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Old 08-17-2010, 07:36 PM
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back to the drawing board on the 350 bulid!!!

ok guys need yals help one more time lol, one of the local machine shops i go to was telling me that increasing the compression on a tbi 350 is a bad idea? that they are ment for stock CR, anymore than that, it has no pulling power.. they said they bulit them b4 with 9.1-9.5CR, even with rv towing cam, and still didnt pull like it should.. another local shop told me that i could up the compression to 9.1 would be the best, and use the eddy's tbi cam, flattop pistons with the stock heads would put me at 9.1, so id rather be sure on this knowing its tbi and got to be careful...what do yal think on this...thanx Tim..

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Old 08-17-2010, 08:31 PM
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I would keep it around 9.1:1. Speed pro ZH670CP pistons will do the job with a .040 gasket and uncut deck.

You could even go with a GMPP .028 thick head gasket for a 9.3:1 CR and an improved quench and not have problems.

Sealed power CS274, Summit K1101 or even a K1102 among many other brands with simular grinds will work.

Been there and done all these.

I have even used the H345p flat tops but with a little rattle getting into the throttle.
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Old 08-17-2010, 09:25 PM
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Quote:
Originally Posted by GMC boogie
I would keep it around 9.1:1. Speed pro ZH670CP pistons will do the job with a .040 gasket and uncut deck.

You could even go with a GMPP .028 thick head gasket for a 9.3:1 CR and an improved quench and not have problems.

Sealed power CS274, Summit K1101 or even a K1102 among many other brands with simular grinds will work.

Been there and done all these.

I have even used the H345p flat tops but with a little rattle getting into the throttle.
I concur. I used GMPP .028 gaskets and got 9.3:1 and had great results on my 350. I also say that the quench was improved as well Good Luck!
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Old 08-18-2010, 03:55 PM
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thanx guys, then thats said, flattops it is, the cam well, ill look into that, im wanting to run the stock converter, its a daly driver, 4x4 so keep all in mind, but i hear the stock swirl port heads r wimppy???
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Old 08-18-2010, 04:24 PM
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Swirl ports suck unless you are keeping at low low rpm all the time. But even in that case pretty much any other heads with equal or larger size valves would be better.
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Old 08-18-2010, 08:26 PM
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hm, i do have a summit k1102 cam on hand, but the only heads i have on hand are a set of 305 heads that had a port job done, but with 1.84/1.50 valves and the 58cc would give me way to much CR with FT pistons, and i really dout they would be werth it even with dish pistons..
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Old 08-19-2010, 07:06 PM
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ok explain to me the diff in these pistons, zh670cp has +11.00cc head volume, the 345np has +5.00cc head volume, whats the diff? one makes more compression than the other??
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Old 08-19-2010, 07:41 PM
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More head volume equals less compression.
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Old 08-20-2010, 08:39 AM
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Quote:
Originally Posted by gofastz
ok explain to me the diff in these pistons, zh670cp has +11.00cc head volume, the 345np has +5.00cc head volume, whats the diff? one makes more compression than the other??

the 11cc has more relief cut into the top of the pistons than the 5cc, therefor when calculating the compression ratio the 11cc will have an additonal 6cc which should lower the compression about a half a point
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Old 08-21-2010, 02:53 PM
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so the 345np's would be a good pick for a good street bulid, with stock heads and the summit k1102 cam, mayb a good sett of headers too??
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Old 08-21-2010, 02:59 PM
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Quote:
Originally Posted by GMC boogie
I would keep it around 9.1:1. Speed pro ZH670CP pistons will do the job with a .040 gasket and uncut deck.

You could even go with a GMPP .028 thick head gasket for a 9.3:1 CR and an improved quench and not have problems.

Sealed power CS274, Summit K1101 or even a K1102 among many other brands with simular grinds will work.

Been there and done all these.

I have even used the H345p flat tops but with a little rattle getting into the throttle.
if the dish pistons "670's" with uncut deck put out 9.1:1 with the .040 head gasket, on that note what will the "345np's" fattops, what will it put out with uncut deck withh .040 gasket with stock 76cc head??
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Old 08-21-2010, 05:49 PM
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The stock combustion chamber size on the "193" casting TBI heads are 64-65cc's. I dont where you are getting 76cc from unless you are using an aftermarket head

The difference in CR from the 670 dish pistons verses the 345 flattops with all else being the same is about .5
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Old 08-21-2010, 08:24 PM
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the info i got from my machine shop, they stock compression with "193" stock heads and dish pistons, is around 8.2:1, now i dont know what it is they know more about it than i do lol, but another ? here, if the heads are 64cc, then with dish pistons thats 9.1:1 rite?if thats true then i need to stay with dish pistons!!??
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Old 08-22-2010, 06:27 AM
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Like I originally stated, use the dish pistons and either the .040 or better yet the .028 thick gaskets and you will be fine.
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Old 08-22-2010, 06:59 AM
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thats cool, heck i didnt know the heads were 64cc, i thought they was 76cc lol, looks like i was fixn to bulid a 10.1:1 motor for a daily driver, thats 93 octane whew, im glad i asked you guys ?'s lol!!......thanx for all the help... Tim..
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