Carb Recomendation?

[WinDancer]

Need to replace the 4bbl carb on my big-horse 454.
What are you running on yours and how happy are you with it?
Any problems?
Thanks for your input-
Dave

[68is4me]

oh boy here we go.

Quadrajet that is built correctly. Good fuel mileage and has the performance when it set up the right way.

I also ran one of original Demon's and really liked it that for adjustability. But I heard they are not as good as they used to be.

[truckster]

Originally Posted by 68is4me

Quadrajet that is built correctly. Good fuel mileage and has the performance when it set up the right way.

Exactly. The only thing better is fuel injection, and even that's not always better.

[Steeveedee]

I have the original Q-Jet on mine and am quite happy with it. If you look around, there are Q-Jets for the big inch Pontiacs that flow up to 800 CFM. What kind of HP are you running? A Q-Jet isn't necessarily big enough, depending on demand.

[WinDancer]

The machine shop that built the heads told me 600 HP based on their specs. I was just going to go with an 800 or 850. I have been a board member for many years and spent many hours reading everything posted about our trucks and specially about the 454. Many folks posted about them 'drowning out' if you over-sized the carb too much, so want to avoid that problem.
I am partial to electric chokes, if it matters
I am doing the last of my work to the truck now and will sell it after the carb and tuneup are done.
Thanks again to all- this is a fairly large expenditure and this board is the authority, for me. I want to get each decision 'right'.
Dave

Thanks,
Dave

[truckster]

You can't over-size a Quadrajet, since the primaries are small and the secondaries work on demand. And the later Quadrajets have electric chokes.

[68is4me]

I think all the later quads are 800cfm.

But if you are just going to sell it I think I would maybe go a different route. Maybe a holley 800-850 with vac secondaries. It is all up to you how much tinkering that you what to do before you sell it. A quad would take some time and nobody likes to work on them. But the Holley name always seems to sell better.

[Steeveedee]

Originally Posted by truckster

you can't over-size a quadrajet, since the primaries are small and the secondaries work on demand. And the later quadrajets have electric chokes.

x2

[rockyrivermark]

Not this again.

[dave`12]

I just replaced my tired holly 650 with a holly demon carb. Runs great out of the box, I only adjusted the idle speed.

It has smaller secondaries for better MPG and a composite bowl for lower fuel temps.

The 750cfm is less that 350.00.

I have a 350cid, not sure how it would run on a big block, but the U-tube reviews are good.

[mike16]

do a search

Several good rebuilders can rebuild your carb and or sell you parts. but be careful

rebuilt carbs them selves are readily available but be careful there too .


rebuild kits themselves are also available

lots of literature on rebuilding them. Service manual and a very good book written by Doug Roe (?) and published by HP are also available.

Avoid the impulse to "hot rod" the carb and any encouragement to do so. mosty permenent irrepairable damage can occur.

Doug's book has been around since the early '80's. It has gone through several editions and has become so popular and respected that its been republished.

If you try to rebuild your own carb go for it! they are not that complicated. And even if it does not work out your only out the money for a kit and a book/service manual. But even then they remain valuable to you in setting up/adjusting your carb.

You did not say why you intend to replace your carb.

I think Buicks had 815 cfm carbs.

[WinDancer]

The existing carb has been thru some bad times and badly abused during restoration and customization of the truck. Total loss. It is far beyond my expertise to rebuild a carb, and tune it, and get it right for reliable driving.

My experience in 69 years has been that carb rebuilds, on anything, are a waster of time, money and effort. So my only viable option is a new one. And though I am going to sell the truck, I want it done right. I am going to do whatever I would do if I were keeping it. I want to look a buyer in the eye and tell them all the work was done properly and that ii is 100% reliable.

Thanks for all the input from everyone. I knew that this was going to open up the two main camps when I started the thread, but this info will be valuable to a few others out there, too

Dave

[68 P.O.S.]

What intake manifold do you currently have on it; stock or aftermarket? The carb has to be compatible with the intake.

