Power Assist Brake Question

[tdangle]

In reading threads from the engine/drivetrain section, I came across that the replacement crate engine I have been thinking about (350/290 hp) only produces about 12" of vacuum at idle. Is this enough to supply the vacuum booster unit for the brakes? the stock 350 right now runs about 18" at idle per my vacuum gauge.

[Jurassic-1]

What type crate motor is it? The stock 290 horse Chevrolet motor should have more than 20 inches of vacuum.

[tdangle]

Yes I referring to the GM long block crate motor. According to the install and spec sheet from GM posted in one of the threads it stated 12" of vacuum. I was surprised also! Here is a link to the document http://www.crateenginedepot.com/pdfs...ngine_Base.pdf

[leftybass209]

The problem with that engine, is it's a random mix of parts. The 224/224 cam it has is a bit much for it. Better flat tappets for it is 214/224, 214/214, or 204/214. (All old technology grinds) newer cams do function better.

It's a good motor, but the compression has been verified several times as being lower than factory rated, and thus, the camshaft is borderline too big. As a matter of fact, camshaft manufacturers recommend a stall converter for cams above 214/224.

12 inches of vacuum is close to the limit out of that engine in base form. GM also recommends not using a vacuum advance, so I assume the 12 inches they state is on a dyno with no vac can.

Many people run that engine with an okay tune in base form. However, to truly maximize efficiency, power, and drivability, either compression needs to come up, or the camshaft size needs to go down, and a vac can needs to be installed with proper rating (around 10-12 degrees advance). Most OEM cans are around 20 degrees and advance way too slow for that engine, which should be all in advanced between 22-2600.

BTW.... I have this motor as well.

[Tdrcreyn4]

You can always wire in an electric vac pump and canister. Simple alternative and easy to hide.