How do I find a vacuum leak?

michael_cini

michael_cini

Well-known member
I must have a vacuum leak. I have a 110 lobe center 264/274 cam in my 250, so the vacuum should be a little lower than usual but mine is LOW! How do I figure out where it is coming from? Thanks.
Michael
 
Spray some carb cleaner on the vacuum lines (there aren't many) and around the base of the carb. If you don't find it by the meeting, I'll help you out. I'm gonna be there to wrench on other people's cars, not my own! =)

When you find the leak, the engine will rev up.
 
Intake also eh? AUS head and all? Thats my next step once I fugure the valve cover thing out.

Ron
 
mike, idle the engine and spray carb cleaner. is that all there is to it?

Mercury Mike":32ed4xa6 said:
Spray some carb cleaner on the vacuum lines (there aren't many) and around the base of the carb. If you don't find it by the meeting, I'll help you out. I'm gonna be there to wrench on other people's cars, not my own! =)

When you find the leak, the engine will rev up.
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Just about. Unless you're me, then you just stare at the engine until it blows the hose loose at your vacuum leak. Then you know. But you have to have that super power. =P
 
Mercury Mike":3abtblo6 said:
Just about. Unless you're me, then you just stare at the engine until it blows the hose loose at your vacuum leak. Then you know. But you have to have that super power. =P
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Goof! :LOL:

Guys, what about a propane torch (unlit of course :roll: ) would that work? I'm trying to track a leak but niether method is working.

Ron
 
I put a new rocker assy in the car and after adjusting it I couldn't get it to idle right (2.25 turns vs 1.25 turns on the air screw and had to dial the idle screw in until it was past the idle stage). I was able to drive it around a bit yesterday but I put a whole bunch of initial timing on it to keep it running. I haven't checked "this week" :roll: to see if the balancer slipped. When I put the rocker assy in I touched nothing but the damper.

I need some of the Mercury Mike power also ;)

Ron
 
Take the number one plug out of the spark plug hole. Turn the engine around until it is on the compression stroke (you will feel air push out of the cylinder, and that means that both valves are closed). Then put a pencil in the spark plug hole, rubber side down, and watch the pencil move to the top of it's stroke, the absolute top is TDC. Now pop open your cap, the rotor should be pointing at the number one spark plug. If you had to add a bunch of initial timing then it is probably because it's coming up to the next cycle, or moving up one whole post on the distributor cap. This is also the time to check to see if the balancer slipped. THE POWER!!!! (y)
 
Mercury Mike":etqmwgdx said:
If you had to add a bunch of initial timing then it is probably because it's coming up to the next cycle, or moving up one whole post on the distributor cap. This is also the time to check to see if the balancer slipped. THE POWER!!!! (y)
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Mike,
I'm a little :roll: confused here, I didn't take the distributor out at all. The only thing I did was add the rocker assy. and "attempt" to adjust? I can make it run at 10* but its outside the idle circuit, if I add timing to it I can bring the idle back down into the idle circuit. Either way, me thinks a dampner check is in order. After man-handling the thing maybe it finally slipped? More fun this weekend! :beer:

Ron
 
RGR WILCO! Maybe I just need to drive it out to Cali and hang with you guys for a few. 8) I still need to get that pesky exhaust leak buttoned up.

Michael, ever find the leak?


Ron
 
I am wondering if your valves are adjusted too tight. The procedures I have read on this site say to tighten until the pushrods can't be rotated between your fingers and then tighten an additional amount. I did that on a 289 years ago and they were too tight. I readjusted again but the second time I only tightened until the end play was gone but the pushrod could still be spun and then the additional amount thinking that I misinterpreted the procedure and that seemed to do the trick
 
ozconv":196rut26 said:
I am wondering if your valves are adjusted too tight. The procedures I have read on this site say to tighten until the pushrods can't be rotated between your fingers and then tighten an additional amount. I did that on a 289 years ago and they were too tight. I readjusted again but the second time I only tightened until the end play was gone but the pushrod could still be spun and then the additional amount thinking that I misinterpreted the procedure and that seemed to do the trick
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I tried the instructions that came with the assembly and then went back to how I remembered to do it. Not much of a difference. I probably need to start another thread because this is Michael's and its about vacuum leaks, not my valves :roll: Get carried away most times. After I check the H.B. I'll start a new post.

Michael, I can niether confirm nor deny the propane deal works. I've never found a leak that way but its info from a very smart guy if you know what I mean ;) I'm thinking right now (dangerous, yes) maybe it is a valve timing/adjustment issue? Didn't you just have the engine rebuilt?

Ron
 
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