I want to hook up a vacuum guage to my Hercules IXB-3 motor that uses a one piece intake/exhaust manifold and an updraft carburetor. I'm considering drilling and taping the manifold for a threaded fitting. This manifold has the embossed "Oliver" unlike plain manifolds with a raised boss. Alternative would be to use a carburetor riser plate but there is not enough clearance between the bottom of the carb and the magneto. Also not sure if the readings would be accurate that close to the carburetor throat. I'm looking to diagnose an intermittent miss and check the overall condition of the engine. Has anyone ever tried this? Would it be effective or is there a better way.
I welcome any suggestions.
Jethrow
You could do it. You can probably use a very small fitting - 1/8" pipe or smaller - and still have a good place to tap for vacuum without defacing the "OLIVER" embossing.
Using a vacuum gauge would help with adjusting the idle mixture, but I don't know if it would help with locating a miss.
Blake
You could also make a spacer plate with the vacuum tap on it and not risk cracking the manifold. A lot of work for negligable value.
I would drill and tap it for 1/8 inch pipe about 1/2 inch above the upper part of the mounting flange. I would also do a cylinder balance test. If you don't have one send me an e-mail address and I will send you a chart on reading a vacuum gauge. John
Jethrow, John, ...Heck Anybody
On your manifolds what's stamped above the word "Oliver"? Mine has "C & H" stamped into the metal right above "Oliver". Is that normal? Yours have C & H stamped above "Oliver"? I guess Oliver shopped out the manifold work around to different places.
Michael
Not to hi-jack the Orig Post..but here is an up close of an OC-3 manifold.
Just a part number on this...no S&H. Not sure of what Oliver model manifold you may
have.
(http://C:%5CUsers%5Cgn%5CMy%20Pictures%5COC3%20Manifold.jpg)
Outback
So what I've done is divert the Vacuum gauge discussion. I can see that's a problem for the original poster. :-Z I'll take this discussion eleswhere.
Subgates,
The space above the Oliver script on the manifold is blank on both my OC3 and spare motors. Both are from Zimmermans and not original to the motors.
I corrected the engine miss when I replaces the valves and valve guides. Big difference, no smoke!
Must have been the valve guides.
Instead of the vacuum gauge approach, I'm planning on buying a color tune spark plug in the spring to tune the carburetor. It has a glass top that shows the combustion chamber mixture. Changing the idle adjustment changes the color shown. Spendy but no hacking of the manifold required.
Jethrow