Summit 8600 and edelbrock timing set

FullSizeJeeper

I'm still working on this vavle timing issue. I've got a summit 8600 cam in my 74 360. I'm using in edelbrock roller timing chain. It has options for standard, 4* adv, 4* retarded. I'm definitely retarded on the vavle timing. I was going to degree the cam this weekend, but I'm having a hard time getting a degree kit in Anchorage. Summit can get me one for $150 including S&H. But I'm wondering if it will do me any good. My concern: if I can only set this at three positions with the timing set, what does degreeing the cam get you. Yes it will tell me exactly when the valves are openning, but if you can not advance the cam to this point, then you know where it should be, but can not get there. Am I missing something? Can you adjust the cam other than using the different crank keyways? The summit tech guys did not have a timing set with more options than the edelbrock set. Does anyone have other options?

82Waggy

How did you determine that the cam is currently retarded?

FullSizeJeeper

Low vacuum throughout rpm ramge, running hot, when you crank with vacuum gauge on Manifold vacuum, it is less than 5"hg and unsteady. It wants to time out at 29* BTDC initial, 50* total, to run. If you get down around 10 to 12 it sputters and coughs out of the carb on WOT. Had several mechanic friends look at it and that seems to be the common thinking. My plan was to degree it where it is at, then go to the 4* advance setting and degree it again. THe main thing is getting that timing to around 10 to 12* BTDC. I do not want to tear into the front cover mulitple times!

tufcj

What kind of shape is your harmonic balancer in? Make sure that it's on the 0 mark when the piston is at TDC. I've seen them slip 10-15 degrees. It makes you think you have all kind of problems that you really don't. Bob tufcj

FullSizeJeeper

I was going to do that when I degree it. What is the most accurate way to do this. I can go to TDC with the plug pulled, hand turn some more and see if comes up further. Or better, put at 20* BTDC and turn it through TDC and watch through the hole. Any better ideas?

82Waggy

FullSizeJeeper wrote
I was going to do that when I degree it. What is the most accurate way to do this. I can go to TDC with the plug pulled, hand turn some more and see if comes up further. Or better, put at 20* BTDC and turn it through TDC and watch through the hole. Any better ideas?

Yes. What you describe above could be off quite a bit.

If you are not pulling the heads you should use a piston stop that screws into the #1 spark plug hole. Rotate the crank clockwise slowly until the piston touches the stop and then mark your balancer at the TDC pointer. Now rotate the crank counterclockwise until you hit the stop and mark the balancer again. Split the difference between these two marks to find TDC on the balancer. If this does not line up with the timing mark on the balancer you know the balancer ring has spun and should be replaced. You should check new balancers for correct mark as well.

FullSizeJeeper

To update this thread, found the problem, not vavle timing :? . The polarity on the pickups in the MSD dizzy were reversed! Took a timing reading the way it was, was at 20* BTDC, switched the leads from the dizzy to the digital box and jumped up to 30*+ adv. MSD says with a digtal box the most adv reading is the correct polarity. (With an analog box the most retarded reading is correct). Also checked the dampner as per above. It was off an additional 7* or so. I remarked the dampner at the true TDC and timed it at 10*. After tuning it, it really likes about 11* inital at 650RPM in drive. Now I'm getting 12-13"hg in drive and 15"hg at idle at 850RPM. Now for some carb tuning, another 700-800 gentle miles and she should be ready for the mud. :evilbat: Well, I'll probalby due a final full compression and adjust the rockers one last time if need. P.S. check out the cam degreeing idea in a new post! 111!!!

82Waggy

Since you have determined the damper has spun, you should make a close check of the rubber and seriously consider a replacement.

http://www.americanpartsdepot.com/

Has new strock replacements for about 150.00.