Which piston for 9.5 to 1 CR - Team Camaro Tech
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post #1 of 10 (permalink) Old Jan 7th, 06, 09:24 PM Thread Starter
 
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Which piston for 9.5 to 1 CR

I want to achieve 9.5 to 1 CR in my 327. I am confused on which piston to use with my 76cc heads to get there. Any help would be appreicated.
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post #2 of 10 (permalink) Old Jan 7th, 06, 09:53 PM
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Re: Which piston for 9.5 to 1 CR

Quote:
Originally Posted by 68 RS 302
I want to achieve 9.5 to 1 CR in my 327. I am confused on which piston to use with my 76cc heads to get there. Any help would be appreicated.
An 11:1 piston (.125 dome) like the TRW L2166NF will get you in around 9.2, you can work with the heads themselves with some additional milling to get it as close as you're trying to the 9.5:1 number. Thanks, Gary in N.Y.
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post #3 of 10 (permalink) Old Jan 7th, 06, 10:18 PM Thread Starter
 
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Question Re: Which piston for 9.5 to 1 CR

I am attempting to build my own 302 from a 68 327 block. I have the block and the heads are the World 76cc with the large valves. Which pistons and connecting rods should I use? I have been reading everything I can and I guess I have come up with 5.94 rods with a 350 piston to accomplish my goal. Does this sound correct?? Or what combo should I use to get there?

I was initially thinking I could do it with a 283 crank (bearing spacers) with just a standard 5.7 sized rod and a 327 piston.
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post #4 of 10 (permalink) Old Jan 7th, 06, 10:50 PM Thread Starter
 
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Re: Which piston for 9.5 to 1 CR

Maybe its just a bad idea and I should just stick with the basic 327 setup and go from there. I was hoping to build a higher RPM motor.
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post #5 of 10 (permalink) Old Jan 8th, 06, 07:42 AM
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Re: Which piston for 9.5 to 1 CR

I'd put the large chamber heads up for sale and get some with chambers in the 55-60cc range. To make a 327, use a 350 piston made for a 6" rod and a 6.125" connecting rod.
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post #6 of 10 (permalink) Old Jan 8th, 06, 09:06 AM Thread Starter
 
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Re: Which piston for 9.5 to 1 CR

Actually I'm picking up the 5.94 rods with .125 dome tops. This should give me close to a 10/10.5 to 1 CR. With my heads this setup should work.

Chevy 302: Chevy 327 or 350 block with 4.0" bore, and 3.0" stroke. Must use Caprice 5.94" connecting rods. Any KB piston with a 1.561" compression height can be utilized. This is not an original equipment Chevy 302. Please refer to the Diametrical Listing.
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post #7 of 10 (permalink) Old Jan 8th, 06, 09:38 AM
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Re: Which piston for 9.5 to 1 CR

Quote:
Originally Posted by 68 RS 302
Maybe its just a bad idea and I should just stick with the basic 327 setup and go from there. I was hoping to build a higher RPM motor.
If you already have a strong 327 rotating assembly, I'd personally go that route...you can get those 327s to RPM way up there too plus you'll have a bit more torque too. Don't get me wrong, I love my little 302, but I think I'd like a similarly built 327 just as much. Plus if you want that 302 to fly, you need a steep gear ratio and if you really want it to rev, you're going to need a high duration camshaft which really needs high compression to work best (see where I'm going with this). Guess I'm just asking you to totally think this through before you spend a lot of money on mismatched parts that only leave you disappointed in performance. As pdq67 has put it before "The General got the 302 about right from the factory". So I'm suggesting that if you want to really build a 302, build it like the General did with respect to compression, camshaft selection, heads, etc...

Does anyone else agree?

Marty Lake
1969 Z/28 fathom green X77

Last edited by 1FASTZ; Jan 8th, 06 at 09:49 AM.
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post #8 of 10 (permalink) Old Jan 8th, 06, 09:56 AM Thread Starter
 
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Re: Which piston for 9.5 to 1 CR

Well I got a 286H cam with 3.73 gears and a 3500 stall converter. So I believe I am on the right track. I just need to know what rods and which piston to get the right CR. I have the World Torquer heads (76cc) with the large valves. I know I need a domed piston I am just trying to figure out which one for sure so I don't end up with parts I can't use. I love the 327's but I have never owned a 302 and I really want to build one. I guess if money were a real concern I would have just kept what I have. I am not interested in owning a 383 or something else, I want to build me a 302. I really appreciate all of the input and I have been reading everything I can. I read one post on another site that all I need is 5.94 rods with 350 pistons. Is that right? Shouldn't I need a 283 crank with 5.7 rods?
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post #9 of 10 (permalink) Old Jan 8th, 06, 10:23 AM
 
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Thumbs up Re: Which piston for 9.5 to 1 CR

I just PM'ed you.

Great, another little motor guy!!

The 286H cam is too big for 9.5 to 1 CR. Go with either the Duntov or a CC 270S solid and even an Isky Z-20 solid at 9.75 to about 10 to 1 CR.!

Plus, a hy-cam WILL not rev as high before it floats as a solid will! A solid will go as high as the valve springs will let it and you have nerve enough to hold it down!

I have a 280 solid cam in the closet now that I plan on shifting above 8,000 rpm!! It's PAW's $45 el-cheapo, 264/246 jobber that I figure is really a 280/246 cam!! A 301 at 8,000 grand is music to my ears!!

pdq67

PS., build it like a stock 302 at 10 to 1 CR. or I am thinking about using 6.25" custom rods and 6" rod, 350 roundy-round pistons. Also, look at the 305HO, -601 heads and Fel-pro #1094 shim headgaskets and flat-top pistons.

The -601's run from about 53 to 58 cc's so you have to cc them to know what they are. Great heads that have a double quench chamber much like the old -461 double-hump head, 1.84"/1.50" valves, hard seats and 160+ intake ports!



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post #10 of 10 (permalink) Old Jan 8th, 06, 10:27 AM
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Re: Which piston for 9.5 to 1 CR

Quote:
Originally Posted by 68 RS 302
Well I got a 286H cam with 3.73 gears and a 3500 stall converter. So I believe I am on the right track. I just need to know what rods and which piston to get the right CR. I have the World Torquer heads (76cc) with the large valves. I know I need a domed piston I am just trying to figure out which one for sure so I don't end up with parts I can't use. I love the 327's but I have never owned a 302 and I really want to build one. I guess if money were a real concern I would have just kept what I have. I am not interested in owning a 383 or something else, I want to build me a 302. I really appreciate all of the input and I have been reading everything I can. I read one post on another site that all I need is 5.94 rods with 350 pistons. Is that right? Shouldn't I need a 283 crank with 5.7 rods?
I can appreciate your desire for wanting a 302 and I think you need to pursue that, otherwise, if you're like me, you'd never be happy. I think you're on the right track. I think there's another way that you can make a 302 using a crank out of a 267 chevy v8, but can't remember the details...I bet you can search for 302 on here and find it somewhere. As far as using the 5.94 rods and 350 pistons, I'm not sure. I'm thinking that you'd want to use 5.94 rods with a 327 piston since the difference between the 327 and 302 stroke is 0.25". The difference between a 350 and 302 would be 0.5" therefore I think you'd still be 0.25" in the hole. Hopefully others more knowledgeable than me will chime in.

I'd have to see some piston specifications on the wrist pin location of the piston to do the calculations.

Marty Lake
1969 Z/28 fathom green X77
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