283 Carburetor thoughts

[RTHarvey]

I've had my 67 C10 for while now. It has a 283 and 4-speed. When I got it, it had a quadrajet off of a 76 Cadillac (according to the numbers) and didn't run very well. I changed to an Edelbrock square-bore manifold and a small (600-650) Edelbrock carb. It runs better, but not perfect. Originally it would have had a 2-bbl carb, and the 4-bbl Edelbrock carb is really too big. I haven't really tried too hard to tune it, but I thought I would ask the forum for ideas on how to tune it, or if someone had a different idea on how to approach the carb problem. There doesn't seem to be much around in the way of 2 bbl manifolds or carburetors on the aftermarket. I've looked around a little for original manifolds and carbs, but they are pretty scarce too, and mostly pretty junky looking. Any thoughts would be appreciated.

[RustyPile]

I would ALWAYS choose a Q-jet over any Edelbrock carburetor, but that's just me.. Like any carburetor, you have to know what you're doing when tuning a Q-jet.. A properly tuned Q-jet will out perform an "Eddy", most everytime..

That Cadillac Q-jet is probably way "over jetted" for that little 283.. Start leaning it down a little at a time and that 283 will tell you where to stop...

['68OrangeSunshine]

Try a 500 CFM Performer.

[Ironhorse]

The 283 would have originally had a 2 BBL or a 4BBL carb in it's early days. The 4BBL carb would have been either a Carter WCFB or Rochester 4Jet carb. Either carb was in the area of 450 CFM. A 500 CFM carb should do well, the Q/Jet would be a too much of a good thing unless the engine was "built" for Hi-performance output.

"IF" you are looking for an original 2BBL or 4BBL SBC intake send me a PM. I may well have either on hand. I run a '64 Chevelle 283 block, bored .030 over with a Melling hyd. cam and TWO Carter WCFB carbs in my 57 Chevy 2dr. sedan and it runs VERY well. Always works best to match the engine cubic inch as "built" with a matching CFM carb/cam combination.

[cwcarpenter98]

I've been running a Quadrajet on my 283 for about 5 years now. Haven't had a problem with it at all, and I drive it at least 3 days a week or more these days. The Qjet I chose was sized for an 80s 305 so I could get one with an electric choke but none of the electronics.

Eventually I would like to stick a wideband O2 gauge in the truck to see where my tune by ear, smell, and feel has gotten me

[special-K]

I've had good results with 4bbls in the 450-500 CFM range on the 283 and 307. I prefer spread bore, especially on the small v8s

[body bolt]

I run a 450CFM Holley 4360 Economaster on my 350. It mostly solved the fuel boiling problem with the original Q-Jet, pulls nicely at the low end plus offers slightly better fuel consumption. It's spreadbore with divorced choke and bolts right on. Even the CCS solenoid operates in the same position. You don't need anymore that 500CFM on a stock 283.

[OregonNed]

I've had excellent results with a 500 CFM Edelbrock on the 327 - this was a change from a 600 CFM - just runs fantastic now.

[HO455]

One thing to keep in mind if your going to use a Qjet is you want to use one that originally came on a smaller displacement engine. Qjets came installed on engines from 230 cubic inches to 455 cubic inches. The non-adjustable parts of the idle circuits were drilled to match the engine application. Cadillac didn't use many small cubic inch engines so it's likely that was part of the problem with your Qjet. The vacuum secondary design of Qjet keeps the carburetor from providing to much air to the engine at wide open throttle.

Finding a good Qjet from a 305 through a 350 cubic inch engine shouldn't be too difficult. You will need to do some research into what carburetor numbers falls into that range. Some mid 70's carbs are listed as 350/400 cubic inch and I would pass on those.

The reality of today is your not likely to buy a new carburetor that is going to be set up correctly for your engine. The aftermarket only seems to provide a generic jetting set up for a 350 cubic inch engine. I've never had much luck getting anyone from Edelbrock or Holley to tell me what jetting the carburetor has installed. But they are more than willing to sell me a jet kit with the carburetor for an extra $50.

The smaller cfm aftermarket carburetors (500-625 CFM) are likely going to have idle circuits that are a better match for your 283. Giving you crisper throttle response and better idle characteristics than larger aftermarket carburetors at the possible expense of wide open throttle power.

