Vilhuer

Porsche cheated. Too late to do anything about it. I would just be happy that there are probably many more pistons available if bad one needs to be changed. Supply of more than 4 years must be much better than only ½ year.

mark kibort

no you shouldnt be happy. you have a 10:1 compression engine, but thats probably ok.

the piston cuts are .39", but the valves can push down near this at full cam lobe. it would be close, but i think i have read the the stock euro cams have near .4" lift. so, if its any more and the belt breaks those pistons that at TDC and those valves that are pushed all the way down, could hit slightly.

I just measured when the valves hit the piston cut outs on a true euro '84 type of valve relief. it hits about .3". so as long as the cam lift is not over .45" you might be ok, with a belt break. proof would be if any one with a euro 82 has ever bent a valve with a timing belt break. again, valves hit at .3" with a .175" pocket depth at TDC


MK

tv

Erkka, could you please explain why the number is not considered a later run?

Isn't it # 5,954? seems real high. My 85 euro spare (m28/21 (5 spd)) is # 278

Vilhuer

Its automatic engine, those numbers started from 5001. Read message #69. Its all in there including why this engine has these pistons etc.

tv

thanks, sometimes i just glance over stuff when i'm busy, i did that here.

Big AL in VA

Oh no... I just checked the part number on one of my cams and it is 928 105 187 DR

This according to my parts CD is a 1983 cam used on M28 11/12 engines. But my block is stamped M28 21/22.

Is this another situation like the pistons? Where Porsche used old parts on early run Euros.

Big AL
84 928S Euro twin distributor monster

Vilhuer

R as 11th digit means casting number, usually these do not tell what part actually is. Where do you find it to be '83 MY cam? My PET lists normal part numbers for both '80-83 and '84-86 ROW S cam variations.

Unlike pistons, first M28/21 and /22 did use same cams as all of them.

chewy8000

AL,

Hows everything else coming along with your head removal/missing screw repair? I should be getting my rebuilt heads back next week. I plan on trying to wrap this up the following weekend.

Big AL in VA

My parts info came from PET. It shows a part number 928 105 187 03 under remarks "83" (i assume this means model year) and engine number M28 11/12

My cam has 928 105 187 DR casted into it.

The same PET shows 928 105 211 00 under remarks 84 and engine number M28 21/22

It is reassuring that the two cams are identical in lift. But at first glance it is reasonable to conclude since Porsche used old pistons they would match it with an old spec cam.

Big AL from Virginia
84 928S Euro twin distributor monster

Big AL in VA

Things are going slow but well. I chose to replace the head studs. I am waiting for them to be shipped via 928 Motorsports who are in turn waiting on ARP.

I have my cam towers assembled. That went very well. The front cam seals went on easily. After assembly both cams turn easily inside their housings. I will post soon a picture of the completed cam assembly and the install of the new studs.

I also purchased used exhaust manifolds from a 85/86 928. They are like headers. I will match them with an X-pipe.

Thanks for asking.

Big AL from Virginia
84 928S Euro twin distributor monster

Big AL in VA

Well, beyond a doubt, the most daunting procedure so far was restudding the block. First of all, I spent hours and hours cleaning the threads in the block and cleaning the holes. The cleaning tap I used was hand made. The cutting threads on the tap were ground off. However, this tap ran tight all the way in and out. Giving me a feeling that it might snap at any point. I have decided to give this tap away for free. Have not decided yet on a fare way to do that.

Then came the problem of inserting the new ARP studs. Many say only fingertight and a drop of oil on the threads. However, after talking to Carl from 928 Motorsports he recommended torqueing them down and using loctite thread locker on the studs. This is the way I did it. His reasoning behind this was logical and he showed a lot of surprise when I mentioned his way was counter than every way I read on the 928 Rennlist boards.

The height of all the studs from the block is max. 2 7/8", min was around a 1/16" less than that.

First I mounted the 85/86 stock exhaust manifold on the heads. These manifolds look more like headers when compared to the cast iron manifolds originally found on this engine.

The head gaskets are marked accordingly for the correct positioning. I installed the heads alone. I do not recommend this because they are heavy and you can easlily scratch the mating surfaces up.

