[Charlie Stylianos]

Can timing as well as the cam lift/duration will affect the compression values.

190psi does sound a little high for a US SC, but I'm not sure what the compression values should be. Maybe you scored a Euro engine? Check he engine # just to make sure.....Cam timing differs between the two engines as well.

Sounds like you are farther along than I am, nice work.

[William Miller]

The engine number and SN indicate a US SC.
It was rebuilt in 1996 and the rebuilder stamped the date and a number on the top at the parting line. As far as the block goes I don't think there are any differences between the US version and the Euro except for the Pistons and Cylinders. The camshaft is the same part number but, as you mentioned the cam timing was different.

The fuel Injection is simular to that in a 79 SC K-jetronic without Lambda Control. There were some improvements over the 79 because I found that the mixture control unit and the fuel distributer have different part numbers. I think the 83 euro fuel distributer has the updated system pressure regulator in it.

Anyway, I guess the only way to find out is with the deck height check.
I was about to get started on this, but found that the only solder I have at the house is not Acid core. I'll be making a trip to the hardware!
I think I might check the deck height on all the pistons to see it there are any variations. Recall I am rebuilding because of a broken ring. I also found that there is an impression of one of the valves on the top of #4 piston. I think I recall another slight mark on one of the others.

I'll let you know what I find.

[William Miller]

I had a setback last week. I realized the intake ports on my heads are smaller than the diameter of the runners. This is because my CIS system is the European version and the block was replaced with a US version.
Last weekend I bored out the intakes on the heads to 38mm which matches the intake runners.

I ended up making a template that centered a 1-1/2" hole saw over the end of the intake on the head. after getting the cut started (about 1/2" deep) I removed the template and continued to bore (or you might say ream) the hole down twards the valve guide. The casting actually opens up as you get closer to the valve guide so the transition was pretty smooth. The only grinding I did was with a air grinder with a little ball shaped rasp in the end. This was only necessary to shape arround the base of the valve guide. I cleaned up the bore with a little cylinder shape sander that fit on the end of my drill.

The finish on the walls inside the bore is simular to what I just saw in your picture, but my grinding was not nearly as pretty.

One question, what are you going to use for a gasket. Do you take the standard gasket and make the hole bigger? What's the easiest way to do this?

I checked my deck height last night. It turns out it is excessive based on Wayne's book. I checked #1 and #4. Both squashed the solder to .081" or 2.05mm. Wayne recommends 1.25-1.50.

What to do? I read somewher that you could take the base gasket out all together. Wayne recommends sealing the joint with the Loctite 574 any way, like the case. Anyone had any experience with this? I installed the heads last night (hand tight, no sealant) I could easily lossen them up enough to remove the base gasket and seal it with the 574.

In any case I guess the 2mm is safe for a street car. I don't know what my CR is. Charlie you mentioned that this could be calculated from the deck height. How much would the .25mm increase it. Should I bother or play it safe?

Any thoughts?

[Charlie Stylianos]

One question, what are you going to use for a gasket. Do you take the standard gasket and make the hole bigger? What's the easiest way to do this?

You know what, I haven’t thought about this yet. I'll probably take a Dremel w/ a sanding wheel to the gaskets and open them up a little. Thanks for the pointer

I checked my deck height last night. It turns out it is excessive based on Wayne's book. I checked #1 and #4. Both squashed the solder to .081" or 2.05mm. Wayne recommends 1.25-1.50.

William, I measured my deck heights last night and had a difficult time using CE's (Wayne’s) solder technique on the JE's. When using this procedure I measured about the same (2.0mm) at the thinnest part of the solder, but by visually comparing the solder to the gap, the solder width looked considerably larger then the P to C top. I repeated this procedure a few times with the same results. I eventually noticed the JE's had a little lip around the circumference (see pic below) where you could use the depth gauge on your dial calipers to measure the DH. I could not get the solder flush enough against the C wall or get it to conform to the P dome enough to get an accurate reading by crushing. My direct DH measurements (from P lip to C top) were ~1.12mm measuring directly. The ~2.00mm I was measuring before was actually my P dome to head clearance (looks like we'll be good for the P to valve clearance also). I don't know if the OEM CIS pistons have this little circumference rim as I don’t have them in front of me right now, but if they do, I'd suggest using this against you C top for your DH measurements.



