Fuel Pressure question

[THUNDERZ]

I have a triple set up and was wondering if it is a good idea to run higher pressure up to the regulator to avoid vapor lock and other typical carb problems. Thanks!

[Guest Z-rific]

I don't see how more pressure before the regulator will affect vapor lock at all.

 

Vapor lock typically comes from overheated fuel. Typically, this is avoided by heat shields, carb spacers or running fuel lines away from exhaust manifolds, etc.

 

Carburetors tend to run fine if tuned properly. Run the recommended fuel pressure to them, keep them tuned porperly, and you should be fine.

 

I'm also not sure what you mean by typical carb problems. Most proplems come from wrong jet/needle sizes, worn parts or gaskets or poor tuning. Fuel pressure is actually pretty lenient. 1 or 2 lbs over or under recommended pressure typically causes no problems.

 

I know there are some carb experts here that may have a different opinion...

[technicalninja]

Increasing the pressure of any liquid increases its boiling point and will reduce vaporlock issues. This is the reason Nissan added a transfer pump in 72. Fuel at 2 PSI is less likely to vaporlock that fuel at lower than atmospheric pressure IE the 70 and 71 Z which had massive vaporlock problems.

Having said that, The tripples that I have worked with have been very sensitive to overpressure issues- Webers will some times puke fuel out of every orifice at 5 PSI; 1.5 PSI over their suggested 3.5PSI. Mikunis seem to be less sensitive.

Use a 3.5 to 4 PSI rated pump mounted back by the tank. I prefer the little square Facet style. Most times I don't use any regulator. I will run a pressure gauge taped to the window for a high speed test drive. If it will maintain 2.5 PSI in 3rd gear full throttle redline its good. If it won't I remove and block return line and retest. Worked so far for me. No vaporlock issues on 15+ cars over the last 10 years even here in Texas. Properly heat sheilding/routing of fuel line is important also.

Every round cylinder "Carter" style pump I have installed failed at some point and had to be replaced. I have never had to redo a "Facet" style pump

Every high capacity/7-15 PSI fuel system has needed serious work to make it work-restrictors,fuel pressure regulators, etc... They have never been worth it.

The Facet style pump is very noisy if you bolt it to the unibody. I mount them with a couple of V.W. radiator insulators. Remember to add a ground strap from pump body to car if your pump has only one wire.