Surge at steady speeds

[Mechanic No. 4]

Hi guys. I have a '67 GTO currently with a 7029262 Q-Jet that surges at steady speeds. Let me say from the start that I know that my engine builder made a poor choice of cam selection, but it's what I have to work with at least for awhile. Its specs. are 227int. dur., 241ex. dur, 107 lobe separation. I have the rest of the specs. if needed. Running a 408 cu. in. with 9.5:1compression and stock #670 heads. Current carb calibration: Idle tube .0370, Idle down channel .059, Upper idle air bleed .070, Lower idle air bleed .070, Idle bypass air .101, Primary jets #74, Primary rods 36B, Secondary rods CV, Secondary hanger O. I'm running 41 degrees total timing and 26 degrees base timing with no problems. I plan on ordering a HP rebuild kit and throttle shaft bushing kit from Cliff, but I really could use some calibration suggestions for jets, rods, air bleed sizes, etc. and any other suggestions you might have to make this combination work as good as it can. Once again, I'm very aware this cam is not the best choice, but it's what I have to work with.  I also have a 7941264 missing the internal if needed. Thanks for your help guys!

[Cliff Ruggles]

That "recipe" is a DISASTER for that carburetor part number.

Call me at the shop when you get a moment and I'll put together a custom high performance rebuild kit with tuning parts to nail that thing down for what you are doing. 

I'm here 7am-4pm M-F EST.

740-397-2921

It's NEVER going to work well like you have it set up now.....tks.....Cliff

[Mechanic No. 4]

Just got my car out of storage and am looking forward to installing the calibration kit Cliff provided. However, the replacement upper and lower air bleeds need to be installed and drilled to size. Any recommendations on sizes and the two required tap sizes needed to install them? Can't wait to get it up and running! THANKS!!

[Cliff Ruggles]

The lower IAB's are fine at .070"

You need to reduce the upper IAB's to .046". 

Idle tubes are fine at .037", DCR's are too big, I'd reduce those back to .052" and see how it works?

All the screw in bleeds I supply are 32 pitch threads.  They will be either 6-32 or 8-32.  You'll have to decide which ones to use in which location based on the hole size once you remove the original brass cup style air bleeds.....