Kurt it astounds me that with Porsche valve guides that they wear out in less than 100,000 kms where most other vehicles their guides last over 3-400,000kms why is that? What is the best type of guide to get so it will last the most? thanks for your video and time..
So guides in the 911 engine are good for about 100,000 miles, (160,000Kms). Typically the exhaust valves are the first to go and a set of intake valve guide can last around 150,000 to 175,000 miles. The reason for the failure is the environment that they live in. Air cooled cylinder heads run much hotter than water cooled engines. An air cooled head runs around 25o to 275 degrees F in normal operation. This means oils will tend to break down faster and parts need to be assembled looser to allow for greater expansion of dis-similar materials. Lately a lot of the heads we are seeing are being damaged by previous work. Machine shops that dont specialize in air cooled motors tend to assemble valves and guides too tight. This causes valves to seize in the guides and material transfer will often occur. I dont know about any guide lasting over 250,000 miles even in water cooled engines. Engines that dont use rocker arms like the 928, 944, and 924 models will tend to have longer lasting valve guides. This is because the rocker arm in the 911 engine places a side load on the valve stem that in turn wears against the valve guide. When the the cam lobe works directly on top of the valve the load on the valve guide is very minimal. As far as a guide material I use a Phosphor Bronze valve guide, and I pay attention to the new installation clearances and I use high quality oils in the engines I build. Kurt
@@klassikats Ok.. Thanks Kurt for your invaluable info if anyone who ask about 911 valve guides it would be you. Would adding upper cylinder lubrication say morey's a brand that's one of the best in the fuel help to lub those guides and help on the valves?
i like using upper cylinder lube especially in engines running unleaded gas. It is great for the fuel system and can help with valve seat life. However it will not help with valve guide life. Kurt
Brian, So every job is so different depending on the starting condition of your heads. The average price range is between $2000 to $2800. However, this does not mean that it cant be cheaper than that if the work and parts required are less. It can also be more than that if the heads are in really bad shape and need welding and seat replacement as well. Kurt
Love these videos. Always learning more about these engines from you. Keep them coming Kurt.
Thanks, will do!
Kurt
Completely entertaining_ I need to come down for a Major Service. Thanks!
Shoot me an email when you are ready Chuck and I will get you on the schedule.
Kurt
Kurt it astounds me that with Porsche valve guides that they wear out in less than 100,000 kms where most other vehicles their guides last over 3-400,000kms why is that? What is the best type of guide to get so it will last the most? thanks for your video and time..
So guides in the 911 engine are good for about 100,000 miles, (160,000Kms). Typically the exhaust valves are the first to go and a set of intake valve guide can last around 150,000 to 175,000 miles. The reason for the failure is the environment that they live in. Air cooled cylinder heads run much hotter than water cooled engines. An air cooled head runs around 25o to 275 degrees F in normal operation. This means oils will tend to break down faster and parts need to be assembled looser to allow for greater expansion of dis-similar materials.
Lately a lot of the heads we are seeing are being damaged by previous work. Machine shops that dont specialize in air cooled motors tend to assemble valves and guides too tight. This causes valves to seize in the guides and material transfer will often occur.
I dont know about any guide lasting over 250,000 miles even in water cooled engines. Engines that dont use rocker arms like the 928, 944, and 924 models will tend to have longer lasting valve guides. This is because the rocker arm in the 911 engine places a side load on the valve stem that in turn wears against the valve guide. When the the cam lobe works directly on top of the valve the load on the valve guide is very minimal.
As far as a guide material I use a Phosphor Bronze valve guide, and I pay attention to the new installation clearances and I use high quality oils in the engines I build.
Kurt
@@klassikats Ok.. Thanks Kurt for your invaluable info if anyone who ask about 911 valve guides it would be you. Would adding upper cylinder lubrication say morey's a brand that's one of the best in the fuel help to lub those guides and help on the valves?
i like using upper cylinder lube especially in engines running unleaded gas. It is great for the fuel system and can help with valve seat life. However it will not help with valve guide life.
Kurt
Love your videos. Could you provide some details on your blasting setup? What media are you using? What is the cabinet? Thanks.
I use a glass bead/Aluminum oxide mix.
Kurt
Hi Kurt. Great videos. Can you share the rough/ballpark $ estimate range for this head rebuild service assuming new guides and valves.
Brian,
So every job is so different depending on the starting condition of your heads. The average price range is between $2000 to $2800. However, this does not mean that it cant be cheaper than that if the work and parts required are less. It can also be more than that if the heads are in really bad shape and need welding and seat replacement as well.
Kurt
👍
Thanks
I noticed that the aluminum parts are being cleaned in a parts washer. What kind of solution is used that will clean and is cast aluminum safe.
I use Ozzie Juice SW4, however you have to be careful with mag parts as it will darken freshly machined magnesium.
Kurt