[mike16]

good used aftermarket carbs turn up at swap meets and often at junk yards some employee has one. but then theres the rebuild thing. They go for about 20 -50 $'s

New or used i like either the Holleys or AFB's

[WinDancer]

It is raining here today- don't want to expose the engine to the rain-
But I believe the intake is a polished Edelbrock-
The intake is a square bore or a round bore- the existing carb was installed with an adapter because it did not match the intake- I would never have approved that had I known- one more reason to replace it. And I want a new one rather than rebuilt. I want everything right and proper before I offer the truck for sale.
I appreciate everyone taking their time to share their opinion with me
Dave

[volksworld]

i'll give a vote AGAINST an edelbrock performer....my 454...edelbrock performer cam, manifold, and carb....never ran right out of the box....fell on its face....spread bore manifold with halfassed adapter plate to square bore carb...really edelbrock? thats your idea of matched components?....50 bucks for a calibration kit, weld in a bung for an 02 sensor and endlessly swap jets, springs and metering rods till i finally tore all the teeth off 1st gear in a muncie 4 spd trying to jet the bog out...stuck the poor little saginaw back in and drove it like a little old lady till it came apart for a frame-off..even changed the primary boosters at edelbrock tech's recomendation...still not done so was never happy....the only reason i went for the edelbrock was the 600 holley on the previous small block used to overfill the rear float bowl because i never really kicked the secondaries in during normal driving....(yes i replaced the needle and seat)...the edelbrock used a common bowl for primary and secondary so i figured that would eliminate the problem...in retrospect i probably should have tried a pressure regulator....

[68 P.O.S.]

Originally Posted by WinDancer

It is raining here today- don't want to expose the engine to the rain-
But I believe the intake is a polished Edelbrock-
The intake is a square bore or a round bore- the existing carb was installed with an adapter because it did not match the intake- I would never have approved that had I known- one more reason to replace it. And I want a new one rather than rebuilt. I want everything right and proper before I offer the truck for sale.
I appreciate everyone taking their time to share their opinion with me
Dave

An Edelbrock is a good intake to have. See what numbers you can pull off of it to identify which one you have. A square bore intake rules out putting a Q-jet on there. A 800 to 850 cfm carb sounds correct for your hp. How about a Holley Sniper? A little more expensive than a normal carb tho.

[WinDancer]

Will try to get some numbers and a couple pics today if the rain lets up for a time.
Very, very hard to find someone honest and reliable that knows their 'stuff'.
Thanks,
Dave

[70CHEVYBB]

I just pulled my 850 Edelbrock thunder serise off my 450 horse 396 in a 72 nova. I replaced it with a 750 quick fuel and I have never been happier. Way better response and perfect idle and with the electric choke start ups cold are better than the edelbrock
Posted via Mobile Device

[WinDancer]

It is an Edelbrock, I think a performer?
Here are some pics- could not find any numbers on the intake

[WinDancer]

And a few more...

[WinDancer]

Can I just unbolt the carb, lift it slightly and look to see what the intake pattern looks like without taking it completely off?
Thanks,
Dave

[Ironangel]

Looks like the RPM Air Gap manifold, they are a square bore manifold. Since you plan on selling the truck, the most economical fix would be to rebuild the existing Holly carb. Next option would be a 750cfm Performer carb from Edelbrock. I wouldn't go any bigger than a 750cfm because a little small is WAY better than a little to big as 70CHEVYBB indicated above. That dont appear to be an 800cfm Holly on there now. You'll waste money and make the motor a pig with an 800...I'm running a 750 Quadrajet on a built L34 396 and I got way more power and response than when it had a Holly 800cfm double pumper on top. PS. Nothing is going to run right without a choke, especially with an Air Gap intake. Your pics show that the electric choke is disconnected. You need to find somebody that knows old school Big Block Chevy's and carburetor's. I dont know what elevation your at or what kind of cold weather you have in Tenio but any cold weather at all will wreak havoc on that carb without a choke. An RPM Air Gap intake magnifies the problem until they warm up.."Just Sayin"

[ZEKE68]

Here is what I am going to run. I can't recommend because it hasn't been fired up yet. 2 Edelbrock 500's.

[bw46]

I vote Holley. I run them on both my street cars, trucks, and race cars. I've run them on mild 350s, 358 race motors, 540" and 600" monster motors, and a 383 in my 71 truck. I find them easy to tune and the knowledge base is common. Qfuel same same. Vacuum secondary probably better for street driven bolt-on set-it-and-forget-it (i.e. happy guy who buys your truck!).

I have tried rebuilding Qjets and I even sent one out for rebuild, not happy with either solution. No doubt there are great ones out there, just didn't work for me.

Good luck!