Cam base circle difference...
10-16-2002, 04:56 PM
#1
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Re: Cam base circle difference... GM states that the LS1 cam has a 19.7 mm distance from cam centerline to lobe heal. Thats 0.776"
Someone here measured there TR224 with a mic. and got a 1.492" distance [across] the lobe. That would equal 0.746" distance centerline to heel. The math says thats .030" less than stock.
Mill .030" off the heads and then you would need the stock 7.40" rods
"I was told .060 difference by Thunder"
They more than likely meant .060" accross the lobe which would be correct. The "across the lobe" distance is acually the cams base circle. You need to cut that number in half to get the cams centerline to lobe heal spec. The centerline to lobe heal number is what is important when considering lifter preload.
Ron,
Someone here measured there TR224 with a mic. and got a 1.492" distance [across] the lobe. That would equal 0.746" distance centerline to heel. The math says thats .030" less than stock.
Mill .030" off the heads and then you would need the stock 7.40" rods
"I was told .060 difference by Thunder"
They more than likely meant .060" accross the lobe which would be correct. The "across the lobe" distance is acually the cams base circle. You need to cut that number in half to get the cams centerline to lobe heal spec. The centerline to lobe heal number is what is important when considering lifter preload.
Ron,
10-16-2002, 05:12 PM
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Re: Cam base circle difference... Also, the stock lifters have a VERY large operating range they function in, you can take off 30 thousanths of preload on the stock lifter and it'll still be preloaded.
In other words, the lifters will make up the difference and all will be well.
In other words, the lifters will make up the difference and all will be well.
10-17-2002, 12:29 AM
#3
Cam base circle difference... Need to know what size the base circle is on a stock 02 cam, and the base circle size on a TR224, or if anyone knows the exact difference, that will be fine. I was told .060 difference by Thunder, but if that's the case, then why did they send me 7.400 inch pushrods? I'm looking to get heads milled to make up for lifter pre-load. I have the TR224/114 now. TIA <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
10-18-2002, 04:40 PM
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Re: Cam base circle difference... </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by AFTICA:
<strong>I spoke to Thunder a couple of days ago about this & they told me .020 smaller.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">As far as the Comp Cams is concerned, it usually varies based on the lift of the cam. Some Thunder / Comp Cams may have a centerline to lobe heal distance .020" smaller than stock. Some are .030", or anything in between.
The correct way to determine the distance would be to measure the distance accross the lobe with a mic. Then cut that number in half. That gives you the cam's centerline to lobe heal distance. Compare that number with you stock cam.
jmX is right...... Hyd. lifters can operate within a varying preload (up to a certain point). It don't need to be exact, however, if possible, you want to get it as close to stock spec. Excesseive lifter preload can cause the lifters to "pump-up" at high RPM resulting in a loss of high RPM performance and may limit Revs. Too loose of a lifter preload may help high RPM operation, but can be noisy. Again, you [must] preload the lifters. I would just say that it's best to get it as close as possible to stock spec.
<strong>I spoke to Thunder a couple of days ago about this & they told me .020 smaller.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">As far as the Comp Cams is concerned, it usually varies based on the lift of the cam. Some Thunder / Comp Cams may have a centerline to lobe heal distance .020" smaller than stock. Some are .030", or anything in between.
The correct way to determine the distance would be to measure the distance accross the lobe with a mic. Then cut that number in half. That gives you the cam's centerline to lobe heal distance. Compare that number with you stock cam.
jmX is right...... Hyd. lifters can operate within a varying preload (up to a certain point). It don't need to be exact, however, if possible, you want to get it as close to stock spec. Excesseive lifter preload can cause the lifters to "pump-up" at high RPM resulting in a loss of high RPM performance and may limit Revs. Too loose of a lifter preload may help high RPM operation, but can be noisy. Again, you [must] preload the lifters. I would just say that it's best to get it as close as possible to stock spec.
10-18-2002, 05:57 PM
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Re: Cam base circle difference... </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
Too loose of a lifter preload may help high RPM operation, but can be noisy. Again, you [must] preload the lifters. I would just say that it's best to get it as close as possible to stock spec.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Well, I've run anywhere from 2 turns preload down to my current 1/8th turn preload, and I have to say, this latest combo runs GREAT and puts out killer numbers. It may be a little noiser than if I had more preload, and yes, it is noisy, but the car just runs good and strong. Closest to zero preload will supposedly give you the most power at the cost of a little extra noise.
On a normal combo, I agree, just shoot for a turn or so of preload. I dont see any reason two turns would be better than one, even if thats what GM sets it at from the factory.
Too loose of a lifter preload may help high RPM operation, but can be noisy. Again, you [must] preload the lifters. I would just say that it's best to get it as close as possible to stock spec.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Well, I've run anywhere from 2 turns preload down to my current 1/8th turn preload, and I have to say, this latest combo runs GREAT and puts out killer numbers. It may be a little noiser than if I had more preload, and yes, it is noisy, but the car just runs good and strong. Closest to zero preload will supposedly give you the most power at the cost of a little extra noise.
On a normal combo, I agree, just shoot for a turn or so of preload. I dont see any reason two turns would be better than one, even if thats what GM sets it at from the factory.
