Rebuild Progress: Discoveries So Far

Jandrews · 07-05-2002, 03:47 PM

I am in the disassembly stage of my 2.7RS rebuild. I wanted to post some findings along the way and get feedback from the board that I can use during the rebuild process.

I can post pics of any of these issues if anyone is interested. All advice, thoughts and ideas are welcome.

Thanks in advance.

1) When I removed the clutch from the flywheel, it appeared that the disc was only wearing on the outermost 1/3rd or so of the disc. Is this normal? For what it's worth, my flywheel has the number 911 102 201 3R and what looks to be a date of 6.9.73. I assume this is the original flywheel since my motor started out as a '73 2.4S. The pressure plate is supposedly new, and is Sachs type GM FZ 225, and carries the number 3032 015 399. What are the minimum thickness specs for that flywheel and do you think a resurfacing or replacement is in order?

2) While cleaning the motor, I noticed some oil seepage coming from the top of the right side chain housing. Upon closer inspection, there is a hairline crack about 5 inches long in the casting. Any ideas on where to get a replacement?

3) Third, and perhaps most alarming, is that the genius who last worked on this motor replaced the throttle body to head gaskets with 32mm size gaskets. My motor has the 36mm intake ports and it was obvious from the markings on the gaskets that this was restricting airflow to the entire left bank of the engine. Would this create a noticeable running condition?

Thanks,

Early_S_Man · 07-05-2002, 04:07 PM

The wear limit on flywheel thickness is 8.5 mm.

Do you mean the left bank had 32 mm gaskets, and the right bank had 36 mm gaskets? Sounds like it would cause an overich, reduced volume airflow to the left bank at higher rpms, and a definite 'roughness.' I guess the 'genius' felt the need to use the 'T' gaskets in the rebuild gasket set ... that were 'left over' at some time ... since both sizes are included in the sets! Too much trouble to enlarge the ID with scissors, I guess!

Jandrews · 07-05-2002, 04:17 PM

You got it, Warren, 32mm gaskets on the left bank and 36mm on the right.

You may even recall from some of my earlier posts that I complained of a "buffeting" noise in my motor after I picked it up from the "genius". I am beginning to think this gasket choice is related to the buffeting at a minimum and possibly the annoying roughness that led my motor to its current resting place - the engine stand!

Couple of other observations that I forgot to post above:

1) My headstuds appear to have a sort of shiny gold cast to them. There also appears to be a sleeve of some kind that is visible in the case where they go in (very similar to Wayne's last engine rebuild pic). Is it possible to identify headstud type and brand by their physical description, and is it likely these sleeves are case savers or possibly timeserts?

2) Part of reason for this rebuild is the low compression readings I was seeing in cylinder number two during seveal compression checks. I have not done a leak-down test yet, but plan to tomorrow to isolate the cause of the low compression. Am I correct in assuming it is still possible to conduct a valid leak-down test on the bench as long as my rockers are still attached?

Thanks,

john walker's workshop · 07-05-2002, 05:19 PM

the gold studs could be dilivar, (which need to be replaced with steel). take a magnet to them. dilivar won't attract it. if the case is inserted, that's one less thing to worry about. a leakdown on a cold engine, with little oil to seal the rings, and the possibility of carbon between the valve and seat, from removing the plugs, is at best sketchy. you're going to tear it down anyway, so you'll most likely run into the problem in the process.

Jandrews · 07-06-2002, 07:30 AM

Thanks John...

Are there some specific things I should be looking for in that cylinder that was producing low compression readings? Upon initial inspection through the intake and exhaust ports, there is no glaring evidence. Valves not "visibly" bent, and no wet oil residue indicating worn valve guides or seals.

I know I should have done the leakdown test on a warm, intact engine, but the clutch pivot pin broke and left me stranded. Now I had two reasons for the teardown, but no way to isolate the problem in cylinder number two.

I did however, notice wet oil residue in the exhaust port on cylinder number 5. That cylinder gave good compression readings, however, so I assume it is just a valve seal.

Any thoughts?

Thanks,

jabb · 07-06-2002, 07:57 AM

Tear down is important.... Mark everything put in zip lock bags and take pictures. Marking things helps during the reaasembly process or if you find starnge things during the tear down or machining you can go back to the parts re-examine and know where they came from.

Jandrews · 07-06-2002, 10:01 AM

Another update...

I checked the valve clearance on the cylinder with low compression and found the exhaust side to have no clearance! This could obviously explain the low compression, assuming the valve is tight enough to prevent it closing completely.

This in conjunction with the restrictive 32mm intake port gaskets would certainly explain my running symptoms. Can you believe this so-called Porsche mechanic who returned my car to me in this condition? $2,500 valve repair and this is what I get back. Doing the work myself should be a choice, not a necessity!