mechanical fuel pump limits?

[rubenski]

Look in the begining of clonebug's thread in here!

[petew]

Hopefully clonebug will jump in here, but here is his thread with the boost referenced fuel pump...

viewtopic.php?f=3&t=127936#p996079

You'll need to read through it all. However, if memory serves me correctly, the limit was not fuel pump. Rather getting the carb to evenly fuel the engine on boost proved to be the issue. He tried every conceivable carb mod, with out a satisfactory result. In fact it killed the motor. Which is why he moved over to EFI. Not that I'm suggesting you should do that, but...

Mike might also be able to shed some light on this. Although he's running drawthrough setups on bigger motors.

[madmike]

I use electric Holley Black/Blue or Red pumps with boost referenced Aeromotive reg, plugged the hose for the big Demon carb

[Clonebug]

i'd like to hear from some of you guys that have boost referenced your mechanical fuel pumps. how much boost did you run, what size motor, was it a stock pump or aftermarket, problems you had with it, etc etc..? i read someone ( i think it might have been piledriver?) said they run 13 psi on stock pump before going efi? on that note, i can appreciate how much you guys love your efi but please dont turn this into a "toss you carb and go efi" thread, those just always end up going nowhere.

I ran up to 13 lbs boost.

Did a Blow thru carb on a 1600 and then a 1679. The 1600 was fine until the clutch slipped at 13 lbs and when I pulled the flywheel to fix a small oil leak I found that the case had a 3 inch long crack and it was 1/2 inch from the oil gallery. This was not caused by the turbo.
I then built the 1679 and ran that for one season on a carb.
Finally figured out the lean running and fixed it but by that time I had all the parts for EFI and I just did the switch.
The solution to the carb leaning out was to extend the float bowl vent up about one inch into the tophat. I'm sure it would work but my goal was FI and I was done with carbs.
I used a Bocar pump boost referenced off the turbo up to 13 lbs. I gave the carb an initial 3 lbs fuel pressure and it worked great for 7000 miles.

I have read that the stock fuel line and pump is good up to 170 hp and I am guessing I was at 120 plus hp with my setup.

Oh... and by the way.... I love my EFI........


There is nothing wrong with running blow thru carb if you don't mind working thru the challenges. I know I spent a lot of time rejetting and it ended up being the hose extension on the float bowl vent that gave me all the fuel I needed. I went all the way back to a stock main jet on the Bocar and it still was running rich.
That was when I found out the limit of the stock clutch. With the crack in the case my 1600 was done.