I've got two problems on my newly started engine, so I break them into two differant threads.

My cam is a Comp Cam 286H. With the vacuum advance disconnected the timeing is set at 12*. When I connect it it goes to 15* with manifold vacuum on the vacuum advance. When I advance the throttle the timmeing mark doesn't stop moving to around 56*. I'm running a brake booster. Could this be taking all my vacuum? This just doesn't sound right.

I just did a vacuum check on the engine. I've got less than 5" of vacuum, which the guage says "late valve timing or leak at intake maifold". I'm wondering if I got the gear drive install on the wrong crank keyway or the cam gear a tooth off?

You have too much mechanical advance..maybe the bushing is worn.At what rpm is 56* ?

I don't have my tach installed yet im still working on the interior. I'm guessing around 3000 RPM. I'm not using a bushing. I think I have the crank gear on the wrong keyway. Too retarded maybe.

Ok that's it, I've totaly lost my mind now. I pulled the timing cover and check it out. The marks line up at 6:00 on the cam and 12:00 on the crank. BUT the distributor is 180* off. I've never seen an engine run with the distributor 180* out. Has anyone else ever heard of that. It's time to start banging my head against the wall.

You need to limit your mechanical advance.
No, the booster is not stealing all your vacume.
Try moving the vacume line to the carb vacume port. but, more importantly, your mechanical advance is goint too far.
This is why I bought an MSD billet distributor.
I can control that.

Dave

Dave, I think I figured it out if you read the post above yours. I never thought an engine would run 180* off at the distributor but this one will. Anyone else seen this before?

With your marks lined up are you sure you are on the compression stroke on #1

yep, If you think about they have to be on #1. The crank has a keyway in it to line up the crank gear and the cam has a dowel pin, and the marks are lined up. The mark on the balancer is pointing at TDC.

With the dot on the cam gear at 6:00 and the dot on the crank gear at 12:00, #1 cylinder is on TDC of the exhaust stroke. #6 cylinder will be on TDC of the compression stroke.

Not enough initial timing for that big a cam and way to nuch total run it like that and kaboom
keep the vacuum advance disconnected and plugged till you get your initial and mech timing dialed in. You should probably have 15-20 degrees initial
if the starter will take it the more the better for low end trottle response.
once you have that limit your mech to 36 degrees
meaning your init. + mech = 36 all in buy 3000 if the car seems to be be sluggish try a 2 stage mech advance
Then you can put some vacuum advance to it around 44 give or take if she pings for secound when you step on it's too high.
mech advance that's what I run on my 68 427 velle
Good luck with her

Originally posted by Fuji:
With the dot on the cam gear at 6:00 and the dot on the crank gear at 12:00, #1 cylinder is on TDC of the exhaust stroke. #6 cylinder will be on TDC of the compression stroke. Chris is exactly right. With the cam marks lining up as you said, the rotor should be pointing at the #6 tower on the dist cap.

Also, cam timing and ignition timing are two seperate animals and have no effect on each other. It sounds like your problem is in the distributor.

I have the same problem,I went back after reading some books ,and verify everything and it was what Chris "FUJI"said 6:00 and 12:00 o;clock ,#1 cylinder is on TDC on the exhaust stroke and cyl.#6 will be on TDC of the compression stroke .
Take a deep sigh graemlins/beers.gif

Ok now, the more people post the more my mind is getting screwed up. I've always belived the marks should be 6:00 and 12:00 and the rotor pointing at #1 plug wire. Where mine is pointing toward #3 & 6.

Line up the dots, and the rotor points to #6. Yup, that's right. Engines do not run with the distributor 180 off.

Your vacuum gauge is "calibrated" for stock, mild cams. With such a cam, very low vacuum could be "late valve timing or leak at intake manifold". You aren't running a stock cam, though. That cam is going to reduce vacuum at idle. The question is "how much" should it be reduced.

You "may" not have too much mechanical advance, either.

You say you go from 12 degrees to 15 degrees when you connect the vacuum can to manifold vacuum. Fine, you have very little vacuum at idle, therefore very little vacuum advance.

When you rev the engine, you build a bunch of vacuum, so both the mechanical advance and the vacuum advance are moving the timing. 56 degrees is not out of line for a stock distributor curve, I've seen more on other, mild engines.

What is important, more or less in the order you need to check: 1. Maximum advance of Mid 30's at around 2500-3000 RPM with the vacuum unit disconnected. Assure that there isn't MORE advance at higher rpm. 2. Assure that the initial timing is such that the engine will idle and start easily with the vacuum can connected. (Hint: use manifold or ported vacuum, whichever works out best for you.) 3. Assure that you have about as much vacuum advance as the engine will tolerate WITHOUT part throttle pinging. Enjoy!

Being that this cam is not that "wild" I don't belive it would gobble up all of my vacuum. I get less then 5" at idle and 12* of initial timing. I can get almost 10" of vacuum but the timing is turned up to 30* of initial timing.