401 nailhead and 2x4????

Toying with the idea of running 2 afb's on my 401. I have the 6x2, but not sure if i want to go that route due to maybe selling the truck in spring. I want to do something other than the single 4bbl on it now. my question is what size afb's would be best? bone stock '66 401 with lakes headers, 4 speed trans, 3.55 rear, in a light 31 chevy truck if that helps.

 

I used the aftermarket carter afbs on my 65 Riv and I believe they are 650's. I like it alot. I find the nailheads like alot of carburation,..helps them breath better. Let me know if you ever want to get rid of the 6x2!! Thanks, Dave

 

Eightbanger is right...nailheads like the cfms.
The afbs on my old nailhead were 550 ea I think. It needed more. That was running that ****py flowing Offy manifold.

 

Run (2) 500's progressive.
I've used that set-up twice and they ran good and even got decent milage.

 

Craig,
you had a built motor, mine is stock. i miss seeing your T!

 

Me too sometimes.

 

As mentioned by CAS, the offy intake doesn't flow worth a ****.

Spend the extra money and get a dual quad Riv intake.

 

A stock Nailhead will want at least 2 500's on a dual quad set up and will take two 600's no problem. The offy's **** though they can be ported to make them decent, You're much better off with a factory dual quad manifold. The best of them is the Edelbrock B262 but those have gotten way expensive.

 

who else made a 2x4 intake? offy (bad) edelbrock????

 

I'm running two 500 cfm Carter AFB's for 5 or 6 years now on my 401 and it runs great with them. I even had to go to a much larger metering rods from what they came with, to reduce gas flow when the secondaries open up. I've always heard nailheads need a LOT of gas, but my set-up works well for me and I'm getting 15 mpg......if I keep my foot out of it.

The car is a '55 Special with a '62 401, B-W Super T-10 close ratio 4-speed, 3.36 gears, Offy intake, and a Poston (NH-400) cam .486" / .495" lift 272°/282° duration and 2000-6000 rpm power range.

 

The Edelbrock B262 is awesome, but they're going for over $1k on eBay.
The stock dual quad is a good one. I've seen a Weiand before but have no idea how it ran. If you can get an Offy cheap you can always port it... I've been wanting to Extrude Hone one for a while...

 

have you done this? just wondering in case i find one and need some guidance...

 

There was someone I thought that was on here that ported an Offy for a Nailhead, it may have been ahotrod. I did one that was mostly clean up and port matching but I couldn't really get to where I wanted to deep inside. I haven't had a chance to extrude hone one, and it is a bit pricey, haven't really had anything extrude honed in the last 10 years, maybe the price has come down, now I need to look. But it was doing wonders for the manifolds on 5.0 Mustangs (intake and exhaust) and they still looked bone stock....

 

I went with two 600 cfm Edelbrocks on a high rise Offy. As mentioned, the manifold took a lot of work. If you go with the Offenhauser, you'll also need straight linkage (the back runners won't feed the front cylinders if you start off the first carb). I dyno'd mine before and after the manifold porting and believe it or not the horsepower difference was 19.

-Lee
www.atomicpinup.com

 

Talk real nice while you are here for Christmas and you might score a factory 2x4 manifold.

PS...bring cash.