What to do? I read somewhere that you could take the base gasket out all together. Wayne recommends sealing the joint with the Loctite 574 any way, like the case. Anyone had any experience with this? I installed the heads last night (hand tight, no sealant) I could easily lossen them up enough to remove the base gasket and seal it with the 574.

I think Wayne recommends CurilT, but this could be just for the base gaskets. I would recheck your DH just to be sure because from the factory they came with the .25mm gaskets (DH from the factory was 1.35-1.50mm). If you didn’t have any machine work done, nothing should have changed.....if anything, the machine shop would have removed material necessitating additional shims.

In any case I guess the 2mm is safe for a street car. I don't know what my CR is. Charlie you mentioned that this could be calculated from the deck height. How much would the .25mm increase it. Should I bother or play it safe?

Well, to measure your current CR, you will need to know your bore (95mm), stroke (70.4mm), piston dome volume in cc's (?), head volume (stock is ~90cc's), and current DH (?). Check your e-mail, I sent you a spreadsheet that will calculate your CR. You can plug in different values to see what the difference of DH will make. Usually for a 3.0, a .25mm of DH will change CR about .25 points.

[William Miller]

Charlie,

The CIS pistons have a flat spot around the edges simular to what is in your picture. I ignored this because like an ape, I have been doing what Wayne recommended in his book instead of thinking. Wayne has a tendancy to write many things down twice with different terminology in different places. Maybe that's just me reading. I think your's right on the money he is describing how to measure the clearance between the top of the cylinder and the piston. I think in the same breath he is referring this to deck height.

As I undersand you and this certainly seems to make sence that the deck height is the difference between the top edge of the piston (If the piston is shaped like your's or mine.) and the top edge of the cylinder.

I looked at this, but did not measure it. My guess is that my deck height is about 1mm+.

In looking at your spreadsheet and your post it seems like I will be able to get an accurate measurement on deck height. What I don't know is the dome volume of my pistons. This is where I jumpped on board your thread (I think) Asside from some casting numbers I can't Identify what pistons that are in my engine. I'm sure they are stock CIS Pistons, but didn't they come in 3 or more different CR's? for SC. I don't have my book, but I recall an 8.?:1 (Early CIS) a 9.3:1 (1980+ US CIS) and the 9.8:1 Euro set.

I guess the only real way to know is to take them back out and get them CC'd.

Can you think of anything else?
If not, I think it's time to button it up!

BTW I think wayne recommended the locktight 574 to seal the P base gasket. Some on both sides of it.

[Charlie Stylianos]

Wayne uses Competition Engineering's method for measuring DH's for high domed pistons w/o this 'lip'. Look familiar

http://competitioneng.com/WaltsPage.htm

I think the key for success with this technique is the get the solder end flat/flush against the C wall. The DH will be the flattest part at the C end of the solder, the remaining will be the P to Head clearance .....I just could not get it to work right for me. Better a direct measurement anyway. Yes, DH is the measurement from the P lip to the top of the C at TDC.

The CR's mentioned below are correct for the different SC years. Remember that Porsche's printed CR specs of 9.3:1 are actually measured around 8.9:1. IF you know this engine has not been apart or has not been modified, you could work backwards with the 8.9:1 CR to find your P volume.

As long as your DH is not less than 1mm and consistent on all 6 cylinders, I can't think of anything else........

BTW: are you sealing everything up as you go and hoping your P to Valve clearances are OK?

[William Miller]

I pulled #1 and #4 heads off last night to take a quick look.
There was only one place on the piston that I could take the measurement (quickly) because the CIS dome is in the way on most of the piston. There is a lip, but it is very hard to get the little rod in the center of the caliper to touch that lip with the flat butt end of the caliper on top of the cylinder. This is true on both sides in line with the wrist pin where the measurement would tend to be most accurate. I was able to measure at the botom of the piston where there really is no dome.

The measurements on both #1&#4 were both +-.04" = a little more than 1mm. I also did not have the cylinder torked down which may have some effect (reducing the measurement).

