Compression question

[CUBuffs]

Sorry TC,

I'm showing my ignorance. Tried it again with both lobes on #2 pointing up. It was hard to tell if any air was leaking out but if it was it was probably coming from the muffler.

[skids]

Normally, bigger gaps at the shim, mean that the valve will not open as far. I have always heard that tis does not cause valve burning, but it can cause the head to retain more heat. I would adjust the valve (and others that need it) and go with it.

[trbig]

If you heard it out the muffler, it's an exhaust valve leaking. Shimming it up to correct specs won't help it close any more. It already has a huge gap between the cam lobe and the shim to let it close all the way. If this is what's happening and you run it, the hot exhaust gasses escaping the unclosed valve will eventually either burn it or worse yet, the valve seat. It is not too much more work to take the head off.
After the head is off, tilt the head to where the exhaust port is facing up... and pour a little fuel into it. If it leaks out.... it's not sealing. You have several options at that point. CAUTION!!!! Do not allow the cams to turn after you take the chain off. There isn't enough clearance to allow 2 valves to be open at the same time... ask TC how he knows this. It would be better to just take the cams out... way easier to re-shim it and no possibility of this happening. Good luck.

Tod

[CUBuffs]

OK, in order to make sure that I'm doing the leak down test correctly I did a little reading. A couple of web sites say to set the cylinder to TDC before inserting air. If I have the crankshaft set on the "T" that is TDC--correct? But is that TDC for 'all' the cylinders or just #1?

[TopCatGr58]

Hey CuBuffs,

TDC on that mark is ONLY for the #1 cylinder, for timing purposes, the other cylinders follow at 180 degree intervals thru 2 rotations of the crank. So...with the valve cover off, you can see the cams and valves being opened as you rotate the crank, so when you see both cam lobes for a particular cylinder rotating into the upward position, then that cylinder is going thru it's TDC portion of it's cycle. You can put a LONG STRAW down into the spark plug hole and watch it drop down as the piston drops, and when it starts to come back up then stop! Then it'll be at BDC. But watch the cam lobes cause you want to catch them when they are farthest away from the lifters, and once the piston hits the bottom of the power stroke, the exhaust cam will be rotating close to the position for opening it up!
T.C.

[Ken Talbot]

Originally posted by CUBuffs
A couple of web sites say to set the cylinder to TDC before inserting air.

That's the way I do it too, with each cylinder being tested at TDC.

More than simply applying pessure to the cylinder, a leakdown tester uses two gauges and an adjuster to give you a comparison of pressure being supplied to pressure being held inside. The lower the inside pressure compared to the supply, the greater the overall rate of leakage. The second gauge on my tester is calibrated in percentage to give you "good, bad and ugly".

[CUBuffs]

TC,

Thanks for that explanation. I did as you said and rotated the crank so that I stopped the piston just as it was starting to come back up and the lobes were both off the lifters. There was very slight air coming out both the muffler and the air scoop, I believe in equal amounts.

Do you think I can just go ahead and adjust the valves first to see what happens with the compression or should I dig into taking off the head?

[CUBuffs]

I have gone ahead with the valve adjustment figuring that I will need to do that anyhow. Have run into a snag on #3 intake....the slot in the top of the lifter is in a place under the camshaft that I cannot reach with my little screwdriver. Is there a way to move the slot into a better position so I can get under the shim or are there any other suggestions as to how to get the shim out? Only 3 shims left to go.

[skids]

The buckets that the shims sit in will rotate when there is a gap between the cam lobe and the shim.

Originally posted by CUBuffs
I have gone ahead with the valve adjustment figuring that I will need to do that anyhow. Have run into a snag on #3 intake....the slot in the top of the lifter is in a place under the camshaft that I cannot reach with my little screwdriver. Is there a way to move the slot into a better position so I can get under the shim or are there any other suggestions as to how to get the shim out? Only 3 shims left to go.

[randy]

With the cam lobe OFF the valve, you can rotate the bucket.

[CUBuffs]

I don't know if this is an anomaly or for real but T.C. told me about squirting some Seafoam Deep Creep into the valves hoping for a sort-of miracle increase in compression. I took his advice and at about 3 hour intervals today I used the Deep Creep. This afternoon I got a little antsy and decided to check the compression.

To my surprise the #2 cylinder which had a reading of 60psi previously now was showing 135psi. Is that for real? Any thoughts are appreciated.

[TopCatGr58]

Gettin' in DEEP!

Hey folks,

Here's the whole backstage story! With the hopes that it was some modest carbon buildup around the valve face and seats, I did a search and found a post about dissolving carbon with SeaFoam Deep Creep spray!! Suggested he take the carbs and headers off, and squirt/spray some of this stuff in thru the ports so it could drip down the valve stems and get onto the seats and faces of the valves, and possibly dissolve the carbon?? Had him rotate the engine a little to ensure that the cams were slightly opening the valves. He did this with several repeat treatments, and then after plenty of soaking time, he then cranked it over many times to pump out any residual Deep Creep, and then did his Comp. test with the engine cold, no carbs or headers on!

It was a shot in the dark, but was trying to do something other than PULLING the head. We'll know more after he puts it back together, and runs it a while, and then rechecks the Comps!

Still, would like to hear any other thoughts about this technique?
T.C.

[CUBuffs]

TC,

Just did another compression test. It came back at 145psi.

[CUBuffs]

Fired it up

Hey TC and everybody,

My parts finally came in and I put the beast back together. It fired up just fine but it's smoking pretty good out #1 exhaust. Does that mean I need to tighten up the mounting screws to #1?

I thought I had it pretty tight and it makes popping sounds when I attempt to tighten it anymore. I don't want to damage it.

I also poured Seafoam (4oz) into the tank and about 2 oz. into the crankcase ( according to the manager at O'reilly Auto Parts). I havent' had it on the road yet but will after I take care of the smoke coming out #1. Should I be concerned about the smoke or could that be because of the Deep Creep I sprayed in the valve?

[TopCatGr58]

Hey CUBuffs,

Smoking is rather common after using MM Oil, it penetrates, and takes a bit to burn off. Just run it for a while and the smoking should diminish after a while! Will be interested to hear what the comp. test shows after you've put 100 miles or so on it!?
T.C.