Does This Mean A Rebuild?

[andersonbw]

Well I mad some progress today. Fabricated a tool to compress the springs and got the valves out. Cleaned the valves and the seats. Things look much better to my novice eyes now that things are cleaned up a bit.

I can clearly see why #2 compression was low. There was definite leakage around the intake valve.

Here are pictures of the valves after much buffing with scotch bright pads and the valves chucked in my drill.

https://photos.app.goo.gl/xadjM7V5hrWpmLnW6

I can see some pitting on the bevel on intake valve #2.

Here are pictures of the valve seats. It is hard to take a good picture of them so I have a "representative" shot or two.

https://photos.app.goo.gl/o84LRaD7MeXmSYWR9

Can you offer any advice based on these photos? (1) Do I need to gring the seats? (2) Do I need to grind the valves? (3) Or will lapping put this thing right?

Thanks for any advice.

[andersonbw]

What oil and u using? Multi weight or straight? Those numbers sound low but my Cubs are usually at 2/3 to 3/4 on an unmarked gauage.

I think you should do the valve job soak the cylinders in seafoam while the head is off and try some oil additives after it is back together.

Again if it does not work you are only out the head gasket if you decide to do the bottom end.

I'm running straight 40 wt -- it is typically hot here in NW Florida. It looks like the head gasket is good. I've put some seafoam in the cylinders. Cylinder #2 leaked down faster than the other three. However, I can see evidence of a leak on the intake valve on #2.

[staninlowerAL]

You can lap the valves with compound and see if it clears the pitted areas. I would suggest a replacment valve for the one that is chipped and lap them until they hold a thin lube like MMO when in the seated position.

[ntrenn]

Grind all the valves then lap the seats. If they don’t come in at a fine line then seats too. Grind is usually only a few dollars per valve. Make sure you get all the lapping compound cleaned up my 65 looked worse than what you have.

[inairam]

One or two of the seats look like they have to be cut. You may not get a smooth surface lapping starting with that surface.

I bought newway cutters which were very easy to use.

The valves maybe can be machined. I bought new but I wish I had my old ones machined. If you get your head machined the same shop will be able to do the valves.

[LynchCub]

INAIRAM, you say to soak the cylinders in sea foam? I currently am in the process of just doing the seals and gaskets kit on my cub. The motor is out on the bench and I ordered the kit today. While it's sitting there are you saying I should just fill the cyclinders with seafoam and let it soak? I am probably 4 weeks away from reassembly due to a trip the family has coming up so is there anything else I should do at this time? Cyclinders and valves look good the rear main seal let go on me. 1947 Cub Took the engine out because I have a bent drive shaft and a couple of other things and it's going to get new paint as well, shooting to having her pulling the firewood wagon in October again.

[inairam]

If the head is off it is easy to rotate the engine so all of the cylinders are down. Pour sea foam in each of the cylinders so the piston head is covered and let it sit. Every few days rotate the engine and repeat. It has time to work past the rings and free them up to work as best they can. It is not a ring job but it is "hope in a can"

My mechanic told me he does that on Saturns because they have a tendency to have stuck rings. I did it on my 49 when I had the head off for a valve job and it helped reduce the smoking. The stuff takes time to work so letting it sit on the rings makes sense to me. give it more time to work as opposed to putting it in the gas or oil.

[Drfting1]

I'm a fan of trying the seafoam first, I thought I was going to have to rebuild the motor on my cub, I had dry 88 70 70 88 when I first checked.. Someone on forum mentioned the seafoam, as I was doing the restore, I was soaking enging through spark plug holes.. Every once in awhile I would give it a half crank.. When I was done, changed oil I had 107 92 90 105 dry, after using it for a year, I changed the oil again, now its up to 118 119 118 118 dry... So glad I went that route, saved me a rebuild