How many psi of boost will an 89 model 1st Gen. un-modified produce??

The combination pyrometer/boost gauge that is in my truck reads to 20psi boost.

The gauge is Hypermax brand.

If I plumb the boost side of this gauge into the intake manifold and boost exceeds 20 psi, will it mess up my gauge or just peg the needle??

 

18psig.

As found here: http://dodgeram.org/tech/dsl/Facts/91specs.html

 

You should only get 15-18 psi.

Most gauges will handle a little overload without problems, but if you plan to turn that truck up at all you need at least a 35 psi gauge.

 

FWIW, one is only wasting money if buying a less than 40psi boost gauge. On a non-intercooled truck that might get turned up in the future, a 60psi will be necessary. You will be pegging the 40psi gauge.

 

I would use that gauge to monitor fuel pressure instead of boost. 20psi is a good one for fuel pressure. Then buy a 40psi gauge at the minimum.

 

I thought a fuel pressure gauge measured vacuum and pressure.

 

Only if you have a really weak lift pump.