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RacerX10
06-08-2011, 02:26 PM
I'm running this pump on a 604 :

http://www.speedwaymotors.com/Speedway-S-B-Chevy-110-GPH-Racing-Fuel-Pumps,23952.html

I'm checking fuel pressure at the log and it won't get over about 3 PSI at any RPM. My fuel gauge is old but I'm assuming for the moment it's reading correctly.

I had a regulator / bypass thing installed but I took it off and the readings didn't change at all.

Any ideas ? From what I've read I need more like 6 PSI.

Thanks.
joedoozer
06-08-2011, 02:47 PM
I believe you can change the pressure of these pumps by spacing them away from the block. Thicker gaskets and things like that. A clogged filter would cause low pressure as well.
RacerX10
06-08-2011, 03:33 PM
I've never heard of such a thing. Seems like there would have been info with the pump if that's what I needed to be doing.
RacerX10
06-09-2011, 08:51 AM
So apparently, you don't even NEED a return line when using a mechanical fuel pump on the block ???

This "stock" stuff is all new to me :)

If I pinch off the return line, my fuel pressure comes up to 6 PSI or so like I expect.

My new plan is to just cap the fuel log at one end and feed it straight from the block mounted pump with no return line.

Any problems with that ?
swaybar
06-09-2011, 09:24 AM
No problem with that - should take care of it.
RacerX10
06-09-2011, 10:04 AM
No problem with that - should take care of it.

Excellent, thanks for the reply !
dirttrackrocker
06-10-2011, 11:40 AM
Yes you are right, no return line with a stock mechanical pump.
RacerX10
06-10-2011, 04:27 PM
Well, I tried it with no return line and it was showing 10-12 PSI at the fuel log, clearly too much. This is with a 7 PSI pump.

I put the regulator back on and reconnected the return line, put a new diaphragm in it and I'm now able to kinda sorta adjust the fuel pressure to around 6 PSI like it should have but it still seems a little flaky.

Guess I'll just race it tomorrow and see what happens.
swaybar
06-10-2011, 05:30 PM
The way I would run that setup is with a diaphragm type regulator - no return. You should be able to adjust the pressure from 4 to 9 or so. Set it at 6 and forget it.
gadirtracer
06-11-2011, 02:00 AM
I believe you can change the pressure of these pumps by spacing them away from the block. Thicker gaskets and things like that. A clogged filter would cause low pressure as well.


I've never heard of such a thing. Seems like there would have been info with the pump if that's what I needed to be doing.

At 12psi, add a few gaskets or stack another plate between pump and block, fuel pressure WILL decrease. 1 gasket should be about 2psi less.

Considering this is an el cheapo, 6 vane, $70 "race pump" what are the chances this was 100% made by a company with proper tolerances/quality control? Get another one, next one may make 2psi!
Not to mention the block, is the pump mounting flange the correct depth, cam in the right place, fuel pump push rod the correct length, all of these factors will affect fuel pressure.
RacerX10
06-11-2011, 07:44 AM
Good to know.

I did swap it out and put a holly brand race pump in there, it did the exact same thing so I think the pump is operating normally.
bigronlm55
07-05-2011, 02:01 AM
You need to have a by-pass regulator , not a standard regulator, in order to run a by-pass return line.........that's why your fuel pressure goes back to normal when you pinch the return line. The regulators look the same but are cast differently insde. Go to holly's website and poke around.......you'll find plumbing diagrams that show the flow charts.