Vacuum at idle with big cams 272 280

[marcmsj]

What kind of vacuum are you guys seeing with your cams?

With my 280's, i'm only seeing about 4 inches and that seems way too low for me. We checked for vacuum leaks but couldn't find any but I'm pretty sure we're missing something.

So what vacuum are you guys seeing just so I can get a base line.

 

[1992awdlaser]

If you have an adjustable timing light, check your base timing like this. http://www.dsmtuners.com/forums/art...-timing-without-using-lower-timing-cover.html

 

[andy4g63]

My idle is 10-12" vacuum, idling @ 1000rpm. If I lower the idle to 850 RPM, it will be even less.

Check the boost gauge. Autometer is neither good or accurate. How do you know it is good???
After I put MAP sensor, I've seen big difference in boost sometimes. For example gauge reading 22-23PSI, real boost was 31PSI/not good/. I have Greddy/electronic now and it is 1:1 dead perfect with the MAP sensor.

 

[marcmsj]

If you have an adjustable timing light, check your base timing like this. http://www.dsmtuners.com/forums/art...-timing-without-using-lower-timing-cover.html

Never seen it done that way before. I don't have an adjustable timing light, do I still want to have the timing marks lined up or slightly offset to have it at 5 degrees?

 

[marcmsj]

My idle is 10-12" vacuum, idling @ 1000rpm. If I lower the idle to 850 RPM, it will be even less.

Check the boost gauge. Autometer is neither good or accurate. How do you know it is good???

I understand what you're saying, however if my gauge is showing only 4 inches, I'm sure something is going on somewhere. With my stock setup, the same gauge was showing me around 18-20" which sounds about right.

Either way, I'll definately be at the shop tonight and i'll be double checking the vacuum gauge, vacuum leaks, and base timing and also making a dsmlink log.

 

[1992awdlaser]

Never seen it done that way before. I don't have an adjustable timing light, do I still want to have the timing marks lined up or slightly offset to have it at 5 degrees?

Your marks should line up as shown in the second video when timing is set correctly with a non adjustable timing light.

 

[marcmsj]

Your marks should line up as shown in the second video when timing is set correctly with a non adjustable timing light.

Got it. I'll check that tonight.

 

[marcmsj]

So I just got finished messing with the car and it's idleing much better now. I'm seeing about 7" (according to the autometer gauge) at 900rpm which is a bit better and it's sounding very nice with those cams.

I wasn't able to double check base timing yet, that's going to be done later this week. I suspect it might be a bit off due to my higher than expected EGT's at idle (around 1050F) but then again the probe is pretty close to the head.

 

[TalonSway]

Bringing this back, I would like to know how this turned out? I have about 7hg at idle and i feel like that is really low. Set base timing, new timing belt with all marks dead on. Only thing left is to fix my last boost leak, and if that doesn't solve it i was just curious to how it turned out for you.

 

[jimsgsx]

Check all vacuum hoses.do a blt. Compression test. Then let us know.

 

[backward_0]

+1 for blt and compression test

 

[TalonSway]

All leaks are gone, and i fixed a little kink in the nylon line that goes to the back of the boost gauge, and checked line for kinks but at idle im at 10hg now and when i cruise im around 15hg.