dual quad inake

[jeds55]

Help

Looking for any information / experience with a dual quad set-up for street use. Is there any way to get the early Cadillac casting to work? Are there any other choices?

Engine is @300cu.in. with Steel Tech heads and mild R2 cam.

I have no racing plans only driving to and from shows.

Thanks for your comments.

Jed

[Mike Van Veghten]

Don't mess with the Cad. manifold. It's a LOT of work to do even close to correctly.

Lional Stone has a nice copy of both the large port and a modified version for the small port heads. By "small"...I mean...more normal heads than the R3 heads.

It's a lot of carburetor. Even with the little Holley 450cfm 4 barrels, it's still about twice the carb. you need.

But carefull tuning, it could be made to run ok.

Lional is still in the hospital from his accident. I have no idea if anyone is manning his phone. Call Phil at Fairborn Studebaker. He may have, or know where to get one.

Mike

[DEEPNHOCK]

IIRC, Dave Thiebalt has some dual quad combo manifolds in stock.
As said already...
Keep the carbs small and do what you can to delay the secondaries from opening right away...
Or stagger the linkage so you drive mostly off the front one and then both...
Jeff[8D]

quote:Originally posted by Mike Van Veghten

Don't mess with the Cad. manifold. It's a LOT of work to do even close to correctly.

Lional Stone has a nice copy of both the large port and a modified version for the small port heads. By "small"...I mean...more normal heads than the R3 heads.

It's a lot of carburetor. Even with the little Holley 450cfm 4 barrels, it's still about twice the carb. you need.

But carefull tuning, it could be made to run ok.

Lional is still in the hospital from his accident. I have no idea if anyone is manning his phone. Call Phil at Fairborn Studebaker. He may have, or know where to get one.

Mike

[jeds55]

Hi,

Thanks for the quick responses.
I am currently running a 600cfm. Edelbrock, with no problems. From the way it sounds, I should be happy and leave well enough alone.

Thanks Again,
Jed

[PackardV8]

quote:I am currently running a 600cfm. Edelbrock, with no problems. From the way it sounds, I should be happy and leave well enough alone.

You got it! The last thing in the world a street-driven normally-aspirated Stude V8 needs is 2x4bbls. Despite the fascination many CASOs have for the bling it brings, are just not needed. At 6,000 RPMs your 300" Stude V8 can only ingest 520 CFM. Your 600 CFM is more than enough.

thnx, jack vines

PackardV8

[buddymander]

Fords in the 60's and 70's ran a lot of 390 cfm holleys. Maybe find yourself a pair of those, or some old RX7 four barrels.

[PackardV8]

Agree, the 390 CFM Holley makes a great street carb for most Stude V8s. I've built a bunch of them and if you can tune, I like them better all-around than an AFB.

However, just asking, since even a big, strong 300" Stude V8 can only use 550 CFM, why 2 x 390 = 780 CFM?

Been there, done that back in the day when I didn't know any better. Here were my experiences - yours may vary:

1. Yes, it really got lots of "Wow."
2. No, it didn't run even a bit faster.
3. No, the Holley bolt pattern doesn't fit the Stude manifold, so they require adapters and this raises the carbs so they hit the hood on most C/K/Avanti.
4. No, it idled worse.
5. No, it got 8 MPG.
6. No, it took four times as long to tune, because the front bowl of the rear carb and the rear bowl of the front carb were so close together, the front carb had to be removed for jet changes.
7. No, it took twice as long to warm up on a cold morning.
8. No, I could never get the linkage and the secondary springs coordinated so the secondaries opened just right.
9. No, it didn't last very long. Determined that since I'd spent the time and money, 2x4 had to be faster than 1x4, I decided more carbs needed the optional R3 cam and and lost a rod at 7,000 RPMs and I sold the setup to a show car guy.
10. No, I wouldn't do it again if someone gave me a 2x4.

You did ask for advice, but as always, your car, your money, your decision.

thnx, jack vines

PackardV8

[winchesterhawk]

Im in the process of putting one on my 60 now. Im using 2 500cfm carbs, chevrolet valves and flat top pistons. I will let you know how it comes out. I put 2 650 double pumpers on a chevrolet headed smallblock. Everybody laughed, the car weighed 3700lbs and run 10.60"s in the quarter and 670's in the 1/8th.

[buddymander]

Even chevrolet ran a 780 Holley on their 327; those numbers don't jive. Jack, your car didn't idle right, it got 8 mpg, and took a long time to warm up...who's your carburetor guy?..Maybe it just had a vacuum leak.

