351 cleveland carb choice?

[redmach69 10]

Hey guys, I have been taking the hot rod stuff ( msd, headers etc.) off my Mach 1, it has a 70 model 4v Cleveland with a slightly bigger than stock cam in it with an Edelbrock intake and a 4 speed. It hade a 780 no choke double pumper Holley on it, I kept the intake but put a new 600 electric choke Holley on it. It runs beautifully at idle or reving up with no load on it, however when I drive it when you let the clutch out, or you come to a rolling stop or some thing like that, it feels like the engine is lugging. You know, like you leave it in too high a gear and give it more gas, sort of bogs around until the revs come up. My question is do you think it could be the carb is too small because of the cam? It is timed and tuned correctly, as I said it runs beautifully sitting still, the choke performs great. It idles around 900 with the cam and if you downshift and keep the revs up, it doesn't have a problem except in 1st when you let the clutch out. The non stock cam is all I can think of, opinions?

[LoneWolf2U 136]

:blink:... You take the free breathing items off of it and choke the flow down without changing the cam and wonder why it doesn't want to run.

What style of Eddy intake?

As you state it runs good in upper rpm band which the C likes to run because of the large ports.

The 600 is small but will work, a 750 vs may be what it needs to help lower end power. Are you using a spacer under the carb?

A 1" four hole spacer will also add to lower rpm power.

[Chris'69Mach 23]

I have the same engine, 1970 351C 4v and dropped an electric choke 770 Holley 4bbl with secondary vacuum assist with a 1" spacer and she loves it. I idle right at 750 rpm and am getting just under 11 mpg even with putting the foot in it.

 

I am seriously sure the cleveland would also handle a 850cfm carb with no issues at all.

 

The 600 you have on there is seriously limiting your Cleveland.

[70Mach03 12]

A manual will let you get away with a little more carb plus you got a cam which likes bigger carbs also. I've got a Holley Street Avenger 670 CFM on mine and kinda wish I had gotten the 770 CFM instead.

[RogerC 136]

http://www.1969stang.com/mustang/forum/showthread.php?t=13733

 

Post #6 dude

[redmach69 10]

Thanks to those of you with constructive comments, I think as you indicate it is the nature of the port size and the cam that I need a larger carb. I am leaning toward the Holley 770 single inlet that would externally be the same as the 600. I have a 1/4 inch phenolic spacer on it now, the only reason I didn't use a thicker one was I am using a stock air cleaner, and was concerned about hood clearance.

Thanks Again!

[69shelbycoupe 11]

It has been proven time again that a cleveland likes a bigger carb. Even stock just bolting on a 750 carb is a good upgrade. It should have been a stock size carb any way. With your intake and cam in my opinion a 750 is a must. I have a Weiand X-celerator intake with the magnum 292H comp cam and I am running an edelbrock 750 carb