[WildBillyT]

When I bought the Nova it had an unknown '74 350. Didn't smoke and ran OK, but I knew it was a low compression smogger motor with 882 heads. I bought a set of 062 Vortecs (already modified for higher lift) with the intention of putting them on with a moderately sized cam (XE274) and RPM intake for a decent street motor with a little power. Going from 76cc to 64cc seemed like it would add almost a full point of compression. This past weekend I did a leakdown test on the motor to check the rings and got around 10% leakdown on the cold engine. Seems pretty solid. But here's where things get interesting. The motor looked bone stock, right down to the paper gaskets and cast iron intake. After the leakdown test I cracked it open and found out that the piston's aren't the stock ones for the block- they are GM 6271097 4 valve relief pistons with a 13cc dish- the ones at the bottom of this page:

http://webpages.charter.net/beckracing/slvpg55.htm

So the last guy replaced the crappy stock pistons with ones that are even worse. Numbers are still on the block so it hasn't been zero decked. Son of a bitch- looks like instead of a 8.5:1 motor it's a 7.9:1. So I'm trying to weigh my options.

Here's what I came up with:

1.) Continue as I was and gamble on a thinner head gasket (.015) and end up at around 9.25:1

2.) Same as above but back down on the cam size to something smaller due to the lower compression

3.) Stop screwing around and get the bottom end rebuilt with flat top pistons (this will waste what seems like a bottom end that's in good shape).


What would you do? Keep in mind that I'm on a tight budget and time to work on this thing is at a premium.

 

[71SS454]

What I'd do is have the Vortecs shaved down. Angle milling would be best, but I don't know what it would cost you. You could easily get the chambers down to 58cc or less with about a 1 degree mill. I've also heard that Vortecs can handle about a .040" flat mill, but to not go farthar than that. This will get you down to around 60cc's. Combine that with a shim style head gasket and you should have fair compression. I'd still run that cam though, but that's me.

Now doing the math, with those pistons and your stock vortecs with a .015 shim head gasket, a .023 deck height I get 9.56 compression. Witht he heads shaved to 60cc I get 9.98 compression. I think you're in good shape. Alot of Vortec heads actually measure closer to 62cc from the factory.

 

[6NOVA4]

that sounds good to me. run the bottom end as is with your cam and double roller chain. at 9.5 to 1 you can run 87 octane and be a decent cruiser.

 

[WildBillyT]

Guys, thanks for your help. I appreciate it very much.

But the more I think about it, the more I think I'll bite the bullet and change out the pistons. It seems like I'm just band-aiding my way around the obvious.

Looking at something like this:

http://www.summitracing.com/parts/FEM-MHP125-311/

Has anybody heard anything good/bad about these kits?

 

[Paul Wright]

Those dish pistons might be stock for that '74 engine. The Federal mogul pistons are heavy but relatively cheap. I presume you are going .030" over so that means you'll need a machine shop. Find the best one you can and let them measure everything and let you know what you need before ordering parts. IMO, You're looking at over a grand to do it right. It may be easier to buy a ready built short block and sell the one you have. Say you get $200 for the short block and buy an $800. That means you spend $600 and don't lose any time (time is money) as opposed to $500 for parts plus $300 machining.

We get these posts all the time. Someone gets a good deal on a used whatever and it winds up costing more to fix it up than just buying a new one.

If you aren't convinced on the economics of that then read all 50 pages of Kev's Budget 350 thread in Best of... I think he's on his third Blue Light Special.

 

[WildBillyT]

Those dish pistons might be stock for that '74 engine. The Federal mogul pistons are heavy but relatively cheap. I presume you are going .030" over so that means you'll need a machine shop. Find the best one you can and let them measure everything and let you know what you need before ordering parts. IMO, You're looking at over a grand to do it right. It may be easier to buy a ready built short block and sell the one you have. Say you get $200 for the short block and buy an $800. That means you spend $600 and don't lose any time (time is money) as opposed to $500 for parts plus $300 machining.

We get these posts all the time. Someone gets a good deal on a used whatever and it winds up costing more to fix it up than just buying a new one.

If you aren't convinced on the economics of that then read all 50 pages of Kev's Budget 350 thread in Best of... I think he's on his third Blue Light Special.

Thanks, Paul!

I am going to ask around at some of the local machine shops and see what they can do for me. Not going to buy anything until I get some more info.

 

[NovaBear]

hmm let me know how that goes, im lookikng to rebuild a 350 block as well. and im only a county away from ya.

 

[WildBillyT]

hmm let me know how that goes, im lookikng to rebuild a 350 block as well. and im only a county away from ya.

I will. I'm contacting some machine shops today to see what they will charge. If it's more than the price of a short block exchange (either via Summit/Jegs/Pace) then that may be the way I go.

Here's what I found last night:

http://www.summitracing.com/parts/MLL-BP3552/

I'm guessing it may be tough to beat $1500, especially if I factor in the time involved. Any reviews on the BP engines?

 

[levisnteeshirt]

if it wuz me

eh , i'd still look around , i think its fun shopping around looking for parts , then starting it up , seeing how its gonna do.

I'd look at these pistons for a budget rebuild , 125 dome , 10.7 with a 64cc head , still outta be able to run premium unleaded ,,
http://cgi.ebay.com/ebaymotors/Spee...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

i hate dealing with a set of milled heads , its a pain , i'd get a piston like those and only clean the heads up with a .005 mill if they need it