302 with dual quads

[colubra]

Looking for viewpoints both pro and con. Seller does not know carb size and has no build documents. Says HP is 345. Too much carb for engine?

[jwd]

It depends on the carb. size and whether or not they are vacuum secondaries. The 283 in my Corvette came from the factory with dual quads and they work perfectly, however they are small with vacuum secondaries. You can't over-carburate with vacuum secondaries as they open only according to the demand of the engine, unlike mechanical secondaries.

[wkooiman]

Pros:
- They look cool, especially with s&h air cleaners.
- Probably makes slightly more HP
- They can clean up the idle on an overcammed engine. Remember how people sometimes drill the throttle blades to avoid exposing the transfer slot? It's less likely on 2x4, because you have 2x the idle adjustment.

Cons:
- Cost
- On a 302 non-Tunnel Ram, they are probably Carter/Edelbrock style, which are okay, but there isn't as much expertise tuning as with Holleys
- Maybe side hung floats, which don't corner as well. When the gas flows to one side, they like to stall the engine.
- Linkage can be difficult if you don't have the right parts

Don't believe anyone that says it is too much carburetor. If you do 2 660's with 1-1 linkage on a 302, yes, it's too much. If you do 2 600's with vacuum secondary with or without progressive linkage, it's perfect.

Remember, the vacuum secondaries only open if they need to, so 2 600's vacuum secondaries are the same as 1 600 double pumper, which runs great on a 302.

[Dwight]

do you have pics of the carbs?


Dwight

[Ron61]

If the engine is running well with no to much fuel then it is most likely OK. As stated before, vacuum secondaries on this engine would be preferable to mechanical ones or a double pumper carb. Also if the carbs on the engine are matched to the cam and other specs you should be OK. Just sticking two carburetors on an engine doesn't necessarily add power. In fact it can decrease the power.

Ron

[Double Venom]

Well answered! I'm impressed.
DV

[Detroit Bill]

My thinking is that it adds unessessary complication. I doubt it will equal added performance.

[olddog]

Originally Posted by Detroit Bill

My thinking is that it adds unessessary complication. I doubt it will equal added performance.

Yes, multiple carbs and beautiful women adds unnecessary complication, but they give ya a woody every time. Well, unless there is something wrong with you.

[DanEC]

You're right.



They do involve a bit more work and tuning but in my case it was worth it.

[Double Venom]

DanEC,
IS that DUAL set up by, "PRICE MOTOR SPORTS?" Ours was by far the most professionally built "After market" product I have ever seen. Bar non...well maybe Wilwood products, Flaming River and maybe a few others. BUT still the best..

DV

[xb-60]

Originally Posted by DanEC

You're right.



They do involve a bit more work and tuning but in my case it was worth it.

Very nice Dan

[DanEC]

Originally Posted by Double Venom

DanEC,
IS that DUAL set up by, "PRICE MOTOR SPORTS?" Ours was by far the most professionally built "After market" product I have ever seen. Bar non...well maybe Wilwood products, Flaming River and maybe a few others. BUT still the best..

DV

No, they were initially set up by Keith Craft but I've had both apart and done a lot of fiddling with them since - and I have to admit they are base line 1850 carbs. I have them on a 63 - 427 low riser intake. But they do run pretty nice and the intake makes excellent torque. After Holley and Carter introduced their bigger carbs in the mid-60s the need for and advantages of the multiple carb set-ups more or less faded. I know - and agree - that they won't out-perform a good single barrel carb on a good manifold. But they do look sexy and I don't mind spending a little more time setting idle mixture and speed.

A good question to ask yourself to see if dual carbs are right for you is - do you mind running points and setting dwell? If points drive you nuts and seem like unnecessary maintenance and you will only settle for an electronic ignition - get a single carb set-up or fuel injection.

[colubra]

Did speak to previous owner and while he did not recall the exact cfm(might be 600), he said the mechanical secondaries had been disconnected. What issues and concerns would this bring about. Thanks to all as I am learning a lot. Will be able to get pics this weekend.

