Brilliant instruction, thank you so much for taking the time to capture ans describe in such perfect detail. Also, thanks for providing safety advice, too many completely forget about this. 👍👍
Thank you Kurt..Us Porsche owners really appreciate your time and effort in teaching us on how to understand how these unique engines are made and serviced..God bless you and your wife also have you heard about the 964 guides..they have a better composite metal than the original brass and can last a lot longer..have you heard of this.
Mike, Valve guide material is constantly evolving as different materials hit the market. I rarely use a Genuine Porsche valve guide as they are just too expensive and generally not in stock as no one really uses them. The valve guides I use are either a Bronze Manganese, or an Aluminum Bronze type of guide. Porsche has used many different materials throughout the range of the 911 air cooled motor. Thanks for your comment Kurt
@@klassikats Thanks for your comment so i'm guessing the manganese would be the longer lasting guide!...and how long would they last in miles!..cheers!
@@john2ndname Mike, Actually the Aluminum Bronze tends to last a little longer. You can expect intake valve guides to go for around 125,000 to 150,000 miles and exhaust valve guides go for 75,000 to 100,000 miles. Kurt
@@klassikats OK..make sense thanks!..your right!..out of all the alloys aluminum is the hardest alloy's out of the these as manganese and magnesium are soft!
These videos are fabulous, thank-you so much. I read elsewhere that if your allowable play in the guide is x then the valve can wobble 2x on the dial gauge, which if true would have meant some of your wear was within the limit.
@@klassikats I think the logic comes from the play in the valve at its head being twice the stem to guide clearance. This is because the valve can move directly left or right an amount exactly equal to the valve/stem clearance. However additionally, by moving the top of the stem to the right, the head can rotate left an amount equal to half the clearance and can rotate right an amount equal to half of the clearance. it's half each way, because it's protruding about half of the length of the guide out of the guide so can only rotate half as far left as the top can move right. So the play at the head of the valve is double the stem to guide clearance. I guess this could be verified or rebutted by measurement.
Yes, I understand the theory you are basing it on, but for that to work, the valve would have to be held perfectly in the center of the guide without touching the guide and always return to the point after being moved to one side or the other. Which we know does not happen. Instead, the valve stem sits against the guide and, therefore, wears against it every time it moves. The rocker arm action adds to this movement because it does not load the valve directly but instead creates a side movement that highlights both wear and movement. One of the ways you can see this wear in action is to have a guide that is worn, and you measure the wear in the direction of the rocker action. Then, turn your dial indicator to 90 degrees and measure the valve rock. Usually, the side-to-side wear will be significantly lower and sometimes even within the wear limit for a valve guide. It will just show you how much the guide wears on the thrust side. Kurt
You would do less damage to the guide bore by first drilling, milling, or boring out the I.D of the old guide to almost close to its O.D to help collapse and kill the pressure from the interference fit. Then they tap out nicely without much force. On installing the new guides, a better way is to freeze the guides so they shrink, and heat the head so the guide bore opens up, then you will insert the guides into the head with much less force and the interference fit will ramp back in when the temps normalize. Both techniques will help prevent galling and raping the material inside the guide bore.
Thank you for your input. However, I dont like drilling the valve guides to relieve the pressure as usually this creates the risk of more damage while removing the guide. The wall thickness needs to be significantly reduced to make any difference to interference which makes it hard to locate a punch onto it without damaging the guide bore while driving it out. A properly sized guide should have 0.05 mm of interference and should tap out/in with minimal force. By removing the back of the guide as specified by Porsche so that it is flush with the cylinder head surface it is easily driven out using a standard valve guide punch. Rarely do I ever get any scoring on the valve guide guide bore. Usually the only time there is damage to the bore is when the head has been improperly serviced and guides have been driven in to tight. It is the same when installing the valve guides. With a properly sized guide and a properly prepared valve guide bore, both lubricated as specified in the Porsche shop and the guides will easily drive in without much effort. Using heat and cooling will make it even easy however most shops lack the proper equipment to do so. The cylinder head needs to be heated to 200C and the valve guides chilled to -197C to achieve meaningful differences to installation. Handling the parts at these temperatures can be an issue. Now we use heat when installing valve seats, however, the interference is significantly higher running around 0.125-0.150 mm. Thanks Kurt
Pedro, I use straight fluted reams, not sure of the brand as it changes on a regular basis depending on what my supplier has available. The hones that I use are a 240 grit ball hone, designed specifically for soft non ferrous materials. Also not sure of the brand. I purchase both of these products from various machine tool suppliers, like Mcmaster Carr or MSCDirect. Thanks for watching, Kurt
Hi Kurt, thank you for doing this amazing work and showing it. Very much appreciated. Would you mind sharing which mill and lathe are you using in your shop? Thanks!
