[goatwgn]

I dont like the single line pumps. They dont allow you to run a vapor return line. I would check your fuel pressure, (it should be 5 or 6 psi or so, but most importantly, it shouldn't drop off a lot when you open the throttle) I've run a factory type (with the big canister) high volume pump with 3/8" outlet and a vapor return line for years on a 455 with no fuel starvation. Make sure that you also have 3/8" line coming from the tank, as well as the pickup. Some were only 5/16". I did run a Carter high volume pump without vapor return line before this and had vapor lock issues in hot weather. I think the Carter pump is a good unit, but running a return line seems to keep the fuel from picking up excess heat before entering the carburetor. Just some ideas, hope this helps.

[74Grandville]

I was looking at the large can stock units. If I where to go that route, which one should I choose?

[goatwgn]

I would get one for a 1971-72 455 HO "F" body car. These should be High Volume large canister types with the lines in the correct position for your car. If you have trouble at your local parts stores I beleive our host may have them.

[PontGuy]

I have a very similar 455 setup to yours but running a stock-style Airtex 40710 big bowl pump with a vapor return (listed for early 70's 400/455s). I installed a new tank and the new stock-style 3/8" pickup is plumbed through the original 3/8" tubing to the pump. I figured it would be enough but now not so sure.

I am about 800 miles into the engine since the initial break in and so still tuning, but have come a long way with it. The shift point feels "right" around 4800 RPM or so but this is just at the ragged edge of fuel delivery. Sometimes it pulls through the shift just fine and sometimes it bogs right at or just after the shift. Also I sometimes get a bit of vapor lock on hot days so having a return line isn't an instant cure in itself.

I am thinking about trying a Robmc pump, but if the original 3/8" fuel tubing is the problem (either restricted somewhere or just too small) then a better pump probably won't solve my problem. I don't want to go electric- been there, done that. It works but at a cost- noise, etc.

Just some food for thought...

Walt

[74Grandville]

Does anyone know the minimum requirement to supply an engine like mine? I would think a stock setup would be enough.

is 3/8" to small of a feed line for a mechanical pump?

[PontGuy]

I asked the same question when I was initially working out the bugs on my new engine and got a wide variety of answers. The street guys had mixed opinions and the racing crowd was unanimous in saying stock is not enough.

I don't think there is a simple answer. Just doing a simple ratio, a 455 spinning at 4900 RPM is sucking approximately the same air/fuel volume as a 400 spinning at 5600 RPM, or a 350 spinning at 6400! So we are probably at the ragged edge for stock components, and it depends on condition of the fuel line, head flow, jetting etc. Going with an OEM style big-bowl 455 pump should help, but it may or may not get you all the way there.

By the way I tried two of the Airtex pumps and never returned the first so I have an almost-new spare that I probably will never use. I'd be happy to drop it into the mail for you to play with, but the inlet/outlet positions are probably not right for your FB.

Walt