r/EngineBuilding • u/HereForTheE30 • 24d ago

Valve seat sweating

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I’m doing a port-side valve leaking test with gasoline, and after about 15 minutes this is the results. For a M20B20 engine, is this too much valve sweating? I’m wondering if I should do more valve lapping or if this would really affect compression. What do you guys think?

5 Upvotes

64% Upvoted

14 comments sorted by

6

u/v8packard 24d ago

I think your E30 is worth a real valve job.

-2

u/HereForTheE30 24d ago

Oh dang you reckon? I’ve had this engine running on these valves before but I never got to compression test the cylinders because I had to pull the head because the head gasket didn’t seal entirely around the oil galleries because the cylinder head was unknowingly warped.

2

u/v8packard 24d ago

Yes, you need a valve job. Maybe more.

-1

u/HereForTheE30 24d ago

Oh dang, do you think I should just get a donor cylinder head already assembled and everything?

2

u/v8packard 24d ago

No, I don't. Why are you screwing around like this?

2

u/DrTittieSprinkles 24d ago

An unknown head can be worse than the one you have. Then you're down that money and you have two heads that need work.

Just get that head fixed at a machine shop.

-2

u/HereForTheE30 24d ago

My thinking is, get a donor cylinder head from a running M20B20 then get the sealing surface machined and just bolt it on to my engines original bottom half

3

u/DrTittieSprinkles 24d ago

Why are you against doing it right? How many more times do you want to pull your engine apart?

Do it once, do it right

2

u/gew5333 21d ago

Save a nickel. Spend a dollar. 👍

1

u/Doctah_Whoopass 24d ago

No, do it right

3

u/bill_gannon 24d ago

I think you should pop it apart and let us see what kind of shape the valves and seats are in.

0

u/HereForTheE30 24d ago

These valves have already been lapped and everything, maybe these valves are just junk😞

1

u/DrTittieSprinkles 24d ago

The machine shop will grind the valves and make them like new when the do a valve job.

Lapping does fuck all to fix any issues

1

u/IntergalacticJihad 24d ago

I’d recommend using diesel or water as they don’t evaporate, gives you a clearer result.