[RTHarvey]

Thanks to all for the ideas. I think this provides me a plan. I'll let you know how it goes. I'm not as young as I used to be, so it will probably go slowly!

[Rust_never_sleeps]

If you do want to run the q-jet, you can ping Cliff's Performance with your casting number and get guidance on how to set it up with the right rebuild parts, or you could just send it in.

[Steeveedee]

Originally Posted by HO455

One thing to keep in mind if your going to use a Qjet is you want to use one that originally came on a smaller displacement engine. Qjets came installed on engines from 230 cubic inches to 455 cubic inches. The non-adjustable parts of the idle circuits were drilled to match the engine application. Cadillac didn't use many small cubic inch engines so it's likely that was part of the problem with your Qjet. The vacuum secondary design of Qjet keeps the carburetor from providing to much air to the engine at wide open throttle.

Finding a good Qjet from a 305 through a 350 cubic inch engine shouldn't be too difficult. You will need to do some research into what carburetor numbers falls into that range. Some mid 70's carbs are listed as 350/400 cubic inch and I would pass on those.

The reality of today is your not likely to buy a new carburetor that is going to be set up correctly for your engine. The aftermarket only seems to provide a generic jetting set up for a 350 cubic inch engine. I've never had much luck getting anyone from Edelbrock or Holley to tell me what jetting the carburetor has installed. But they are more than willing to sell me a jet kit with the carburetor for an extra $50.

The smaller cfm aftermarket carburetors (500-625 CFM) are likely going to have idle circuits that are a better match for your 283. Giving you crisper throttle response and better idle characteristics than larger aftermarket carburetors at the possible expense of wide open throttle power.

Yup. The 200+ Cu. In. bigger engine in a Cadillac has a pretty different calibration beyond jets and metering rods. When I worked in a parts store, we had a "universal fit" Q-Jet replacement carburetor. People just wanted their cars to run OK, not at peak tune, and that carb seemed to work for them. We had Motorcraft and Carter for the other mfgs, too.

[MikeB]

While a 500 CFM carb would be a better match for a 283, your problem has nothing to do with your current carb's CFM rating. Its front two venturis aren't any larger (and maybe even smaller) than a stock 307 2-bbl carb. And that's all the engine uses until air flow demands more. And then the secondaries open slowly, as needed.

What are the symptoms?

Do you have this owner's manual?
https://www.edelbrock.com/media/wysi...ers-manual.pdf

[Palf70Step]

Since I am in a hot climate, but I do it aways, is to run a 1" phenolic spacer to help lessen the heat impact on the carb. It always seemed to help.

[MikeB]

Interesting information about 283 carburetion here. https://www.jalopyjournal.com/forum/...r-283.1184691/

Based on CarbKing's post, I'd guess the primaries on a 600 Edelbrock flow around 250 cfm -- total.

[body bolt]

Originally Posted by HO455

I've never had much luck getting anyone from Edelbrock or Holley to tell me what jetting the carburetor has installed.
.

I've been able to find the Holley info in their numerical listing.

[MikeB]

Originally Posted by body bolt

I've been able to find the Holley info in their numerical listing.

And Edelbrock jetting info here: https://www.edelbrock.com/media/wysi...ers-manual.pdf

For example, page 12 for the popular 1406 carb.

['68OrangeSunshine]

Originally Posted by MikeB

And Edelbrock jetting info here: https://www.edelbrock.com/media/wysi...ers-manual.pdf

For example, page 12 for the popular 1406 carb.

Edelbrock used to send you a printed Performer Manual for free if you called them and asked for it. There were also blank charts in the back you could use to notate all your Rod/Spring/Jet changes, and when you did it.

When I had to change the jets and rods for a super lean setting on the 1405 on my 292 to pass emissions every Fall, I could refer to my log and restore the carb for performance, after I got registration renewed.

[HO455]

Thanks for the information.

[MikeB]

Originally Posted by '68OrangeSunshine

Edelbrock used to send you a printed Performer Manual for free if you called them and asked for it. There were also blank charts in the back you could use to notate all your Rod/Spring/Jet changes, and when you did it.

When I had to change the jets and rods for a super lean setting on the 1405 on my 292 to pass emissions every Fall, I could refer to my log and restore the carb for performance, after I got registration renewed.

