Hot Rods Intake/carb question???

I put vintage speeds dual carb setup on my intake and it appears as though it doesn't completely cover part of it the intake manifold. Not to sound stupid here, but can i just make a thin metal spacer plate that covers this? can it be left uncovered? pictures attached. Thank you for the help
Trevor Fitzpatrick

 

That is an exhaust port! If you plugged the crossover in the intake it won’t make any difference, if not you will have an exhaust leak. I have drilled those and tapped them and screwed bolts in them with sealer and cut them off. If you do this, do both.






Bones

 

Do the manifold carb stud holes line up with the adapter,or do you need a adapter plate under the carb adapter?It appears like the stud hole doesn't line up.

 

Actually, there is a stock part from GM that covers that. I had a '68 Corvette that was missing it (a shiny thin piece of metal, almost like a metal carb gasket), and it wouldn't run for shit until I put it back on.

Speaking of "putting it back on", consider getting a Quadrajet if you have any interest in increased performance at all.

 

The dual carb adapter actually bolts down to the manifold?
One would think it would be for a holley style carb..and not a quadrajet

 

Don't matter if it fits or not .I always thought those things look cheesy . Spend extra money to make your car run slower ?
A well built Q-jet would stomp the crap out of that setup. Not to mention be easier to tune.
You dual carbs get a real dual carb manifold.

 

To make it work you need a Q-jet to square bore adapter plate, Mr Gasket part #1932
Without the adapter the carburetors won't even open all the way, butterfly's may hit the dividers on the cast intake
There is one on E bay for $12.00 or new at Summit racing for $21.00

The best way to run this would be with more open a square bore intake

You may also need to find a way for crankcase venting the rear of the block
(Please don't drill those nice Corvette covers for breathers)
I have had good results drilling and tapping the rear of intake manifolds for a 3/8 pipe thread to screw in a 5/8 hose nipple for venting the rear of the engine. Install a valley tray or make a oil deflector shield under the pipe fitting

 

There is no way that the butterfly's would hit with that tall spacer.. you thinking of just putting a holley carb on a Qjet manifold.

But yes the OP should just run a Holley style manifold.

Some just want a "LOOK" and not so much on the performance aspect..

 

Your intake manifold is of the "spread-bore" type:

http://www.thecarburetorshop.com/Four_barrel_mounting_flanges.htm

While not a fan of the conversion you have even if you have the "square-bore" manifold; I don't believe it will work at all, even using a spread-bore to square-bore adapter with your current intake.

Even the spread-bore to square-bore conversion is basically for the used-car salesman at Ssnake-oil Motors!

Do the math. If you have a square-bore 750 CFM (AFB, Holley, clone, whatever), the primary side is 375, and the secondary side is also 375. That spread-bore manifold is designed for a Q-jet with 150 on the primary, and 600 on the secondary. So if the air transition from one to the other is perfect (it won't be) the maximum would be 150 on the primary, and 375 on the secondary. Your 750 CFM is now less than 525 CFM.

Now adding the 2x2 conversion for even more volume loss, and I believe you will literally STARVE the front cylinders leading to engine failure!

I understand wanting "the look"; but not at the expense of the blowing the engine.

Suggestion: if you really want to use the 2x2 conversion for "the look", find an aftermarket, open plenum aluminum SQUARE-BORE intake for the engine. Then install the 2x2 conversion, if you wish.

As far as performance, well, that is an entirely different story.

Good luck, and please let us know how you proceed.

Jon.

 

I agree with everyone else, ditch the spread bore intake manifold and install a square bore. They are not that expensive. By the way, I like your dual carb conversion.

 

Jon,
Are you referring to one of the Edelbrock performer rpm intakes like this?
https://www.summitracing.com/parts/...MI_PmDv63b5wIVkB-tBh0EkwwYEAQYASABEgLkm_D_BwE

 

Do you mean a regular edelbrock performer rpm intake?

 

And, i forgot to mention this is the monster chevy 262 v8

 

Actually, I was referring to one with a completely open (not divided) plenum. Not sure how the conversion will work with a divided plenum.

