Need help about how to feed my new motor. I have a 326HO car that I am putting in a 455 with 4 barrel. The original motor only had a single line from the gas tank. Do I need to upgrade this to a dual line and new sending unit?

Thanks, Wade

Depends on how you're going to drive it. For normal operation what you have will probably be fine. If you want to drive it like you stole it then you'll at least have to upgrade your fuel pump. Your 3/8" fuel line should be able to supply enough fuel as long as there are no restrictions.

Are you asking about the vapor return line when you say dual line?
A lot will depend on which carb and fuel pump you intend to use.

I did mean return line. I just wasn't sure if the original size line would feed enough fuel and if I needed a return line.
Would I be better off using an electric fuel pump or staying with the mechanical unit on the motor? Doug what did you do with your new 400 to feed it?

When I put the new engine in last year I thought I needed a better fuel pump and put a holly high volume on. Had problems with vapor lock and carb tuning. Ended up going back to stock pump with return line. 3/8" feed and 1/4" return. Feeds 400hp and no problems.

I put in a 1/4 return line and matching sending unit. Not to bad of a job but not that much fun. I really had to bend the hell out of it up by the motor. When I researched this it just seemed that all the performance pumps had return lines. I got some good info about the difference on the PY site.

What I didn't realize was the stock 3/8 line was not going to do it for the Q-jet small fuel bowls and the thirsty 455. I have purchased the RobbMc fuel sending unit and I still need to get the 1/2 prebent fuel line from inline tube. I could have always went with an electric pusher pump too and kept the 3/8 line.

My brother ran into this with both his cars as well. The cars would just die off in the upper RPM and not rev up any higher. He bypassed the metal line with a rubber line and resoved the issue. The rubber line has a larger inner diameter then the metal line.

My car would hit around 4800 rpm and not rev much higher.

most people are saying the gas formula today is horrible for our performace cars. It quickly evaporates in the carb and pulling the gas makes it vapor lock more easily.

The electric pusher pump sounded like a cool way to prim the carb before starting up. I guess there is a carter pump that works really good if you plane to use the mechanical pump as a primary and the electric pump as needed. Thus the mechanical pump can pull through it.

Lots of good info. I think that I will have to try what I have and know that I may need a larger line if I run into starvation issues.

Thanks, Wade

My car would hit around 4800 rpm and not rev much higher.

And it would rev higher with a bigger fuel line? No other changes? Sounds like about the time stock valve springs give up.

I can't really say about a 455 because I've never run one before but my 400 would run out of gas about the 1K foot mark with the stock single line and pump. Changed over to an elect and the problem disappeared. Electrics are noisy though.

You can in fact get away with the stock single fuel line with no return line. HOWEVER, as mentioned above, you WILL need a better fuel pump. Here is a trick that I learned and have shared on this site several times. Buy a stock fuel pump for a 1973-74 Pontiac SD (Super Duty TransAm) 455. The gas resevoir on the bottom of the pump is about 3-4 times bigger than a stock fuel pump for any other Pontiac engine.

Then, if you want to use a stock metal hard line to connect the fuel pump to the carb, order a pre-bent pump to carb fuel line for the same car (73-74 455 SD). This will solve any potential fuel delivery issues. Simple solution as everything fits and you are using stock parts. Guys will tell you that you need to run an electric fuel pump etc. Not true. The old 455 SD TransAm ran just fine back in the day with no fuel delivery issues...

I had to go to an electric pump. I will take your advice nd go with that stock one as the electric pump was noisy!

Does the stock SD pump use the return line?

I beleive it has the outlet for the return line, but I simply plugged it as my car did not have a return line. It worked flawlessly on my Bird and I was pushing 405hp at the rear wheels. My friend Mike who has a built 455 in his 65 Tempest did the exact same thing and it works great.

Prior to using the SD fuel pump my Bird used to run out of fuel at the top of 2nd & 3rd gear. Once I installed the SD pump, NO problems at all. I think just having the larger bowl/resevoir solves the "running out of fuel" issue. At least it did for me and my friend Mike...

That's what I thought. You hear people talk about plugging the return line and running the risk having the pressure overcome the diaphram and filling the crankcase with gas but that's probably just one of those old urban legends. Seems alot of peole do it and it seems to work out.

Thanks Earlybird and everyone else who posted thoughts and dialog. I'm going to get the SD pump and line and move forward with that solution.

Thanks, Wade

No prob and good luck. I bought the pump and line from NPD as they were the only ones at that time to have both in stock. NAPA would likely have the pump as well but I wanted a steel pre-bent line as well. I did not want to run a rubber fuel line from the pump to carb.

Firebob, I can't say that I have ever heard that before and can only go by my own experience as well as our group of Pontiac friends here. None of which have a return line hooded up and no issues...

Does the 73 SD carb have the front facing inlet for the fuel filter like the earlier carbs? I am assuming so, but there was no mention of it? You say a direct fit correct?

All Pontiac carbs are front inlet.

Not for the Sprints, they came in from the side.

Hang on here. I am talking about a 73 SD fuel pump NOT the carb.

And again, if you do switch to the 73 SD fuel pump, you will need the 73 SD pump to carb fuel line as your current line will not reach the inlet on the 73 SD fuel pump as the resovoir hangs down MUCH lower on the SD pump (hence the reason it is less likely to run out of fuel at high RPMs).

Or you can always run a rubber line from the pump to carb but I DO NOT recommend this. NOT a good idea! Ask me how I know...

How do you know?

LOL Rubber line bent & cut off fuel supply, stalled the car. Pulled over, straightened the line driving down the road it got too close to something and burned a pin hole in the line, sprayed gas all over under the hood. Luckily no fire but had it, oh boy would have been ugly. Bottom line, go with the correct hard line and save yourslef any potential problems...

Do you recall the part number or description from NPD for the 73 455 SD fuel pump?


If I want to replace my tank-to-pump fuel line, should I be going for whatever metal line matches my car in the NPD catalog? Or should I be looking into something different?

Thanks!