Carb Problems?? - Need Help

[mrmustang]

Bill,

You keep forgetting that those engines were burning a different level and octane rating fuel source. The same engine today, with just a set of hardened valve seats to run modern fuel will run better with a small carb than the original carbs that they came with. Again I'm not saying these things just to see myself post, I'm telling you what the last 5 years of real world experience with a computerized chassis dyno that compensates for day to day weather changes and air fuel ratios has taught me. If you want to continue on with the old school way of thinking without giving a new idea a try, then you are the one who is no longer open to a better way of doing things. My case in point will be a 351W/385HP Ford crate engine, which started life with a 750cfm Holley Carb that both Ford Motorsports and Holley suggested, then went through a set of Holley street avengers of the 670 and 770 variety, another Holley 650cfm dp and ended up with a 600cfm dp in the end. The 600cfm DP not only produced the cleanest runs across the spectrum (part throttle, full throttle, and throttle response from 570 rpms (idle) to 6,200rpms (where I chickened out), but made more than 22hp and 28ft/lbs of torque more than any of the other carbs (all tuned to the best they could be)........These are not numbers at the flywheel, but at the rear wheels after going through the entire drivetrain and their inherent loads........Now, back to your examples posted below, taking into account that these engines were set up on an engine dyno and tweaked for full throttle performance and not partial throttle performance, again, which would you choose now knowing that they could not even think to take into account the real world drivetrain loads when they decided on which carbs to plunk down on a particular engine back in the 60's?


Bill S.

PS: You want to give me unlimited funds and a car with each of those engines listed below in stock (+ hardend valve seats for modern fuel) form, I'll be more than happy to rent the local chassis dyno and prove my point for you up close and personal.......

PSS: The other example would be the 427 Sideoiler in my last ERA Cobra, when I bought it it had a 850cfm Holley carb on it that the original engine builder set up. When I switched it to a 650CFM carb, I made almost 41 more HP and 62ft/lbs of torque when on the chassis dyno. Throttle response was crisper and cleaner, and the engine just wanted to scream past redline.........Where the original carb, even after two hours of tuning time (at $150/hr) on the dyno, still ran terrible....

Originally Posted by Cobrabill

Mr Mustang-then please explain the following:

The following carbs came from the factory:
MOPAR 340-625cfm
MOPAR 340-1050CFM
MOPAR 440-1350 CFM
426 HEMI-1200 CFM
455SD & 455HO-850cfm
454Chevy-850cfm
455Olds-850cfm
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Joe,a return line is typically a 4AN line(on a carbed motor)that returns fuel to the tank.This does two things:
1-it keeps the pump from "deadheading"
2-it keeps fuel cooler by circulation

I would have placed the P-guage at the end of the run also.In fact,my guage is at the end of the fuel rail on my car(FI motor).

Again,there are two common ways of plumbing this set-up:
1- is to use a regulator to return fuel to the tank.
2-a fitting can be tapped to except a Holley jet of the appropriate size to regulate the returning fuel.