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Old 03-15-2007, 05:56 PM
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Cams!!

Im rebuilding a 350 and i want flat head pistions but i wana knoe whats the bigest cam i can get be for it hits the pistions?????

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Old 03-15-2007, 06:15 PM
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What type of heads are u using? I think minimal clearance is .050'' between the two. What is your deck height?
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Old 03-15-2007, 06:31 PM
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it all depends, combustion chamber cc, deck height, rocker ratio...
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Old 03-15-2007, 07:28 PM
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Quote:
Originally Posted by sdime1984
Im rebuilding a 350 and i want flat head pistions but i wana knoe whats the bigest cam i can get be for it hits the pistions?????
Usually on a SBC you want to check valve to piston clearance when installing a new camshaft on any flat tappet camshaft that has more than 248deg@.050".
A cam with this much duration is pretty big for a street motor.
A roller cam has much faster lift rate especially in the critical area when the piston is within 30deg of TDC.
So I would check any roller cam that is bigger than 240deg @.050"
The full valve lift spec is irrelavant because when the valve is at full lift, the piston is already more than half way down the bore.
The critical valve to piston clearance point is when the piston is within 30degrees on either side of TDC
Big cams with tight LSA have less valve to piston clearance than big cams with Wider LSA (more or less valve opening at and near TDC.)
Milling the heads and decking the block will reduce valve to piston clearance.

Advanceing the cam in the motor will reduce intake valve clearance. Retarding the cam in the motor will reduce exhaust valve clearance.

What camshaft do you have in mind for this motor?
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Old 03-15-2007, 11:11 PM
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The only way to know for sure is to check it yourself with either of two methods, clay on the pistons or the "checking spring" method. Scroll down and read how to do it......
http://www.iskycams.com/camshaft.php
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Old 03-15-2007, 11:38 PM
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Quote:
Originally Posted by sdime1984
Im rebuilding a 350 and i want flat head pistions but i wana knoe whats the bigest cam i can get be for it hits the pistions?????

In most cases the "biggest" cam is not usually the way to go.There are so many factors that need to be looked at in accordance to a good cam selection. For example: How well do your heads flow?...Are you using cast iron exhaust manifolds or tubular headers?....valve diameter, intake manifold and carb setup are also important. Do you want a smooth idle or an idle so rough that it'll bang your head against the drivers window? And where do you want your engine to make it's power? Down low in the bottom end....mid range... at the top end....or evenly across the entire rev range. So first decide how you want your cam to function, then give your wants and your other engine specifications to your cam grinder and together you will have a cam which is not necessarily the "biggest" but certainly the "best" for your package.
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