valve/piston clearence
06-13-2008, 03:40 PM
#3
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Location: NJ
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06-13-2008, 03:56 PM
#4
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Join Date: Jan 2006
Location: Puerto Rico
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RE: valve/piston clearence
With the Intake opened .050" @1° BTDC and Exhaust opened .050" @5° BTDC (cam degreed and installed to specifications) during the overlap (when PtV occurs)....... most likely not, but you need to check anyway.
you'll need to clay the pistons
06-14-2008, 01:04 AM
#6
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Join Date: Sep 2007
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Posts: 798
RE: valve/piston clearence
As stated, peak lift is nota factor for piston to valve clearance.
There is no way to go off lift numbers to see if you will "most likely have clearance problems."
I had .560"/.556" for my camshaft, with stock pistons. No clearance problems whatsoever.
Anyways, advancing or retarding the camshaft can gain you a bit...although it compromises your performance and powerband.
Advancing the timing opens the intake sooner and closes the exhaust sooner. That will gain you some clearance on the exhaust valve, but you will lose clearance on the intake valve. Retarding the cam causes the timing to open the intake valve later, and closes the exhaust later. You'll gain clearance on the intake, and lose clearance on the exhaust. So changing the cam timing won't result in increasing clearance on both valves.
You need to see which one you need most...
Keep in mind, adjusting either way can shift the powerband +/- ~ 200RPM that direction...
The general rule of thumb is .080" on the intake side, and .100" on the exhaust side.
The exhaust side needs a little more clearance due to a couple reasons:
- Piston chasing the exhaust valve as it is closing (spring has less control).
- Heat expansion
- Chain stretch(retards the camshaft)
There is no way to go off lift numbers to see if you will "most likely have clearance problems."
I had .560"/.556" for my camshaft, with stock pistons. No clearance problems whatsoever.
Anyways, advancing or retarding the camshaft can gain you a bit...although it compromises your performance and powerband.
Advancing the timing opens the intake sooner and closes the exhaust sooner. That will gain you some clearance on the exhaust valve, but you will lose clearance on the intake valve. Retarding the cam causes the timing to open the intake valve later, and closes the exhaust later. You'll gain clearance on the intake, and lose clearance on the exhaust. So changing the cam timing won't result in increasing clearance on both valves.
You need to see which one you need most...
Keep in mind, adjusting either way can shift the powerband +/- ~ 200RPM that direction...
The general rule of thumb is .080" on the intake side, and .100" on the exhaust side.
The exhaust side needs a little more clearance due to a couple reasons:
- Piston chasing the exhaust valve as it is closing (spring has less control).
- Heat expansion
- Chain stretch(retards the camshaft)
06-14-2008, 08:26 AM
#8
5th Gear Member
Join Date: Jan 2006
Location: Puerto Rico
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RE: valve/piston clearence
ORIGINAL: jkrum10238
im gunna call crane and see what they say, let them do the hard work haha
im gunna call crane and see what they say, let them do the hard work haha
Again, most likely it won't have a problem but you need to check..... or install it, crank the engine and cross your fingers.
06-14-2008, 01:39 PM
#9
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Join Date: Jun 2004
Location: Charles Town WV
Posts: 2,288
RE: valve/piston clearence
ORIGINAL: Joel5.0
Do you think Crane personnel will check PtV for you?...... or do you expect a "PtV certificate" for that cam?
Again, most likely it won't have a problem but you need to check..... or install it, crank the engine and cross your fingers.
ORIGINAL: jkrum10238
im gunna call crane and see what they say, let them do the hard work haha
im gunna call crane and see what they say, let them do the hard work haha
Again, most likely it won't have a problem but you need to check..... or install it, crank the engine and cross your fingers.
= check ftw
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