Holley 600cfm on 350V8

[regal1973]

I have a 600cfm square bore vac sec on my 350 Buick the mtr has a 40tho bore with a mild torque cam,shift kit in the 350 turbo auto & stock 2.73 diff gears.
The problem I'am having is trying to work the jet sizes out currently they are size 66 that comes with the carb from factory. I'am finding it bogs down when I floor it & lots of black smoke pumps out the exhausts then the car goes very well & on long trips it runs smooth only if I boot it seems to pump to much fuel in. The carb is new as the guy from work I bought it off fitted a 750cfm on his 351 Cleveland & had the 600 that he sold to me for a very reasonable price.
Would fitting smaller jets only fix the bog down & how many sizes would you normaly try without spending a small fortune on jets & gaskets.

[69GSCAL]

Set the float level and check your fuel pressure before changing jets; both of these have a large impact on way your engine runs and it'll be impossible to get teh correct jet combination with a problem in one of these areas.

[71stage1conv]

Why run a 600 cfm when Buick put 700cfm Qjet on the higher performance 350's, and many of those upgrade to the 750 cfm that came on 455's?:PUZ:

[TXGS]

I agree with a larger carb, however I drove my car with a 600 edelbrock for a few years. It functioned fine and was good for economy. Save your pennies and upgrade a little later.:BEERS:

[gsdave]

A few years back I had a 72 skylark with a 350 2 barrel motor, I put a stock 4brl intake and a carb off a 69 430. After some tuning with the float level and secondary adustments the car ran awesome, you do not need to spend big money on carbs. The car got 17-18 mpg on the highway doing 80. Get the buick gs facts and figures book by steven dove. It has many great tuning tips on the 350 and 455. Just because this carb might have ran good on a ford doesn't mean it is dialed in for your Buick.

[regal1973]

Get the buick gs facts and figures book by steven dove

I will look into getting the book thanks




Why run a 600 cfm when Buick put 700cfm Qjet on the higher performance 350's, and many of those upgrade to the 750 cfm that came on 455's?

Mate I thought the 600cfm was to big for the basic stock type SB Buick mtrs. What size was none performance carbs? I only brought the 600cfm as it was new and very reasonable in price & I had fitted the old Buick Qjet onto my Holden V8 ute to sell it while I was building the Buick up.

[TXGS]

The factory carbs are 750 Qjets. I have a performance 350 and run an 850 Demon. Buick 350's like fuel.