[Mike Van Veghten]

Just remember...those 390's aren't cheap...!
They would work, but still too much cfm. Especaily for a mostly stock engine.
I have a long range plan for a cross-ram and two 390's for my 299 Stude. It's not a stock combination though.

winch -
Not saying it won't work...it just won't work very well.
You can ask my friends...I'm a master of the strange and weird..twin four barrels (on a Lionel manifold) IS a might do for the future of one of my Studes.
BUT...a THOUSAND CFM.
Good luck.

Mike

P.s. - please don't say the 500cfm carburetors are two barrels...!

[Gunslinger]

Chevy put a 780 on the early Z-28 with a 302 engine. It was an engine designed to operate at high rpm's where the 780 would be an advantage. For the average street car, it was way over-carbureted. A high school buddy had a '69 Z-28 and replaced the 780 with a 650 and it ran far better on the street as he didn't race it. Too much cfm makes for low end stumbling. The GM Quadrajet was a different animal...the small primaries gave excellent low end response and good fuel economy while the large secondaries would open as needed. The Q-jet is probably the best street carburetor designed, though it did take a person who understood it to get the best out of it.

To add so much cfm to a small displacement engine would require a big cam and high compression to handle it, and even then street manners would suffer. The big carbs love rpm's and need them.




Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, cocky and in general a malcontent.

[buddymander]

See that's the thing about two fours. It's like having a small double pumper. All you have to do is limit the secondaries and it's like you're running a smaller cfm carb. I've done stuff to quadrajets since 1973 and I can appreciate them for what they are, but they have limited low end response and then are overkill when the secondaries open. A square bore carb is better for normal driving because it gives a broader range of opening before the secondaries kick in. I've had a lot of two barrel motors that were great for around town; better than a spreadbore, but they did lack the high end. But the high end is seldom used.

[hotrodstude]

i've been running mulit. carbs on my cars since i was 14.i'm 60 now. it seem to me that you best bet is to run 2 2-barrels on the manifold. you would have a much better streetable engine and could have better economy.but would have a impressive looking set up.i would use either the holley 2300 series 2-barrel or the autolite 2100 2-baqrrel carbs. do not use the autolite 2300 or the 2vv 2-barrels. both the autolite and holley 2300 has been on fords since 1957 so the are common as dirt. now getting the carbs on to the manifold? offenhauser to the rescre, offy part number #5413-a,or you can use summit part #sum-g1406. the throttle linkage can be modified or use a universal linkage. if you use the autlite carbs get a couple of extra accel. pump diaframs because of the gas problems. they are the only trouble are of this carb. when going to a junk yard or parts store check the side of the float bowl for a clock looking casting mark with numbers in the middle of the clock it should be something like 1.42 or 1.74.this id the diam. of the venturi. smaller number more low end.smaller engine get a matched number on both carbs and you have a matched set.the autolite are usually around 220 cfm -325 cfm,same as with the holley except the racing 2300's which are 350 and 500 cfm. [^]

good luck i hope you can use any of this info.i installed a summit sum-mo8600vs which is an updated autolite made by holley.installed one on my r-1 engine and it purrs like a kitten,good throttle responce and great driveablyy.[8D]

2006,f-150,2x4,v-6,5-speed manual,8ft bed, will post stude info when i get it on the road.

[PackardV8]

quote:See that's the thing about two fours. It's like having a small double pumper. All you have to do is limit the secondaries and it's like you're running a smaller cfm carb.

Spending three times the money for a 2x4 manifold, two carbs, two fuel lines and two linkages, then don't let the secondaries open so the 2x4 can behave sort of like a small single double-pumper?

quote:I have no racing plans only driving to and from shows.

Jed, I will apologize for not noticing your show car goal and focusing on the daily driver stuff which is not applicable to you. If you are just going to show the car and you want as many SDCrs as possible to stop and look, then dress it like a full R4 clone with all the chrome and badges; it will attract ten times the attention as will a mild modified. Go for it.

thnx, jack vines

PackardV8

[Dan White]

Here is a picture of a Detroit Racing dual quad manifold I have had for some time. It is from a Studebaker that was setup for drag racing in the late 50s. It was originally for a Cadillac but was heavily modified for the Studebaker heads. It was what I call a medium rise dual quad intake, but for very small 4 barrels. I keep thinking of putting it on ebay but just seem to hang on to it. My buddy and I were going to put it on a dual supercharged Stude but it is a project that will never happen.





Dan White
64 R1 GT
64 R2 GT