LOST 10mph AND ABOUT 6 TENTHS

[MR DERBY CITY]

Originally Posted by monte8616

Did the fuel system test - all good - the welding is an interesting thought... batteries are pretty new - Racepak shows all good with fuel pressure... but something to think about with the volume - thanks everyone! Keep the ideas coming!!

Just curious, how much did it pump in 30 seconds,.....carry on....

[monte8616]

Gallon in 18 seconds so volume is good

[Jeff Stout]

Not to bash, but it was a Barry Grant pump. It was aerating the fuel. So the gauge was actually air/ liquid pressure. No O2 sensor at the time. Also at the time I was not to smart and threw about 1500.00 and 7al, wires, new tach, plugs. Checked valve springs twice. Cam timing, compression test. Three different outings at track. It was a real learning experience.

[monte8616]

Originally Posted by Jeff Stout

Not to bash, but it was a Barry Grant pump. It was aerating the fuel. So the gauge was actually air/ liquid pressure. No O2 sensor at the time. Also at the time I was not to smart and threw about 1500.00 and 7al, wires, new tach, plugs. Checked valve springs twice. Cam timing, compression test. Three different outings at track. It was a real learning experience.

I don’t have an O2 sensor yet either... we did the new plugs and wires too! Brand new MSD too lol - what’s interesting is that we originally thought that it was the MSD box because when we changed the box and made a pass, it went back to what it should’ve been running - then, after that, it went back to being slow again... ugh

[Bill Marshall]

[QUOTE=Jeff Stout;629310]Not to bash, but it was a Barry Grant pump. It was aerating the fuel. So the gauge was actually air/ liquid pressure. No O2 sensor at the time. Also at the time I was not to smart and threw about 1500.00 and 7al, wires, new tach, plugs. Checked valve springs twice. Cam timing, compression test. Three different outings at track. It was a real learning experience.[/QUOTE
Jeff This car use to be fuel injected and it still has the high pressure pump in it with regulator to knock down the pressure. regulator is set at 7.5 lbs also we dyno'd the engine and it still has the same power from when it was built

[rognelson777]

grounds. disconnect, add serated washers and no lock nuts. nylon in locknut can melt from cranking engine when wire gets hot.
fuel lines. any rubber can actually close down and limit flow when hot

[Chuck Gallagher]

I agree, grounds are most likely weak.
Run a redundant ground wire from the side of the engine block back to the battery ground. Or, if your ignition box is inside, as most are, to the ground that is common with the ignition box and battery.
Use a good size wire and a star washer under the connector at the block.
Also, if you don't have a good size ground wire from the box to the battery negative post put one in.
Grounding to the chassis is always a crap shoot in a race car and the root cause for the majority of electrical problems.
Good Luck
Chuck Gallagher

I should have said this about engine block grounding. The most important task your battery does in your race car is provide a steady, high level of amps (current) to your ignition system. Racers in all forms of motor sports have been able to make more power over the decades by putting more fuel and oxygen inside the combustion chambers and completely igniting that mixture with higher power spark across the plug gap from the coil. The power (amps) of those sparks will never be greater than the resistance of the current path from the threads (ground side of the plugs) of the spark plug back to the negative post of the battery.
A weak engine to battery ground path does not always produce engine miss, usually just incomplete combustion resulting in less power.

[monte8616]

Originally Posted by Chuck Gallagher

I agree, grounds are most likely weak.
Run a redundant ground wire from the side of the engine block back to the battery ground. Or, if your ignition box is inside, as most are, to the ground that is common with the ignition box and battery.
Use a good size wire and a star washer under the connector at the block.
Also, if you don't have a good size ground wire from the box to the battery negative post put one in.
Grounding to the chassis is always a crap shoot in a race car and the root cause for the majority of electrical problems.
Good Luck
Chuck Gallagher

Thanks so much! Think we will be taking this car apart almost completely to check it all out!!

[ss3011]

[[/QUOTE
Jeff This car use to be fuel injected and it still has the high pressure pump in it with regulator to knock down the pressure. regulator is set at 7.5 lbs also we dyno'd the engine and it still has the same power from when it was built[/QUOTE]

If the engine ran good on the dyno , then what parts are different between the car and the dyno ? Usually the dyno has it's own ignition box and it's own fuel system . Maybe check these two systems out to start with .

[Larry Hill]

Does the car have a timing retard box. I hade one go bad. I had the box checked, MSD said it was good. Hooked up box and car was slow, removed box and the car was fixed.