Hello everybody, I am running a TA perf mechanical fuel pump with 3/8" supply line with 1/4" return. Took the car to the track last week and it fell on its face after 60' line. backed off the throttle an let it compose its self than feathered it back to WOT, and then it pulled real hard. The temperature was mid to high 90's and humid. I am on the fence with running an electric fuel pump, or a Robmc mechanical with 1/2" supply line. The engine is making between 500-550hp 464ci Scotty Brown CNC Eddy's with his 230/246 cam, performer intake, Cliff Ruggles 800 CFM Q-Jet, long tube headers. Please help me make a decision!
You need to monitor your fuel pressure to see what is happening, even if you rig up something temporary.
Thanks for the response Larry.I monitored fuel pressure , and yes it dropped to about 2psi... I guess my real question is, should I go to larger mechanical pump with 1/2" supply line, or just go electric? I want to know if people are having any problems with vapor lock with pump gas (10% Ethanol) with a mechanical pump?
I can tell you that with the system I have (Robb Mc 1/2" pick up, CV Products pump) that I have no problem with vapor lock. I do notice that when I get stuck in heavy stop and go driving in hot weather, the fuel pressure drops off, sometimes as low as 4-5 psi, but as soon as I get clear and up to speed, it recovers to this pump's normal 8-9 psi. I am sure that the fuel gets heated by the pump somewhat. I have insulated the braided line where it gets close to the headers, and that helped somewhat. This has NEVER been a problem at the track, and this pump has never let me down, or nosed the car over under power. The Robb Mc pump includes a tee to run a return, but it entails teeing into the supply line. That will reduce the pump output a bit in the same way it would any pump. I have no return with my CV pump. Interestingly enough, I did have some vapor lock symptoms when I got the car out first time in the Spring. The fuel pressure would become very erratic dipping down near 3psi. I attribute it to the Winter blend gas I had filled the tank with in December of 2017. Winter blend gas is much more volatile for colder temperatures. As soon as I ran most of it out, and started filling the tank with Summer blend, the symptoms completely disappeared. I think what I will do this Winter is run as much of the E10 gas I have out of the tank and then fill it with 10 gallons of this stuff,
Yeah, I am very familiar with fuel RVP values, and the winter grade stuff is almost double the RVP of Summer grade. Are you running a Holley carb? 9 psi is a bit too high for a Q-Jet. What did you modify your fuel sender for 1/2" line?
Robb Mc makes a 1/2" sender for our Buicks, http://www.robbmcperformance.com/products/1069_gmsend.html I selected the -8AN fitting option, then used Aeroquip push lok hose up to the pump, -6AN hose to the carburetor.. I run both a Holley type (AED) 1000 DP carb (track), and a Q-jet on the street. Neither minds the 8-9 psi of fuel pressure. Later Q-jets can take up to 11 psi of pressure with their better float design. This is right from Cliff Ruggles himself. The early Q-jets gave that carburetor a bad rep due to their weak float design. Read this thread, http://www.v8buick.com/index.php?th...e-do-during-acceleration.253488/#post-2088866
Apologies for misdirection/hijack first. I have been looking around my area for ethanol free options and/or high octane race fuel using an app for my phone called PureGas. I called the small plane airfield I get my boat fuel at. They sell eth-free 91 octane unleaded and an eth-free leaded 110 octane. Can I use the 110 leaded? Should I mix it down with the 91? Again , apologies, Jim
Fuel system being slack wouldn't have fully recovered and pulled hard would struggled all the way down once it lost its volume from my experience anyway. Try it with 3/4 tank of fuel
True, need more clarification from the OP. Did it pull hard for the rest of the run, or did it just recover and he got out of it once it did.
Yeah, fell on its face after 60' would not recover until I completely backed out of it. once it recovered, it pulled hard(after the traps!) I did have at least 3/4 tank of gas though...
I work with Rob Ross, we discussed using the new Aeromtive Phantom stealth pump kit. This kit is a bit pricey but will cure any fuel starvation/vapor lock problem.
The Holley mat is a good alternative also for less money, but can't go wrong with Aeromotive stuff either
