I checked my vacuum today, and the gauge said a little more than 8". From what i've read, i should have A LOT more than that, but i can't figure out why its so low. My cam is degreed (didn't have a wheel, just set #1 piston at TDC and lined up the marks), ignition timing is set fairly advnced (only way it runs), and i spent a good deal of time lashing the valves, and fairly certain i did them right (although i may need to do it again). The weird thing is that it backfires, sometimes so bad that it blows off the intke hose (homemade intake). The wires are at the right cylinders, so the firing order is correct. Still a pretty much stock chip though. I don't think my rings are shot, because i'm not getting any white smoke (no leaking oil into the engine). it runs fairly smooth once warmed up (idle at about 650-700). Oh, and the powerbrakes still work fine. Its a new vacuum gauge and i hooked it up to the fuel pressure regulator line. Any body have any ideas? What have done to my car is in my sig. Please help. open to all suggestions. Thanks guys.

 

Anyone??? Just trying to narrow my problems down.

 

TPort,

First, your cam isn't "degreed". If you don't measure the lobe centerline in relation to the crank position, you really don't know where it has been ground. That's not really an issue, since it's very rare to get a cam that has been timed incorrectly from the cam sprocket dowel pin. As long as the timing set was instaleed correctly, your valve timing should be O.K., but it isn't degreed to verify that.

That aside, the low vacuum reading can be caused by incorrect valve timing, but there are many other factors that can cause low idle vacuum. And you need to verify your readings by checking the gauge. It's possible the one you have isn't calibrated correctly. The gauge can be checked on an engine that is running normally, or tested with a handheld vacuum pump. The primary reason I suspect the gauge is that power brake boosters normally lose effectiveness at any vacuum below 12" Hg. If your power brakes are working normally, your vacuum is likely well over 8" Hg.

You should check the vacuum on a direct manifold port. The FPR fitting should have been a good source.

 

Cool! Thanks a lot Vader. I'll go and do a few double checks. Learn somethin new every day . Do you think a low vacuum might have something to do with the rich running and advanced timing? I'm just trying to work out some of the mechanicals before i get tuned. I realize its not going to run beautifally with a stock chip, but it should at least run when timing is set to zero, shouldn't it? Because right now, it won't.