Replace valve guides when rebuilding head?
#1
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Replace valve guides when rebuilding head?
I think I've decided I want to rebuild the head on my '95 since I've come to blame my oil consumption issue on bad valve seals, and I'm trying to figure out the best way to go about it, doing all the necessary work but without spending an arm and a leg.
I'm at 183k miles on the stock motor, so I want to take care of as much as possible in one shot to avoid problems down the road. So far I have the following plan.
- Fully disassemble head and get hot-tanked, do a mild porting job, clean and lap valves
- Valve seals
- Valve guides
- Cam seals
- MLS head gasket
- Timing belt and water pump
- Replace or have lifters ultrasonic cleaned
- Spark plugs, and misc other bits and pieces
Am I missing anything? Should I skip the ultrasonic cleaning and just get new lifters for the peace of mind? Keep in mind that I'm not boosted and probably won't be for quite some time, so I'm just looking for a solid refresh and maybe a little something extra from the 'ol butt dyno.
I'm at 183k miles on the stock motor, so I want to take care of as much as possible in one shot to avoid problems down the road. So far I have the following plan.
- Fully disassemble head and get hot-tanked, do a mild porting job, clean and lap valves
- Valve seals
- Valve guides
- Cam seals
- MLS head gasket
- Timing belt and water pump
- Replace or have lifters ultrasonic cleaned
- Spark plugs, and misc other bits and pieces
Am I missing anything? Should I skip the ultrasonic cleaning and just get new lifters for the peace of mind? Keep in mind that I'm not boosted and probably won't be for quite some time, so I'm just looking for a solid refresh and maybe a little something extra from the 'ol butt dyno.
#3
I would measure (or have your machine shop measure) the valve guides before doing a wholesale replacement of all of them. If they are egg-shaped or overly worn then get them replaced. I'd also get a quality multi-angle valve job done rather than just lapping the valves in the seats; at nearly 200K miles..I question the quality of valve seal you'll get by only lapping. I'm not sure if the stock Miata valves are single piece (the SS aftermarket valves are) or two piece (head welded onto stem). Depending on your budget, replacing all the valves with oversize valves would give you better airflow and fresh "higher" seat cut. I'd also get check the open closed seat pressures of all the valve springs.
There is an article (on Miata.net) detailing how to dissassemble and clean the Miata hydraulic lifters; if you are on a budget this can save you the cost of the ultrasonic cleaning or lifter replacement.
There is an article (on Miata.net) detailing how to dissassemble and clean the Miata hydraulic lifters; if you are on a budget this can save you the cost of the ultrasonic cleaning or lifter replacement.
Last edited by sn95; 03-26-2010 at 12:17 AM. Reason: added lifter comment
#10
I'm in the process of rebuilding a head. It's a 99 with 120k miles according to the seller. I'm using new +1mm intake and +2mm exhaust super tech valves.
The exhaust valves seem to be pretty loose in the oem guides. I can get a decent amount of wobble in it. When I measured the clearance they all fell on the upper edge of the allowable clearance to falling just outside the spec by a couple thousandths.
The intake valves seem to fit well with the proper clearances.
For those experts in the field, do you typically replace valve guides when rebuilding a head? Is it something that should always be done as a security measure or only as required based on millage and wear. would it be fine to just replace the 8 exhaust valve guides or should I do the intake as well while I'm at it.
So far I've found these option:
OEM-$10 a guide through mazda motorsports development
supertech - $7 a guide
miata roadster - $90 for all 16 guides
has anyone tried the miata roadster one or should i just stick with the OEM?
http://www.miataroadster.com/miataro...i-1964291.aspx
The exhaust valves seem to be pretty loose in the oem guides. I can get a decent amount of wobble in it. When I measured the clearance they all fell on the upper edge of the allowable clearance to falling just outside the spec by a couple thousandths.
The intake valves seem to fit well with the proper clearances.
For those experts in the field, do you typically replace valve guides when rebuilding a head? Is it something that should always be done as a security measure or only as required based on millage and wear. would it be fine to just replace the 8 exhaust valve guides or should I do the intake as well while I'm at it.
So far I've found these option:
OEM-$10 a guide through mazda motorsports development
supertech - $7 a guide
miata roadster - $90 for all 16 guides
has anyone tried the miata roadster one or should i just stick with the OEM?
http://www.miataroadster.com/miataro...i-1964291.aspx
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