Hi there I have a question regarding using vacuum advanced on the distributor while having boost.
Right now I have a bone stock 440 with a turbo that im currently running at 4psi(just beginning and tuning. Im running a holley 850 DP and it does have a timed timing port on the front metering block. Right now the timing is locked out but the motor is lazy(stock cam low compression) when not being boosted. My question is can I use the vacuum advanced for cruising? How I see it is when under normal driving conditions the vacuum advanced will function but under boost since there will be no engine vacuum that will cut off the signal to the distributor. Also I could install a one way check valve so boost doesnt enter the vacuum pod. Am I right? Im also running a MSD boost retard box as well.
Thanks!

Is this a blow through or the other suck through application?
If blow through try it and see what happens, if suck through same deal but it may have a stronger signal to the vacuum pod on the distributor
Can you have someone rev the motor up enough against a load on the brakes to make boost? If so check the timing at boost to see what you really have

Its a blow through application. And there is no way for me to load it and check timing the turbo kicks in around 4200 rpm

Wow so you have a dump truck turbo with a 1.6 a/r then if it's so slow to spool on a 440.
Do the check valve to protect the vac adv.

You don't make boost at cruise, or you shouldn't be anyway. So that should not affect using vacuum advance for cruise.

I would probably want to make sure that if I put a check valve in that it would not keep vacuum in the advance can when it closed. Probably won't, but check.