honaker

I need the formula to calculate CFM for a 383 that i'm building? :smash:

Ganey

Honaker

A formula is not really needed. Give cam specs. & intake single or dual plane.

:cool:

honaker

Comp Cams 270 with Eldebrook Preformer 2101 dual plane. I intend on grinding a little out of the center plane. Small amount though.

Ganey

Holley 750. You can get a spacer in there.

:cool:

honaker

I was looking at some Barry Grant Demons. Just haven't selected one yet. Trying to figure out which size.

Matt Gruber

it depends on how much HP. 1.6 CFM per HP is a good rule of thumb.

honaker

Thanks man, you have been a great help.

robzr

I highly recommend that you reconsider that intake manifold. I ran a Performer on my 388 and quickly swapped it out for a Performer RPM type intake. In hindsight I would have gone with a Victor Jr. The RPM will fit under your hood easily, as will a Victor Jr.

As far as your carb choice goes it depends partially on your driving style and personal preference, as well as like Ganey mentioned your intake choice. You can go a little larger with a dual plane intake than a single plane without hurting your low end too much. A 750 will get you a bit more top end, while a 650 will help out your bottom end and gas mileage a little bit. So that is personal preference, as is vacuum vs. mechanical secondaries. Seems all the performance nuts go for mechanical.

If you do decide to go with a Demon, and decide on a 750, I have a good deal on a 750 mechanical if you are interested. I'm moving up to a Race Demon, so I have a 750 twin squirter with an electric choke (new in box), a BG -6 fuel inlet kit and some -6 stainless hose to connect to your fuel pump, over $540 new from summit for this stuff, I'll take $400 for it. It's in beautiful shape, I was just taking it apart yesterday to compare it to my Race Demon, and it's even in better shape than I remembered. I'm putting new gaskets on it as well. Email me if you are interested. It was a great carb for my 388. I have a pic on my webpage.

Rob

honaker

Thanks for the input. I'm running with the Performer because of the low end performance. That's my main target area 1000-5500RPM's. It's going to be my daily drive(weather permitting). I'll probaly look into an Airgap down the road. I have had the Performer for a while and have had success with it. I'm currently polishing it myself. Man what a job :eek:

I would like to take you up on your deal for the carb, however, i'm trading in my Holley 1850 and my Qjet cores for a really good deal on a New Barry Grant. It's obviously not a two for one trade, but the guy is going to give me a reasonable price on the cores and a discount on the Barry Grant. :D

robzr

That's cool, good luck on that. If you really are targeting 1000-5500, gas mileage, and a daily driver type scenario, then I would recommend you go 650 cfm on that Demon, for sure with mechanical secondaries.

Rob

gkull

Rob - I also moved up to the 825 cfm Race Demon. It still has a bog during a 1500 rpm power braking at the drag strip if you instantly go WOT. I drilled out the squirters to .045 (Stock was .034) So I just need to play with it. I made 16 passes at the drag strip goofing off and I learned to ease into it at the lights. I got a bunch of 2.00 60's with my old street tires. But I can floor it in lockup 4 gear OD at 2000 rpm and it it just goes. I had my 750 Speed Demon figured out better.

To the poster. The 750 Vac secondary Demon would be a good choice for a mild 383. The 670 Holley Avenger might also work nice.

As far as milleage. I put on nearly 2800 miles in two days of driving and averaged 18.3. So big double pumpers and solid roller motors can get great MPG

79 vette

I would go with a 650 I second that 670 street avenger would work good(elec choke vac secondaries) :seeya

robzr

George - did you get a General Competition? I got a GC, kind of wish I had a RS but they are so expensive at that point it's hard to not justify just going EFI. You'll have to keep me posted on how tuning the Race Demon goes, I will be firing mine up for the first time in a month or two. What kind of times did you run at the strip? That's some real nice gas mileage BTW...

Rob

Nomad78SA

Honaker77,
Checked out your web page and looks like you are doing it up right. I really like how you did a special recognition for those who have helped you out. You are about 3 hours from me so we ought to meet sometime.
I am running a worked over 650 Pro Vac Quickfuel technology carb on my 388cu motor.
I have done a frame off or body off resto on mine and have built it to live in the streets. Mine is a 78 Silver Anniversary or will be when I get it all back together...Keep up the awesome work and vette on
Neil in Tenn