Compression Problem Revisited - Update - See p2

[BILL WILLIAMSON]

Lots of ????? here, first, need a real leakdown tester & then slowly try to iron out the confusion??
Ever any air out of oil filler??? Bill

[James Rogers]

Originally Posted by Pilotdave

Steve, at one point I tried putting a teaspoon or two of oil into #2 through the spark hole. That didn't make any difference in the compression result.

This means it is either the valves or the head gasket.Oil will seal the rings and bring the compression up some. This works even if the rings are not on the piston.

[Pilotdave]

I haven't heard air out of the oil filler.

However....

I just re-torqued the head to 55 ft-lbs. Carefully followed the specified order. Most nuts were anywhere from 1/2 to about a turn too loose. Started engine and warmed it up thoroughly. Reran the compression test with these results:

Cyls 1,3,4 - Now at 57-60 psi, 5-8 psi better per cylinder.

Cyl 2 - Now at 37 psi, about 20 psi better.

As I think back over the events since I installed the head last fall, I KNOW of at least two times that it was re-torqued before today. Yet it still was off spec today.

Also, I inspected the old head gasket. The area between #2 and #3 shows a noticeable stain about 2" long and 1/2" wide, dark green to black in color. The stain starts on the #2 side and extends part way to #3. I'll try to take a picture to see if that sheds any light on this quest.

Now I'm headed out for a test drive as it's 59* and sunny. Too nice a day for a Model A to sit in the shop.

Back from test drive. Did about 20 miles. Engine ran well, and my co-pilot agrees that it has more pep. Now, here are pictures of both surfacea of the old head gasket. A question - is there a 'down' side and an 'up' side to the gasket? The first three pictures are of the side that lays against the head and the last 2 pix are on the block side. Is the large oval hole between #2 and #3 part of the cooling envelope?

All of this is bringing me to think that my leak down test was not done properly, leading to bogus results, and that the issue is/was head gasket. Any thoughts? Thanks for any help!

[1931 flamingo]

I believe the ring side goes up. You've improved the psi's but you're still 20# below the others. Did you have the head "surfaced" before you replaced the gasket??

Maybe try another re-torque tomorrow?? What large town (worcester?) is Grafton near??
Paul in CT

[Pilotdave]

Paul - I found info in Andrews' book (p 149) indicating that the rolled side goes down - ie, facing the block. You are quite right about the delta on #2....I'm wondering if the new head gasket that I installed has been damaged by whatever caused the trouble with the old gasket. I did not resurface the head when I replaced the gasket.

Will re-torque again - likely tomorrow. Grafton is about 10 miles south of Worcester.

Thanks for your input!
Dave

[dratzy]

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How about a very weak or broken valve spring?

[Pilotdave]

dratzy, based on the effort needed to compress those springs when I replaced the valves, my guess would be that they are okay. But it's worth checking. Thanks!

[James Rogers]

Originally Posted by Pilotdave

I haven't heard air out of the oil filler.

However....

I just re-torqued the head to 55 ft-lbs. Carefully followed the specified order. Most nuts were anywhere from 1/2 to about a turn too loose. Started engine and warmed it up thoroughly. Reran the compression test with these results:

Cyls 1,3,4 - Now at 57-60 psi, 5-8 psi better per cylinder.

Cyl 2 - Now at 37 psi, about 20 psi better.

As I think back over the events since I installed the head last fall, I KNOW of at least two times that it was re-torqued before today. Yet it still was off spec today.

Also, I inspected the old head gasket. The area between #2 and #3 shows a noticeable stain about 2" long and 1/2" wide, dark green to black in color. The stain starts on the #2 side and extends part way to #3. I'll try to take a picture to see if that sheds any light on this quest.

Now I'm headed out for a test drive as it's 59* and sunny. Too nice a day for a Model A to sit in the shop.

Back from test drive. Did about 20 miles. Engine ran well, and my co-pilot agrees that it has more pep. Now, here are pictures of both surfacea of the old head gasket. A question - is there a 'down' side and an 'up' side to the gasket? The first three pictures are of the side that lays against the head and the last 2 pix are on the block side. Is the large oval hole between #2 and #3 part of the cooling envelope?

All of this is bringing me to think that my leak down test was not done properly, leading to bogus results, and that the issue is/was head gasket. Any thoughts? Thanks for any help!

OK, here is the deal on copper head gaskets. Always install the gasket with the overlap ring to the head. This is because, over time the ring can wear a groove in the adjacent surface. If it does, you want it to be in the head surface since it can be repaired easier.

From the looks of the old gasket, looks like the head needs resurfaced and my initial assessment was close if not right on. If the head is out by more than .005 it will leak and yours looks like more than that. You could never get a gasket to seal properly if it is out more than that. With the increase in compression resulting from the re-torque I would guess you need to have the head surfaced and possibly a new gasket. If the gasket doesn't distort or crush from removal, you might be able to reuse it.