The lathe is an old Victor and the mill is a Bridgeport clone that I bought new about 8 years ago. I also have a tormach CNC lathe and a Milling Masters CNC mill which is built on a Bridgeport clone mill.
Seat interference is typically 0.12 to 0.15 mm (0.005" to 0.006"). You should always heat the the cylinder head and chill the seats before attempting to install. Kurt
Jump, To be able to press out the valve guides using a press you would have to build a special fixture to hold the cylinder head on the correct angle so as to push the guide straight out. You would have to make two different fixtures because the exhaust guides and intake guides are at different angles and would have to be held differently to press valve guides. It just does not make sense to try to use a press. Thanks Kurt
@@klassikats u are right. but u can adjust the angle of it with vise just like when u milled valve guides. cos hammering precision parts is not looking good.
@@busytirex2366 a vise will not work in a press and all valve guides are driven in either with a hammer and punch or an air hammer. Even the original manufacturer drives in guides with an air-operated punch. There is also a reason that valve guides are supplied unfinished, because until they are machined and sized to the valve. they are not a precision part. This is standard procedure on all models and all valve guides
@@klassikats that was help full. cos when i was looking for valve guide for my engine, in catalog of manufacture(metelli Group), it shows that the ID bore is exactly same with the size of spec
@@busytirex2366 the catalogs will usually always show the finished size, however in reality it will not be the case. all valve guides require correct finishing to suit the valve and the engine specifications they are used in. One of the most common issues I see with the 911 engines and valve guides is that they are sized way too tight. The operating clearance required in an air-cooled engine is larger than that of a water-cooled engine. This often results in valves sticking in the guide and hitting pistons. Valve guide internal finish honing is also an important part of the job.
Brilliant instruction, thank you so much for taking the time to capture ans describe in such perfect detail. Also, thanks for providing safety advice, too many completely forget about this. 👍👍
You're very welcome!
And thanks for watching
Great video! I never realized there was so much to installing new valve guides.
Glad you liked it!
Thank you Kurt..Us Porsche owners really appreciate your time and effort in teaching us on how to understand how these unique engines are made and serviced..God bless you and your wife
also have you heard about the 964 guides..they have a better composite metal than the original brass and can last a lot longer..have you heard of this.
Mike,
Valve guide material is constantly evolving as different materials hit the market. I rarely use a Genuine Porsche valve guide as they are just too expensive and generally not in stock as no one really uses them. The valve guides I use are either a Bronze Manganese, or an Aluminum Bronze type of guide. Porsche has used many different materials throughout the range of the 911 air cooled motor. Thanks for your comment
Kurt
@@klassikats Thanks for your comment so i'm guessing the manganese would be the longer lasting guide!...and how long would they last in miles!..cheers!
@@john2ndname Mike, Actually the Aluminum Bronze tends to last a little longer. You can expect intake valve guides to go for around 125,000 to 150,000 miles and exhaust valve guides go for 75,000 to 100,000 miles.
Kurt
@@klassikats OK..make sense thanks!..your right!..out of all the alloys aluminum is the hardest alloy's out of the these as manganese and magnesium are soft!
These videos are fabulous, thank-you so much. I read elsewhere that if your allowable play in the guide is x then the valve can wobble 2x on the dial gauge, which if true would have meant some of your wear was within the limit.
No not at all. I dont know where you read that but it is not true.
Kurt
@@klassikats I think the logic comes from the play in the valve at its head being twice the stem to guide clearance. This is because the valve can move directly left or right an amount exactly equal to the valve/stem clearance. However additionally, by moving the top of the stem to the right, the head can rotate left an amount equal to half the clearance and can rotate right an amount equal to half of the clearance. it's half each way, because it's protruding about half of the length of the guide out of the guide so can only rotate half as far left as the top can move right. So the play at the head of the valve is double the stem to guide clearance. I guess this could be verified or rebutted by measurement.
Yes, I understand the theory you are basing it on, but for that to work, the valve would have to be held perfectly in the center of the guide without touching the guide and always return to the point after being moved to one side or the other. Which we know does not happen. Instead, the valve stem sits against the guide and, therefore, wears against it every time it moves. The rocker arm action adds to this movement because it does not load the valve directly but instead creates a side movement that highlights both wear and movement. One of the ways you can see this wear in action is to have a guide that is worn, and you measure the wear in the direction of the rocker action. Then, turn your dial indicator to 90 degrees and measure the valve rock. Usually, the side-to-side wear will be significantly lower and sometimes even within the wear limit for a valve guide. It will just show you how much the guide wears on the thrust side.
