Vacuum test help
#1
Vacuum test help
Hello all, just did a vacuum test on my mostly stock ( went from 2bbl to 4 bbl, olds a4 intake)1972 350 to make sure all is well before I go and blow money on headers and nitrous. The needle fluctuated very slightly from 16 to 16.5 in hg. I am thinking maybe the air fuel mix is a wee bit rich? It's about zero outside and I let it warm up for about 5 or 10 minutes before testing and connected to power brake port. The 16 inch reading seemed a bit on the low side. Any ideas what im looking at here? Any and all second opinions on these readings would be greatly appreciated.
#2
I would think 18-20 on a bone stock engine. Did you adjust your air/fuel mixture screws for the highest vacuum on your gauge? Are the screws about equal in turns from the fully closed position? It could be a little low due to the gauge also.
#3
I wouldn't be to concerned with what the gauge is reading, just that you get the highest reading when adjusting the mixture screws. Those gauges don't all read the same and as long as the needle is just fluctuating and not vibrating madly I'd be happy.
#8
hey guys thanks for all the great replies, its been hellishly cold over here in chicago and i havent been out to the garage all week long. when i do get out there im going to play with the mixture screws and see how high i can get the gauge to go. will post results when i finally get out there. oh and the timing is set at 14 degrees, two degrees above stock so i know it cant be timing.
#9
oh and as far as the timing chain condition it doesnt seem to have any slop in it but when i had the motor apart last year when putting it together i definitely should have replaced it. i was very inexperienced back then and working at a diesel shop this past year has taught me alot but if the mixture screws dont do the trick and a compression test shows that its not worn rings thatll be the next place il look.
#10
hey guys thanks for all the great replies, its been hellishly cold over here in chicago and i havent been out to the garage all week long. when i do get out there im going to play with the mixture screws and see how high i can get the gauge to go. will post results when i finally get out there. oh and the timing is set at 14 degrees, two degrees above stock so i know it cant be timing.
Are you running your vacuum advance off ported or manifold vacuum?
Thread
Thread Starter
Forum
Replies
Last Post
shamusj
Big Blocks
15
March 4th, 2016 06:48 AM
ToronadoGuyDenver
Brakes/Hydraulic Systems
12
March 18th, 2007 02:52 AM