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Vacuum leaks

2K views 12 replies 5 participants last post by  68cougar29 
#1 · (Edited)
1968 Cougar 302" Engine has less than a 1000 miles on it. New exhaust system
Built by Engine Performance Center
Installed a Comp Cam Receipt said Com 31-218-3
Emailed Comp they said no such number I did a search
and they make a 31-218-2 cam ,so maybe it's a typing error.
Comp says 31-218-2 will not effect the vac

Specs:Stock timing 6 degrees Dwell 30-33
I set the timing at 12 degrees Dwell 30 may have to retard slightly

Question: I blocked off all vac hoses and the manifold reads 13½-14"
What is the best thing to use to check the manifold leaking? And carb
to manifold gaskets?
I checked the manifold bolts
I don't want to start a fire, carb cleaner?
The carburetor is an exchange rebuilt
 
#5 ·
All I know, it's a stock manifold,we bought the car in 1983 ran great
After we installed the rebuilt engine with a mild street cam, my brakes were lousy
low vacuum issue. I installed a Crane reserve system to compensate but
I still would like to find the cause. Thanks
 
#6 ·
You have another thread going on at the same time. Well your vacuum is exactly what I would expect from that cam. That is all I got from mine once the timing went to 15 initial. At 10 initial the car had 8 mmHg. So I don't think you have a leak.

One thing I found out about about our 302s was to look inside the distributor to see what the setting is. I was surprised when I saw that my J code had only 20 degrees mechanical. On top of that Ford said to use 6 initial which gives a total of 26 degrees??? Unbelievable. I immediately moved my initial to 15 degrees to get within the 32-36 degree range for a high compression engine. What a difference that made in all aspects. Retarding your timing is not what you want to do to help out your vacuum.
 
#8 ·
Now I am confused I set the timing to 12* and was told to set at 10 (stock is 6 degrees)
To set it at 15-17* I'll have to pull the distributor and move away from radiator
hose. I would do it,but how do I tell when it's to far advanced?
Pinging? Light/heavy throttle? Thanks
 
#9 · (Edited)
You want the most advance the motor can use without pinging.
On stocker distributors I modify to limit the total advance to around 40* so I can set the initial high enough for the engine to idle OK but not so much total advance that the engine will ping.

If you can't adjust to 15-17*BTDC your distributor is installed wrong anyway.
 
#12 ·
How is the timing on the cam set ? that cam has 3 positions, retarded, 0 and advanced timing, usually it´s the straight up, 0 setting that is used.
 
#13 ·
I didn't build it but I'm starting to catch on.
Right now I don't know if that is the case or the harmonica balancer was built wrong.
Anyway maybe I'll do some more pull tests-bump it up some and retry until I hear it
pinging. They built the engine in 1998 and no longer in business, I should have gone
back to them for more Info. Wife's car and I was to busy.
 
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