low vacuum.

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J

jaxle

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i have built myself an engine that only seems to draw about 6~7 pounds vacuum. the cam is 241@50 duration with 484 lift. the engine is 10 to 1. is this normal for this much cam or should i be seeing higher vacuum draw?
 
is it the xe274??? ive heard people going to up to i think 18 and i have seen people with 500 lift get 10-13
 
Sounds like a Purple cam. A high overlap cam will have low vacuum.
Installing it off by a few degrees will do this as well. Leaks around the carb/intake/heads will show low vacuum.

Oh, it would be not pounds, but inchs of mercury

Welcome aboard jaxle
 
I have somewhat the same situation. I checked my vacuum the other day and with the car in park and idling at about 700 rpm's I was only gettng around 6-7 in's of vacuum. My cam I purchased was thru Edelbrock I also added 1.5 ratio roller rockers.......the specs are in the attached file
attachment.php

Is the 'norm'.....???......The car runs like a scauled dog.

Greg.......mtn_jake

340-Cam Specs.jpg
 
ya mine runs fast as hell too, just never seen vacuum this low. i have checked all the bolts around the the intake many times over. rumblefish you say that the cam will cause this if its out? which way, advanced or retarded or either?
 
I'd say that's about normal vacuum for a cam that size. I had a Comp cams 274XE in my 360 and it pulled 8-9 inches of vacuum. I now have a Lunati 60404lk in it and it only pulls about 6-7 inches.

Advancing the cam drops the vacuum somewhat I've heard. Never tried it so It's just hearsay.
 
Advancing the cam will increase vacuum and give better bottom end power and retarding the cam will move power to the high end and soften the bottom.
 
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