[BILL WILLIAMSON]

Always check a head for straightness by a competent machine shop, and surface if necessary.
Chief always taught me, "Never patch anything, except an inner tube, patching will come back to bite you in the butt, patching is ONLY to get you home!"
I feel that re- using a head gasket is "patching!" I don't put NO goop of anykind on them, they don't need it!!
I use the modern high tech gasket, super clean installation, re-torqued properly several times, COLD, and they're "FOREVER." Yes, they're a bitch to scrape off if you ever had to have the head off for any reason. LOTS OF THINGS IN LIFE ARE HARD, BUT THAT KEEPS US STRONG!!
Yes, copper head gaskets do look prettier though!
(Opionated? Yes! Practical? Yes!) Bill W.

[Pilotdave]

So.....my education continues! Paul and James - interesting that you both recommend installing the gasket with the rolled edge side up. [I was asking mostly in order to establish from which (#2 or #3) cylinder was more involved in the head gasket staining, though I imagine that I installed the new gasket last fall rolled side down.] I'll have to pull the head and have it checked.

How much can the head be milled before it becomes unusable?

Bill - what is the name of the "modern high tech gasket" that you mention? Something like the Premium Head Gasket (A-6051-M) as listed in Synder's catalog?

When running a compression test, should you leave other spark plugs installed when testing each cylinder? I tested compression yesterday with all plugs removed.

Thanks again!

[1931 flamingo]

Other's will chime in I'm sure, but on a stock engine the gasket you're using is probably the best. I believe there were were some problems with the "silicone" gskt ??
Paul in CT

[James Rogers]

I have seen heads that have been milled as much as .125 and still work. The counterbore is .125 +/-. I have racing heads with no counterbore ie: flat with combustion chamber at 8-1 CR. You shouldn't have to mill more than .010 or so to get the head flat.

I do compression tests with the plugs out and the throttle propped open to maximize air intake.

Personally, I don't like the "new and improved" head gasket. I always use copper unless the customer furnishes something else.

[RonC]

You should always check your head surface with a straight edge since it's off. I like to use head gasket spray tack or aluminum paint. It doesn't look like you used any? Sounds like you didn't correct the valve situation. Did you recut the valve seats? What did you set your valves at? Hopefully you did all the valves since it's apart? What head tighting sequence are you using?

[George Miller]

My advice is to pull the head and have some one grind the seats. You said you lapped them and got a ring on the valve, but how about the seat. It sounds like the seats were bad and did not get fixed, but like James said a 1000 miles away makes it hard to tell what is wrong. But it is ether valves, head gasket or piston and rings.

[Pilotdave]

James/Paul - thanks for the input. I used a copper-clad gasket with an extra adhesive made for copper clad gaskets when I installed the current head gasket.

To clarify - the pictures I posted were of the OLD head gasket that I replaced last fall - not the gasket that is still in the engine! The old gasket was not installed with a sealer, so it lifted off with no effort. The one that's on the engine now may be a different story! And I won't reuse a head gasket - just not worth the risk.

RonC - I'm not sure that I have a valve problem. I need to improve my leak down test technique and retry the test. When I installed the new valves in #2 last fall, I adjusted all valve clearances following the technique in Andrews' book. Got the intakes as close to 0.013 and exhausts to 0.015 as I could manage. I did not re-cut the valve seats in #2.

[RonC]

Everything you report points to a bad valve. You need to cut the valve seats. I would do a complete job on all the valves. I would also replace all the valves and springs. Have the head checked for straightness. The gasket will work either way but putting the rolled edge up toward the head is prefered as mentioned. Good luck and let us know how you make out.

[Tom Wesenberg]

If you grind the valves, be sure to tape a covering over the cylinders to keep any grit from getting in.

If a gasket isn't very old and looks good, I'd try reusing it on my own engine. It might save me a fair amount of money and if it doesn't work, it only cost me my time to R&R the head.

[Pilotdave]

Thanks, all of you.

This engine has valve seat inserts - is it better/easier to replace them?

Dave

[George Miller]

Originally Posted by Pilotdave

Thanks, all of you.

This engine has valve seat inserts - is it better/easier to replace them?

Dave

No it is not better plus you would still have to grind them if they were replaced. You have a couple of choices. Have some one come and grind them at your house or take the car to a garage that can grind them. You can have the valves out and ready to grind. I would do all the valves.

[J Franklin]

Before the expense of a valve grind I think a close inspection would be in order. Unless you had badly burned or warped valves a proper lapping should have been effective. Prussian blue is a good indicator tool.