Rebuilt engine with low compression?

[boomerang]

Thanks,

I don't have any Prussian Blue with me. Just to be clear on the procedure. I take a black sharpie and do both the seat and the valve. I spin it a few times and it the seat is making contact I should see a ring (OF NO INK) on both the valve and the seat??

Yeah I know the RTV is weird, just that I will have to order these gaskets, wait for them and all this shit. I won't run it with RTV just want to abs verify.

This is a simple cylinder head (aluminum billet style). There are not coolant passages. They sell (all metal) head gaskets that have a history of being re-used. People would spray some copper around them and slap them back on. The one's I had were the fiber type with a very thin metal foil core (came in a gasket pack!!!)

Yes on the black sharpie procedure. Just try not to cake it on. A nice even swipe will do the trick.

I understand the reasoning on the RTV but if you know for certain the valves are fully seating, it is not necessary.

And I hear ya on the gaskets. Fiber type gaskets compress and pretty much become NG afterwards for head gasket sealing even if they were to peel off intact. Metal ones can sometimes be reused especially on a motor such as this for the reasons you gave. Sealing compression is one thing. Sealing compression, coolant and perhaps even oil is another.

I adjusted the valve clearance on my mower before putting it away for the season. I actually did end up using it one last time though. When I took off the valve covers, on both, a portion of the gasket stayed on the head and a portion on the rocker cover. Just fiber type gaskets. It was like breaking the gasket in half with one part stuck on the head and the other on the cover, not bits and pieces. I carefully kind of 'indexed' the gaskets when I tightened down the valve covers and they aren't leaking. I figured if they did, I would replace them in the spring. You can get away with a lot more when it's not a cylinder head. A cylinder head is a far bigger deal.

 

[steppinthrax]

Yes on the black sharpie procedure. Just try not to cake it on. A nice even swipe will do the trick.

I understand the reasoning on the RTV but if you know for certain the valves are fully seating, it is not necessary.

And I hear ya on the gaskets. Fiber type gaskets compress and pretty much become NG afterwards for head gasket sealing even if they were to peel off intact. Metal ones can sometimes be reused especially on a motor such as this for the reasons you gave. Sealing compression is one thing. Sealing compression, coolant and perhaps even oil is another.

I adjusted the valve clearance on my mower before putting it away for the season. I actually did end up using it one last time though. When I took off the valve covers, on both, a portion of the gasket stayed on the head and a portion on the rocker cover. Just fiber type gaskets. It was like breaking the gasket in half with one part stuck on the head and the other on the cover, not bits and pieces. I carefully kind of 'indexed' the gaskets when I tightened down the valve covers and they aren't leaking. I figured if they did, I would replace them in the spring. You can get away with a lot more when it's not a cylinder head. A cylinder head is a far bigger deal.

Is there any relationship between the "contact thickness" and the sealing quality. Example if you have a thick band where most of the valve face touches the seat v.s. a narrow band.

Also if you don't have 100% and you continue to lap, you would eventually touch right? Meaning you could correct a valve that's not making complete contact with just lapping right?

Thanks

 

[JulesMaximus]

Wow! Filing, huh? That's pretty interesting in a scary sort of way.

Anyway, best of luck.

Oh, and you don't need anywhere even close to 150 psi. Hopefully you have a regulator you can use to ramp up the pressure. It will leak at very low pressure. You'll only need to increase it to the point that you are certain you are hearing what you think you're hearing and to locate the source of the leak. Air out the intake, the exhaust in your case into the crankcase which I would ignore for the reasons I gave.

I've wet sanded valve shims for a Ducati engine. It's pretty easy to do actually.

 

[boomerang]

Is there any relationship between the "contact thickness" and the sealing quality. Example if you have a thick band where most of the valve face touches the seat v.s. a narrow band.

There are specs in the manual for seat width. It's important especially for the exhaust valve because when that valve is on the seat it is then able to transfer it's heat through the valve seat to the, in this case, barrel. The width is important and where the valve contacts the seat is important. It should be roughly in the center of the valve face. If it's too near the margin, the valve can fail prematurely. Edit: Figure 7-8 in your manual. Seat width .037 to .045.

Also if you don't have 100% and you continue to lap, you would eventually touch right? Meaning you could correct a valve that's not making complete contact with just lapping right?

Thanks

No. The point I'm trying to get across, that I am evidently doing a poor job of, is that in your case I believe you either have a valve seat or seats that are out of round and perhaps worn out valve guides or stems. Lapping is not a machining process. You could lap for hours and take so little off that it would be nearly immeasurable.

Based on what you're saying, you have full contact around the circumference of the valves. Do you? Do you have a gray ring from lapping all the way around the circumference of the valves? If you don't you have a bent valve.

Do you have full contact around the circumference of the valve seats? Do you have a gray ring from lapping all the way around the circumference of the seats?

Once again, if it is hard to tell and it absolutely can be hard to tell, use the sharpie on the seat, insert the valve, push down and give it a quarter turn. The residue from the marker should be removed or smeared around the full circumference of the valve seat. If you don't have contact all the way around, the seat is out of round. You will NEVER fix it by lapping. NEVER. It must be machined. Lapping is for verification, not refurbishment. I just cannot stress this enough.

 

[boomerang]

I've wet sanded valve shims for a Ducati engine. It's pretty easy to do actually.

How much did you take off?

My concern for starters is that the valve stem and lifter material are so soft that they can be filed. But, steel can still be at a reasonable hardness and be filed. Obviously, in this case, because the valve stems and tappets aren't mushrooming.

