punch the block 2.5mm from 77.5mm to 81mm then you got a 4a block
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rer233
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Re: 1985 Chevy Nova pistons.

Post by rer233 »

Not sure you can punch our blocks that much without going thru to the cooling passages...
if it aint there, there's a good chance it won't break!
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Re: 1985 Chevy Nova pistons.

Post by BaileySims »

what is this punching of blocks of which you guys speak? my block is now .40 over due to the wrist pin. i haven't been able to find any .40 over 3ac pistons and i had remembered someone saying the the nova stuff might work.
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Re: 1985 Chevy Nova pistons.

Post by jimcrazy »

I have spare 3a block and a 4a block all apart,,will check in the morning to see if the passages are thicker on the 4a
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Re: 1985 Chevy Nova pistons.

Post by jimcrazy »

o the 4a pistons would be .098 over size
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Re: 1985 Chevy Nova pistons.

Post by NWMO »

Bailey,

I am getting ready to tear down a JY Chevrolet Nova 4a engine in a few moments. I know they are a bolt-in engine replacement after swapping the oil pans, intake, etc. Petros has indicated they allow better coolant circulation than the 3a engines, but that may have more to do with the head. If the blocks are the same, it would seem boring to the 4a piston spec wouldn’t be a problem, as I may need to bore for over-size pistons that are available for the 4a engines.

Chris

PS - If going to that much trouble, you might be better off sourcing a 4a engine to rebuild. I found mine for $200, should know soon if the block and head are sound. If you increase the piston size and maintain the 3a head, compression is increased as well.
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Re: 1985 Chevy Nova pistons.

Post by BaileySims »

The only reason I ask is because I went through all the money and trouble fixing my original 3a block when the wrist pin scored the cylinder wall. I did find another complete 3a and threw it in the car and haven't had a problem with it. It just sucks that I have this complete 3a engine sitting on my computer desk lacking pistons. I would like to put it together just to have a spare but I cannot find any 3a .40 over pistons. All i have found so far was .40 rings, which was one of the last remaining ring sets I could find.

Anything 3a or 4a is impossible to come by around here. I don't really want to sink much of anything into another block because I have plans to build a 2j mini truck early next year, I hope.
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Re: 1985 Chevy Nova pistons.

Post by rer233 »

Why not have the bad cyl sleeved and stick with std 3a bore?
if it aint there, there's a good chance it won't break!
83 SR5 Silver/Blue (Snowmobile/work beater)-totaled but drivable
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87 fwd silver wagon a/t
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Re: 1985 Chevy Nova pistons.

Post by BaileySims »

rer233 wrote: Sat Dec 16, 2017 1:54 pm Why not have the bad cyl sleeved and stick with std 3a bore?
Didn't even think of that until it was too late. All are 40 over and to have it re-sleeved it would run me 600 bucks. That's a lot of money for a not so worthy motor.
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Re: 1985 Chevy Nova pistons.

Post by Petros »

I am surprised you can not find .040 3a pistons. the Nova used a 4ac engine, with a larger bore. there were repeated stories of 3a engines blowing out the water jacket with a .040 over bore, so going to a .o98 over bore sounds rather risky. the factory fix btw, was to sleeve the engine.

I do not think putting a 3a engine in a Tercel is worth the effort, go 4ac, you will not regret it.
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Re: 1985 Chevy Nova pistons.

Post by BaileySims »

What do you suggest I do with what I have now, just sell it all?
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Re: 1985 Chevy Nova pistons.

Post by NWMO »

BaileySims wrote: Fri Dec 15, 2017 6:24 pm what is this punching of blocks of which you guys speak? my block is now .40 over due to the wrist pin. i haven't been able to find any .40 over 3ac pistons and i had remembered someone saying the the nova stuff might work.
Bailey,

I didn't check shipping, but here is a set of pistons, pins, rings, etc. from our Australian neighbor for a reasonable price. My math indicates a set of .040" over will equal +1.0 mm.

https://www.ebay.com/itm/Toyota-Tercel- ... ND&vxp=mtr

Chris
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NWMO
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Re: 1985 Chevy Nova pistons.

Post by NWMO »

NWMO wrote: Mon Dec 18, 2017 7:58 am
BaileySims wrote: Fri Dec 15, 2017 6:24 pm what is this punching of blocks of which you guys speak? my block is now .40 over due to the wrist pin. i haven't been able to find any .40 over 3ac pistons and i had remembered someone saying the the nova stuff might work.
Bailey,

I didn't check shipping, but here is a set of pistons, pins, rings, etc. from our Australian neighbor for a reasonable price. My math indicates a set of .040" over will equal +1.0 mm.

https://www.ebay.com/itm/Toyota-Tercel- ... ND&vxp=mtr

Here is one from the US.

https://www.ebay.com/itm/NOA-Brand-040- ... II&vxp=mtr

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
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Re: 1985 Chevy Nova pistons.

Post by Petros »

the term "punching the block" is a slang expression for overbearing the cylinders, as it "punching it out to...", making it a larger bore.

keep looking for 3a oversized pistons, and 1 mm over size is about the same as .04". BTW, the block should not be overbored until you have the new pistons. the machinist is supposed to match the bore to the actual piston size. If it is already bored with the the new pistons, it would be a miracle if the pistons you buy actually fit properly. the skirt should only have .003" clearance, not any more, nor any less.

If you can not find oversized pistiosn, switch to the 4ac engine and sell or scrap the 3ac. You will not regret the extra power of the 4ac.
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