JoeRags

Hi all,

I currently have a 383 being built for me at a local shop. I have a Speed Demon 650 that is next to new off my old 350 that I would like to use on the new motor. I am not familiar with carb modifications at all. What should I do? Will this carb flow enough for thid motor?

Thanks

LAvetteman

I would go with a 750 on a 383.

The Dude

Or an 800.

Lohkay

I think you need to change carbs... jetting will only let you set how rich/lean your engine is. Unless you have one of those fancy carb where you can change the sleeves.

Jasonty

I use a 650 on my 383, and it works fine. There's a calculator on the web somewhere, and for my displacement engine, it said to use something near 630CFM... 800 is waaayyy too big for a 383, and with a 750, you're going to have tuning issues trying to make it work.

Brettmc

Brett

C3w4sp

The 650 Speed Demon is proving to work just fine on my 383

Jasonty

What? Seriously, 800 is too big for a 383. Unless there's some serious horsepower output from that engine... But I'm curious, tell me what's on your mind...

MEAN72

carl a

i was running a 750 on my 383 and it was too big , i switched to a 670 street advenger and i feel its still to rich- the walls in my garage are black with soot from starting the car in there with the 383-with the 750 and i still notice a lot of black carbon from the 670 too

The Dude

The short answer is that's a TUNING issue, not a sizing issue. But don't take my word for it.

Paging Dr. Grimsrud. Dr. Lars Grimsrud to the C3 Forum...

Brettmc

Yup. Lars has proven this time and again. Read some of the past posts on this subject.

I'm now in the process of tuning my 850 with an O2 sensor. Details to follow.

Brett

comp

your jeted to rich, if it's "sooting" your garage

81ZZ4

650 is way, way too Small
Volumetric efficiency dictates a 650 for an average engine.

If it's just a 383 with meduim performance heads, mild cam your ok...
other than that you need larger or I'll spank you with my 350 with a 750 Holley