I just converted my stock 250 to a 4bbl.
Started off as a stock 250, stock single exhaust, powerglide-3.08 Nova.
Tried both Clifford 4bbl intake and also the Offy 4bbl intake.
Tossup between the Clifford and Offy intakes, but both of them gained a clean 0.2 sec and 2 mph over the best 1bbl intake and carb setups I had.
That change equates to a gain of about 0.3 sec and 3mph in the 1/4 mile, and calculates to a gain of about 15hp in the Gonkulator from just adding the 4bbl and intake.
I tried many different carbs on each intake so the above is just a summary. One interesting note, during all this thrashing, the 4bbl setups got BETTER gas mileage than the 1bbl Rochester carbs.
The above started out in the "Engines" section but I posted it here too since it might be a better fit.
MBHD Hank asked about the testing above -
Most of the testing I do is Gtech, but some at the strip - which also serves to compare the Chrondeks and the Gtech on the same run. They are NOT the same, at least my Gtech is a couple percent optimistic, but that is ok as it is consistent once you get used to it. Also, the Gtech spits out MPH via a different measurement than at the track. So I calibrate the Gtech results to what the Chrondeks would say at the track, and also correct all runs for weather and weight of the car (even down to how many gallons of gas and my tools). Trying to make it as comparable as I can.
I plan a more full writeup at some point but here is a summary.
This is a stock Nova powerglide 3.08, about 3040 lb including me, some tools, and an extra carb or two. Stock single 2" exhaust, mystery muffler sounds pretty healthy but it is not a flowmaster or polished stainless magnaflow or anything.
The 250cid in there is stock, loose but not tired, just very low friction (and kinda low oil pressure....).
I tried a lot of 4bbl carbs on each intake, Holley, Carter/Edel, Autolite, Rochester. For the 1bbl intake, I ran just the Rochester B jug but 3 different venturi sizes.
Quick Summary: Best 6 Runs by Intake, and the best 1bbl run (way down on the ranking list)
60ft
1. Offy+390cfmHolley – 2.574
2. Clifford+610cfmAFB-2.580
3. Offy
4. Clifford
5. Clifford
6. Clifford
17. Best 1bbl Run-2.609
660ft-ET
1. Offy+450cfmHolley-11.238
2. Clifford+610cfmAFB-11.266
3. Offy
4. Clifford
5. Offy
6. Clifford
14. Best 1bbl Run-11.429
660ft-MPH
1. Clifford+390cfmHolley-62.870
2. Clifford
3. Offy+450cfmHolley-62.506
4. Clifford
5. Offy
6. Offy
27. Best 1bbl Run-60.607
I was kinda surprised that the Clifford did as well as it did down low, since it looks like a big tunnel ram compared to the Offy. And, I was surprised that both 4bbl intakes launched better than the 1bbl intake/carbs - and that the 4bbls were getting better gas mileage. Then again, the primaries of the 4bbls are about the same size as the bigger 1bbl carbs so maybe some of this makes sense.
The secondaries were starting to open, some of them just barely, but none were fully open for sure, as I checked with the paper clip test.
My bottom line right now is kinda that, if I were at a swap meet, and had the chance to pick up either a Clifford or an Offy, I'd get whichever one I could get the best deal on, at least for the type of build above. In cold weather the Offy probably has an advantage, better cold behavior, less puddling, etc - but for builds beyond the stock level the Clifford should gain an advantage so it is a tossup but a close call, closer than I thought it would be at least on this near-stock comparison.
