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Old 07-06-2013, 10:49 AM
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I have a gm 350 4bolt main .060 over, with a steel crank cut .20 with flatttop pistons. I have the victor cruz tunnel ram intake. With that being said, What size of Cam and Heads should i use to get the most out of this 350 without having to change to high octaine gas??
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Old 07-06-2013, 11:04 AM
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Quote:
Originally Posted by LOPEZ H.D. View Post
I have a gm 350 4bolt main .060 over, with a steel crank cut .20 with flatttop pistons. I have the victor cruz tunnel ram intake. With that being said, What size of Cam and Heads should i use to get the most out of this 350 without having to change to high octaine gas??
You need to know the CR of the motor.

Here is a link for you to read.
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Old 07-06-2013, 11:08 AM
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I Cant see the link boss, but what do you mena by CR ?
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Old 07-06-2013, 11:13 AM
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whats the deck height of the piston?what are you planning for carb,purpose of the car,what kind of car? other wise its a guess
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Old 07-06-2013, 11:33 AM
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To be honest im not sure about the height, they came with the pistons. And its a '73 trans am. I Have a 750 double pumper Holly carb. And i want it as a my weekend car. Its going to be a street running car so i dont want to go compleatly all out on the engine. Just wanna hit some good hp and torque. Its a muscle car so I want to defend itself against Ls1's.
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Old 07-06-2013, 11:38 AM
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Quote:
Originally Posted by LOPEZ H.D. View Post
I have a gm 350 4bolt main .060 over, with a steel crank cut .20 with flatttop pistons. I have the victor cruz tunnel ram intake. With that being said, What size of Cam and Heads should i use to get the most out of this 350 without having to change to high octaine gas??
You need to know the CR of the motor.

Here is a link for you to read.
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Old 07-06-2013, 12:08 PM
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CR = compression ratio. If you don't know that, tell us how far in the hole the pistons are, what cylinder heads/combustion chamber volume, gasket thickness and we can figure it out.

Here's a link to an online calculator, one of many:

Interactive JavaScript to Calculate Engine's Compression Ratio (CR)
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Old 07-06-2013, 02:20 PM
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Sorry for all my double post. Trying to do that on a phone sometimes doesn't work.

Here is the link.

http://www.crankshaftcoalition.com/w..._compatibility
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Old 07-06-2013, 02:55 PM
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Quote:
Originally Posted by LOPEZ H.D. View Post
I have a gm 350 4bolt main .060 over, with a steel crank cut .20 with flatttop pistons. I have the victor cruz tunnel ram intake. With that being said, What size of Cam and Heads should i use to get the most out of this 350 without having to change to high octaine gas??
As a rule of thumb, most fellows today will agree that you want to use 9.5:1 or less static compression ratio with iron heads and 10.5:1 or less with aluminum heads. The camshaft you use should be matched to the static compression ratio you use, using the intake valve closing point to match up with the SCR.

In other words, if you had a 10.5:1 SCR and closed the intake valve at.....say.....25 degrees after bottom dead center @0.050" tappet lift, the motor would make such high cylinder pressure that you would have to use alcohol or race gasoline to operate it without the motor detonating itself to death.

On the other hand, if you had a 9.00:1 motor and used a cam that closed the intake valve at......say.....60 degrees after bottom dead center, then most of the compression would be blown back up the intake tract by the ascending piston and you would be left with a very weak "bang" and little power.

It is a balancing act that requires quite a lot of understanding of how camshafts work......or......you can just call up your favorite cam grinder and talk to their tech person. Given all the stats of the motor, they can suggest the best camshaft profile for your motor.
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Old 07-06-2013, 06:29 PM
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To add to what techinspector just posted,,,Make sure the cam tech is actually a technician with math skills.You can read the cam catalogue as well as anyone else.Some guys that answer the phone just quote a popular grind that the community uses a lot of. If the guy asks you what gear ratio you are running in the diff,then ask him why he needs to know that? Make sure his answer sounds good. Also ask him about different intake center lines and different lobe displacement angles...You dont need to know the answers,but the guy making the recommendation better be able to explain to you why.If he stumbles,ask for another technician
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