Vacuum Leak Test

[haulnazz15]

Is WD-40 sufficient to check for intake leaks, or is starting fluid the choice of the pros (outside of using the smoke machines)? I just don't like the idea of starting fluid in an enclosed area like the boat bilge. Granted, I'm going to be testing while on the boat trailer, but I don't keep starting fluid on hand so I figured carb cleaner or WD-40 would be a viable option. I am still getting 11-13 on vac @ idle, where it should be 18+, especially on a new engine with less than 15 hours on it. I believe this vacuum leak is causing some detonation @ WOT around 3K RPMS, and also the reason it won't get much above that because the vacuum isn't enough to activate the carburetor's vacuum secondaries.

Thanks for any advice/quick tips.

 

[Don S]

Re: Vacuum Leak Test

Get the starting fluid off the boat completely, it shouldn't be there for any reason.

WD40, break clean, even water will do the job. When you hit the leaking area, it will change how the engine runs.

 

[haulnazz15]

Re: Vacuum Leak Test

Lol, Don. I was trying to get across that I don't own any starting fluid, but had seen it specified in several threads when I searched. I didn't want to have to buy any if the WD-40 or B-12 Chemtool I have on hand would suffice. I'm hoping maybe there's somehow an open port on the Edelbrock manifold that is letting the air in. I know there's a 3/8" NPT port (which is normally plugged, but using for vacuum gauge), but there are several cast-in posts on the rear of the manifold that I thought were just mounting locations for brackets, but could be open. I really don't want to have to pull the manifold out with the engine in the boat as it's darn near impossible.

 

[spdracr39]

Re: Vacuum Leak Test

You could eliminate those bolt holes with your finger

 

[haulnazz15]

Re: Vacuum Leak Test

I actually have some threaded plugs that should take care of it pretty easily, lol. I just never thought about it until we ran into the low vacuum issue. The engine idles/gets on plane great, so we never had cause to suspect it until it wouldn't reach recommended WOT rpm's.