4779 carb replacement

[Tuner]

Take a swing at it, go .076 or .078. Go bigger until it gets better or turns stupid so you see what effect it has on the A/F meter so you learn the approximate range of the IAB's effect. That would have been the first thing to try before drilling things. Change the threaded things first because you can change back if it isn't an improvement. On the plus side. .070 holes in the throttle blades shouldn't tip it over and the cam is big enough it probably needed them. You have enough initial timing or locked?

[Walter R. Malik]

Tuner
I do not have gauge pins over .060 ,so I used a number 51 number drill that measured .070. So the size of IAB would be .070

I am pretty sure that a number 51 drill is .067" ... number 50 is .070".

[amc fan]

Tuner I am not sure of the timing. I believe the owner has the largest stop bushing that came in the MSD kit. Total timing is 34 degrees BTDC. He has no start retard at this time, so you can not lock out the advance. I believe the spark box is a Jacobs "Pro-Street, and I am not sure how to make it retard timing at start up. I tried to find out but no one I know knows if you can do it or how to do it. He is bringing car to my place tomorrow, and I will double check the timing at idle. I can also turn the distributor to 34 at idle to see if helps . I will do one thing at a time when he brings it over.

[Tuner]

Tuner I am not sure of the timing. I believe the owner has the largest stop bushing that came in the MSD kit. Total timing is 34 degrees BTDC. He has no start retard at this time, so you can not lock out the advance. I believe the spark box is a Jacobs "Pro-Street, and I am not sure how to make it retard timing at start up. I tried to find out but no one I know knows if you can do it or how to do it. He is bringing car to my place tomorrow, and I will double check the timing at idle. I can also turn the distributor to 34 at idle to see if helps . I will do one thing at a time when he brings it over.

I didn't meant to be suggesting locking the timing, I just wondered if you had enough initial to be worrying about tuning the carb. The largest MSD bushing should give 18 crank degrees (however with production tolerance it might be 16 or 20). Many engines seem to have a threshold of 18 deg. minimum for acceptable idle with radical cams.

[amc fan]

We put the carb on Yesterday after noon . It seems to be pretty close. I had to turn both primary and secondary curb idle screws out 1/3 of a turn, because it idled too fast. The idle mixture screws are about 1 to 1 1/4 turn out and when you turn them in the idle starts to drop down.