My 455 continues to vapor lock when the motor reaches 190 degrees. I have wrapped the fuel line from the pump to the carb. The heat actually appears to be coming from the pump itself. The pump is very hot. The suction line is aluminum and it is cool but as soon as it hits the pump it is hot enough that you cannot put your hand on the pump or hard line.

The temperature sending unit that provides me the 190 reading is in the left front of the aluminum Edelbrock intake manifold.

The electric fan I am running pulls the voltage down to 11.8 at an idle and after running for a period in town the motor starts to spit and sputter. When I get it back out on the open road she is fine after a short distance.
How much voltage will toast a battery. I currently have 13.9 when the fan is not running and at speed with the fan running it is around 13.2. Should I install a larger amperage unit or have the alternator change to provide 14 to 15 volts?

Thanks for any ideas you might have!

Daryl

I put a 80amp alternater onto my 350 as with stereo system & lights on & heater fan it was dropping below 13 volts now it runs 14 to 15 volts all the time now.
I put a 3 core radiator in the car and a 180deg thermo and have not had any over heating issues.

regal1973

I have a 100 amp alternator that I could put on but was not sure if that would improve the problem or not. I am also going to increase the idle speed from 650 to 750 and see if this helps.
The radiator cools the engine fine. I have vapor lock of the fuel line.
Would plugging the vent tube on the fuel pump possibly enhance this heat problem? I started thinking this morning about unplugging this and running a line back to my fuel inlet to the tank to see if this will help.
Thanks!
Daryl

I was running a holley blue electric pump with reg but it let me down about 21/2 hours from home. So I ended up fitting a stock pump from a 350 V8 without a return 1968-1970 vintage. With both pumps I have never suffered this strange how it comes in at 190deg. I think its a overheating problem or poor air flow in engine bay
regal1973

For those that care!

I have found out what causes vapor lock. There is an insufficient amount of fuel supply to the cylinders which causes lean burn. I am using a Holley 3310-4 and the stock jets were #72 I have recently put in #74 and if this does not work I am told that #76 will.

As far as the voltage problem is concerned this is what I have done.
I upgraded to a 140 amp alternator with a very very small pulley which makes the alternator come on immediately. When doing this it is imperative to change the battery wire to a size 6 or larger to enable the current to return to the starter or battery, whichever route one chooses.

Thanks,
Daryl

just as a refresher... "6 gauge or larger" should probably read "6 gauge or smaller." With wire size, the smaller the number, the thicker the cable. I personally run 2 gauge wire for everything in my '63 Buick Riviera. I put in a 94 amp 12SI alternator and experience practically no voltage drop even with all accessories and high beams burning my awesome Sylvania Silverstar bulbs.

A 1000 amp alternator will do no good if the regulator is not behaving properly.

Remember that an alternator is a current generator, not a voltage generator.

An 80 amp alternator will not charge a battery any faster than a 40 amp alternator if the voltage regulator doesn't allow it! I assume your 140 amp alternator has an internal regulator- I have seen these perform poorly. If your problem doesn't go away, you can replace the internal regulator (should take < 1 hour) and boost up your voltage.

In my car, I fought low voltage for a long time before replacing the internal regulator (also a 12SI) with a Delco unit, and that is what finally made the difference. The parts-store replacement alternators often include the cheapest regulator the rebuilding company can find, which may be a problem sometimes. The ones sold at your GM dealer generally work very well.

Just some thoughts.

-Bob Cunningham

I understood a vapor lock to be an air lock in the fuel feed line to before the carburator. If this is so, I question that a jet change will help. The problem was generally solved by running a return line to the tank from mechanical fuel pumps. This kept the fuel cooler.

The most likely place to develope the "lock" is where the fuel line is exposed to excessive heat. Most problems are found when a fuel line has been bent and passes too close to the block.

I had a truck that used to vapor lock on long steep hills. I had replaced the exhaust system with a set of duals and even though it was a good distance from the fuel line, the mufflers got hot enough under these condition to vapor lock the system.

I am interested in what you learn about the heat apparently entering the fuel at the pump. I don't think this is good. I am considering adding the same pump to my car this winter.

Sergio,
I agree with the number being smaller to have a larger wire size but I was talking about size not number. Thanks for the clarification, others may have been confused with my wording!

Bob,
You are correct on current not voltage with the alternator. The alternator used now is the 4th one and it is maintaining the voltage while suppling adequate amperage. I think the smaller pulley is a great advantage because the stock size would not keep up at idle. The current alternator was built by a friend of my brother, who owns a starter and alternator rebuild shop in Tennessee, that builds a lot of them for the guys at the drag strip. If I have any further problems I will put in a GM Delco regulator. Thanks for the input!


rcull,
Vapor lock can be and air lock in any portion of the fuel system.
The jets size increase did improve the problem by prolonging the it but did not cure it totally. The fuel in the bowls still boiled after driving longer distances and stopping in traffic due to the heat generated from the intake manifold. I had a built up style spacer (6 gaskets & 4 aluminum plates, every other one) but it did not raise the bowls high enough. I put in a 1" thick 4 hole phenolic spacer. I am currently running the stock mechanical pump and so far so good. I still have the electric pump under the car but have bypassed it in favor of the mechanical. I still do not know why the mechanical pump gets so hot. If problems continue I will be in touch!

Thanks,
Daryl

Back at it again!

This problem was actually two areas not just one. The carburetor is no longer a problem as far as boiling the fuel. The phenolic spacer took care of that, but the fuel pump and fuel line are still causing problems. I routed the fuel line out of the pump to the left inner fender well and ran it against the firewall to feed the carburetor from the rear. At this time the fuel filter no longer has fuel boiling in it! YES!!

I am going to go back the electric fuel pump as soon as time allows just to insure that the fuel pump heat never causes this problem again. The pump still gets so hot that you cannot touch it. This appears to be from the electric fan blowing the heat from the radiator on the entire front of the engine.

Thanks!
Daryl

Sounds like progress!:thumbsup:


Thanks for keeping us posted...

I have the electric pump installed. I changed the fuel line so that it comes up the left firewall next to the inner fender and then up over the transmission to feed the carburetor from the rear. So far, this is the coolest the fuel filter and line have been.
Daryl