What if your carb is too big?

[RallySnake]

Ford 428,

You beat me. I was thinking rotor phasing, too. Having too large of a carburetor will NOT cause this problem. Save your money.

Paul

[tdsmith]

I think I'm ready to end this thread...

Here are the changes I made:

1. Switched Intake from single plain to dual.
2. Switched to 'high flow' air filter
3. Replaced the stock fuel pump with a Holley blue label
4. Replaced and re-gapped the plugs to .040
5. Reduced primary discharge nozzle from 28 to a 25
6. Reduced the primary jets from 71 to 69
7. Reduced the secondary jets from 80 to 79
8. Re-curved the distributor to get total advance @ 2600
9. Set total advance @ 38 deg.
10. Tuned the car on a dyno…


Before all this my car had 273 rwhp @ 5200 and 312 ft-lbs @ 3600 and as you all know lay down @ 5200 FAST. Now, I am getting 313 rwhp @ 5250 and 339 ft-lbs @ 4250. But the best part is the HP now stays above 300 all the way to 6500. We didn’t test above that.

I don’t know which changes made the biggest difference, but my guess is changing the fuel pump, air cleaner, and advance made the biggest difference. All I know is that this engine was rated @ 410 HP when it was built…. If that’s true then I’m only losing 18%.... remember, I’m in Denver, so that is fantastic results.

By the way, after we got the car tuned, we put the old cobra air cleaner on to see if it made a difference. I lost 14 rwhp and 18 ft-lbs. Now that a hard fact….

Oh, the other fact I learned in all this is that the stock in-line fuel pump is rated 2.5 – 4 lbs. When I turned on the bump without the car running I got 3 lbs of pressure for it, but once the car stated and you got the RPM above 2500 the pressure dropped to 1.5 lbs of pressure. Holley recommends 6 – 8 lbs for their carburetors. With the new pump I have 7 lbs no matter how hard the engine is running. It’s louder than the stock pump but I think its better solution.


Thanks for everyone’s advice and help on this. I think I am now getting the most out of my engine I can without any significant changes.

Troy SPF#578

[shaps]

Congrats on the Fix, Troy! Enjoy!
Which "High Flow" air cleaner did you switch to and which one were you using before??
Thanks!
Shaps

[tdsmith]

I had the standard 'Cobra Oval' with a brand new element. I switched to a 10" circle S&B with the breathing top. IT's jsut like the Extrem ones from K&N but the lid is a bit more solid; the top doesn't sag.

Troy