[cycleguy55]

Originally Posted by colubra

Did speak to previous owner and while he did not recall the exact cfm(might be 600), he said the mechanical secondaries had been disconnected. What issues and concerns would this bring about. Thanks to all as I am learning a lot. Will be able to get pics this weekend.

You can get the carb specifications from Holley if you have the carb number(s). The list number for most performance and factory 2 and 4 barrel carburetors will be found stamped into the upper right hand corner of the airhorn or sometimes called the choke tower. On the 4150 HP models that do not have a choke tower the list number will be stamped into the mainbody behind the throttle linkage. This number is used to identify the carburetor and also used when needing service parts or renew kits. Source: https://www.holley.com/support/faq/

Once you have that number(s), go to http://documents.holley.com/techlibr...al_listing.pdf and you can get the specifications and service part numbers.

[jwd]

Originally Posted by colubra

Did speak to previous owner and while he did not recall the exact cfm(might be 600), he said the mechanical secondaries had been disconnected. What issues and concerns would this bring about. Thanks to all as I am learning a lot. Will be able to get pics this weekend.

Sounds like they are trying to make a terrible set up work. They disconnected them because the engine would bog and die when you stomped on it. A 302 at 100% volumetric efficiency (not usually possible with a street engine)will only flow 567 CFM at 6500 RPM. Even an unstreetable, full out, ballz to the wallz, purpose built race 302 can't flow more than 800 CFM at 7500 RPM.
If you want this car, plan on either getting two correct carbs. or better yet, a single carb. and manifold. What's on there now is garbage.

[colubra]

What would be a solid setup for the single carb and manifold?

[jwd]

Originally Posted by colubra

What would be a solid setup for the single carb and manifold?

Not enough info. to make that decision. Cam? Heads? Trans. gears? Rear Gears?
Intended purpose?
A starting point for a good street engine is a dual plane intake and a 600 CFM carb. with vacuum secondaries.

[Karl Bebout]

Colubra, do not rule out an Edelbrock,unless you've just gotta have a Holley. The ones I've had were about as close to plug and play and I could hope. Good response, easy to tune, reasonable price, good quality. For street driveability and within a natsazz of equal performance, an Edelbrock on a dual plane intake, is the way to go.

[wkooiman]

There you go... The 2x4 setup is for sale, because the previous owner tried to run 2 double pumpers on a 302. My bet is the carburetors are 450 Holleys. Would you run a 900 CFM mech secondary carburetor on a 302? That's essentially what he was trying to do. With few exceptions, it's going to run like crap.

So, if you buy this setup, plan on buying 2 new carburetors, because you won't be able to use the mech secondary carburetors. Factor in another $1200 - $1500 for new carbs, and it will run very nice. But expect to spend the extra money to make it run right.

There are many options for 1x4, and as others have said, it depends on what you have, and what you want to do with it. Given that we're talking Cobras, it's hard to do better than the high rise Cobra dual plane intake. You can make more HP with other intakes, but they will always look like a hot rod intake. You can even do a turkey pan and a single S&H air cleaner to complete the look.

[Davekmd]

I'm thinking dual 4bbl on a 302 is just fine if the motor is stroked to say 325-350CID and will rev to 10 grand as an operational design center. They'd sit on a super tunnel ram intake manifold and idle horribly at 2,500RPM. The intended use of the motor would be drag racing. You'd launch at 6 grand, rev to 10 grand, hit the lights and shut down. After a day of drag racing you'd load the car up on the trailer and drag it home behind a Ford F250/F350 where it'd sit in the garage until the next drag race event.

Expect to trade/sell/give the induction system away. A 302 street motor that redlines at 5,500 RPM consumes 480CFM of air at 100% volumetric efficiency. We're told to assume 80% VE and so a basic 302 only needs a 384 CFM carb.

They 100% look wonderful but on a street 302/small block they are so overkill that they would hardly function.
Now if all you want to do is trailer the car to a show, push it off the trailer and show the car, well they'd be fine.