Vacuum gauge and valve adjustment

chicklin · Post by **chicklin** » Mon Feb 06, 2012 11:05 am

Still working on getting my engine dialed in as best I can. Finally got the vacuum gauge on there and discovered that things were not as rosy as I'd hoped. The needle was twitching around quickly between about 14-16 lbs.

I don't think the timing gears are worn as when I put the timing light on it, the line held rock steady. So, my assumption is the valves need adjusted, which I was going to do anyway (and should've probably done first).

Does that sound right? If I'm reading the diagnostics pages correctly, that sounds right, but I'm also concerned that I have a valve or two sticking.

chicklin · Post by **chicklin** » Mon Feb 06, 2012 11:09 am

FYI, this was at idle. Giving it just a little throttle will let it hold steady at 20 lbs. and the needle bounces down to 0 and up to about 24 as expected when you goose the throttle. So, I don't think there are any intake leaks. Compression is also good at 125 psi across all 4 cylinders.

artificer · Post by **artificer** » Mon Feb 06, 2012 2:46 pm

Sounds pretty normal for a new engine which should always be set @ above normal idle speed for run in.
As well it is not abnormal to use the vac gauge @ 800 to 1200rpm either. you need to ensure the cam dwell is correct [point gap] & ignition timing is close then you can fine tune timing with your vac gauge.

chicklin · Post by **chicklin** » Mon Feb 06, 2012 2:59 pm

Sorry, wasn't clear on that. It's not a new engine. It had been sitting for who knows how long so I've been trying to go through everything and get it dialed in as best I can without doing any major engine work. The compression numbers lead me to believe it is reasonably healthy, but who knows when was the last time someone adjusted the valves.

BullRun · Post by **BullRun** » Mon Feb 06, 2012 9:39 pm

Yep, check those valves... the last L-head engine I worked on in running condition that had been parked for many years had the valves so cranked down on adjustment there was no gap at all. Once adjusted correctly everything seemed to work fine. Probably why the jeep got parked long ago...

chicklin · Post by **chicklin** » Mon Feb 06, 2012 9:52 pm

Tore into it tonight and checked the first intake valve. No gap whatsoever. Got pulled away by the Mizzou game (go Tigers!), so I'll go through the rest of it tomorrow. I'm guessing I will find them all over the place in terms of clearance.

bbloom · Post by **bbloom** » Tue Feb 07, 2012 8:30 am

Where in KC are you?

chicklin · Post by **chicklin** » Tue Feb 07, 2012 10:51 am

bbloom wrote:Where in KC are you?

Platte City

chicklin · Post by **chicklin** » Thu Feb 09, 2012 7:46 pm

Holy cow, what a difference! All the intake and exhaust valves were really tight. Backed them off to spec and it's like a new motor. The clacking is a little louder now, as expected. I suspect the tappets are worn a bit, so it's a little loose. I'll adjust them again later after it warms up and maybe go down to .017 and .015 and see if that quiets her down. But, for now, I am thrilled. Purrs like a kitten.

artificer · Post by **artificer** » Thu Feb 09, 2012 7:56 pm

We are talking of an F head Jeep engine? This is copied from elsewhere & if you valves/tappets are woprn you can adjust by Pete's method which will get rid of your noise & have the valves adjusted properly. My method of adjusting tappets works on both F & L head engines.

I'll post it again here:

Here's a tip for adjusting valve clearance when the tappet is worn cupped and it can't be done properly with a feeler gauge. The tappet thread is 24 threads per inch. To find out how much the tappet adjuster moves in one revolution, divide 1.000 by 24. This gives a movement of almost .042" per revolution. There are 6 flats on the adjuster screw, so we divide .042 by 6, and get .007" per flat. Now, with the cam in position to adjust a particular valve, unscrew the adjuster to the point where the tappet just quits revolving freely This is zero lash. Then screw the adjuster in the proper number of flats to get the correct clearance. For .014", that will be 2 flats .002" is just a smidgen more.
Write this in your manual, and you'll be able to duplicate this every time. Courtesy of Pete SILFVEN

I'll post it again here:

As for adjusting valves it should take about 10 minutes or less assuming the side cover is off spark plugs are out:

Get No 1 @ TDC compression....No 4 valves will be on the rock & not be easy to turn or exhibit "clearance" & 1 valves will both be loose exhibiting "clearance" & be ready to adjust.
Adjust both valves on No 1 then put a chalk mark on the crank fan belt pulley in the TOP vertical postion....now put another mark @ the bottom of the pulley 180* [opposite the first mark]
now turn the pulley slowly clockwise till the mark positions are reversed & adjust both valves on number 3 cylinder
next turn the engine until the original mark is back @ the top & adjust valves on cylinder 4
& finally turn another 180* so the other mark is @ the top so No 2 cylinder is @ tdc & adjust it's valves.

Replace the side cover, spark plugs, leads & you are done.
Print this & put in your TM for future reference also. Courtesy of John GIBBINS

wilfreeman · Post by **wilfreeman** » Fri Feb 10, 2012 1:26 am

Much easier method for those of us that don't get a lot of practice at it. Thanks John!

Matt

artificer · Post by **artificer** » Fri Feb 10, 2012 4:18 am

Just so nobody comes back....I do not know what the threads per inch is on the F head [overhead portion] adjustment screw.

When you do know the TPI [someone can tell us] you use the same logic as Pete did to establish how far to turn the screw before you tighten the nut.

The side valve portion is exactly as Pete suggested.

Post by **wesk** » Fri Feb 10, 2012 11:34 am

5/16-24

artificer · Post by **artificer** » Fri Feb 10, 2012 3:30 pm

Thanks Wes....

Provided the rocker arm ratio is 1:1 [ie. equal distance either side of the fulcum thru rod] you would tighten the screw down till no play then out watching how far your screw driver blade moves.

If not equal you will need to reduce the adjustment movement by dividing by the rocker arm ratio to compensate.

You can also easily use a dial gauge [cheap @ HF] for accuracy on an OHV engine or on the OHV part with F heads.

Post by **wesk** » Fri Feb 10, 2012 9:50 pm

The rocker arm ratio should not come into play since the adjustment screw is on top of the pushrod. Had the adjustment screw been on top of the valve stem the ratio would then be an issue.