I'm going to be taking my 915 J heads to the shop soon for guides and a valve job.
The engine has a 292* .508" purple cam. I don't know what springs are on the heads now. They're single, with a damper.
I'm checking spring pressures at installed height and full lift, just to practice, as I know I'll lose pressure when the valves and seats are ground. I have an installed height mic ordered (More accurate, takes the wobble out of the retainer?), but I'm using snap gauges for now. The installed height on the one I checked is 1.799". Minus the .508 is 1.291". I'm getting 78# and 230# respectively, including the .057" shims that were on the heads. (The engine wasn't too eager to rpm.) Should be about 103# and 260#, according to specs I found for this cam. Plus, of course, what I lose during the valve job.
Four questions:
-What pressures will I need for this cam? 6500 RPM, at the most.
-How accurate do the height measurements need to be? It seems getting to the thousandth is unnecessary. But not hard to do.
-The shims on it sit just below the step on the valve spring seat. Assuming I don't run into coil bind, can shims be stacked, or will they walk? I guess new springs are in my future if they can't be stacked to or above the seat step?
-What seals should I use? It's street/strip, not much street, but I'd like a seal that could be used for a lot of miles, if the engine ever goes in that direction. It had umbrella seals on it. They had about .125" clearance from seal to the bottom of the retainer.
I know the shop can do all of this, but I like doing what I can, and learning. It's a retirement project. I've read about this stuff for years, but it's different when you do it yourself!
Oh, and I'm using a Howard's Cams pressure gauge. It seems a bit overkill having a 600# max. I wish I bought something with a lower max. I'm guessing it would be more accurate at lower pressures.
I have it set up on a small drill press. I read that you can use a press, but my press is nowhere near precise enough for this kind of work.
The engine has a 292* .508" purple cam. I don't know what springs are on the heads now. They're single, with a damper.
I'm checking spring pressures at installed height and full lift, just to practice, as I know I'll lose pressure when the valves and seats are ground. I have an installed height mic ordered (More accurate, takes the wobble out of the retainer?), but I'm using snap gauges for now. The installed height on the one I checked is 1.799". Minus the .508 is 1.291". I'm getting 78# and 230# respectively, including the .057" shims that were on the heads. (The engine wasn't too eager to rpm.) Should be about 103# and 260#, according to specs I found for this cam. Plus, of course, what I lose during the valve job.
Four questions:
-What pressures will I need for this cam? 6500 RPM, at the most.
-How accurate do the height measurements need to be? It seems getting to the thousandth is unnecessary. But not hard to do.
-The shims on it sit just below the step on the valve spring seat. Assuming I don't run into coil bind, can shims be stacked, or will they walk? I guess new springs are in my future if they can't be stacked to or above the seat step?
-What seals should I use? It's street/strip, not much street, but I'd like a seal that could be used for a lot of miles, if the engine ever goes in that direction. It had umbrella seals on it. They had about .125" clearance from seal to the bottom of the retainer.
I know the shop can do all of this, but I like doing what I can, and learning. It's a retirement project. I've read about this stuff for years, but it's different when you do it yourself!
Oh, and I'm using a Howard's Cams pressure gauge. It seems a bit overkill having a 600# max. I wish I bought something with a lower max. I'm guessing it would be more accurate at lower pressures.
I have it set up on a small drill press. I read that you can use a press, but my press is nowhere near precise enough for this kind of work.
Why only 6"?
