[455rebel]

With 455 rebuild, approx 400hp, do
I need to upgrade to a 3/8 fuel line?
Feeding a cliff spec, q-jet, with a mechanical pump.
Works now ok, to 5K.
Want to occasionally hit 5500.
Anyone still running 5/16 with big cubes?

[1967Tempest]

Im still running 5/16ths. Have not had an issue so far. That said, I will be going up to 3/8ths when she gets restored.

[Chief of the 60's]

First off, is this going to be regularly raced or just a street car? If its just a street car its not really going to be a matter of "need". It will run fine on 5/16". However, flow is just as critical as pressure. The more flow, the better the performance at the track and if its going to be at a track 1/2" is what you should be considering or leave it alone.

[steve25]

It's also the G forces that come into play to stall the fuel out in the whatever size line you have as the car accelerates harder.
I would take the time and funds now to atleast install a electric pump back by and below the tank.

[Chief of the 60's]

A car launching with 400 horse doesn't have too much to worry about when it comes to "G forces".

When G-forces do come into play, a sump is more critical then comes a bigger fuel line.

An electric fuel pump wouldn't help much if the flow ability isn't there.

[Skip Fix]

I'll disagree a 5/16 will work at 400 HP. Even my 180 HP 78 400 with a mild cam change started running out of fuel with a 3/8. Had to add a small pusher pump. Adding a 420 HP 455 finally had to go to electric pump and finally 1/2" to the carb. Still has stock tank and 3/8 pickup and can run int he high 10s @124. And electric pump is not below the tank about half way level.

[455rebel]

Ok, thanks. I have a pusher pump in line as far back as possible. I installed to prime carb after setting for weeks at a time during winter months, got tired of grinding starter minutes before ignition. I'll try as is and upgrade later if run out of fuel.
On the other hand, it's original 1970 steel line, might be future trouble?
If I do change to 3/8 ,how do I handle the pickup in tank, it will be 5/16?
Splice after sending unit?
Or change pickup?
Not many AMC 3/8 pickups ,left,? LOL

[Sirrotica]

If it were my car, I'd probably remove the 5/16" line from the tank unit and replicate it with 3/8" steel line using the old line for a pattern. Drill out the tank unit for 3/8" line and solder/weld the line to the old tank unit. I wouldn't bother with a sock on the end of the pickup tube, just make sure it has a large capacity fuel filter inline before the carb.

I did an engine swap in a 1973 Jeep pickup with a 455 Pontiac with a Q Jet, it also had 5/16" line in it (AMC product during that time, 360 V8 originally). It was in the late 70s when I did the swap, so maybe my memory isn't perfect. I however don't remember it running out of gas even with 4.10 gears and just a mechanical pump. Of course I was street driving it, not racing it. Still there were a few impromptu exhibitions of acceleration with other vehicles..........

[77 TRASHCAN]

Originally Posted by 455rebel

Ok, thanks. I have a pusher pump in line as far back as possible. I installed to prime carb after setting for weeks at a time during winter months, got tired of grinding starter minutes before ignition. I'll try as is and upgrade later if run out of fuel.
On the other hand, it's original 1970 steel line, might be future trouble?
If I do change to 3/8 ,how do I handle the pickup in tank, it will be 5/16?
Splice after sending unit?
Or change pickup?
Not many AMC 3/8 pickups ,left,? LOL

I'd go 3/8, no question...
Might want to pull the fuel tank, first see what you've got to deal with...the AMC folks had some different ideas about how to do everything...sometimes they tripped over the word "cheap", beware...

[tjs72lemans]

Pontiac built several cars over the years with 300 hp and a 5/16' line with no issues.

[lust4speed]

"Marginal" comes to mind. My '67 GTOCruiser with 400 engine when running the Quadrajet wound occasionally go soft at the top of 2nd and it was only dyno'd at 363 horsepower*. It had an Airtex mechanical pump, 5/16" stock line, no sock, no filter in the carb, and a free flowing filter in line.

Also just finished working on a friends 67 GTO 406 engine with stock 5/16" line, a mild HR cam and aluminum heads and mechanical fuel pump. Two out of three runs felt great through the gears while one run definitely had the engine going just a little soft at the top of 2nd. Quadrajets have so little reserve that they are the most susceptible to fuel issues. Holley's with their two big fuel bowls are much more forgiving.

Sometimes the drop can be so minor it can't be noticed. Had another friend that thought he was running well until upgrading his fuel system and cut a tenth off his E.T. with the better fuel delivery.

* 363 horsepower with 8.6:1 compression running 87 octane California gas.

[Skip Fix]

Mine went "soft" with 7.8:1 400 and only a 228@ 0.050 cam in a freshened '78 400 2.56 rear gears and 3/8 line.

Here is an AMC sender if it is an AMX
https://www.robbmcperformance.com/pr...7_amcsend.html

[77 TRASHCAN]

Originally Posted by Skip Fix

Mine went "soft" with 7.8:1 400 and only a 228@ 0.050 cam in a freshened '78 400 2.56 rear gears and 3/8 line.

Here is an AMC sender if it is an AMX
https://www.robbmcperformance.com/pr...7_amcsend.html

I’d almost bet that will fit his rebel. The AMC folks didn’t spend money to re-engineer parts for every different model the made...

[455rebel]

Well for 189$, I'll solder a 3/8 line in mine. I've already had my tank apart to flush. My gauge works fine, I'll try to mod the line pickup?
And the last time at the track, it did get soft in 3rd. It made it through 1st and second, fine, then just before finish fell off.
After that I installed pusher for startup only. But I started turning it on, when red light brawling. Never went soft again.
The 3/8 aluminum line they sell in a roll ok, will it solder to pickup hole?

[455rebel]

I'm also looking for 5in round headlight buckets, and mounting bracket? Can find bucket, can't find mounting bracket with adjusters?

[Sirrotica]

Aluminum will not solder to steel, you need steel or copper to solder to your pickup assy.

[KEN CROCIE]

Classic Industries has the 3/8" pickup assm. for $50.00
Old fuel lines get rusty inside and restrict flow.
When H-O was up and running, we observed that a stock T/A fuel system would not supply enough fuel when installing headers and a Re-Jet kit. That was when the cars were relatively new.

[steve25]

Just all bends in the stock fuel line make for a restriction.

[Half-Inch Stud]

3/8" line, Elec Pusher pump, and Mech pump is minimally sufficient for a modern 455.

[track73]

Has anyone installed the RobbMc PowerSurge.