convert 750 to 650

[rubbinsracin]

ok guys, i run a 4150 750 on my 602. Has worked good for the most part but i am hearing i am giving up alot buy not running a 650.

i have located a 4777 650 main body and was wondering if all my stuff on the from the 4150 750 would bolt right on to it. the 650 main body is bare, so literally everything would have to be bolted on to it.

is this doable?

[DaveBauerSS6]

Metering blocks are not the same. Will bolt up, but A/F will be junk. Butterflys are different on both carbs, I have'nt done it, but you are changing transition flow out of boosters thru venturi and thru butterflys. That's a job for a flow bench and dyno. Drag guys changed 750 body and 850 base plates, but with proper testiing.
I wouldn't chance a motor for it.

[50j]

650 and 750 have the same butterflies i believe, and 850 is bigger. Still won't run right like dbss6 said.

[DaveBauerSS6]

650 and 750 have the same butterflies i believe, and 850 is bigger. Still won't run right like dbss6 said.

Correct, thanks. The base plate could interchange if the air passages match. Venturi diameters are different.

[dynoman14]

Not a bad deal to do if you know a little about carbs.

Both carbs need to be 4 corner idles so you will have to line up the idle holes in the baseplate that come off the transition slot that is cut into the baseplate.

If your 650 has those provisions you can swap the baseplate over to the 650.

Now all you have to do is swap the metering blocks and bowls over.

Both should run ok with the same jets as a 72-76 is a common range.

If it more than you want to handle, I can swap it for you for labor and a gasket kit, and I will run the first dyno pull on it for FREE on the 750 and then the first dyno pull on the 650 for FREE just to make sure it runs ok and is making good power. You have to send the 750 as is and the 650 body, prolly $25 shipping. Basic clean and re-build runs $125 and I'll swap in the center section for you for FREE. Any additional dyno pulls to make power run $25ea.

While I am at it I can match the carb to the burn curve of your fuel if you let me know what you are running. Takes about 4-6 pulls to get jets, air bleeds and PV right, if you want to change metering blocks it is a little more.