"Barn find" 1986 911 turbo

[5.7 GT1]

What a great story. Very inspiring. Love the resourcefulness of everything.

[reclino]

I am really just doing it for the sponsors. Oh wait, I forgot to get sponsored. May have to go sit in a dark room making car noises and re-evaluate my life goals.

[reclino]

By the time it came to the edge of the Forest, the stream had grown up, so that it was almost a river, and being grown-up, it did not run and jump and sparkle along as it used to do when it was younger, but moved more slowly. For it knew now where it was going, and it said to itself, “There is no hurry. We shall get there some day.
A. A. Milne

New 98mm forged Mahle pistons, bigger but 9 grams lighter than the stock ones.
Wrist pins are 19 grams lighter.

I am going to measure the bore of the cylinders and see if Mahle hones them with taper, starting with the 964? Porsche honed the top of the cylinder a bit smaller because when warmed up, the top of the cylinder expands more than the bottom.......

[TurboKraft]

Nice
May need a new circlip tool

[reclino]

Did a bit of careful measurement of a cylinder today. The top of the cylinder is about .0003-.0004" smaller than the bottom. So indeed there is a bit of taper, which will go away once the cylinder warms up at the top. Surface roughness is spot on at 6 RA and feels just a bit rougher to the touch than the reworked cylinders. Now to clean everything and check the ring gap.

[reclino]

Checking the Mahle cylinders on the surface plate. Height from "top" of cylinder to shoulder. All check within tolerance, 4 are close to zero difference, 2 seem to have slight variance from side to side.
(Each division on my gauge is .0005")
Well within tolerance.




This is the worst cylinder. Maybe that's .00025" reading between the lines. May try to find a better indicator just to put a number on it.
Tried another indicator.but the adapter I am using won't hold position.
As head of the metrology department here I can find no fault with these parts. I will forward the parts over to the team lead for engine assembly (also myself) to perform another fit check to verify deck height.

[reclino]

So my first born who has appeared in some of this build blog was accepted to University of North Carolina Charlotte, and has expressed an interest in the Motorsports.Engineering program. I fired off a couple of emails and got us a private tour of the lab and shop spaces. Wow is all I can say. My son seemed to be more interested in it than other schools.we have been through. Now to sit back and wait for it all to filter through his brain.
In other news I scored a DAS sport bolt in roll bar from the for sale forum. A good friend in NH picked it up for me today. I will retrieve it in a few months.

[Bucketlist]

Great to have a friend to pick it up for you. I've always wanted a roll bar, don't know why, don't race it, just looks cool and i'ts a good place to mount a camera. For me i'ts too big to ship, don't have any friends, so i'll just have to make do.

[krasuskyp]

YUGE CONGRATS to your family on your son's UNC-C acceptance! Awesome. Goin thru same here w/ my youngest's (twin girls)... both got into their 1st choices, and w/ decent to incredible packages. WOOT

cool score on the roll bar... if your travels to / from NH take you thru sunny CT here, hit me up for a bier enroute heh heh

[reclino]

I don't have any great pictures to share because cleaning stuff really isn't much fun to photograph.
Remember the rule of engine building.
ALL parts are dirty and shall be cleaned.
The new Mahle motorsports pistons and cylinders looked and felt clean, however using some clean lint free lab wipes and high proof isopropyl alcohol (IPA) one wipe of the ID cylinder shows black on the wipe.
Let's think about this for a minute, the ID is nickel with silicon carbide particles plated into the surface, then honed with a diamond hone to size. That black stuff I wiped off is likely laced with ground up bits of silicon carbide. So your nice new rings are going to take there first trip on that $hit.
So after the IPA wipes came out clean I switched over to automatic transmission fluid on the wipes. Then hung all the cylinders in the smoker and warmed them up. Wiped them down again at 125 deg F and again at 250 deg F. There was a bit of smoke rolling off then at 250 deg. Double layer of nitrile gloves under a pair of clean kevlar cut resistant gloves kept the burning of my hands to a minimum.

[reclino]

It feels a little wrong to use the surface plate this way, but it was a clean horizontal surface.



The pistons got scrubbed down with a soft toothbrush in a bath of hot water and dish soap, followed by blowing off with compressed air, and wiping down with ATF.