But I can't imagine the agony of trying to remove even .010 using a file between the valve stem and tappet inside an area as tight as the recess where the springs lie. But my real concern is trying to remove the filings. You have to have the barrels on the block, tightened with a gasket in place. But, it's the procedure. If I was rebuilding engines I would have a valve grinder that could grind the stems and that's how I would be performing that task. Cleaner, quicker, more accurate.

Edit: However on page 62 of the manual it says;

If clearance is insufficient, grind end of valve stem until correct clearance is obtained. Make sure stem is ground perfectly flat.

No mention of filing. That's kind of curious ...

 

[JulesMaximus]

How much did you take off?

Very little, like a couple thousands of an inch. These are what the shims look like. Basically, you want to be able to get .004" feeler gauge between the opening shim and the rocker and you want a .002" gap between the closing shim and the closing rocker.

 

[tracerbullet]

Not to beat a dead horse but on the head gaskets - a lot of them I've been around have a metal ring that goes around the openings for the cylinder bore, it's a thin piece of metal wrapped around a wire ring. It'll crush slightly when the head is torqued down, and is basically a one-time use thing.

I know you were planning to replace it anyhow but I dunno I guess I'm throwing it out there as another consideration in the chance anyone someday considered reusing a head gasket that appeared to come off intact.

 

[steppinthrax]

Not to beat a dead horse but on the head gaskets - a lot of them I've been around have a metal ring that goes around the openings for the cylinder bore, it's a thin piece of metal wrapped around a wire ring. It'll crush slightly when the head is torqued down, and is basically a one-time use thing.

I know you were planning to replace it anyhow but I dunno I guess I'm throwing it out there as another consideration in the chance anyone someday considered reusing a head gasket that appeared to come off intact.

Do you realize how much fucking money I've spent on this little 17 - 20 hp engine ...

I got it from a package deal of two JD tractors. I checked the engine to determine if it was even worth rebuilding. The KT17s had major issues with the SERIES I, they lacked a fully pressurized lube system, so if you had it on a hill, they had a history of conn rods breaking. I was ecstatic to find this was actually a series II, however the conn rod was still broken (due to other reasons [low oil]).

Tore this whole engine down. First thing first, they don't make parts anymore, so I was able to snag a new/used piston of the SAME CASTING for 80 bucks (yeah that is one piston for 80 bucks). Then a single conn rod of the SAME CASTING FOR 75.... When the conn rod broke the remaining rod snapped the skirt off the cylinder barrel, I could have reused it since the piston never comes in contact with that area, but I decided to replace it anyway 75 bucks. Then I needed new rings. Cheapest I could find a set of rings was 35 bucks a set. But a distributor was selling a complete gasket set with new OEM rings and head gaskets for $115.00 sealed, so I got that instead. Among the other odd and inn things (nuts, bolts, lube, oil pressure gauge).

I was able to refurbish the crank journals aluminum transfer using acid (The works toilet bowl cleaner). It will eat the aluminum deposited on the journals, instead of the steel.

I got the entire engine back together one day. Ran it and it ran good for a few seconds. Oil pressure dropped! Checked the usual stuff. Guess what, there was 2 shards of aluminum (from the broken rod), that were inside of one of the oil galleys. It made it way to the oil pump and the tolerance of the pump is soo damn tight it will stop the pump from turning. Broke the oil pump shaft pin on the gear.

I ordered the pin and the lazy mother fucker took a week mailing me a 1.50 roll pin. And no, ACE hardware didn't sell the size I needed. It had to be 3/32 x 1" and they only had 3/32 x 3/4"

 

[tracerbullet]

^ Ouch! I can share stories of general car repair, engine specific repair, and 12V electronic repair that have chain reacted and gone bad, but - not quite to this extent!

 

[RLGL]

^ Ouch! I can share stories of general car repair, engine specific repair, and 12V electronic repair that have chain reacted and gone bad, but - not quite to this extent!

Yep, another one bit the dust.

 

[steppinthrax]

Well I think I found a possible cause.

When the valves were lapped last time it made no difference, the valve stem end literally was making contact with the tappet while the valve was spinning. In other words the valve sealing surface was never making contact with the seat to "grind". I was able to verify this with a feeler gauge.

Crazy thing was each and every valve didn't meet the min specs for clearance. The exhaust valves required more clearance than the intake. The exhaust valve that was leaking was mostly making contact with the tappet. As the engine became hot, it would essentially never close. The clearances for all valves were wrong.

I took each and every valve out, placed them in a vise (with a towel wrapped around). I used a level file and carefully removed material from the end of the valve stem end. I then inserted it and test for clearance. I hit the "min number" for each valve. I had to do this two to 3 times on each valve (didn't want to remove too much material. I finished the valve with a wire wheel to remove "sharpness" before putting it back into the engine.

I used a Dry Erase marker and marked up the valves. I found two were not making 100% contact with the seat. I did a lap job on those two and now they have a wide band of contact between the valve and seat. It seems there were a combination of non-sealing either due to valve to tappet clearance and/or non-married valves. Previous lap jobs that were done when the barrel was off was very conservative. The drill lap job that I was doing was useless, since the valve was spinning around on the tappet....

So I'm going to hopefully cleanup tonight and try to find a way to put the springs on w/o taking off the barrels. I will post compression check results soon.

Thanks everyone...

 

[steppinthrax]

Well great news. This engine is tight like a fucking drum.

Got everything back together, put the compressor up to 110 and shot compressed air into the spark plug holes of both sides.

The valves aren't leaking at all, no noises, not even seepage.

Thanks Boomarang and everyone for helping me on this.

Now I need to wait for the Head Gaskets to come in and I should start testing again...

 

[crashtech]

A leakdown tester would make this a lot easier in the future, imo. Shoot for single digit percentages once the rings have seated.