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I'm building a 327 and have some good forged 350 Pistons with about a .125 dome. I'm using a 5.7 rod and know the piston will be in the hole but was hoping the dome will make up for it. The heads are 66cc chamber and have been milled a bit but don't know how much for sure. The block has been decked -.020 and am hoping this will get my compression back up a but also. My goal is to be anywhere between 9.5:1 and 10.5:1. I heard e85 was pretty good if I wanted to raise compression more. Any thoughts
 

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With E-85 you are leaving power on the table if you use less than 11 or 12:1. With a mild performance cam you can run up to 13.5:1 compression with no problem. Well, until you try to run E-10 in the engine.
 

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I'm building a 327 and have some good forged 350 Pistons with about a .125 dome. I'm using a 5.7 rod and know the piston will be in the hole but was hoping the dome will make up for it. The heads are 66cc chamber and have been milled a bit but don't know how much for sure. The block has been decked -.020 and am hoping this will get my compression back up a but also. My goal is to be anywhere between 9.5:1 and 10.5:1. I heard e85 was pretty good if I wanted to raise compression more. Any thoughts
You have no idea where you are, so you have no idea of where to go from here. I'll give you the same advice I gave another poster just a few minutes ago....
Scroll down to post #29 on this thread....
http://www.hotrodders.com/forum/chevy-350-hp-444609-2.html

Once you know the piston deck height, we can help you from there....
 

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I'm building a 327 and have some good forged 350 Pistons with about a .125 dome. I'm using a 5.7 rod and know the piston will be in the hole but was hoping the dome will make up for it. The heads are 66cc chamber and have been milled a bit but don't know how much for sure. The block has been decked -.020 and am hoping this will get my compression back up a but also. My goal is to be anywhere between 9.5:1 and 10.5:1. I heard e85 was pretty good if I wanted to raise compression more. Any thoughts
Bad deal, and still incredibly low compression. Typical .125" dome 350 piston measures out to a 4cc dome volume....put that figure, bore, stroke, deck height, the amount block is cut, and typical head gasket thickness of .041" thick and you get 9.1:1 compression....and miserable, terrible quench.

Engine is going to be a turd.

If it is a large journal 327 then just get a 350 crank to go with those pistons and be happy with a near 10.8:1 compression ratio, like the pistons are meant to be.....if you have a small journal block you're just flat screwed, you need actual 327 pistons.

Nobody makes a 5.762" rod, which is what you need to have the 5.7" rod 350 pistons work with the 327 crank.

You need to really re-think your idea, it's not good.
 

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welcome 15B

I haven't had enuff coffee yet, but
I think what there saying is
with 350 pistons and 327 stroke and a stock 5.7" rod,
your compression will be like 6:1
your stroke/rod/piston length/height is 1/4" or .250" inches too short to work..
 

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Bad deal, and still incredibly low compression. Typical .125" dome 350 piston measures out to a 4cc dome volume....put that figure, bore, stroke, deck height, the amount block is cut, and typical head gasket thickness of .041" thick and you get 9.1:1 compression....and miserable, terrible quench.

Engine is going to be a turd.

If it is a large journal 327 then just get a 350 crank to go with those pistons and be happy with a near 10.8:1 compression ratio, like the pistons are meant to be.....if you have a small journal block you're just flat screwed, you need actual 327 pistons.

Nobody makes a 5.762" rod, which is what you need to have the 5.7" rod 350 pistons work with the 327 crank.

You need to really re-think your idea, it's not good.
I made a couple mistakes here yesterday...,

I should have said you'll need a 5.825" rod to make a 5.7 rod 350 piston work with a 327 crank....you can come close with the slightly longer 5.850" rod which is available from the aftermarket. Eagle makes one in the $300 price range. This will actually work out well on an undecked block, help maximize compression and minimize quench clearance while allowing you to use a common composition head gasket.
The 5.850" rod combination will get you to 10.82:1 compression.

With a 5.7" rod and the 5.7" rod 350 piston and a 327 crank your actual compression ratio is 8.05:1, not the 9.1:1 I posted above.....really in the toilet despite the dome on the piston(the .125" dome 350 piston is a 4cc dome).