With the pistons and cylinders clean I went ahead and cleaned the rings, wipe down with IPA, then ATF, them checked the end gap in the cylinder they would stay with for life. Then they went into a sandwich bag marked with the cylinders serial # and the gap measurement.

[reclino]

Risk Management
Remember I am not an engine builder, however careful I am there is no substitute for experience. At the start of this engine saga I reached out to a local Porsche engine expert just to get a few tips, he offered to come to my little garage and spend a day with me putting the bottom end together. He said, just get everything organized and clean and when your ready I will come over.
I am almost ready to take him up on that offer. Maybe his face will appear in the photos on this blog, or.maybe he will remain anonymous, that's up to him.
I am so happy to have found a group I can share this build with. Family.and friends have been asking for years when the Porsche will be finished, instead of having to give a long winded answer I often send them a link to this blog.

[flightlead404]

Originally Posted by reclino

Did a bit of careful measurement of a cylinder today. The top of the cylinder is about .0003-.0004" smaller than the bottom. So indeed there is a bit of taper, which will go away once the cylinder warms up at the top. Surface roughness is spot on at 6 RA and feels just a bit rougher to the touch than the reworked cylinders. Now to clean everything and check the ring gap.

Is this what we refer to as "choke" with aircraft engines? Or is this technically something different?

[reclino]

I am not sure, the more that I think about it .0003-.0004" is less than I would expect if they were trying to account for thermal expansion difference from top to bottom of the cylinder. I don't work with any piston engine aircraft so have zero experience in that.

[MikeD930]

You are doing great job...thanks for sharing your rebuild. I'm looking forward to see the result of your work.

[TurboKraft]

Originally Posted by reclino

I don't have any great pictures to share because cleaning stuff really isn't much fun to photograph.
Remember the rule of engine building, all parts are dirty and shall be cleaned.
The new Mahle motorsports pistons and cylinders looked and felt clean, however using some clean lint free lab wipes and high proof isopropyl alcohol (IPA) one wipe of the ID cylinder shows black on the wipe.
Let's think about this for a minute, they are plated with nickel with silicon carbide particles plated into the surface, then honed with a diamond home to size and surface finish. That black stuff I wiped off is likely laced with ground up bits of silicon carbide. So your nice new rings are going to take there first trip on that $hit.
So after the IPA wipes came out clean I switched over to automatic transmission fluid on the wipes. Then hung all the cylinders in the smoker and warmed them up. Wiped them down again at 125 deg F and again at 250 deg F. There was a bit of smoke rolling off then at 250 deg. Double layer of nitrile gloves under a pair of clean kevlar cut resistant gloves kept the burning of my hands to a minimum.

We have an engine in the workshop that's got considerable ring wear and cylinder scoring thanks to insufficient cylinder cleaning. Yes, that residue from the honing is still trapped in the oleophilic cylinder wall, and it rapidly wears out the parts that come into contact with it.

It's not just Mahle: one of our techs went through a brand new GMPP crate engine, adding a few more go-fast parts.
"Hey Mike, do you think you should wipe down the cylinder walls before reloading the pistons?"
"No. Why would I, it's a brand new crate engine."
Wiped it down with clean room wipes and MMO, and you wouldn't believe how much residue came out of the honed cylinder walls. Just awful.

It bears repeating: even if it's new -- clean it.

[reclino]

Had to open up the head gaskets to 98mm.
Helps to have friends with a machine shop in their garage.

[TurboKraft]

No head gaskets used with 98mm Mahle cylinders.

That was only for the 1991-92 97mm Turbo cylinders and heads.

[reclino]

Well, according to Fred Apgar this is the way. He has built this configuration many times before. RUF also used this head gasket with their 98mm cylinders. I know of one way to check to see if he is right.
As described by RUF this is a thermal break between the cylinder and the head. It will remove a bit of heat load from the head.
Always good to have a bit of controversy in a build thread. As long as we don't say the word Dilavar I think we will be ok.

[reclino]

So the Supertec Performance Head Studs have a slightly larger shank diameter than stock head studs, and this would cause interference with the head gaskets.....
After much careful measurement and thought, the offending material was removed in the 4 spots of concern.
My friend Ted the machinist didn't have a rotary table for his mill, so had to get creative indexing the locations. He used a micro boring bar in the lathe to shave down each spot.
All 6 gaskets were cut at the same time in the nice fixture he made.
I am 100% sure that these head gaskets are more expensive than stock.