My engine builder is just about ready to install a 555 HP 406 (Dynoed) in my 77. The car has a high performance mechanical pump that will accommodate a 1/2" line and it also has a QF 750 carburetor. The engine builder is recommending that the stock 3/8" fuel line be replaced with a 1/2" line.

I do not intend to take the car to the track but once I have the opportunity to drive it that may change. The stock line is probably fine for day to day street driving but what will happen if the engine is pushed to wot for 10 - 12 seconds @ the track?

Right now the engine, transmission, suspension, brakes, steering, etc... is off the car and it is being prepared for chassis and engine bay paint. If I am ever going to change the line now is the time.

So..... Is the change necessary? If it is then;

Is there a source for a 1/2" line?
How can it be installed without lifting the body?

 

3/8`s line is all you need......have your wrench look at the tiny hole in the carburetors fuel nut.....and L88`s use the same size......what you may change is the mild steel OE line to stainless , but 3/8 is all that's necessary

 

When I bought the current cam for my 427 from Harold Brookshire, owner and highly respected cam designer at Ultradyne Cams at that time, he recommended that I change my fuel lines to 1/2" if I planned to race the car. Your engine builder is not steering you wrong on this although some folks will say otherwise. Harold has a serious racing background and knows more about cams and feeding engines than most folks out there. He gave examples of cars at your power level he had been involved with that picked up a noticeable improvement through the 1/4 mile after making the change. I told him that it wasn't practical for me at that time and he said that if I ever made it to the track and found that my engine nosed over or stopped pulling hard towards the end of the 1/4 I'd know I needed to go to 1/2". I'll finally make it to the track this spring to find out.

Bottom line, IMO since you're in a great position to upgrade before you button things up I'd go for it now rather than regret it and have to do it later. If the cost is an issue that might change things but as much as you must have into the engine I'd want to know that it won't run out of fuel when being used as intended. You're probably going to want somebody local with a strong rep to bend a system for you. Your builder should be able to point you in the right direction. Whatever you decide to do, you are in for quite a ride with that motor. Have fun.

 

Are you going to change the pickup tube in the tank to 1/2" or leave it 3/8"?

 

This is really the answer. AN 6 is fine for what you have, but who knows what engine you might want in the future? Do a top-notch plumbing job now including a supply-side filter and a return line (capped since you don't need it) while it's easy to do.

AN 8 steel tube and benders are available in a roll from any of the major online vendors (Summit, JEGS, etc.)

 

Is the 1/2 inch line required? "NO"

Is the high output pump required? "NO"

Is the return required? "YES, if you have a hot rod motor in a hot climate"

All you need for higher fuel demands is to change the needle and seat to high flow units (bigger diameter) I used to run the titanium or alki N&S. I've since changed to NASCAR type high flow anti foaming. Having your foot on the floor for 11- 12 seconds in a 1/4 mile is nothing. The Main straight at Miller Race track is over 3000 feet long. I never had a hint of nosing over.

People run these big pumps and regulate them way down to 6-7 psi kind of waste on a little 406 motor. You don't have a 1200 CFM Dominator Carb on a 632 ci monster!

The return line keeps a good supply of cool fuel going to the carb bowls. trapped heat in the engine bay causes vapor lock in non return type setups. You shut off your car in the store parking lot and you come out and it won't start.

You got to be smarter than the stuff you are working on!

 

If you decide to go 1/2" fuel line, make sure you either sump the tank or go to a 1/2" pick up.... Here is a source for the pick up..



http://www.robbmcperformance.com/pro...vettesend.html


You will probably be fine with the 3/8" fuel line but if you are going to be racing the car a lot, particularly 1/4 mile, I would change the fuel line and pick up.

I am about to go through all of this myself as my system will not hold fuel pressure through the traps.

 

Or if sometime in the future he goes to an electric fuel pump for something big and fuel-injected.

The frame's nekkid - now's the time for ANYTHING that MIGHT be needed later. 15' of AN 8 tube is cheap

 

id stick with 3/8
Went to all 1/2. Sure the pipe will flow more but can the pump keep up the psi and the supply...thinking psi may drop at some point

Looking back 3/8 was probably fine (around 580-+hp)

If that helps

 

1/2 inch only if you plan to race. i mean really race. jmo

 

Thanks for all the replies - keep them coming and let me know if there is a source for a pre-bent 1/2' line.

I see no down side to replacing the line at this point.

 

If you can dont use stainless.

Ordered one up in steel and had it duped in Stainlesss did not fit.
Spent a bunch and hassles getting it cut flared etc to fit.
There is no give with stainless the mild steel line you can bend and tweak some. Would not do it again (just haaaad to have shiny stuff under the frame noone will see or care about though at the time lol).

 

Smokey Y. says use 1/2" for a racing motor but he raced mostly circle track endurance. If replacing line from tank i would install only hard line most of the way to pump.

cardo0

 

If you are running gasoline I still stand ny the stock 3/8th and the return line.

If you ever intend to use E-85 where you burn nearly twice as much fuel, by all means do a 1/2 stainless hard line the full length.

I've done a few race cars with stainless. I just use the steel with rubber mounts brackets and use self tapping stainless screw and run it on the inside of the frame rails.

You have to use a good quality flaring tool because stainless is hard metal