4-71 blower help custom cast intake.

[El Guapo]

can any one give any pointers on rebuilding one of these blowers. Im going to put one on a 250 Chevy L6, so any tips are welcome. Im casting an intake for this supercharger in class, so any advice on placement, or runner volume and design are cool.

[southerner]

If the blowers still assembled, check it for tight spots by rotating the rotors. If thayb is okay, strip it down and replace the diesil bearings with aftermarket double ball roller bearings on the gear end. And definitely replace the annular roller bearings with a single roller bearing. Replace the blower oil seals as well.

while the bloer is apart cut off the 2 mounting lugs with a band saw this tidys up the case and if inclined now is the time to polish the end plates and case.

A manifold for an inline six the runners dont have to be equal length but make sure you have a good size plenum under the blower to cut down on pulsing and run a blowoff valve.

I would suggest that the blower be top mounted so that no raw fuel collects or puddles in the blower itself as it could in a side mounted unit, the trouble with raw fuel puddling in the blower as side mounted you could get an initial backfire on start up and goodbye blower.

The manifold obviously supports the blower and it's drive so make it as rigid as possible.

[El Guapo]

Thanks for the reply but What is this?
"replace the diesil bearings with aftermarket double ball roller bearings " all i have seen in a rebuild kit is single roller ball bearings , and they are sealed.

When you mean a large penelum , would the intake volume be as much as the displacement of the engine. The general rule of thumb i have heard for NA engines is displacement * 1.6.

thanks.

[southerner]

Exactly, With the stock GMC rebuild bearings, with sealed bearings they dont let the oil circulate through, so they therefor build up heat and fail at higher automotive speeds. What you want are the double ball race ball bearingsfor the front, and the single ball race none sealed for the rear packed in grease for lubrication

The plenum has to be the same size as the blower discharge port and as high as the intake port cross section height.