Im not sure if this will help me as our fuels might be different between the US and Australia. I am runnin' 91 at the moment no probs, standard 292 motor B manifold with 600 Holley.

We know they are a little bit big to run on these motors and there is a flatspot , Just wondering what the average main jet size people are running? I have in that the moment 67.  Plugs look at little dark , I was thinking about coming down a couple of sizes and then change the pump squirter and then cam blokcks to try eliminate the flatspot.



"Came too close to dying to stop living now!"

What’s the list number on your Holley?  With there being at least a couple of dozen different 600 Holleys over the years, jetting varied in their as delivered states due to specific air bleed and PVCR sizes as well as venturi booster design.  The baseline number is always what the carburetor was supplied with when new and then adjust up or down from that point.  With alcohol laden fuels here in the U.S., increasing the jet sizes is normal just to compensate for the reduction in BTU’s of the alcohol and to keep the engines from running on the lean side.  Quite a few of the stock 600’s Holleys do come with 65 & 66 primary jets so #67’s is not out of line and especially if the quality of the fuel or the BTU content is low.  Many of the earlier 600’s came with a #25 shooter but many of the newer ones now come with a #31 shooter.

 

Between accelerator discharge nozzle sizing and pump cams, I’ve found the pump cams to be a much quicker solution to eliminating hesitation issues.

Lorena, Texas (South of Waco)

Ted, If I remember its an odd number like 3298 or 9832 ? Had a play yesterday with it . The pump was a 31, so I went for a 35 to try, went well. As for the main jets, had in 67 and was fine made a real nice note when the foot was down! tried a 65 and that to was fine didnt seem to be down on power or anything, however it has made the flatspot harder to eliminate, richening up the idle mixture helps however that makes it feel "fat" on the takeoff. So I need to sort out the pump cam as you say and that will get it damn close, I have a pinkish colour in at the moment and I have tried 1 and 2 positions 1 is good for stop the start 2 is better for a rolling stat eg; going round a roundabout..

Any ideas on pump cams??



"Came too close to dying to stop living now!"

Just an update for anyone wth the Holley 600 situation... I am runnin 64 main jets [so far] and have gone up to a 35 squirter and am using the heavy "blue" cam for the pump which I  can only get on no. 2 possition. This is working well and I dont need to much throttle to get her going. Fuel economy.. well ..??? I dont think these heavy ol' busses get fuel economy do they??



"Came too close to dying to stop living now!"

I pulled the plugs to have a look as its been running like this for a while and they look ok.. bit fluffy around the edges but I have only been doodering around, so has to be close



"Came too close to dying to stop living now!"