carnot

Key engine info:
OBDI H23a1 – built bottom end and stock head; approximately 20,000 miles on both
550cc injectors, AEM fuel rail and AFPR, 255lph walbro
Hondata s200
ARP head studs

This engine ran with a turbo for about 15,000 miles before going back NA to diagnose an oil burning problem.

I removed the head from the engine to have the valve guides replaced; engine burned oil on cold startup and under high vacuum….I replaced the seals first but that did not solve the problem so it must have been the guides. I had a spare cylinder head that I had the head work done on to limit the amount of down time. After inspection, it was found that the exhaust guides on this head needed to be replaced. I had the guides replaced, complete valve job, new seals, pressure tested for cracks, light mill pass to make sure it was flat.

Before installing serviced head I made sure the block deck was clean and flat using a precision straight edge and feeler gauge. I used new OEM head gasket and dowel pins. Installed head and torqued ARP nuts to 80ft.lbs in three steps using ARP assembly lube. At this point I did a leakdown test to make sure all cylinders were sealing properly and they were. Put the engine back together and made sure valve lash was set properly.

The current problem after driving ~200 miles:
40% leakdown on cylinder #2
70% leakdown on cylinder #4
<10% leadown on cylinder #1 and #3

All leakdown appears to be coming from exhaust valves as I can feel the air rushing from these ports. There also seems to be coolant in the oil. The coolant in the oil tells me bad head gasket. After having a valve job how can these valves not be seating right? Again, I made sure the valve lash was set properly so I don’t think they were burned that way. I don’t think the car is running lean because it was running just fine before this other than the oil burn problem. Are the valve problem and coolant/oil mix problem related? The car never overheated. Let me know what you guys think.

gstrudler

did you re-torque the head gasket after initial warm-up?

carnot

No, since you have to take the cams out to do that I was going to put about 500 miles on the engine before re-torqueing the head nuts. Does anyone know if having a leaky head gasket can cause elevated combustion chamber temps?

mattsnooz

The valves were "lapped" upon installation?

A head gasket leak does cause a car to run hot from what I know.

carnot

They were not. I watched the guy do the work and after I left I had the same question. He did a 3 angle cut on the valves and reconditioned the seat. After putting the valves back in he applied vacuum to all of the exhaust ports to make sure they were holding a vacuum. Is it possible that the exhaust valves were seating properly before the engine ran but after a few hundred miles they aren't? As far as I can tell from looking at the service manual, the only "compound" used when doing a valve job is the Prussian Blue compound that helps you make sure the seat is contacting the valve cut in the middle of the 45degree cut. The lapping idea is a good suggestion, thanks.

mattsnooz

Thats sounds like exactly whats wrong carnot.
Call him and ask him if your supposed to lap the valves upon installation. See if he knows or not.

carnot

Thanks mattsnooz. You think I can get away with lapping the valves myself or will they need to be re-cut? Does anyone have experience with how many miles you can put on stock valve springs before their spring constant starts to degrade?