It isn't bad with the heads off to turn over. Yeah, starting over in few minutes. I will look at the Comp method. Looked at Lunati, Crane and Erson as well.
Degreeing my Performer cam
- Thread starter olds307 and 403
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565bbchevy nailed it, just by running the piston tot the top you still have maybe 10 degree of crank rotation as the piston stays at the tdc before rod pulls it down, thats why its important to turn engine both directions till piston hits a stopper and marking what the degree wheel says, then split the difference, if one direction shows 10 degree and the other way is 8 then you would move pointer to the 8 or 9 degree mark on the 10 degree side, then rotate engine again and it should be the same on both sides, if not redo it and fine tune it, so now the zero is your true tdc. I think this is right, youtube can be helpfull too
Tried my best to get an accurate TDC on the wheel. With the stopper and sitting on the floor, I can see when the piston fitst hits it. I adjusted the wheel a couple of times, I think it is close to right. Not so easy to do. Ok, so I calculated the intake centerline. I found maximum lift and put the dial on 0. Went .050" clockwise then around till it hit .050" again. I got 153 and 62, 215 together divided by 2=107.5 ICL. The cam spec is 106 ICL. I still get 10 degrees advanced on the intake opening point, cam card says 4 ATDC.
You need a piston stop - basically a plate that bolts to the block such as https://www.amazon.com/dp/B003QYHETC/?tag=gbody-20
Once it's bolted onto the block with the stop hitting the piston approx 1/4" from tdc. Then spin the engine in one direction until #1 hits the stop (record the number on the wheel), then spin the engine in the opposite direction until it hits the stop (record the number). During this process it doesn't matter where the degree wheel is set to. Then calculate the difference between the two points and divide it by two, or remove the stop and spin the engine to the exact middle point between your two previously found marks - you are now at TDC. Reposition your wheel and/or point to identify this new position as TDC.
I have a homemade stop with a 3/8" bolt threaded into it. In the link I attached it's the blue piece.
This also can be down with a magnetic base and dial indicator as well.
This biggest issue for me that creates inaccuracy is not having the stop or dial indicator needle directly above the wrist pin.
Once it's bolted onto the block with the stop hitting the piston approx 1/4" from tdc. Then spin the engine in one direction until #1 hits the stop (record the number on the wheel), then spin the engine in the opposite direction until it hits the stop (record the number). During this process it doesn't matter where the degree wheel is set to. Then calculate the difference between the two points and divide it by two, or remove the stop and spin the engine to the exact middle point between your two previously found marks - you are now at TDC. Reposition your wheel and/or point to identify this new position as TDC.
I have a homemade stop with a 3/8" bolt threaded into it. In the link I attached it's the blue piece.
This also can be down with a magnetic base and dial indicator as well.
This biggest issue for me that creates inaccuracy is not having the stop or dial indicator needle directly above the wrist pin.
I already have a stop, a paint stirrer with 2 7/16" holes and a 3/8" bolt threaded in the center, works very well. I did that with the numbers for 0. This cam is known to bled compression, I will probably put it in the advanced position. The dots line up perfectly with TDC.
If it is not made of steel I feel this would flex when bumped and give an inaccurate reading.
I can actually see it hit and flex slightly at TDC. Olds pistons sit about .025" in the hole and the 14cc dish let's me see into the cylinder very clearly for making contact. Is it flexing the issue? I can thread it in a bit more and maybe copy it in metal.
Flexing is an issue, the stop has to be designed so it actually "stops" the engine from rotating.
My BBC's pistons all have domes so my stop has to go across the flat portion of the piston to have a solid stop.
I have a similar stop to the one posted earlier and it works well and has a lot of adjustment to it.
It might explain the 10 degrees advancement on the ATDC on the intake number at .050". See what I can do.
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