Kurt
You would do less damage to the guide bore by first drilling, milling, or boring out the I.D of the old guide to almost close to its O.D to help collapse and kill the pressure from the interference fit. Then they tap out nicely without much force. On installing the new guides, a better way is to freeze the guides so they shrink, and heat the head so the guide bore opens up, then you will insert the guides into the head with much less force and the interference fit will ramp back in when the temps normalize. Both techniques will help prevent galling and raping the material inside the guide bore.
Thank you for your input.
However, I dont like drilling the valve guides to relieve the pressure as usually this creates the risk of more damage while removing the guide. The wall thickness needs to be significantly reduced to make any difference to interference which makes it hard to locate a punch onto it without damaging the guide bore while driving it out. A properly sized guide should have 0.05 mm of interference and should tap out/in with minimal force. By removing the back of the guide as specified by Porsche so that it is flush with the cylinder head surface it is easily driven out using a standard valve guide punch. Rarely do I ever get any scoring on the valve guide guide bore. Usually the only time there is damage to the bore is when the head has been improperly serviced and guides have been driven in to tight.
It is the same when installing the valve guides. With a properly sized guide and a properly prepared valve guide bore, both lubricated as specified in the Porsche shop and the guides will easily drive in without much effort.
Using heat and cooling will make it even easy however most shops lack the proper equipment to do so. The cylinder head needs to be heated to 200C and the valve guides chilled to -197C to achieve meaningful differences to installation. Handling the parts at these temperatures can be an issue.
Now we use heat when installing valve seats, however, the interference is significantly higher running around 0.125-0.150 mm. Thanks
Kurt
Thanks Kurt, I will definitely keep your contact info.
Sounds good!
Great lesson...
Glad you enjoyed it. Thanks for watching
Excellent lesson!
By the way, could you please provide the brand and model of the two honing tools
Thank you
Thanks! 😃
Pedro,
I use straight fluted reams, not sure of the brand as it changes on a regular basis depending on what my supplier has available. The hones that I use are a 240 grit ball hone, designed specifically for soft non ferrous materials. Also not sure of the brand. I purchase both of these products from various machine tool suppliers, like Mcmaster Carr or MSCDirect.
Thanks for watching,
Kurt
Hi Kurt, thank you for doing this amazing work and showing it. Very much appreciated. Would you mind sharing which mill and lathe are you using in your shop? Thanks!
The lathe is an old Victor and the mill is a Bridgeport clone that I bought new about 8 years ago. I also have a tormach CNC lathe and a Milling Masters CNC mill which is built on a Bridgeport clone mill.
@@klassikats Thank you so much Kurt. Much appreciated.
Awesome video!
Glad you enjoyed it
Looks like a great shop. Is this your regular business and if so where are you located?
Yes it is, We are located in Arizona.
Thanks for watching
Kurt
What type of interference fit do the seats and cylinder head typically call for? .007?
Seat interference is typically 0.12 to 0.15 mm (0.005" to 0.006"). You should always heat the the cylinder head and chill the seats before attempting to install.
Kurt
why u didnt press valve guides out with a press?
Jump, To be able to press out the valve guides using a press you would have to build a special fixture to hold the cylinder head on the correct angle so as to push the guide straight out. You would have to make two different fixtures because the exhaust guides and intake guides are at different angles and would have to be held differently to press valve guides. It just does not make sense to try to use a press.
Thanks
Kurt
@@klassikats u are right. but u can adjust the angle of it with vise just like when u milled valve guides. cos hammering precision parts is not looking good.
@@busytirex2366 a vise will not work in a press and all valve guides are driven in either with a hammer and punch or an air hammer. Even the original manufacturer drives in guides with an air-operated punch. There is also a reason that valve guides are supplied unfinished, because until they are machined and sized to the valve. they are not a precision part. This is standard procedure on all models and all valve guides
@@klassikats that was help full. cos when i was looking for valve guide for my engine, in catalog of manufacture(metelli Group), it shows that the ID bore is exactly same with the size of spec
@@busytirex2366 the catalogs will usually always show the finished size, however in reality it will not be the case. all valve guides require correct finishing to suit the valve and the engine specifications they are used in. One of the most common issues I see with the 911 engines and valve guides is that they are sized way too tight. The operating clearance required in an air-cooled engine is larger than that of a water-cooled engine. This often results in valves sticking in the guide and hitting pistons. Valve guide internal finish honing is also an important part of the job.