newbie needs some mechanical help

[mlmccauley]

I'm a "wire guy" replacing the Rochester carb on a Chevy 350 with a MS I driving a stock GM 2 BBL TBI unit. I do fine with basic mechanic work, but I'm for sure no ace mechanic hot rodder.

I got a really cheap deal on what I now believe (having read more in the FAQ and some other sites) to be the wrong fuel pump for what I'm trying to do.

The pump is a MSD Fuel Management p/n MSD 2225, which evidently is a "performance" unit capable of producing up to 125 PSI (at zero volume, I would guess), but still 30-50 PSI at a fair output volume (according to the flow graph on their site).

Given all this:

Will this pump "overpower" the internal TBI 10-13 PSI regulator, forcing it to output too much/erratic pressure to the injectors, or am I OK?

If this is a problem, can I fix that problem with an external regulator set for a low pressure, maybe 20-30 PSI?

And if I do that, can I plumb the return line from the extra regulator into the same return line the TBI uses without producing problems? It's a non-stock gas tank setup, and getting to the tank to add another return port would be a big pain, to say nothing about me really not wanting to do any machine work on a gas tank.

Or, is all of the above futile, and I should just get a different pump? If so, any recommendations for an outside-of-tank electric unit?

Thanks a LOT for the help!

Mike

REF:
1960 Chevy PU
stock Chevy 350 V8 w/ 4SPD AT
stock Chevy TBI unit
MS I, firmware 3.0

[MegaScott]

I've run this same basic pump on low pressure TBI's with no problems.

You need to make sure that the return line is at least 3/8" hose all the way to the tank with no restrictions.

This ain't a bad way to go....you won't have to change the pump when/if you eventually switch to port injection.

[mlmccauley]

Thanks for the tip! As long as I know that TBI regulator can deal with the input pressure, I'm good to go.

Understood on the need for the 3/8 return. If that line pressurized at all, there would be no way to maintain control.

Thanks again,

Mike

[mlmccauley]

Interesting! I hadn't considered the problem in that light. Makes perfect sense, though.

The case you described sets up a much wider functional window that what I had in mind, which is obviously good.

Very good to hear that you use the same p/n pump on a GM TBI installation. You just about can't beat a "worked before, I'll work again" solution to a problem.

Noise isn't a factor for me, though. The racket in the cab of that truck is such that I expect the only time I'll ever hear that pump is when I turn the ignition on before the engine starts. A Lexus it ain't!

Once again, thanks for your help. You guys are really great. It's very good to know that a pool of expertise exists to help me get past rough spots.

Mike