Question about stabbing a distributor

[Gaz64]

Originally Posted by Gaz64

All very good info lads.

As others have pointed out the OP needs to check the balancer ring has not shifted by verifying TRUE TDC.

Ken, have you verified TRUE TDC using the positive stop method?

[Ohio Ken]

Originally Posted by Gaz64

Ken, have you verified TRUE TDC using the positive stop method?

Yes pointer and balancer show 0 when I put a rod in spark plug #1 with piston at highest point.
Everything looks right as I have now verified the following.

Dropped dist right on 10*btdc
Mallory mech advance dist has 24* max advance
At 850 rpm times at 20* and at 3000rpm times at 34* so that is 24* plus 10*
I don't think I can get better than that, except for adjusting the advance curve. But I am not racing, just touring the country side with an occasional hard rip through the gears.

In the end, I didn't take into account that the mechanical advance, was giving me 10* extra advance at idle. I bought the car last spring and it ran fine all summer. I never checked the timing until I had to pull the dist to replace intake gaskets
So in my opinion mystery is solved thanks to every one here!
Thanks to all!
Ken

[Gaz64]

Ken,

Seems a little odd that your distributor is supplying 10 degrees under 850 rpm, and yet doesn't reach max until 3000 rpm.

I'd say either a spring is missing/not fitted, or one is broken.
It may have given the result the previous owner wanted, and if you are happy with how it is, that's all that matters.

So in the end, you have 10 BTDC cranking, 20BTDC at idle and 34BTDC at 3000 rpm. If the timing is steady, you have the best of all worlds, low timing to allow easy hot starts, and enough for a quality idle.

http://i155.photobucket.com/albums/s...llory-2010.jpg

[Ohio Ken]

Originally Posted by Gaz64

Ken,

Seems a little odd that your distributor is supplying 10 degrees under 850 rpm, and yet doesn't reach max until 3000 rpm.

I'd say either a spring is missing/not fitted, or one is broken.
It may have given the result the previous owner wanted, and if you are happy with how it is, that's all that matters.

So in the end, you have 10 BTDC cranking, 20BTDC at idle and 34BTDC at 3000 rpm. If the timing is steady, you have the best of all worlds, low timing to allow easy hot starts, and enough for a quality idle.

http://i155.photobucket.com/albums/s...llory-2010.jpg

To clarify it it does not Take until 3000 rpm to reach 34*. It simply does not exceed 34*. As you rev it up it gradually advances . I did not pay particular attention to when it reaches 34*, but I noticed it advancing along with the revs.

[olddog]

I recall you saying the vacuum is a bit low at idle. For vacuum advance to work correctly, it has to change the timing over the range that your cam/engine operates in. More importantly, if you use manifold vacuum (as opposed to ported vacuum), the vacuum advance must be sized to pull in all its advance (hard against the stop) about 2 "Hg less than the engine idles at. If not, the timing will be bobbling around at idle, and the rpm will jump all over. Timing has a very fast acting, major impact on torque and thus idle speed.

A GM engineer named Lars Grimsrud wrote one of the best write ups, I have seen. If memory serves, it was on a Corvette forum. I believe I found a link to that from this site. If you are a do it yourself guy, do some searches and educate yourself, before you start purchasing. If you cannot find it let me know and I will try too.

Good luck with whichever direction you take.