P80 Burned Valve Discussion Thread - attendant with Data set

Post by **abscate** » 05 Feb 2016, 09:36

data set here

https://www.matthewsvolvosite.com/forums ... =1&t=74239

greg850r · Post by **greg850r** » 04 Mar 2019, 10:55

: burned valve.jpg (246.37 KiB) Viewed 3044 times

I bought a 96 850 Turbo with a burned exhaust valve in #2. Since I got it from the original owner I texted him a list of questions that will hopefully return enough info to make it worth entering in the burned valve database. In the meantime, I have it apart and was wondering; if one had a stack of heads in the barn to rob the valve(s) from. How do I tell the turbo from the non-turbo ones so I don't take an N/A head with me to the machine shop by mistake? It was 3 degrees out there this morning and I don't want to spend a lot of time sorting through them.

I got lazy on this one and left the exhaust and turbo all in the car as a unit. When I cracked the head loose I just pulled it forward enough to clear the remaining exhaust studs. I hope to put it back on the same way by using the one piece exhaust gasket that is available (Mahle #MS19361) and trimming one of the ends to fit with a tin snips.

edit: I noticed something about the difference in #2 exhaust port and to a lesser extent the top of the piston that makes me wonder if something went wrong with that injector to cause the problem. Or, could it just be the result of running it with a hole in the valve on that cylinder?

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: pistons.jpg (78.2 KiB) Viewed 3038 times

Post by **abscate** » 04 Mar 2019, 11:50

How to tell a bare turbo from a non turbo head?

Crap, I don't know that.

Exhaust valves are sodium filled on turbo - not too helpful.

greg850r · Post by **greg850r** » 21 Mar 2019, 21:43

I decided to do this head myself instead of sending it out and took all the valves out tonight. The cause of the burned valve was evident as soon as I got the head apart. Several of the other exhaust seats were black in spots, not silver. Black on a valve seat indicates no contact with the valve in that area. Eventually it erodes metal from the valve as hot gasses pass through because the seat in the head has enough mass to dissipate heat and run a little cooler. Carbon build up on the exhaust valve stems prevented them from closing all the way. A clean ring around the valve guide on those show where the hard carbon on the valve stem was crashing into the head when the valve closed thus preventing a good seal at the seat.

My solution is to Run Marvel Mystery oil in my gas to prevent the build up, but buying them used it could be too little too late.

tardcart · Post by **tardcart** » 22 Mar 2019, 04:32

it looks like it was running rich or oil entering. You will perhaps find a bad temp sensor or bad thermostat (open) gross vacuum leak, jammed fuel damper slow ox sensor, clogged cat. The na heads have higher lift cams with different part number is one thing to differentiate them. I wonder if the bare casting is the same? I think the higher compression of the NA is from the pistons. If you do have one, use the cams for 10 more hp Ive heard. Adding Mystery oil will only clog the cat and make more carbon.

Post by **abscate** » 22 Mar 2019, 04:57

Closeup for those wondering

Post by **erikv11** » 22 Mar 2019, 07:33

tardcart wrote: ↑22 Mar 2019, 04:32 I wonder if the bare casting is the same? I think the higher compression of the NA is from the pistons. ...

Yes, same casting, yes it's from the pistons not the head. You can swap heads NA<>turbo the fitment is perfect, however as discussed the turbo head has sodium exhaust valves the NA doesn't so the swap should only go one way, turbo head unto an NA is ok.

Post by **June** » 22 Mar 2019, 07:59

Wouldn't the heads be different as the compression ratio is different between turbo and NA? It is my understanding the difference is space volume controlled by depth of valve area of the head? June

Post by **erikv11** » 22 Mar 2019, 08:37

The head castings are identical, the volume difference is achieved by altering the dish in the piston head.

I've done head work but never measured or compared these two, just read a lot over many years from people who (may) have ...

Post by **abscate** » 22 Mar 2019, 08:56

erikv11 wrote: ↑22 Mar 2019, 07:33
tardcart wrote: ↑22 Mar 2019, 04:32 I wonder if the bare casting is the same? I think the higher compression of the NA is from the pistons. ...
Yes, same casting, yes it's from the pistons not the head. You can swap heads NA<>turbo the fitment is perfect, however as discussed the turbo head has sodium exhaust valves the NA doesn't so the swap should only go one way, turbo head unto an NA is ok.

Those Volvo Turbo exhaust valves with Sodium (not NA

) are a scant $85 each by the way - thats $850 in valves if you replace them all.

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