Make sure you plug the coolant and oil ports up. I found the head nut easily will go down these ports the hard way. I extracted the nut using a high power magnet. Torqueing these nut down was uneventful and easy. I found that 90 newton meters did not feel hard to me on the torque wrench. For some reason I thought it would be a harder pull. I was confused about which torqueing method to use. Mainly because the 400.00 dollar studs have a differnet thread pitch on the nut size. So angle torqueing would not work out. So, I used the 3 step procedure in the WSM with a final torqued value of 90NM.

I set up a small work are to recondition the head load bearing washers. I put a nice smooth surface on one side and a scratched surface on the other. As per WSM. Using a medium grit emery paper.

Here are some pictures and feel free to ask me any questions.

Big AL from Virginia
84 928S euro twin distributor monster with large valve cut outs

chewy8000

Nice work Al. Looks like your getting there. You have any good advice for removing the gasket material from the block? I used a straight blade and carefully got it down to smooth but there is still some trouble spots. Someone recommended a 3M scotchbrite pad the other day. Yikes. I know these alluminum blocks are very soft.

Big AL in VA

You are right. The block material is surprisingly soft. The head gaskets that came off mine was all metal. Then I used a very fine emery paper to dress up some areas of the mating surface showing some discoloration.

Big AL from Virginia
84 928S Euro twin distributor monster with large valve cut outs

Big AL in VA

Here is a picture of my engine mostly reassembled after the block up rebuild. Notice the green paint marks on the head bolts. Cam covers were powdered coated and intake runners polished as well as the oil filler.

It has been slow going especially the fuel piping and vacuum lines. I did take some digital pictures before disassembly 6 months ago. This is definatly a hobbiest job. This would have cost a small fortune to have a Porsche mechanic do this job.

Also, a picture of the exhaust. This 84 euro uses 85 86.5 manifold headers and I added an X-pipe with high flow cats. All in stainless steel.

BIG AL from Virginia
84 928S twin distributor monster with large valve cut outs in pistons

Big AL in VA

I have the engine running and everything head and block related looks good. No visible exhaust or bad smell.
However, I found several coolant leaks. First the water pump was leaking all the way around it. I had used the wrong type of Permatex sealant. I used a fast drying (yellow) sealant. Also, I forgot to seal the threads of the bolt for the idler roller. So, their I was pulling the front of the engine back off. And then bad luck strikes. While trying to lever the idler off wiith two screwdrivers I crack the boss. Now I am looking for a new water pump. I buy a new one on ebay. This water pump came and it had no 928 part number on it. The casting was a little rough. So, I decided to put it on with a bit of regret after installation. I have the timing belt back on now and tensioned. After putting fluid in the block via the top radiator hose, I see now some coolant leaking around the thermostat housing. Now I have to take that off and check the O-ring. I found a post here on Rennlist that some O-rings shipped with thermostats have a too small of a diameter.

Anyway, it seems as though the biggest challenge so far is chasing down leaks after initially starting the engine.

Other leaks include the power steering pump, possible leak at the crossover o-ring, and hopefully I am just burning off oil that I smeared over the bottom section of the cam tower covers. That was really scary seeing smoke rolling off both sides of the engine. After idling for 5 minutes the right side stopped smoking and the left side was still smoking but a lot less.

I feel at this point I still have a way to go to get it back on the road. I am finding out more and more how delicate this motor is. In other words, everything you do to the motor must be near perfect to have success. I find myself getting fed up at times and wondering if selling would rid me of the headache. But, I must get it done and get it done right. I do not want to sell it until it is perfect. But, the irony here is if it is perfect I might want to keep it.

I hope I can stick it out. It gets pretty frustrating at times. I have big hands and I am 49 years old. Working in these tight spaces can be difficult for me. In saying that, I can see why this car is so expensive to work on and labor intensive.

I will post pictures when the motor is complete and not leaking. At this time though, I must look at the positive, the motor runs and throttles up strong.

Also, I received a waiver yesterday from the department of Enviromental quality in my state of Virgina. Thank God, no more emission checks.

Big AL from Virginia
84 928S EURO twin distributor monster with large valve cut outs on the pistons.