Originally Posted by Sieg (Post 468648)

Back to business..........

I fiddled with the fuel screws and throttle positions and obtained near 12" vacuum at 1K rpm which is as good as it gets with this cam IMO.

Throttle response right off idle felt good actuating it by hand. The initial timing was 13-14* with 21* mechanical. I decided to experiment with initial timing and see how the motor would respond. I bumped it to 15-16* and immediately had a big flat spot right off idle. WTF? Dropped it to 12-13* and still had the flat spot. Put it back to 13-14* and the flat spot was still there......I managed to create a flat spot without touching the carb settings, just changing the initial advance. :headscratch:

I list timing as 12-13*, 13-14*, 15-16* because that's what it is when locked down.

I've had subtle doubts since this motor went back together...........something hasn't seemed quite right and this latest issue is supporting my suspicions.

Gear drive or distributor possibly creating issues?

Originally Posted by Vegas69 (Post 469318)

Did the engine temperature change? That amount of timing shouldn't make much difference to a bog. You aren't going to tune out a stumble with idle mixutre and transfer slot. It's time to start playing with accel pump cams.

Originally Posted by intocarss (Post 469324)

When you give it gas right off idle, (bog) does it cut out or does it blubber then catch?

Originally Posted by Sieg (Post 469327)

Big flat spot (as I'd call it) no blubbering, then it's fine. If I rev it and don't let it come all the way down to the 1K idle, say 1500 rpm, and crack the throttle it's fine. This has all been while actuating the throttle by hand.

Originally Posted by Vegas69 (Post 469331)

One degree of fluctuation isn't worth thinking about. Battery voltage or a slightly different signal to your light could easily cause the difference. You can verify the timing is reacting properly with your timing light. If it is, I'd rule it out. Especially if the drivability problem is present. A fully warmed up engine vs. colder engine absolutely will change a stumble. Everything I advise you is from experience.....

Originally Posted by intocarss (Post 469341)

Then I agree with Todd's posts.

Blubbering = to much fuel

Dead spot = not enough fuel. ie squirters or accelerator pump or cam. Is the accelerator arm adj properly?

You could try and push the primary accelerator pump arm almost all the way down by hand just as you crack the throttle from idle or a split second before, which will send a bunch of fuel in. If it doesn't have a dead spot then this will tell you it's lack of fuel right at the hit. Just and old school trick. YES eng temp can effect and or make the stumble too

Originally Posted by Vegas69 (Post 469384)

Mine came with Pink as well. It's for drag racing and absoutely horrible for throttle response. I'd jump up to orange as it delivers better volume on tip in..... I'm pretty positive that's the cam I used.