Holley question

[427TJ]

'55 Chevy, 327, Duntov solid cam (rumpy idle), MSD mechanical advance dist (no ignition box--has the blue box under the base), Holley Street Dominator intake, supposed to be a 10.5:1 engine, headers, turbos, 4-speed, 4:11s.

Has an ancient Holley 650 spread-bore now that needs rebuilding/replacing.

Is a 650 double pumper (new in box) too much carb?

I re-read the carb section in "How to Hotrod Small Block Chevys" and they say 650 is as big as you want to go for a street/occasional strip SBC. Book also recommends the Holley spread-bore and the vac-secondary units as good street carbs over the double-pumper. I was thinking double-pumper due to the big cam (too big, really).

Recommendations? Thanks in advance!

[Keith Tedford]

I would think that the 650 spreadbore would be next best thing to a Quadrajet. I'd rebuild it. I'm doing one for our el Camino which has a mild 350.

[VintageMusclecar]

My $.02;

If it's only going to see street driving duty, I would strongly recommend an early 3310 "EH" or a 3310-1. I've said time & time again, the early 3310 is one of the best "all-around" carbs Holley ever built.

As far as the spreadbore carbs...I have never been, nor will I ever be a big fan of them. If you want to run a spreadbore carb, run a Quadrajet.

Eric

[CamarosRus]

Bill, I would go with ERIC's advice and be done with it !!!!!

[MosportGreen66]

I would also take Eric's advice... Here is a neat write up about the 3310 in this month's Hot Rod!

[ORIGLS6]

I agree 100%, and not just because the Carb Guru says so.

Like others including Sammy (in another thread) have said, I had no good experiences with the Holley spreadbore, and I'm a HUGE fan of Holley carbs.

As far as the 3310 that Eric recommends, I ran one on a 292 CI SBC with a GM aluminum hi-rise and the old .030-.030 cam and loved the way it performed. The 3310 is an extremely versatile piece. Just jet it correctly and you'll be happy.

[427TJ]

Thanks again everybody, I have PM'd Eric for more advice.

In 1980 I had a '67 327 (built for Friday night street races) 4-speed Camaro. I bought a 780 vac-sec Holley off of a bulletin-board ad in the local speed shop for about $100. The seller was a Holley engineer (he said) and called the 780 I bought a Z/28 carb. It needed NO jetting or adjustments of any significance and it performed very well. I was sorry to have let it go when I sold the car. I remember thinking that I should buy a new Holley and put it on the car and keep that great 780. Oh well!

[Keith Tedford]

I was just going on the personal experience I had with a 650 spreadbore that I used many years ago on a 350. Must have been lucky, because it worked quite well for me. On the other hand, the experienced guys here see a lot more carbs than I ever will. I'd take their advice.

[VintageMusclecar]

Keith;

Sometimes the spreadbore Holleys run fairly well depending on the application...they key words being "sometimes" and "depending on the application."

The reason I'm not a big fan of them is because compared to a Quadrajet, they're barely more than a controlled fuel leak in regards to metering precision. The primary metering system on a QJet is a fantastic design, and incredibly precise under nearly every imagineable driving situation. The Holley metering system is "primitave" at best in comparison to a QJet in this regards, which is why I recommend a QJet over a Holley if someone is set on using a spreadbore design carburetor.

OTOH, while it is possible to tune a QJet to deliver big power #'s and low e.t's at the digs, the QJet does have some inherent "issues" (i.e. flaws) in comparison to a Holley <u>when pressed to the extremes</u>. A QJet only has one needle&amp;seat assembly, making it difficult to provide adequate fuel flow into the carb. (it is obviously possible, but it's done using a huge nedle&amp;seat that doesn't lend itself to street use because of fuel control issues). A Qjet also has a limited fuel storage capacity inside the main body, which can require some modifications to provide an adequate fuel supply under extreme conditions.

Lastly, no matter how you slice it, a spreadbore design will nearly always have some distribution issues because of the small (relatively speaking) primaries and manhole cover-sized secondarys.

Again, both QJets and Holleys have their places, and can both be made to work in a variety of situations, but when it comes to running a spreadbore, the QJet has the Holley beat hands-down.

Eric

[Keith Tedford]

Eric, I am a big fan of the Quadrajet as well. Our '72 Lemans had a '70 455 with a 230 degree by .480 lift cam, headers, and a '69 Ram Air III Q'jet. That car was much smoother to drive than our L78 Chevelle, made considerably more power as well, and gas mileage was about 4 mpg better to boot. I plan on buying a wide band O2 sensor to better tune the carbs. Some people see fairly big gas mileage improvements, basically because the carb was so far off in the first place. Being retired now, I thought that I would have all kinds of time to play with this stuff. Not so. I don't know how I had time to go to work and get the stuff around home done too. A common lament. I'm keeping you in mind when I get the 4346 from our 427 restored. Our mild 350 el Camino has a 4010 Holley. Starting is excellent and it drives fine but gas mileage is not all that good. I'm afraid to take it apart because I don't know if I can even get a rebuild kit for it. At least it gets me down the road the way it is. I have a q'jet of the shelf that will probably get a rebuilt and a home under the hood.