Engine Rebuild Part IV - The saga of the valve guides..and carbon..
#1
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Thread Starter
Engine Rebuild Part IV - The saga of the valve guides..and carbon..
I thought I would post a thread on the heads themselves. I took it upon myself to take one of my heads (#1 piston is a good choice) apart to see what the wear on the guides are...
Here is a shot with the valve springs/retainers removed. The smaller valve (the one on the right) is the exhaust valve, the other of course is the intake. The intake passages are covered in a light coating of varnish from the fuel but are pretty clean. The exhaust side is another story. The combustion chamber is actually pretty clean in that there is a coating of carbon but no thick buildup.
Here are the valves. You can see part of a retainer above the valves. They hold the valve springs onto the valve stem. I measured these valves, the exhaust appears to be worn beyond the limits and the intake is marginally OK. I will let the machinist take his own measurements and we will discuss it.
Here is the exhaust port close up. You can see the SAI passage entrance just right of the guide entrance. Its pretty small. Notice all the black gunk on the port walls...these walls are ceramic lined althought you would never know.
I wanted to see how clear the SAI passage was so I dropped a drill bit down the hole...it was a loose fit and it went in no problem. The hole is a straight line and perhaps it could be drilled out a little larger as suggested in part III.
Here is the end of the drill bit poking out of the SAI outlet in the exhaust port. It would be no problem to enlarge this port at this time if I knew there was enough meat in the head.
Oka, for fun and no profit, I setup my trusty gauge to see what the wiggle would be at the head of the exhaust valve. You normally are supposed to use a new valve but I do not have them yet.
When measuring the valves you have to have the head off the seat so the exhaust valve has been pulled off the seat by 10mm or so.
So what did I find? Well the wiggle appears to be about 0.6-0.7mm at the head of the stem. If you wiggle it it definitely moves back and worth quite a bit. Its not just a little bit loose is quite loose. I am sure they can get looser but I can see how heat would have problems transferring from the valve to the head when they are in this state.
The intake is also worn but not as much as the exhaust. The seats in the heads look OK in that they to not appear to be beaten up too much but the machinist will take a look.
I definitely needed valve guides!
Next installment? We take off the P/C's and split the case
Cheers,
Mike
Here is a shot with the valve springs/retainers removed. The smaller valve (the one on the right) is the exhaust valve, the other of course is the intake. The intake passages are covered in a light coating of varnish from the fuel but are pretty clean. The exhaust side is another story. The combustion chamber is actually pretty clean in that there is a coating of carbon but no thick buildup.
Here are the valves. You can see part of a retainer above the valves. They hold the valve springs onto the valve stem. I measured these valves, the exhaust appears to be worn beyond the limits and the intake is marginally OK. I will let the machinist take his own measurements and we will discuss it.
Here is the exhaust port close up. You can see the SAI passage entrance just right of the guide entrance. Its pretty small. Notice all the black gunk on the port walls...these walls are ceramic lined althought you would never know.
I wanted to see how clear the SAI passage was so I dropped a drill bit down the hole...it was a loose fit and it went in no problem. The hole is a straight line and perhaps it could be drilled out a little larger as suggested in part III.
Here is the end of the drill bit poking out of the SAI outlet in the exhaust port. It would be no problem to enlarge this port at this time if I knew there was enough meat in the head.
Oka, for fun and no profit, I setup my trusty gauge to see what the wiggle would be at the head of the exhaust valve. You normally are supposed to use a new valve but I do not have them yet.
When measuring the valves you have to have the head off the seat so the exhaust valve has been pulled off the seat by 10mm or so.
So what did I find? Well the wiggle appears to be about 0.6-0.7mm at the head of the stem. If you wiggle it it definitely moves back and worth quite a bit. Its not just a little bit loose is quite loose. I am sure they can get looser but I can see how heat would have problems transferring from the valve to the head when they are in this state.
The intake is also worn but not as much as the exhaust. The seats in the heads look OK in that they to not appear to be beaten up too much but the machinist will take a look.
I definitely needed valve guides!
Next installment? We take off the P/C's and split the case
Cheers,
Mike
#4
there had previously been extensive discussion on valve guides. what are they? are they shown in your photos? if not, could you take a photo of the guides? thanks
my 993 is OBD1. are there any SAI ports to be cleaned as in case of obd2 cars?
my 993 is OBD1. are there any SAI ports to be cleaned as in case of obd2 cars?
#5
Very interesting -- great pics and commentary!
How much gunk (carbon, I assume) came out of the SAI port when you pushed the drill bit through it?
I'm also curious about the mileage on this engine...
How much gunk (carbon, I assume) came out of the SAI port when you pushed the drill bit through it?
I'm also curious about the mileage on this engine...
#7
Nordschleife Master
Join Date: Jun 2005
Location: Neither Here Nor There
Posts: 5,351
Likes: 0
Received 7 Likes
on
5 Posts
Originally Posted by gst
there had previously been extensive discussion on valve guides. what are they? are they shown in your photos? if not, could you take a photo of the guides? thanks
my 993 is OBD1. are there any SAI ports to be cleaned as in case of obd2 cars?
my 993 is OBD1. are there any SAI ports to be cleaned as in case of obd2 cars?
Mike, very cool pictures!
Trending Topics
#9
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
So, are things going as smoothly as you are writing them?
With your conclusion, it looks like your work was timely. Looking forward to Part V when you split the case.
By the way, you are really doing Rennlist a service, posting all of this info. I really, really appreciate you taking the time to show all of us what's going on at each step. Good luck!
With your conclusion, it looks like your work was timely. Looking forward to Part V when you split the case.
By the way, you are really doing Rennlist a service, posting all of this info. I really, really appreciate you taking the time to show all of us what's going on at each step. Good luck!
#11
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Thread Starter
Originally Posted by simpateko
hi mike
how many miles on your car?
thanks.....jeff
how many miles on your car?
thanks.....jeff
Originally Posted by gst
there had previously been extensive discussion on valve guides. what are they? are they shown in your photos? if not, could you take a photo of the guides? thanks
my 993 is OBD1. are there any SAI ports to be cleaned as in case of obd2 cars?
my 993 is OBD1. are there any SAI ports to be cleaned as in case of obd2 cars?
Originally Posted by YA911Fan
Very interesting -- great pics and commentary!
How much gunk (carbon, I assume) came out of the SAI port when you pushed the drill bit through it?
I'm also curious about the mileage on this engine...
How much gunk (carbon, I assume) came out of the SAI port when you pushed the drill bit through it?
I'm also curious about the mileage on this engine...
Originally Posted by Martin S.
Incredible post, we await Part 2 of the saga!
Originally Posted by Adrienne
So, are things going as smoothly as you are writing them?
With your conclusion, it looks like your work was timely.
With your conclusion, it looks like your work was timely.
Originally Posted by Toga
One question on the engine stand you're using: did you build it by yourself? Could you post a few pictures of it?
Thanks
Thanks
Here are some pictures...
Cheers,
Mike
#13
Exceptional detail and data. Really is impressive what you've done.
So once you remove the cams you have to reset them? Like some engines you can replace them without reseting the timing.
tim
So once you remove the cams you have to reset them? Like some engines you can replace them without reseting the timing.
tim