Sbc Vacuum problems

[Orange Bomber]

I had my vacuum advance and BOV hooked to the nipple on the front section of the carb base plate. When i couldn't get the BOV to work I got my vacuum tester to see what was happening. I found that my truck would idle at about 15 Hg, when I raised the rpm the vacuum would dip slightly for a sec then it would just increase. I saw upwards of 25-30Hg. I'm completely lost at what to do now, any thoughts or ideas would be greatly appreciated.

Thanks, Cam

 

[dyeager535]

What's a BOV?

 

[Orange Bomber]

BOV is the abbreviation for a blow off valve. My bad on not saying that the first time. So I played with it a little more last night and I disconected my supercharger to see if that is what was screwing things up but no luck it still had the same problems.

 

[dyeager535]

Do you have them hooked up to a ported/timed vacuum port, or manifold vacuum?

Which SHOULD the BOV be hooked to?

 

[Orange Bomber]

The bov should be on full manifold vacuum and that's what I have it hooked to. I've tested the front lower nipple the ported nipple on the metering block the nipple on the the back of the base plate and another port off the manifold all do the same thing.

 

[dyeager535]

I mean it sounds high, but up to 22" is high average, and apparently higher can be ok.

Hopefully someone with supercharger experience can chime in, how the BOV is affected by vaccum is not something I know.

 

[Orange Bomber]

So I guess this whole time I've been chasing a phantom problem, feelin a bit foolish now. I been under the impression that when Rpms increase the vacuum decreases. But really it dips then Rises just like what I got going on. And for my bov not working I think my Sc belt slips a bit so it's not boosting fully to pop the bov off.

 

[dyeager535]

Yes, under load (driving) vacuum will drop and stay low, at idle there is no load, so it stays high.

Glad you got that worked out, hopefully the belt slippage cures the other issue!

 

[Orange Bomber]

Yea I got a 10 rib belt ordered today so hopefully that fixes that. I'm super excited to see how this thing rips with the sc on and working properly. Thanks dyeager535 for helping out I really appreciate.