Needless to say, the 5.7" rod with the 350 piston in a 327 isn't going to make any power unless you add a turbo or a supercharger.
 

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me too
1/8" or .125" too short
8.11 compression ratio

that's what happens when I do it in my head, without enuff coffee..
 

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Discussion Starter #8
Thanks for all the responses. I didn't actually think of the idea for this engine. This is the first one I'm building and am getting help and taking advice from a family friend. I think he knows what he's doing because he's built some pretty remarkable engines on the past but is getting older and maybe he was trying to experiment. i actually have a set of old forged 327 Pistons with a very small dome like what would've came from the factory on a high output 327. Thinking about just running those.
 

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We have actually already had the motor together and ran it and drove it a little before finding out we had a cracked head. The engine seemed like it had some power. Didn't hear any knocks when we ran it. The car we put it in had a 3.06 gear in it so its hard to tell how much power it might have. It sounded loud like it had about the 10.5 compression our friend told us it would have. I'm just lost at this point :confused:
 

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if you have the heads off,
just roll it up on TDC and see how far down the piston is from the top of the block???
 

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I also want to use the 350 Pistons I have because I've spent some time lightening them. Took off about 50g. The motor seemed to be balanced pretty well when we ran it on an engine stand. Really thinking about just buying a 6.0 rod upping the compression and running e85
 

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a 6.0" rod will be way too long..
that's a .300" longer rod..
the motor will never turn over with the piston sticking out of the block, it will hit the heads..

as Eric said
you need a 5.825" rod.. that's 1/8" or 1.25" longer than a 5.7"
 

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a 6.0" rod will be way too long..
that's a .300" longer rod..
the motor will never turn over with the piston sticking out of the block, it will hit the heads..

as Eric said
you need a 5.825" rod.. that's 1/8" or 1.25" longer than a 5.7"
If the block hasn't been decked the 5.850" rod puts you perfectly at zero deck at the factory deck blueprint dimension of 9.025" tall.

That's why I said the 5.850" combo would work out so nice with the 5.7" rod 350 piston and a 3.25" stroke 327/307 crankshaft.

You'll never even get the heads on with a 6.00" rod and that same piston, the quench section of the piston will be .150" above the top of the block and the dome will be .275" above the top of the block(over 1/4"). :spank:
 

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IMO, I would get a 350 crank and get it over with. 327 pistons are harder to get. Beside you have 350 pistons. Cost wise I think 350 are cheaper. I built a 350 using 307 rods, a 350 bare block for $100, 355 forge pistons( Cost me the most), and a 350 crank for $50 at a swap meet. The motor ran for about 15 years before I sold it and picked up 406 sbc for $1000.
 

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Is it just me? It seems like all the intelligent answers that a youngster gets on these forums just go unheeded. It's like they don't read what we write or if they do read it, it is wasted on them. Is this the new generation, the millenials, that know nothing and don't want to know anything? I'm used to getting intelligent input from what I write, but that just doesn't happen any more. I used to really enjoy writing and helping these youngsters.....not so much any more. Maybe I'll have to put my time to better use and stop trying to jam info down the throats of fellows who obviously don't appreciate that I'm trying to keep them from making the same mistakes I did for the last 60 years. :spank:
 

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Is it just me? It seems like all the intelligent answers that a youngster gets on these forums just go unheeded. It's like they don't read what we write or if they do read it, it is wasted on them. Is this the new generation, the millenials, that know nothing and don't want to know anything? I'm used to getting intelligent input from what I write, but that just doesn't happen any more. I used to really enjoy writing and helping these youngsters.....not so much any more. Maybe I'll have to put my time to better use and stop trying to jam info down the throats of fellows who obviously don't appreciate that I'm trying to keep them from making the same mistakes I did for the last 60 years. :spank:
I have noticed the same! Like they say, You can lead a horse to water but you can't make them drink! Keep talking, you provide interesting reading for me and useful information for others who are willing to listen!
 
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