Need Opinions. Have nothing to compare to.
Thanks Mattax. Lot's of good information you provided. Carburetor is the Barry Grant pre-Holley double pumper style design, not the new "Street Demon" square style carb (Edelbrock style). I have not been able to find any numbers on it to find out exactly what it is. It looks like a Road Demon or Speed Demon. It has a choke horn, but no choke installed, and mechanical secondaries.
To answer some of your questions:
Perfect. Only suggestions are to note RPM at initial timing, and if to plug the vacuum hose with a golf tee or similar (if you haven't been).
13* at 600 or 800 rpm would be good for a stockish cam.
With a hot cam, the engine will probably like a bit more advance. With a manual transmission, its harder to test idle under load. OTH its not as important. But if its a little 'lazy' or wants to die when you gently slip the clutch, these suggest a little more initial advance would be good.
Try 15* or 16*
Yes, vacuum ports were capped off while checking initial and full mechanical advance at 2600 (33*) RPM was about 750-800 RPM idle while checking initial.
Agreed. This advance canister must be adding 4* at 13" of vacuum. Going to ported vacuum for the advance control as you've done is generally the easier and better approach for a hot rod. (But in some situations it turns out that it is better to use manifold source. The right way is whatever the engine wants. :) )
Actually,... the vaccum advance was connected to the ported vacuum when I bought it, but it didn't run as well this way and ran hot. I have it connected to full manifold vaccum port now. It seems to run better and it is running cooler at idle and cruise now.
Need to know the vacuum as well. Then if you plot out the mechanical advance curve so you have the timing w/o vacuum at 2600, you can figure out the vacuum advance contribution.
Another way is to use a hand operated vacuum pump (eg Mityvac) while the engine is idling.
I will have to get a vacuum T so I can check vacuum at ported vacuum port, but I know the mechanical advance is at 33* without vaccum attached, so wouldn't my ported vacuum be contributing 4* at 2600 if the total timing (when connected to ported) was 37*?
a. Driving at a steady highway speed (with rpm between 2000 - 4000) note the max engine vacuum.
b. Back at the shop, set up the timing light and a vacuum pump attached to the vacuum advance. Bring the engine to the 2600 rpm and the vacuum pump to the vacuum found in step a. See what the timing is. For an B or RB engine, they recommend 56*. Adjust the vacuum pod as needed.
I will do this and see what we get. I can get a longer vacuum line and bring it in the car to see what the vacuum is while running 2500 rpm down the highway (60 mph Cruising speed)
If that's a steady full throttle pull in 3rd (or 4rth), the fueling doesn't look right to me. It should be much flatter, staying within 12.8 to 13.2 AFR on racing gasoline and probably a little richer on street fuel.
Yes,.... That was steady full throttle pull and was done in 3rd gear. Fuel was 91 octane with NO ethanol from local private party full service station.
I will check into the rest of the things you suggested as weather permits. It has been holding right around freezing temperatures here so I don't want to mess too much with tuning right now.
