Mike J

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

c993k

Superb Mike, Thanx, Chris

simpateko

hi mike
how many miles on your car?
thanks.....jeff

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?

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...

epj993

Great work Mike! Can't wait for the next installment

InTheAir

There are definitely SAI ports in 95' 993's (even earlier). The only difference is that the OBDI system does not measure for blockage and, thus, does not trigger a Check Engine Light (CEL).

Mike, very cool pictures!

Martin S.

Incredible post, we await Part 2 of the saga!

Adrienne

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!

Toga

Excellent post Mike! Great pictures!
One question on the engine stand you're using: did you build it by yourself? Could you post a few pictures of it?

Thanks

Mike J

75,000 miles. The first 50,000 were in Toronto which gets very hot in the summer and when I got it the engine cover was on.

Search the archives, there are lots of info on guides. The guides are the tubes that the valve run in, you can see the guides in the pictures of the two valve seats above as well as the top of the guides which are the brass colored tubes sticking out of the heads (see the shot with the drill bit)

Actually not too much. The drill bit went through pretty easily. My symptoms were not SAI faults but high oil consumption and a bad leakdown numbers.

You mean part V, VI, VII and so on?

Well its not too bad so far. What is not shown is all the hours it takes to do this, especially the first time. Once I do something to one side of the engine the other side is much quicker. I can see if I do this for a living you can get pretty quick at it. The parts are precision and come apart quite smoothly. I only have broken two bolts (one on the intake of one of the heads) and had a few near calls with crapped out allen heads from the factory. Other than that its been very smooth with no suprises. The wear is not too bad, in fact its likely less than the factory specs as "worn out", even for the valve guides.

What I am using for a stand is a cheap 2000lb stand with a new post made of a piece of scrap tube with a piece of 1/4" plate welded on the top. Its a big ugly the it works. I regret not getting the square based stand but its bought and welded so no returns...the yoke and clamp are standard Porsche tool issue . The system works really well since you can spin the engine to get to the stuff you are working on...it makes changing the plugs a breeze!

Here are some pictures...





Cheers,

Mike

Toga

Thanks Mike!
I can imagine how easier it is to work on the engine with your stand!!
This could be my next project.
Cheers

tam993

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

tam993

I mean replace them if you don't move the crank etc.
Tim

pcar964

Great thread, keep it coming!