Bad leakdown test after lapping valves (HELP!)

[GeertGo]

Hello!

I'm currently refreshing a M42 engine. By refreshing I mean taking everything apart except the crankshaft + pistons (cause there was nothing wrong with them). When I first got the engine I did a compression test to check the health of the engine to know if I bought a rotten apple, luckily all 4 cylinders measured in at 175PSI / 12 Bar (out of the car + cold). Fast forward, I took everything apart and cleaned it up cause I had to replace the leaking profile gasket anyways. Before putting the head on the block I also put in new valve seals and lapped the old valves, none of this had to be replaced cause they didn't look bent and they were in very good condition. When lapping the valves I accidentaly switched the intake and exhaust valves, so I lapped a couple intake valves in the exhaust side before realising what I was doing (I was very tired lol). The following day I started over lapped the correct valves thoroughly, first with the rough compound and then with the smooth compound. After putting on the head and timing the engine I wanted to double check my work with a leakdown tester so I ordered one online. Today I tested all four cylinders and they had about 80% leakage, then I turned the engine over a couple times and checked again, now 2 cylinders were at 75% leakage and the other two at 65%. Finally I sprayed some partscleaner over all valves and blew it out with compressed air because maybe I had left some lapping compound on the valves. Now I'm measuring 60-65% leakage on all four cylinders, purely coming from the valves (I'd guess about 70% from the intake valves and 30% from the exhaust side). I haven't found much info about this topic online so I don't know if I should leave it and just try to run the engine or that I should take it apart again and bring it to a machine shop? Any help is appreciated!!

Kind regards, Geert

[moatilliatta]

New valve seats need to be machined in.

Lapping is old school when equipment wasn't quite as precise, but a good back yard fix that can help valves seat that are a little rough.

[digger]

seats and valves need to be either recut or reground. The guides need to be in good conditon to do this properly

how did you put new seats in? do you mean seals?

Lapping is purely the final check of the contact patch with bacially no material removal. Lapping is not supposed to fix or correct problems with sealing.

take it to a machine shop and tell them to check, diagnose and fix as required

[GeertGo]

seats and valves need to be either recut or reground. The guides need to be in good conditon to do this properly

how did you put new seats in? do you mean seals?

Lapping is purely the final check of the contact patch with bacially no material removal. Lapping is not supposed to fix or correct problems with sealing.

take it to a machine shop and tell them to check, diagnose and fix as required

I meant valve seals, not valve seats. I've edited this in the post. Sorry!
So you're saying that I couldn't have messed up that valve seats by lapping them because it takes away so little material? If the valves were already leaking wouldn't I have had a lot lower compression then I tested before taking it apart? The engine looked very good on the inside with no signs of wear, when performing the leakdown test theres zero air escaping from the dip stick or the oil cap.

[Shangsta]

I meant valve seals, not valve seats. I've edited this in the post. Sorry!
So you're saying that I couldn't have messed up that valve seats by lapping them because it takes away so little material? If the valves were already leaking wouldn't I have had a lot lower compression then I tested before taking it apart? The engine looked very good on the inside with no signs of wear, when performing the leakdown test theres zero air escaping from the dip stick or the oil cap.

From the way you described what you did you pulled all the valves and did not mark what what position they cam from. When you reassembled them the they didn't go back to the same spot they came from so not you essentially wiped out the previous valve job. If you have pulled them and lapped them to the same seat they came from you probably wouldn't be in the position you are in but now you need to go get valve jobs done on all of them.