Need Engine Help Low Vacuum Reading

[CJPilot]

Well I finally got my engine back together after my oil pump seized and took out the cam.  Now I�ve got a new problem.  The engine will start but has very low intake vacuum reading (5 inches) as measured at the threaded port in the intake manifold. 

Things I�ve tried

Checked for a vacuum leak using a propane tank
Plugged the PCV port
Replaced the carburetor gasket to eliminated the sleeves
Sprayed the intake, carburetor, etc with WD40
Adjust the timing
The carburetor was rebuilt.
Re adjusted the valves to .016�cold

I but I can�t find any leaks�

I should mention that this engine has never run correctly for me.  I'm as they say fixin it up!!

The exhaust manifold is new as well as the heat control diverter.  My research on low intake vacuum says to look for a leak at the intake manifold or heat riser or late valve timing. The cam has just been changed so could I have screwed anything up putting it back together? Here is a picture I took of the cam gear before I buttoned it up. 



Guys, any ideas?



 

[1955CJ-5]

I'd try a compression check...

[garage gnome]

Could be a worn throttle shaft or warped intake.

[CJPilot]

The compression reads right about 90psi dry, all cylinders, a little low. The rings might not have seated in yet?  The carburetor was rebuilt by Scoutpilot and I think he put in an oversize shaft.

I�m thinking I might have to pull the intake and have a good look at it.  I�m just surprised the propane/WD40 didn�t have any effect on engine speed if in fact the intake has a leak.

[scoutpilot]

[size=12]Replaced the carburetor gasket to eliminated the sleeves What do you mean by "eliminated the sleeves"?
Sprayed the intake, carburetor, etc with WD40 You need to use either propane or starting fluid (spray ether). Don't worry. You won't start a fire.With the engine warmed up and running start at the front of the manifold and spray, in short bursts, every conceivable location for a leak as you work your way to the top of the carburetor. I can conceive of cracks in the manifold itself. Check it very closely.

How many miles have you put on that rebuilt motor?[/size]

[Carls_jeep]

WD40 no longer uses propane as a propellant. That change was years ago.

[CJPilot]

The little cooper sleeves are below.  I read that some people have had problems with these not crushing and causing leaks.  I just wanted to test so I removed this installed another gasket and started it up. Ran the same.


This is a picture of my propane leak tester.  I used it generously around the intake manifold, heat riser, and carburetor, no joy.




I only tried WD40 after the propane didn�t find a leak.  I�m really at a loss on this one right now. 

[1955CJ-5]

You say that it runs poorly...can you be more specific?

Does it pop and backfire, or does it just accelerate very slowly or not at all?

Hard to start?

spark plugs black or grey?

I found that i had the wrong studs in my intake manifold and was unable to squeeze down the copper eyelets in the diffuser gasket even though the nuts were tight....there were not enough threads to fully tighten the carb to the manifold..so I had a leak...

Video maybe?

[scoutpilot]

[size=12]I agree. Exactly what is the motor doing/not doing?[/size][/b]

[CJPilot]

Thanks guys.

I knew I was looking for a vacuum leak, but didn�t find one, so I had a thought.  Maybe the fan was pushing enough air causing my propane testing to fail and giving me an inaccurate result.  So I pulled the fan blades off.  Not much different but I  did notice  a tiny change as I applied the propane to the #3 and #4 intake / block interface.   Next came out the starting fluid and that confirmed a leak.  It doesn�t seem like a big leak but at least I have a direction to go in.  Once everything cools down I�ll pull the manifold off and have a look. 


My take is starting fluid works a lot better that propane, and Carl your right WD40 doesn�t work any more for finding leaks.

[Ryan_M]

I had a heck of a time with an exhaust leak around the manifold on my 3A. I tried a variety of gasket/sealer combos and just couldn't seem to stop it. I finally bought one of these last year and it has held tight ever since. No sealant of any sort needed.  Not the exact same problem you are having but it could have the same solution.

http://www.ebay.com/itm/Jeep-Willys-MB-GPW-NOS-exhaust-intake-manifold-to-block-gasket-134L-/291140676661?pt=Motors_Car_Truck_Parts_Accessories&hash=item43c9562c35&vxp=mtr

[CJPilot]

I checked flatness on a surface plate and it�s O.O.F. by .008� at the #3 and #4 intake location.  Doesn�t sound too bad to me but I�ll machine it flat just to be sure.

Ryan that�s a good thought.  The last time it ran I was using a Felpro gasket this time I think it�s an Omix-ADA. Maybe the Felpro was able to handle the O.O.F. condition?

[1955CJ-5]

You can also loosen the four bolts that hold the two manifolds together and see if that doesn't allow enough movement to eliminate your  .008" gap....

I left those four bolts loose until after both manifolds were securely fastened to the block and then tightened them.  You need to be careful if the fit is way off but if it's close it should be OK...

[CJPilot]

[size=12]

You can also loosen the four bolts that hold the two manifolds together and see if that doesn't allow enough movement to eliminate your� .008" gap....

I had left them loose when I assembled the manifolds. 


I put everything back together and it still runs horrible.  I did a leak check by spraying everything with starting fluid and no leaks detected.  Did another compression check and a couple of cylinders are now at 95PSI.  Rechecked the valves.  I read that they can be set to .017� on a new engine to compensate for run in so I set them to.017�.  I did a cranking vacuum check and it�s 0.  I can put my hand on the carburetor as I crank the engine over and feel very little vacuum.

I�m going to pull the manifold off and separate the intake from the exhaust.  Really running out of things to check.  It�s time to have a few beers.
[/size]

[Ryan_M]

Are you getting a good seal with your vacuum gauge? And are you sure your timing isn't completely out of whack or a couple plug wires mixed up? A faulty reading on your gauge and ignition issues could give you the results you are seeing.  A video of this thing running would be a huge help.