PTV issues
07-29-2011, 07:41 AM
#13
If you just threw on the timing set with the marks at the 4* retarded position, you don't know anything. You need to install a degree wheel and CHECK timing first, then compare it to the spec sheet to see where you are.
DO NOT base pushrod length on PTV clearance. There is one way to determine pushrod length. You must check the rocker wear pattern on the tip of the valve stems. Never mess with pushrod length to get valve clearance.
If you degree the cam to mfr specs and repeat the clay exercise, you will see where you are really at. Then you have two choices: Thicker/Thinner headgaskets OR fly cut valve relief into pistons. A third option, NOT the right way to achieve clearance, is to degree the cam to some place that it gives room for safety. This is absolutely a compromise on power for clearance. The right place to degree the cam is where you get the power characteristics you want. Without testing on your own dyno, you only have the mfr spec sheet to go by. I would follow their instructions if you expect to get the results they advertise.
DO NOT base pushrod length on PTV clearance. There is one way to determine pushrod length. You must check the rocker wear pattern on the tip of the valve stems. Never mess with pushrod length to get valve clearance.
If you degree the cam to mfr specs and repeat the clay exercise, you will see where you are really at. Then you have two choices: Thicker/Thinner headgaskets OR fly cut valve relief into pistons. A third option, NOT the right way to achieve clearance, is to degree the cam to some place that it gives room for safety. This is absolutely a compromise on power for clearance. The right place to degree the cam is where you get the power characteristics you want. Without testing on your own dyno, you only have the mfr spec sheet to go by. I would follow their instructions if you expect to get the results they advertise.
07-29-2011, 08:30 AM
#14
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Join Date: Dec 2005
Location: Lil' Rhody
Posts: 22,376
If you just threw on the timing set with the marks at the 4* retarded position, you don't know anything. You need to install a degree wheel and CHECK timing first, then compare it to the spec sheet to see where you are.
DO NOT base pushrod length on PTV clearance. There is one way to determine pushrod length. You must check the rocker wear pattern on the tip of the valve stems. Never mess with pushrod length to get valve clearance.
If you degree the cam to mfr specs and repeat the clay exercise, you will see where you are really at. Then you have two choices: Thicker/Thinner headgaskets OR fly cut valve relief into pistons. A third option, NOT the right way to achieve clearance, is to degree the cam to some place that it gives room for safety. This is absolutely a compromise on power for clearance. The right place to degree the cam is where you get the power characteristics you want. Without testing on your own dyno, you only have the mfr spec sheet to go by. I would follow their instructions if you expect to get the results they advertise.
DO NOT base pushrod length on PTV clearance. There is one way to determine pushrod length. You must check the rocker wear pattern on the tip of the valve stems. Never mess with pushrod length to get valve clearance.
If you degree the cam to mfr specs and repeat the clay exercise, you will see where you are really at. Then you have two choices: Thicker/Thinner headgaskets OR fly cut valve relief into pistons. A third option, NOT the right way to achieve clearance, is to degree the cam to some place that it gives room for safety. This is absolutely a compromise on power for clearance. The right place to degree the cam is where you get the power characteristics you want. Without testing on your own dyno, you only have the mfr spec sheet to go by. I would follow their instructions if you expect to get the results they advertise.
08-01-2011, 02:12 AM
#17
I would put a degree wheel and dial indicator on it and see how it compares to this. I still believe there is limited value in arbitrarily advancing or retarding a cam if you have no means to test the results. For some, trial and error at the track will do.
'91 5.0 HO Cam:
208/212 duration @ .050
266/276 advertised duration @ .006
115.5 Centerline
.445" lift with 1.6 rockers (.278" at the lobe)
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08-04-2011, 06:19 AM
#20
2nd Gear Member
Thread Starter
Join Date: Apr 2009
Location: Massachusetts
Posts: 435
yeah i think i got screwed, i had to replace all but 2 of the valves. the others were all bent! the old ones are stockers. could i get a valve job on them and put in my bigger valves? could i even sell the performers? thanks mike