That's pretty clever leaning out the carb to pass emissions. I recently changed the primary jets and rods on my 1406, and made a note in the back of the user manual showing the parts and the date. Otherwise I'd forget what I did in a few days!

Some guys say Edelbrock carbs suck, but I think they're just fine for a mild engine making at least 18" of idle vacuum. Also, the relatively new AVS2 is getting rave reviews even from Holley guys.

They are also very easy to tune. I ran a 1406 when I lived in the mountains, and got it jetted for 5000-7500 ft elevation using the user manual chart. When I moved back to the lowlands, I spent around 15 minutes re-installing its "as delivered" jets and rods.

Just don't bolt any of them them directly to the manifold, but instead use a wooden or phenolic spacer/insulator to keep the the ethanol in fuel from boiling on very hot days.

Edelbrock #9266

['68OrangeSunshine]

[QUOTE=MikeB;9209696]That's pretty clever leaning out the carb to pass emissions.[QUOTE]

I have a Carter AFB 9635S on the V8 350 in my '71 GMC Jimmy. When Federal Mogul stopped marketing the Carters, Edelbrock became the only game in town. Both were made by Weber in the same plant. It was all marketing. Edelbrocks got a shine and a red decal, Carter Perrormance AFBs got a black aluminum tag to sport on the front. I took mine off when I saw that carb cleaner spray ruined the lettering on the tag. I use a 1'' thick phenolic spacer on the V8. I tune the 9635S as an Edl-1405.
If you tell the Edelbrock tech rep you have a Carter, he will clam up -- for liability reasons, I guess.

When I rebuilt the Stepside's 292, the Federal Mogul Carters were off the market, so I had to go with Edelbrock. It's the same thing. The L6 intake is offset from the engine block, so a spacer is unnecessary.
Clifford Performance recommends running heater hoses under your carb to keep the carburetor at a proper temperature. [Their intake has plumbing taps.] Living in Tucson, I never needed carb heat.

I found a discarded Carter AVS on a movie set in the Mid-'90s. I ran the numbers. It was for a big block Mopar. The original AVS had a three-step metering rod/cupped jet system. The intermediate step was for mid-range performance -- while towing, maybe. Edelbrock's AVS2 did away with the 3-stage parts, and just used the AFB system.

Three step Carter AVS tune-up parts are now unobtainium.

[body bolt]

Originally Posted by MikeB

And Edelbrock jetting info here: https://www.edelbrock.com/media/wysi...ers-manual.pdf

For example, page 12 for the popular 1406 carb.

A lot of good info in there.

[RTHarvey]

It's been a while since I did the original post. For those that are still following, I put on an Edelbrock 500. Works better. I think a little tuning and I will be OK. Thanks for the ideas. I'll try to report back when I get some tuning done. I got the manual and tuning kit for this carb from Edelbrock.

[MikeB]

Originally Posted by RTHarvey

It's been a while since I did the original post. For those that are still following, I put on an Edelbrock 500. Works better. I think a little tuning and I will be OK.

I just now read through this entire thread, but never did see what kind of problems you were having initially. And why does the new carb need a "little tuning"? I ask because if you're having the same problem to a lesser degree, it could be caused by something external to the carburetor.

Typically, an Edelbrock carb will work pretty well right out of the box on a stock or mildly modified engine. All it should need is idle mixture and idle speed adjustments. However, if the engine has a slight hesitation off-idle, I have found they like a little more ignition advance -- say 12-14 degrees instead of 10. And worst case, an accelerator pump rod adjustment.

Rarely would a 500 cfm Edelbrock carb be over-jetted for a stock 265-327. Or even if it was, it probably wouldn't be noticeable w/o looking at the plugs.

[RTHarvey]

The original problem was that there would be a bit of a miss at most speeds, and then at WOT the secondaries would open, and it would stumble pretty badly. Just too much open area above the manifold, I think. With the 500cfm it is much better. About the only issue is that at WOT there is just a bit of a miss. Not really a miss, just a bit of a lack of smoothness? My guess is (only a guess) is that it might be a little rich, particularly in the secondaries. it isn't hard to change the jets and see how it behaves, The timing idea is something worth looking into too. Thanks for that.