Frankie the Fink

True...its probably a 'wash' weight-wise. I stated that in my second posting... Of course the extra 4-bbls means you have 4-5 ounces of extra gas in the carb bowls weighing you down!

1snake

Very true. In fact, a good high-rise and a Holley would beat them, and the 2X4's, as well. Mostly because nobody, including the dealers, couldn't get them to run right. I've removed a few in my life. Lucky to get $100 for the whole F.I. set-up. One buddy threw his in the garbage after we removed it and put on a carb. If I only knew what they would eventually be worth.

Jim

Audiophobe

I'm a big guy. I better hold out for the duals!

MikeM

Way back, I did some comparison testing between a 270 2 X 4, Lt-1 manifold and 780 Holley and '63/later FI's. Drag strip wise, the FI was quicker. Not much. That was on a stock FI engine. Not modified. In any case, I've never heard of the FI being removed from a Corvette because it was slower than the carb jobs. Could be though.

The trick to getting a FI to run right is to let the damn thing alone after it's set up. I've run several of them for over twenty years and never turned a screw on them. One of them, I gave $15 for and I ran it from '69 until about 1995. Previous owner told me his car didn't run right and he took it off. After he got it off, he tuned up his car (plugs, wires, cap, rotor, timed it, etc) and told me it ran much better than before and was glad to be rid of the junk FI unit.

1snake

780 on a 327 is waaaay toooo big, even with vacuum secondaries. A 650 DP (4777) will out perform it all day long.

Jim

Stewart Allison

What is it with people over carbying a car. A stock 327 would only need a 600 -650 max.... I run a 600 on mine and it's a 350 the 2 650's I tried on the pump gave me lower power pulls.
The cast 1x4 barrel manifold is so, so heavy. The alum dual 2x4's has to be lighter than the single barrel ! Stewy

brucep

maybe this has been said, but i remember reading somewhere that the dual quad setup was offered for marketing appeal reasons (sales) not to improve actual performance

MikeM

That's a commonly held opinion. My results were different. In any case, the FI unit(s) outperformed all of them.

I tried the 585 cfm, a 650(?) and the 780, all on the LT 1 manifold. Drag strip wise, the 780 won. Street, the 585 wins.

Dont forget the 780/800 was on the factory 302.

I never owned a DP so I don't know about it.

MikeM

That might be the case for the 427. Not for SBC or the W series engines.

Stewart Allison

Too many variables to believe that a 780 would be the choice by times on a drag strip. I would need to see dyno figures to prove that a larger carby would be a better choice. A 780 on a stock 5 litre is way over kill I would believe your smaller carbs were faulty.
I have a Dodge NASCAR motor that is 357 cube with a 4 barrel on it. It makes 747hp with a 850. I have tried dozens of combos larger than that and they all make less power through the RPM range. Why would a stock 5 liter need 780 cfm. My motor would be making 3 times that amount of power so why would you need a 780cfm ! Stewy

Frankie the Fink

I can tell you that anything over a 650cfm drowned my souped-up HiPo '66 Mustang 289...even with the enhanced 'breathing' I bolted on with 351 heads...

MikeM

Maybe but then Ford released the 2 X 4 carbs/manifold for the same 289 engine. I know they would run better than a single four barrel from personal experience. That's speaking a stock 271 hi-po four barrel vs. the Cobra 2 X 4 stuff.

Your 2 X 4 setup that you like on your 283 engine probably flows 385 cfm times two = 770 cfm. The same setup was released for the 265 cubic inch engine. Seems like that, (according to a few here) that is way too much for these engines? If anything over 650 CFM was too much for a 289, how is it okay to use 770 CFM on a 265/283?

According to the discussion in this thread, everyone admits the 2 X 4's give more power so there seems to be somewhat of a contradiction here.

MikeM

Beats me. Why would I?

I'd have to guess the "dozens of combos" you tried larger than the 850 carb were obviously faulty.

The time slip shows what wins drag races, not a dyno sheet printout.

Frankie the Fink

I'm speaking empirically (I don't have the engineering background to argue volumetric efficiency and all the other parameters involved). My 289 had a Holly dbl pumper 750cfm that I had to jettison for the 650cfm to get it to run right...that's all I can tell you. My Mustang buddies warned me that would be the case but I'm a little hard headed and had to learn for myself.

I don't know if my 283 car ever sees the theoretical 770cfm air flow with those secondary flappers and counter weights controlling things...if it did it may well be over-carbed. Such 'overkill' wasn't that unusual back in the muscle car 'more is better' days.

In ANY event the OP's question seemed to center on whether or not an optional induction system's 'look' and supposed performance increase was worth the extra money they command. For me the answer was yes with the dual quads but I couldn't see it with the F/I...purely personal opinion and preference.

Stewart Allison

Ok dual carby technology is pretty simple. The smaller the carby the faster the low down air speed. So lets put 2 carby's on top nice and small we will get real fast low down air speed while the car starts to rev up the air speed is not as detrimental. It's the same principal as a twin turbo set up compared to a big single turbo. The twin turbos spool up way faster than a single so you get much more grunt at lower RPM. Same principle with the twin carb ! That's why they went to Tri carby's over a massive single 4 barrel. People don't realise while driving on the road in street use it's not the same as on a strip. Hence massive Hi stall Autos for strip use. When in street use you need to have heaps of low down grunt while your putting along at 1500 rpm and see a gap to overtake or just want to have some fun you need that instant power. Two different engines for two different purposes. Race engines for race and street engines for street. A big single carby for the street on a small cube motor means lots of lost low down torques ! Stewy Stewy

devildog

Mike,

I wasnt trying to spin anything. I observed, in the late sixties, that several serious (maybe not professional) racers had replaced the FI with 2 x 4's. In fact my 61 was originally an FI car, but the original owner was a dedicated racer and put the 2 x 4's on it beleiving it was faster in the 1/4.

He also did some road track racing and did use the FI on the course.

Today, my buddy John has an FI 283 and we go fooling around from time to time, it seems my 2 x 4 283 is a bit quicker than his FI. He has had the car for many years and seems to know and enjoy tuning his FI.

Not very scientific, but what i have seen on a limited basis.

The magazine articles of the day show the 283 Corvette engines options were all pretty close in performance.

However, If anyone wants to trade their FI for my 2 x 4's, I will deliver today. FI's are way too kool.

Joe

MikeM

If you'll go back and carefully pick through what I wrote in posts #3, 7, 10 and 28, I think you'll agree that I agree with what you said in this post.

MikeM

I agree that in straight line acceleration, the twin WCFB's and the FI are close in performance. In road racing, different story. FI, hands down.

I guess I assumed we were talking about comparing engines with all factory parts and not something ordered from Honest Charley or JC Whitney.

wmf62

now there's a 'blast from the past'....
Bill

MikeM

We are talking about the "past" here. Honest Charley was going great guns in the C-1 era. So was JC and Warshawsky. Even Sears, Roebuck & Co. (not just Sears) was selling engine rebuild parts.