Bigger cam
Thread Starter
Intermediate
Joined: Mar 2002
Posts: 25
Likes: 0
From: Roscoe Il.
Bigger cam
My 79 had a larger cam installed by previous owner (he is a mechanic) I read in a vette magazine that doing that will mess up your vaccum. In my case that seems to be the case. My headlights dont come up, they move a little but not all the way. I realise there could be other problems but has anyone dealt with low vaccum caused by bigger cam?
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: Bigger cam (Flyinglow)
Have you measured the vacuum at idle? If memory serves me someone had 12 inches and the accessories still worked. If the vacuum is low, you might get a little more with tuning. Also check for vacuum leaks.
But finding what the vacuum is at idle is the way to start.
Scott
But finding what the vacuum is at idle is the way to start.
Scott
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: Bigger cam (Scott78)
I only have about 8 inches at idle and my headlights work fine. I have a fairly large cam for a 350. Sounds like yo u might have problems elsewhere. check the vacuum at idle and if it is above 10 you should have working headlights. If not you might have a leak or headlight problems.
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 6
From: Indiana
Re: Bigger cam (Flyinglow)
Before switching to my current cam, the old one produced about 8-10" of vacuum at idle. The headlights were very slow, but would still come up. A quick tap of the throttle would speed them up a bit. With the new cam, I'm pulling about 12-14" at an idle and the lights open fairly quickly. Both the old and new cam are far from pulling as much as a stock engine, but still more than enough. The first thing I would do is to disconnect all vacuum accessories from the engine and get a baseline vacuum reading. Anything above 8" of vacuum should be enough to open the headlights. If you have a higher reading than this, it will indicate that you have problems elsewhere in the headlight system.
