Strange timing issue

[MikeyM]

Hi all,

Happy holidays. In chasing down an off idle stumble in our '69 Bee 383 (Holley 600 80457-2), before I was able to get an adjustable timing light, my initial timing looked to be about 12*. I got the stumble about 99% cured with carb adjustments and the car was responding to throttle input very nicely. THEN I got my hands on the digital timing light in order to set up the full advance with no vacuum and all that fun. I was shooting for 34* due to ethanol, safety, etc. and after landing at 32ish, the initial landed on 14*(Seems to be a MP perf adjustable vac adv dizzy). The odd thing is now the stumble is back... a bit; and I did readjust the carb afterwards. When I aim the timing light at the balancer and then increase throttle, the timing mark seems to retard a few degrees then increase. And at speed, say around 200-2500 RPMs, the timing mark is stable. I've adjusted the accel pump to where the pump arm moves right when the throttle is touched and I have #35 squirters. I was about to change jets to the next size up but wanted to post up here first to see if you guys had any ideas on the timing thing. I was thinking timing chain but the balancer mark doesn't seem to jump around at speed. The Holley was on the car when we got it so I'm trying to work with it so we can enjoy it for a while. The original jetting, according to the Holley site, is 66 and it has 65s in it so I was going to go back to 66s to see if that makes it happier. Anyway, any input you all have is most welcome.

Thanks for the read,
Mikey

 

[Doorkicker]

I've read this several times to make sure I'm understanding you... and i think I'm there. I will say that the marker jumping back before moving forward is likely just the inductive pickup. Each timing light has different levels of accuracy. If it's SUPER consistent, then I would check for a lose timing chain by hand. It "could" explain continued idle choppiness... but the odds are not a stretched chain. How old is the chain/engine?

As for the overall stumble... are you certain the markers (the marker on the cover and the mark on the damper) are in the correct spot?

 

[MikeyM]

Ahh.. good to know on the timing lights. Didn't realize the that about inductive pickup, thanks.

As for the mark on the balancer, etc. it's the original engine with under 70k on it. To my knowledge, it's never been out of the car. The timing cover is stock, so is the balancer and I tried grabbing the balancer by both hands to see if it would spin at all, but it does not. So that leads me to believe that both are seemingly in their correct spots. And I don't, and never have, heard any engine pinging.

Regarding the stumble, the carb has a the stock 6.5 PV in it. I have a 10.5 PV but not sure if that would help as the stumble seems to be in the transition ckt.

Thanks,
Mikey

 

[ruffcut]

I was thinking loose timing chain also.

 

[steve340]

Try a 30 or 31 squirter - can't hurt.

 

[lewtot184]

80457's are lean on the main jets. Big squirters don't work for what your doing. Try a .025 squirter with tubes and a white 218 pump cam in the #1 position.

 

[MikeyM]

Thanks, everyone,

I will give the suggestions a shot. What about going from a 65 to a 66 main jet? Also, I currently have the orange pump cam in there now. Is the white a little more aggressive?

Thanks,
Mikey.

 

[Canadian1968]

The timing mark retarding is the adjustable timing light . I went threw the EXACT same thing with mine. Felt kinda dumb once I figured it out ! Set your new digital light to 0 and check it again, bet it doesn't retard.

As for the stumble . I would try disconnecting your VA and see if it still does it

 

[MikeyM]

Ahh.. good call on the vacuum advance. I'll give it a shot. Will do on the timing light. I think you're right now that I'm starting to remember

Thanks,
Mikey

 

[steve340]

The orange cam is most likely the one you need.