Proform carbs

[MadBird69]

Any opinions on them? Been running a Holley 770 S/A on my 383 which was on the car when I bought it, but its been nothing but headaches. Seen the 750 Proform at the local speed shop. No choke w/ mechanical secondaries. The salesman says they're great carbs,(of course he will) but I'm not too familiar with the brand. Been looking to replace it with something in the same CFM range... maybe go with a double pumper instead of Vac secondaries. The engine is running a 509 purple cam / edelbrock single plane intake.

 

[george68hemirr]

go with pro-systems.....give patrick a call

 

[MadBird69]

Just an FYI.. Proform carbs - assembled in the USA with the components coming from China. Frig that. I dont do Chinese garbage... especially when it comes to the Roadrunner.

 

[Roadcuda]

Just an FYI.. Proform carbs - assembled in the USA with the components coming from China. Frig that. I dont do Chinese garbage... especially when it comes to the Roadrunner.

I agree with ya on that one but it's getting harder and harder to do with more and more of that garbage coming over here.

 

[MoparErike]

I love my Speed Demon. :cents:

 

[pro-streeter]

Pro Form made in China. Have had problems with just the components using them with true Holley. Poorly manufactured. Also if you are running an automatic do not use a mechanical secondary. Go with vacuum. 4 speed is fine with mechanical secondary's.
Stick with an older Holley. A lot of them out there. 750 cfm vacuum secondary for automatic trans.

 

[zupanj]

What would be wrong with an Edelbrock carb?

 

[Bee Keeper]

What would be wrong with an Edelbrock carb?

Good carbs, I prefer them over Holly's for street use.

 

[68 HEMI GTS]

why by a new carb? tune the one you have.

 

[MadBird69]

Got the Holley running fine now. The thing was very rich at idle, then very lean under power... surging and backfiring. Was pulling my hair out trying to figure it out. Tried different jets, changed power valve, needle and seat, squirter etc.. with little improvement. After all that, the last thing I noticed was that the float in the primary bowl was hanging just a bit... was barely noticeable, but apparently it was just enough. Hung a new float... problem solved.

 

[A12]

Glad you figured it out, it's a good carb IMO. If you were still having issues I was going to suggest (I'll get flamed a little on this I'm sure, but the Nomex suit is still working :biggrin that you try the Holley 670. I'm using the 770 Holley SA on my 440 '69 GTX and had the Holley 670 SA on my '68 383 road runner. The 383 ran GREAT with the 670 SA with a little lumpy Comp Cam, an Edlebrock intake, electronic ignition, stock exhaust manifolds and Dynomax Ultra Flo's. Both cfm's were plug and play on both cars but the 383 got even better playing with the power valve size and the secondary spring.

Thought at first with the 383 about trying the 770 but thought it might not be as responsive on the bottom as the 670. How is it on your 383 with the 770?

 

[MadBird69]

It runs good with the 770, especially on the top end. It's got the 509 purple cam, and an old Edelbrock TM6 (Tarantula) single plane intake. The low end isnt too bad... its driveable, but the thing will take off like a rocket once it starts making power at around 3000 RPM. Been thinking of switching to a dual plane to make it more street friendly.
I had gotten a 670 SA and it was waiting in the wings just in case the float change didnt work. It was the last thing I did on the carb. Thankfully, the new float cured everything, so the 670 got returned to the store.
What size power valve are you using? I've got a 5.5 in mine since I'm getting about 11 psi vacuum, and 72/75 jetting.