So my conclusion: (Simular to your's I think.)
My block and heads are pretty much virgin (No Machining on the case or the heads or the cylinder base mating surfaces.

My deck height is right around 1mm which is not excessive. (Possibly a little less.

My Piston to head clearance (measured by the squish test) was 2.05mm.
Simular to yours and I think this is safe.

Asside from replacing the main and rod bearings w/ new std/std and replacing and honing the wrist pin bushings to standard. I have done nothing to really change what was working well before.

My primary concern was to try and identify what caused the intake valves to hit the tops of the pistons. #4 worst #1 slight. I suspect this may have something to do with the top ring on #4 piston to wear excessivly to the point of breaking. The side clearance on this ring grove was within wear limits. The other thing I found was that the valve guide wear was most noticable on this one as well.

My guess at this point is that the valve guides were very sloppy, the valve springs weak allowing a lot of float wich allowed the piston to hit the valve before it was fully closed. I think the valve timing might have been off as well. Somewhere on this post was a discussion that the valve timing will have an effect on a compression test. My readings on every compression test I ahve done seemed higher then I have seen posted or written anywhere. 190-195 psi. Wayne explained in his book that the valve may be closet to the top of the piston at other points in the stroke besided TDC.

I would imagine this point may vary depending on the timing of the camshafts.

The valve timing was modified a few times during the production of the engine. US SC 930/16 #1 intake opens 7deg BTDC; Euro SC intake opens 1deg BTDC 84 Carrera intake opens 4 deg BTDC These all use the same camshaft.

Anderson's book goes into some detailed discussion about this. I recall that one end of the range (Can't remember which at the moment) helps to produce more torque, or more tourque at a lower, more usable RPM. The other end of the range produces the most HP at the top end of the RPM range. He mentioned that in 84 with the carrera they split the difference.

Because I'm building mine to be driven, I will probably tune the camshafts for the torque side of the range.

You asked me if I was going to do the dry build as described in Waynes book to check the valve clearances before I sealed it up.

I think I'm really in a situation where that is not warranted. Because I really didn't change anything. I think I'm in a pretty safe zone at the moment. I didn't seal the base gaskets at the time because I wasn't yet sure about the deck height and valve clearances. It's funny that I think the only place my engine was not leaking was at the base gaskets.

I think I'm going to take my chances with that too.

In regards to the CR, I'm sort of in a catch 22 because I don't know what pistons are in there. Not that it matters because I'm not going to spend the money to change it anyway. The only cheap thing I could do is to eliminate the .25 copper base gasket. I now think that is a bad idea because it's the only place that can compensate if the 3 cylinders in the bank are not exactly the same. I think part of it's function is as a seal, but I think the other part is to provide a small measure to compensate for small varances. (Just my thoughts)


I'm getting itchy to get this project finished. It's been since the end of April since I drove the car. I'm going away next week so I'm probably not going to get the engine back in until sometime arround labor Day. If I'm lucky!

Do you have a shot of your intake runners from the head side?
How much did they end up boring them out?

[William Miller]

Charlie, just clicked your link to CE's tip page.
I noticed the dry roker shaft installation section.
He converts the spec. torque to 13 ft. lb. what is the conversion for the torque he recommends? 2.8kpm?

[Marc A]

It converts to "As tight as you can get it without striping anything" and I'm not kidding.

When I did mine, the guys at Dulles IM said use a 5mm & 8mm hex wrench and tighten as much as you can. The 8 mm will have to be cut down because of clearance problems on the ends. I can lend this to you as well if you like.

Also put the RSR seals on the rocker shafts. This is a no brainer.

[William Miller]

I have the seals.
I have a set of allen wrench ends that are mounted like on the end of a 3/8 drive socket. The ends stick out of the socket about 1". The tool is shorter than the shaft so it fit's in the area where the shaft is installed.

On the part that sticks out of the socket. I slipped the box end of a 5 mm wrench. Sears actually makes a double box end wrench with "ratchet action". This worked very well. I thnk the end with the nut is 8mm which you hold with a standard allen wrench. Is this what you are refering to?

What I don't recall is if my torque wrench will fit in that tight space on the end of the allen socket?

Waynes book say's to install them so the bolts are pointed in. That's the 5mm end.