HawkX66

I'll try the piston stop method today. Just for my own knowledge, if I'm getting the LSA spot on, is it possible to do that if my TDC is off? I know some measurements don't rely on TDC.
I'm not sure if the foot is exactly the curve profile of the roller. I would imagine that's what the designers planned on, but I'm not sure.

Mbam

Piston stop is best. The piston slows down near TDC so looking for the highest point and calling that 0 is tough if not impossible.

Set the stop a good distance down. Doesn't matter what it is. Come up on it gently from one direction, note the # of degrees, rotate the other direction until it stops again. If equal than you are good to go. If not move the wheel 1/2 the difference and check again. Repeat until equal from both directions.

You could also do this with an indicator just pick a target height maybe 1/2" down at least but the stop is easier to deal with. One less moving part.

As far as a measuring tool for the best accuracy I would use the actual lifter that is going to be installed. As SB pointed out the foot would need to be the exact radius of your lifters.

At the end of the day a few degrees off does not make much difference.

Tahoe540

I just installed a new Bullett cam that I couldn't get the numbers to match the cam card.

I ended up installing it 6 degrees advanced and it finally matched. I called Bullett and the tech said run it if you have piston to valve clearance.

I also talked to my machinist about this and he said he has seen as much as 8 degrees.

TomZ

iTrader: (2)

Let me know how it comes out. If you’re not happy with the results, we’ll meet up to swap them out.

ICDEDPPL

iTrader: (1)

Cam specs to you should be like tow ratings; insignificant, so just put it in and run , who cares

HawkX66

Wow. 8 degrees off is crazy. I was tempted to adjust it, but I'd rather it was just right from the get go.
Thanks Tom. I checked it three times and came up with basically the same results as the first time. Here was my last one using a roller lifter instead of the tool. I used the piston stop too. PTD clearance didn't change, so my original TDC was spot on.

Ex Opens 47.5*
Ex Max lift .2825" × 1.7=.480"
Ex Closing 3*
Ex Duration .232*
Ex C/L 162*+67*=229 /2=114.5*

In Opens 3.5*
In Max lift .482"
In Closing 48.5*
In Duration 232*
In C/L 117.25*

LSA 115.875*

Here's a couple pics because posts without pics suck.

HawkX66

FWIW, this is my last motor that I built using the same methods. 525hp/550lbft. It gets wound up pretty often in my 69 and has held together for almost 10k miles so far. I built the whole car including the motor, trans, rear end etc. Every single nut and bolt so all this stuff isn't new to me. I know I don't have to convince you Tom. This is just for others to know my background. Using my Lunati Cam card the method I'm still using to degree that cam worked out ok so I'm not sure what's going on with this one. I'm having a hard time believing a GM ground cam is this far off.

TomZ

iTrader: (2)

Can't say anything for GM's quality control. It's the factory cam out of my '98 502 MPI. I know it worked the way it was supposed to. Have you tried messing with the timing?

TomZ

iTrader: (2)

What was you math like on degreeing via intake centerline method?

And are you positive there isn’t something up with your timing set? That part of why we degree the cam. Do you have another timing set to try? Perhaps your machinist has something to try?

HawkX66

Hey Tom. I was over at my buddies machine shop all last night. I'll shoot you a text a little later. Unfortunately the cam is what it is.