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I have a 76 L48 manual and bought some basic tools to check/adjust the timing.
I read quite a few threads on the forum and Lars papers as well as seen a few how to videos on youtube (no Corvette unfortunately), but I am at a loss here.
Simply put, I cannot get a reading of the timing. The timing mark does not align with the tag whatsoever. The tag actually reads Mr Gasket, I suspect it was a later add on to the car (see pic at the bottom).
I suspect I am missing a very basic step in the process or misinterpreted what I read.
I tried the followings (and others not worth mentioning):
1/ Vacuum manifold disconnected and plugged, rev the engine at 2500-2800, take a reading. I cannot lock on anything, cannot find the mark no matter what timing I dial in.
2/ Vacuum connected, idle (1000 rpm): this is the only setting I can see the mark with, it reads at around 4-8 deg but way off the tag (see red arrow in picture).
3/ Vacuum disconnected and plugged, idle at (now) 800rpm: cannot lock on the mark.
If so, turn the timing light to zero and check your timing at idle with the vacuum disconnected and plugged. The timing mark on the dampner should register somewhere on the timing tab, 4*, 6*, 8*, etc. (If not, the dampner has slipped or you are not hooked up to the #1 spark plug wire.)
If that goes well and you have the advance curve/spring rates correct, turn the dial back timing light to 36* (the timing mark will disappear from view), then have some one run/hold the engine at 2800rpm, while still holding the timing light and pointing it at the timing tab, turn the distributor until the timing mark on the dampner comes into view and aligns with the ZERO on the timing tab. Your done, the timing will be set for 36*@2800rpm, tighten the distributor.
If you then let the car go back to idle and turn the timing light back to zero you can read your timing at idle. It may be 10*-16*, but idle isn't what your worried about. Where ever it is, it is.
You'll probably need to re-adjust your idle speed on the carb. With more timing at idle they tend to idle faster.
36 degrees may be okay for racing engines but it isn't a hard-and-fast rule for street engines as that can invite pinging under a heavy load if the gasoline isn't up to par. I prefer to play it safe and run 32 to 34 degrees at max revs.
Go to Harbor Freight and spend 18 dollars on an adjustable timing light. Set the light to 36 and try it again. Its really that simple.
Using a non adjustable light is fine for stock settings of 8-12 degrees, but when you get into this level of tuning, you really HAVE to have an adjustable light.
The damper can be rebuilt, or purchase another. I rebuilt the original on my car.
I used Damper Doc.
They cut additional degree marks (each 90*, etc). Did a bang up job.
Determine where your Mechanical Advance STOPS. Rev the engine to approx 2500 to 3k and make a note where the timing mark on the balancer stops moving.
Dial your timing light to desired setting. Rev engine to where you noted the mechanical advance stops. Keep it there. Rotate distributor until the timing mark is lined up at zero on your tab.
Lock it down.
36 degrees sounds a bit much to me too. My motor is pretty rowdy and I'm at 33 degrees total.
Last edited by Chinaski; Jun 19, 2015 at 07:21 PM.
So I made a foul of myself... I was pretty certain that I had a point distributor and hence connected the clamp on the #1... But no, 76 have a HEI! So I was on the wrong plug
Without any adjustment, I read 8 deg when idling , vacuum disconnected and plugged, and 27 when at 2600 rpm. There is a bit of room for improvement.
So thanks again for the sanity check, it helped a lot!
No, you are right, they time on #1.
According to my Haynes manual, the factory setting where #1 is differs between HEI and point distributors.
I followed what the manual said for a point distributor.
I did not trace the wires back for my first attempt. I know better now...
So Revi and the others were right, I was on the wrong wire.
I very much prefer that to a slipped damper.
I hope this makes sense.
#1 does not differ, it is still the first cyl on dr. side. you should be hooking up there, not assuming where it is at on the dist. cap. technically, #1 could be anywhere on the cap, depending on if someone ever pulled the dizzy and re-timed it...never trust a picture of where #1 should be, go right to the plug. I have seen people start #1 on the cap all sorts of places...especially when they pull the distributor and disturb the engine, then have to put to TDC and start from scratch...it happens...
Timing: did I miss something?!