Jon.

 

https://anchorage.craigslist.org/pts/d/anchorage-old-school-edelbrock-sbc/7073799578.html

 

It would work,but your really mixing "era" parts with a Torker.I would think you would want a lower profile manifold to look more 50"s-ish.

 

good point sir

 

What I think you really need is a 1957-59 ish Chevy 4 barrel manifold.It has a square 4 hole pattern.There are some on Ebay to look at.Go to a parts store,and get a 57 4 barrel carb base gasket.It will tell you if your adaptor will bolt on.If the throttle shaft plates open all the way it should work.If not some sort of 1/4 to 3/8 inch tall spacer should make them clear.

 

The mounting surface on your manifold (third picture) looks like it has a bunch of old crap such as gasket residue (or rust) under the paint.
Hopefully the head mating surfaces aren't the same.

 

Yeah, you don't need an aluminum aftermarket manifold, you just need a SBC cast iron manifold for a square bore carb. Look on eBay, you'll see lot's for sale there, though they're over priced IMO. I bought one a while back at a swap meet for $25.

 

Just for the record, I was not intending to recommend aluminum, so much as an open plenum; and if an aluminum recommendation was implied, my apologies.

Chevrolet may have made a cast iron open plenum manifold of which I am unaware.

An original cast iron divide manifold, with the dividers milled away should be as good (or better) than an aftermarket aluminum manifold.

Gasoline molecules mixed with air do not like corners. If one thinks of water flow in the bends of the river, where the current basically is forced against the far side of the curve one can understand this better. And the faster the water current (corresponding to higher RPM with increased runner velocity) the "smaller" (in effect) the runner becomes. There have been a number of flow diagrams of intake manifold runners that demonstrate this. Thus the more corners the adapter require, the unhappier the gasoline molecules.

Jon.

 

To add fuel to the fire, let me relate my experience. I attempted a project where I tried to run a QuadraJet (Spreadbore) carburetor on a flathead (I had a bunch of extra carbs and a Sharp 4BBL manifold I wasn't using, so I thought I'd take a shot at it). I used a Spreadbore to a regular Holley adapter modified to fit the Squarebore pattern of the manifold (are you following this?). To make a long story short, I couldn't get it to run worth a shit. I have given up on it (temporarily; I may get back to it someday). I think that you (like me and my experiment) have an agglomeration of parts that will never work together satisfactorily. I would listen to "carbking" on this.

Here's the thread : https://www.jalopyjournal.com/forum/threads/quadrajet-on-a-flathead-part-ii-implementation.1111638/

 

like this one?

https://www.ebay.com/i/251040030422...29687&itm=251040030422&pmt=0&noa=1&pg=2386202

 

That particular one may not be your best choice. First it needs a "Squarebore" carb or adapter, which may or may not be easy to find. Second, when the word "Corvette" shows up in an ad for Chevrolet parts the price goes out the window; especially with this seller, who is one of the biggest Corvette dealers around. When I look at the eBay listing, there is one down on the page ('66 Chevelle) that looks loke it would be a better choice. That one also seems to be grossly over-priced as well. Look at it this way : going to Swap Meets and looking for the parts you need is a lot of fun!

If you haven't already done so, I would suggest following "cabrking"'s link and familiarize yourself with carburetor mounting bolt patterns. I know I was confused before I did.

 

this may work instead of buying a new manifold. The 2x2 carb manifold is not intended for a Q-jet intake.

 

i think i am going to give this kit a try.

 

Changing the intake for one stock intake for the other, is a waste of time! Make sure you have clearance on all butterflies at WFO! I thought this and linkages problems were a give me!!!! We check this every time on our race car! Racing 101! Just my thinking!










Bones

 

At minimum you need to go with a open plenum adapter, to help the air go around the corners.
Note the difference between your kit and Ricks post #26, turn the plate in Ricks post upside down to make the spread bore adapt to the more open square bore.

 

If you want to try one of those adapters send me your address, I can send you one to save you some money.