Valve Job

mitsudriver · Post by **mitsudriver** » February 6th, 2006, 10:19 pm

I have a 93 4cyl 16v and I was wondering if anyone has had a valve job and if so about how much the machine shop charged you. I just pulled teh head and one of the exhaust valves is chipped and needs to be replaced. Should I go ahead and have them all replaced or just the one? Car has 120k miles on it.

Bochek · Post by **Bochek** » February 6th, 2006, 10:21 pm

wow ok, you have the EXACT same problem i did

i just replaced the bad valve(s) lapped them and put it all back together, runs like a charm now

by any chance did your valve look like this?

Bochek

MazdaKiller · Post by **MazdaKiller** » February 6th, 2006, 11:03 pm

cool tnx

Tunes67 · Post by **Tunes67** » February 6th, 2006, 11:19 pm

Those arent chipped valves those are burned valves.. that condition happens as a direct result of infrequent oil changes. The valve seals on the exaust valves get very hot... if they are not kept properly lubricated with fresh oil.. they will harden up.. once they harden up.. oil starts to get past them and cokes up on the valve seat and stem. Eventually.. some of that carbonized oil chips off.. leaving a small groove that the hot exaust gases escape past.. this has a blow torch effect and burns the V shaped groove into the valve. Exaust valves should not be reused. Replace them.. they take a LOT more torture due to temps than the intake valves. The intake valves can be reground and often reused as long as none are bent. When buying new exaust valves.. try to find ones that are "Parkarized" This is almost a powdery black coating to the valve and valve stem.. it helps as a lubricant. Its also usually a signature of a quality valve. Most exaust valves should be parkarized.. if you find ones that arent.. likely bet they are cheapos and their quality should be suspect. Hope this helps... oh and yeah.. I know all this stuff cause the same thing happened in my head a year ago

Found it right after I bought the car more or less. Cheers

Tunes67

Tunes67 · Post by **Tunes67** » February 6th, 2006, 11:24 pm

Oh.. here are some guestimates on head rebuild prices.. if you have a shop do all the work.. and source all the parts.. probably somewhere between $800 to $1000 for the work. If you strip the head down.. have the machine work done on the head.. then reassemble the head yourself.. probably around $600 cost.. but you will need to find a deal on the valves.. the valves arent cheap.. Locally the lowest price I could find for the exaust valves was $14.99 each.. One last thing.. DO NOT COLLAPSE YOUR HLA's!!! Yes it will make reassembling your head easier... but could (and in my case did) result in nice annoying ticking lifters. Cheers

Tunes67

Bochek · Post by **Bochek** » February 7th, 2006, 7:26 am

Tunes67 wrote:Those arent chipped valves those are burned valves.. that condition happens as a direct result of infrequent oil changes. The valve seals on the exaust valves get very hot... if they are not kept properly lubricated with fresh oil.. they will harden up.. once they harden up.. oil starts to get past them and cokes up on the valve seat and stem. Eventually.. some of that carbonized oil chips off.. leaving a small groove that the hot exaust gases escape past.. this has a blow torch effect and burns the V shaped groove into the valve. Exaust valves should not be reused. Replace them.. they take a LOT more torture due to temps than the intake valves. The intake valves can be reground and often reused as long as none are bent. When buying new exaust valves.. try to find ones that are "Parkarized" This is almost a powdery black coating to the valve and valve stem.. it helps as a lubricant. Its also usually a signature of a quality valve. Most exaust valves should be parkarized.. if you find ones that arent.. likely bet they are cheapos and their quality should be suspect. Hope this helps... oh and yeah.. I know all this stuff cause the same thing happened in my head a year ago Found it right after I bought the car more or less. Cheers

Tunes67

So your saying whoever owned the care before i did didn't change the oil at schedualded intervals?

It looks as tho its allmost mechanical dammage tho because of all the marks in the valve.

Bochek

mitsudriver · Post by **mitsudriver** » February 7th, 2006, 8:40 am

Thanks for all the replies. The valve that needs replacing doesn't really look like the one in the picture. Its alot cleaner but about a 1/4 of it is broken off. The car never smoked or burnt any oil just was only running on 3 cylinders because (well obviously) no compression in the one. You could actually drive the car just with alot less power (if thats possible). I've got the head off and cleaned up so i'll probably just get the parts and have a shop replace just the broken valve. Is that something I could do in the garage or is it definately going to need some machining to seat right? I've done tubo swaps, supercharger installs, spring kits, clutch kits, and a transmission rebuild so i'm pretty well versed in turning wrenches.

Tunes67 · Post by **Tunes67** » February 7th, 2006, 10:55 am

Bochek - That is the most common reason.. yes. A rare cause could be a defect in the valve itself.. but considering that I have seen this now on 5 different valves from 5 different 4 cyl cars.. all had hardened valve seals.. and according to my machinist.. that is why it happens so frequently. The head is made of aluminum which transfers heat changes rapidly. So you get a lot of heating up and cooling down on the valve seals.. and the exaust valves are even more prone to this just because of their function of passing hot exaust gasses.

Mitsu-

I would have the valve seats redone by a machine shop - regrind the intake valves, and REPLACE ALL of the exaust valves. If your engine has more than 80k miles on it.. you would be far better off in the long run to replace your exaust valves rather than risk future issues. Be sure to have your machinist check your other valves and ensure none are bent. Also.. while you have it apart.. replace the valve seals as well.. your machinist can check your valve springs as well.. Mine were fine with 120k miles on the engine... so likely the valve springs can be reused.. but should still be checked. Also.. if you get a valve spring compressor tool.. you could have the shop do all the machining and then you could reassemble the head once you get it home. Its not that difficult to do. Hope this helps.

Tunes67