advanced my cam and lost vacuum!

[D347643]

i advanced my stage 1 cam 2 degrees and now im only pulling 5 inch of merc.
When i had it dot to dot it pulled about 15 and now only 5! My car runs great though, no surging or anything. is this normal when advancing a cam?

any info would be greatly appreciated

thanks

Drew

 

[D347643]

come onnnn does anyone know about cams?

 

[D347643]

this is lame as hell, come on guys this is tech help me out

 

[Daggar]

It sounds to me like you've got it set up so that valves are opening too early. If it runs good then hell... leave it alone and upgrade either the brake booster/master cylinder, or try installing a vac cannister to see you get any improvement.

Prior to that, I'd be looking around for ANY vac leak. I'd busted the unused nipple off of the vac tree up against the firewall and didn't find out until it was "almost" too late.

 

[90mustangGT]

Did you use a degree wheel or just the marks on the chain sprocket?

How does it run powerwise?

Too far advanced and the exaust valve will close too early leaving exaust pressure in the cylinder and then the intake valve opens exaust backs up into the intake a little. That's just a theroy/guess.

 

[D347643]

hmm well i degreed the cam and everything was up to snuff and then i just moved to the appropriate tooth based on the instructions i got with my crane asjustabel timing chain. i had the heads off also so i could watch the position of the pistons. yeah i guess there could be a leak but when i had a vac leak before i could def tell it was surging like crazy