351C carb size

600 vac secondary.

candoo said:

Hello, new around here.

Currently running rich on a 750.

Thanks

Click to expand...

You can try smaller jets.

Yeah, I would say try to tune the 750. That's not too big for a 351C-4v.

BTW, howcome I can't drag and drop the skivvies OFF the Zwinky? Oh, and now you're going to tell me you didn't try.

For a mild 351/auto, that is a touch large. I second the 600 vacuum secondary choice.

What 750? If it's a vac secondary Holley, it's perfect, you just need to take th etime to tune it and tailor the secondaries to suit the engine's needs.

750 is perfect for that engine.
The only way a carb runs rich is by being over jetted.
Jet it down.
Learn the carb inside/out. Read voraciously on how to tune it.
Otherwise you will end up hating Holleys and never get the best performance you can from your engine.

Do you have the MSD running on points or full MSD ignition?
If you still have points, an effective and cheap mod is to pull the Duraspark distributor out of a 351m/400/460 engine at the boneyard and install it into your Cleveland. They never came with electronic and MSDs are pretty blatant copies of the Duraspark.
You just have to make sure the system gets full voltage and you get a good coil.
The stock ignition feed wire is a resistor and must be bypassed or replaced.

Good luck
Dave

Edit: Make sure you don't have a blown power valve.
This is a common problem on Holleys over 10-12 years old.
Since then Holley has added a PV protection circuit.
If your carb does not have one, save yourself some grief and add one.

Edit2: I see now that I thought you had a Holley.
You don't actually say. I got the impression from later posts.
If you don't have a Holley, disregard my post, then GET ONE.

750 can easily be made to work well on a Cleveland.

Here's my thinking: there's a big difference between "can be made work" and the right carb for the application. For a mild small block with an automatic trans, driven only on the street, an 1850, vac secondary Holley is a MUCH better carb. My wife's 427 Corvette runs a 650cfm Holley and delivers 17 mpg. With the 750 that was on it when she bought it, we got 10-12, amd I honestly think it runs better with the smaller carb. But to each his own...

I have heard that Holley 750 vacuums don't actually flow 750, more like 650. No knowledge if that is true or not, but I ran a 750 vacuum on a stock 351w for years until it was time to do the motor. Got 16-17 on the highway. This was a carb right out of the box.

I know lots of guys like larger carbs, heck I've done it myself and in fact currently have a pair of 390 Holleys on my 302. But as a rule, I've found smaller carbs work better on the street. They improve low-end response and mileage without really hurting top end enough to notice on the street. Now if we were talking drag racing, I'd suggest an 850 Holley for a 351, since drag racing tends to favor more of everything. But with tight converters, freeway gears and a stock cam, a smaller carb will work better.