putting L98 back together with profiler 195's, cc503 cam and 1.65 rockers. Ran into major PTV issues on the intake, like .100

Retarded the cam 2* and it has all sorts of clearance now.

Just wondering if maybe the ramp rate of the 1.65's is pushing the valve into the piston a little early or if the offset intake valve of the profilers is just running out of the valve relief a bit on the stock L98 Pistons. Anyone have experience with these heads on an L98?

 

I've been piecing this car together for so long I forgot that I'm running .015 head gaskets and the heads are shaved .035 lol

 

Seems odd that 2 deg would make that much of a difference. Are the pistons still .02-.025 in the hole?

And the 1.65's arent going to make huge changes over 1.5's. 0.010-0.015 ish maybe with that cam, you'd have to measure the lift of valve where it contacts the clay, when piston is near tdc during its sweep and divide the difference in rocker ratio

 

Pistons are .025 down yes. The 1.65's add around .050 on the intake.

Total lift wasn't really the issue, I couldn't even get half way through the intake stroke and it would contact. Then I retarded the cam 2 degrees and had all kinds of clearance so it's a valve event issue.

Not sure if comp grinds some advance into the cc503 or not. But perhaps the ramp rate with the 1.65's and shaved heads was just a little too much.

 

P2V clearance issues happen only in a range of between about 20* before and after TDC between the intake an exhaust stroke AND AT NO OTHER TIME. By the time you're at, say, 45* before or after TDC the piston is sitting more than an inch and a half down the bore. No way there could be contact with the valve at that point.

2* cam change being the difference between actual contact and plenty of clearance? No way.

Perhaps you lined up on the wrong keyway/pointer when you first stabbed it in?

 

No it was definitely on zero.

 

Well something was seriously off on the first test lol but what matters is its installed correctly and clears now

Cam should be 112 lsa and call for a 108 icl. Degree wheel to check

 

Here's the timing gear I'm using




Here's it's set at -2

 

instead of relying on the cam card and the timing gears, get a degree wheel and a dial indicator and dial out the cam.

 

I really should when I have time. So far I just did the old cranking compression test. 160 at -2, 155 at -4

I could try it at zero but would likely end up with zero compression lol

 

Def do the degree wheel some timing sets are known to be off QC has gone to hell in the last few yrs

Shouldnt have a PTV issue. Running way more lift (know thats not the end all be all)at one point just under .700 with mucho head shaving and domed pistons .015 down no issue? Something else is going on.
If the timing set cks out id be half temped to stick that cam on a Cam Dr a good machine/head shop will have one it will tell if exactly what that cams doing if somethings off.

 

Yeah it seemed just too advanced.

 

 

Put my custom chip in, tuned the car and went for a test drive. I had to basically max out my fuel pressure with the 30lb injectors just to get around 14.5:1 AFR AT WOT, then after 5000 it went to 18-19... Dang

Looks like I need need bigger injectors and a pump.