Hi I have recently purchased a 1407 Edelbrock carb. However I suspect I may have bought a carb to big for my mildly worked 390 Cadillac engine. The engine has worked heads with 3 inch extractors and Isky cam. Currently I run a Cragar manifold with 4 Stombergs which performs well. However as I get older I would like the option of a 4 barrel on the factory intake manifold. The car is an Allard J2 replica built on an Allard P1 chassis with period parts. The engine is mated to an early Corvette 4 speed. The engine was dynoed at 305 hp. My question is would the 1406 Edelbrock be more suitable or could the 1407 do the job?
Well 170 x 4 = 680 with the 4 Strombergs you have now. Then we get to the question of is it now slightly over carbed or under carbed now?
Cool car, the 750 is likely a little more CFM than optimal, but it can still be tuned to work just fine. Just because it’s 750 CFM rated doesn’t meat it’s putting 750 down the intake when it’s not calling for it. Most of the time the secondaries are closed. You should be able to tune it to work fairly well. With jets and metering rods and springs. A lot of guys don’t like them but I’ve always had good luck with them.(AFB style carbs) They're not the best choice most of the time for all out racing performance, but that are a good choice for street driving and mild performance. They are sensitive to too much fuel pressure and also heat soaking. If those issues are addressed when I initially installed it should be able to be tuned to be street friendly and drivable.
Good answer I should have reflected on the cfm they currently flow. The present set up works well no hesitation of dead spots. So I assume it’s just right. Sounds like the 700 CFM Edelbrock 1407 should be OK. Thanks CadAllard
Thanks for the comprehensive answer. Heat has being an issue with the present carbs in traffic due to the vey snug fit of the engine. The extractors don’t help the heat issue. However a recently installed push fan has helped greatly. The Allard is primarily a cruiser for 98% of the time, however on Occassion I do need those secondaries to work with out hesitation. One again thanks for the helpful advice.
I believe the mis-calibration of the imitation AFB you have is more important than its size. I run two 625's on a Ford 390, and it runs like a scalded dog. I would suggest a genuine Carter AFB DESIGNED FOR THE CADDY 390 (and yes, it is smaller) would be a much better choice. I don't think the carb is too large; although the 625 original should easily be adequate. It probably is not jets/rods although the jets/rods calibration is FAR from optimal for the Caddy engine. The imitation carbs have an airvalve that is designed for a "screamer" engine, not a "torquer" engine. The airvalve opens too soon, causing an instantaneous lean until the engine can catch up. Then, if the jetting is close, would run pretty well. If I had a dollar for every Buick, Cadillac, Chrysler, Ford, and Pontiac enthusiast that has called me with this problem, and then solved the problem with the originally calibrated Carter, I could buy Hawaii, and retire! EDIT: one other comment. Your avatar shows open hood, and wind screen. Don't even think about an AFB in an open hood environment without an aircleaner (or wear a "gas mask" because you will have a face full of gas. The design of the AFB is such that air velocity across the bowl vents will syphon gas out of the vents, and throw it back into your face. SECOND EDIT: another comment. The AFB can be made to race exceptionally well. For going fast around corners, one needs two modifications: (1) overhead bowl vents similar in design to those Carter used on the Chevrolet WCFB dual quads (as far as I am aware, they don't exist, we fabricated the ones we used); and (2) baffles in the float bowls for the primary jets similar to the ones used on the secondary jets. Again, as far as I am aware, non-existent, but easily fabricated. Jon
What an informative response Jon. I now have a better understanding of what carburetor is appropriate and suitable for the Caddy. I'm totally convinced and would now like to purchase a reconditioned AFB Carter for my Caddy. What is the best way to contact The Carburetor Shop and will you export to New Zealand? Regards Sabin
Sabin - thanks for your comments. However, my comments on this and other forums are NOT done to generate business, rather to try to "pay back". The old car hobby has been my business now since 1973. I am sold out of Carter AFB's for the Cadillac 390, and this would be your best starting point. Here is a link to the Cadillac portion of my website, with engine displacement and original carburetors from 1957 and newer. Make a list of those that fit the 390, and search for one. https://www.thecarburetorshop.com/Kcadillac2.htm Jon.
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