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Author
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Topic: after market cams
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bomrrman84
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Member # 7244
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posted
 
 
whats the biggest i can run a cam without fly cutting the pistons?
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91' GT convertible 331 under construction
91' GT hatch daily driver
Posts: 93 | From: suisun city | Registered: Nov 2006
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JohnB
Tech Moderator
Member # 969
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posted
Depends on the type of cylinder head used, valve size, duration of the cam, rocker ratio....
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Thirteen Twenty
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Member # 7961
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posted
couple of things, cheapest way is to bring your #1 piston to top dead center by checking your mark on the balancer, make a leverage tool and set up a dial indicator, then force open your valve until it hit's the piston, or you get coil bind on your valve spring, check the reading. now know that you will need at least .040" clearence between the valve and piston, so subtract that. then compress again to that level and check that you have at least .040" between your coils on the springs. Lastly know that a good cam is chosen mostly on duration and lobe seperation, not lift. Running to big of a cam for your combo will kill bottom end power and offer little up top if you don't have the compression and cfm flow to support it. You could run a smaller cam and go with a bigger ratio such as 1.6, 1.7, or 1.8 to speed up the opening and closing of the valve as well as gain lift while maintain good duration for your engine.
Posts: 647 | From: union city | Registered: Oct 2007
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turbo50
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Member # 6700
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posted
quote:
Originally posted by bomrrman84:
whats the biggest i can run a cam without fly cutting the pistons?
Nobody really knows the honest answer to this. There are so many variances that it just isnt worth the risk on not properly checking piston to valve clearance.
It is a little time consuming but well worth it in the end.
Justin described the ghetto version of it and you dont want to rely on TDC from your balancer reading, you want to verify this by using a spark plug stopper or something to that effect, but whatever works.
Just be sure to check it regardless of camshaft.
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.........when was the last time YOU built something with YOUR own hands?
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Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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2stangs69-91
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Member # 1951
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posted
quote:
Originally posted by Thirteen Twenty:
couple of things, cheapest way is to bring your #1 piston to top dead center by checking your mark on the balancer, make a leverage tool and set up a dial indicator, then force open your valve until it hit's the piston, or you get coil bind on your valve spring, check the reading. now know that you will need at least .040" clearence between the valve and piston, so subtract that. then compress again to that level and check that you have at least .040" between your coils on the springs. Lastly know that a good cam is chosen mostly on duration and lobe seperation, not lift. Running to big of a cam for your combo will kill bottom end power and offer little up top if you don't have the compression and cfm flow to support it. You could run a smaller cam and go with a bigger ratio such as 1.6, 1.7, or 1.8 to speed up the opening and closing of the valve as well as gain lift while maintain good duration for your engine.
lol that is absolutly the wrong way to check this. Like John B mentioned it depends. Why don't you at least post up what heads you have what year engine. What you want to do? I think then you might get some feedback that will help you out.
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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