i'm new at this
i'm trying to do my own mechanic work on my car and so far i'm doing ok but i have a question i talked to a couple of mechanics
about my fuel line to my fuel cell one tells me that i need a return line to the tank becouse of vapor locks???????? another tells me that i don't
need a return line if i'm using a carburator that you only need a return line if your going with a fuel injection engine who is right and who is wrong?????? so i went with no return line
the car starts but i haven't ran it yet
everything on the car is stock exept for the engine
engine is modefied as you can see on picture
that else can i do?????


ted

 

are you using a mechanical or electric fuel pump.

i think the small blocks had return lines but the big blocks didn't from the factory.

if your running an electric pump it would be good to run a return line so you don't have the pump being overloaded but it is not always necissary.

by the looks of that engine i don't suspect that you'll be idleing in traffic in rush hour .(doesn't look like a daily driver) so i'd say it isn't needed

 

Vapor lock is when the fuel in the fuel line or carburetor bowls gets so hot that it vaporizes. You then loose fuel pressure and the motor dies. I've actually been battling this problem lately. With the small engine compartment in our c3's and a stout motor that produces a lot of heat it is a fairly common problem if you are running small fuel line and no return hose. There are different ways of fighting vapor lock.
Any way of reducing underhood temps is an obvious start. Running a return line (regardless of carb or fuel injection) will also help cool the fuel because it is in constant flow and flowing fuel is going to be cooler than fuel dead-heading into your carb or regulator. Another option is running larger fuel line or insulating the line.

If you're just drag racing your car then you might not have to worry about it. Most drag cars don't sit idleing very long and therefore don't have to worry about it much. If you run it on the street then you can just try tooling around as-is and see if you get vapor lock after sitting at a light or after a cruise and you shut the engine off. If it does vapor lock, all you can really do is let it cool off for 20 min or so and it'll usually start back up.
Hope that helps.
You got any pics of your car and motor? Looks pretty sweet!

 

After installing a BB in my car I fought a vapour lock problem for a while. NOT FUN !! Always quits at the most in-opportune time

You can try wrapping the lines & fuel pump with an insulation, but the most reliable fix (got it from an old time streeter) is to purchase a cheap 4-6lb electric fuel pump & mount it back by tank. Problem solved , never even removed the stock fuel pump feeding the quad carb

 

thanks for all the information
wan't to see more pictures click on the picture
and go to my home page
thanks again

 

Ted,
Do you know any of the specs on the motor? I've got a very similar looking setup to yours and I'm interested in how you've done a few things. Do you have any pics of your alternator setup and what's driving your hydraboost setup? Feel free to IM me if you don't want to clutter up this post.
Thanks.

 

Over here the city temp year round is mid to high 90s and sitting in traffic is a daily occurrence. I went craze for over a year with the engine not holding idel in traffic. I finally had to put an electric fuel pump in the tank and run a small return line frown the carb to the tank. I did remove the mechanical fuel pump at the same time. Now there is no problem.BTW small block 350 with 650 Eld carb

 

Not quite. Vapour lock is strictly when the fuel pump cannot pump fuel up to the carb because the pump is full or partially full of vapour instead of liquid. The carb eventually runs dry and the engine dies.

If gas turns to vapour after the fuel pump (also common) then this may cause other problems but that's not vapour lock.

The stock GM solution to this problem was to introduce a fuel pump with three ports- an inlet, an outlet and a bypass or return line. The bypass line allows a constant circulation of cool fuel from the tank which in turn keeps the vapours to a minimum and eliminates vapour lock. It also tends to reduce fuel temps in the lines and carb which eliminates idling problems when stuck in traffic.

I'm always amazed when people downgrade their cars by substituing a two port pump.

 

No offense, but what 3 port mechanical fuel pump do you know of that will adequately supply a 6-700hp big block? A stock one starts having problems supplying enough fuel at around the 600hp level.

 

No offence taken. I can't really answer your questions for three reason:

1) I only know of a few street driven Corvettes with genuine 600-700 hp engines.

2) none of these can use the 600-700 hp output for long enough on the street to notice the effects of a low-flow fuel pump and still stay legal- ie not street racing

3) none of these cars would also sit in traffic conditions long enough that would induce vapour lock.

The point of my post above was to clarify that vapour lock occurs in and around the fuel pump, not at the carb or inlet hose.

 

How would you easily run a return line to the tank when the car was a one line system originaly?

 

Mike,
I am one of those fortunate, or unfortunate (depending on how it's viewed), that falls into the category of a 600hp street driven vette that does need a higher capacity mechanical pump. And even though I don't race on the street I do race it at the track occasionally and many with big motor'd street cars do also. The question I'm not sure answered is if the original poster is driving his on the street much or not.
You're right though, most guys with fairly stock engines don't really need to "upgrade" a stock fuel pump and return system. But looking from the pics, the original poster's motor doesn't look anywhere near stock.

sxr6:
You'd need to install a bulkhead fitting to the tank. And if you're not planning on lifting the body, then running a braided type flexible fuel return line is your easiest option.

 

You're the 'fortunate' type in my book. I've always wondered what the upper limit of a stock 3 port pump was, you've provided the answer

Thanks

 

Don't thank me, thank Jim (427Hotrod). He was able to use a stock fuel pump just fine right up until about that level. I didn't want to go the electric route so I ended up using a RacePumps mechanical pump. Has no problems keeping the fuel up on my motor (as tested on the dyno and at the track) but I've been fighting a vapour lock problem. I may have it solved now but I haven't driven it enough in hot stop and go traffic to know for sure.