Carpokes Porsche Forum

Impressive work! It always amazes me the things that many like yourself are able to do. The amount of time taken is far less important than the awesome job being done.

The quality of work ,especially since you were actually teaching yourself how to do things along the way is simply " Wunderbar!!"

Like blueline mentioned, the talent you exhibit is great, but the persistent and particular effort made to do things top notch is to be commended and admired.

I know many of us will be looking forward to seeing your " Brand New " 944 in the near future!

INCREDIBLE! Very nice work!!

Thank you very much for such kind comments everyone.

When it came to the engine, I had no records of it being opened up, and there were no clues suggesting it had. So, I started the disassembly, not sure what I would find. It turned out things were pretty good. The cylinder walls were smooth with no scoring or other marks. The crankshaft journals looked good to the eye. The valve train looked fine, all the seats looked good and, aside from the normal carbon, there was nothing strange looking on the cylinder heads or piston tops.

I initially took the pistons, rods, cam, crank, block and head to a specialist machine shop for checking and normal work (e.g., crank was polished, rods were resized and all wear dimensions were checked accurately with equipment superior to what I had.)

New valve guides were installed in conjunction with a stock valve grind.

Everything did measure within the allowable range, but one thing I did notice was that, although perfectly clean and smooth, I could detect the slight undulation from wear when running my finger from top to bottom of each bore. It was not visible, but I could feel it. However, there was no discernible wear ridge at the top, just a coloration difference showing where the travel of the upper piston ring stopped.

At this stage, I decided to reassemble the motor with new bearings, rings, etc., but with the original pistons and bores. This was in 2008.

I got the motor mostly built up, but there were two thoughts living rent-free in my head:

1) That small amount of wear I could feel on the cylinders (it was a nearly 160K mile engine after all)
2) The (very) mixed opinions on how successful re-ringing Alusil cylinders is in terms of ring seating and subsequent compression and oil consumption.

In the meantime, the 911 project came into my life, and for that car, I used brand new Mahle pistons and cylinders, so I was starting to re-think things.

After consulting with Ernie Jakubowski at Mantis Racing (a well-known 944 expert in these parts), I decided to take apart the motor again and have the block machined 0.5 mm oversize and put new Wössner pistons in. Mantis Racing did a lot of 944 and 928 work and had all the correct Sunnen equipment. This time the block needed to be more fully stripped (the head studs and dowels had to come out). So in early 2015 the disassembled block went to Mantis where it was bored for the pistons (which I purchased through Mantis) and the block was also decked.

It's all pretty confusing, but I will just concentrate on the second time I built up the engine.

I’m still not sure if this was the best approach, but I am here now.

Anyway, this is some of the original parts after cleaning and machine work:
This is the block how it originally was, just cleaned:

Knowing what I know now, it may have been good just to have the cylinder walls “honed” with the felt pads & Sunnen paste. My understanding now is that the paste actually etches a very small amount of aluminum from the surface, leaving silicon “proud” on a microscopic level, and it is this hard, exposed silicon that allows the new rings to seat. Given the excellent condition of the original pistons, this may have been the way to go.

That said, at the time I got them, the supplier for the coatings Wössner used for the pistons was well-established and Ernie’s (and others) experience was without issue, so I think they will prove fine.

So, I began building the engine up for the second time in 2017. As the original head studs had all needed to come out for the block machine work, I replaced them with a set of new OEM. I measured the deck and cylinder head and it looked like I could safely use the normal thickness head gasket. However, I went with the thicker OEM alternative, just to be cautious.

The new pistons came complete with new pins and rings.
The oil pick up was also replaced as a precaution:
And here are the new pistons in the freshly machined block:

Most of the engine build up occurred through 2017 into 2018. Everything seemed straightforward but I went really slow. By this time, the 911 project (for which I did a full engine rebuild) had been back on the road for a few years and was performing perfectly, so that helped my confidence. However, I had been very slow and methodical and was trying to be the same way with the 944. As of this writing, I still don’t know if it will work out as well!

Once the pistons were in the oil pan and oil pump could go back. I used a new OEM seal for the pan, as it seemed the aftermarket ones had mixed reviews. Also spent a lot of time fussing with the flushness of the girdle-to-block seam for the oil pan.
As mentioned previously, new head studs were used. I set these in with the Loctite and then put moderate torque on them overnight, so the Loctite would set with the studs under tension. The next day I torqued the cylinder head in stages as per the FSM.
Once the cylinder head was torqued on, the camshafts could go in. The chain is new, and for the tensioner, I could have been fine with a just changing the plastic pads, but I went with a new tensioner unit and the updated oil feed line.

I'm very glad you kindly waited until I had my car (largely) back together to start this thread! Fantastic work

About your disassembly and boring adventure (granted, with one whole rebuild to my own name....):

Though it is possible to re-expose the silicon like you mentioned, that process doesn't really remove much material. You'll see a vastly better surface after remachining and then proper exposure! Also, going +0.5mm over is definitely sufficient to clear up any ovality/egg-shape your bores might've developed, which wouldn't have happened otherwise. Plus, new pistons means new ring lands and so on.

Timing the cams is an important stage, as the exhaust cam sprocket has slotted adjustment relative to the shaft. Normally two dial indicators are used, one to get accurate TDC and other to get accurate valve lift.

I have ONE good dial indicator, so my timing had to be an iterative process. What I ended up doing was first using the dial indicator to locate exact TDC, then I affixed a sewing needle to the cam sprocket and a corresponding edge marker on the cam housing. The needle and edge made a very easy to spot precise location possible. Then I used the dial indicator on the valve lifter to get the specification (1.4 mm of intake valve lift at TDC).

I tested my ability to find accurate TDC using the marker (and confirming the dial indicator) a million times, and felt it was perfect, then the adjustment for intake lift and then double checked that a billion more times by rotating the crank through the full two turns and re-checking. At the end of the day, I felt confident that I had 1.4 +/- 0.02, which is well within spec (1.4 +/- 0.10).

Thank you four0four for that feedback. The points you make are all with merit and do add weight to the “pro” column.

After the cams were timed, then the balance shafts were set, and then all of the peripheral items could go ahead.
All of the sensors were replaced and the DME harness is a new OEM unit.
I found a 3D printed oil cooler alignment tool that worked well lining things up.
Earlier I had the exhaust headers ceramic coated, and they are loosely bolted in place ( I will torque them after the engine is in the car, just in case I need to take them off while installing the motor).
I used a kit from Arnworx to reseal the throttle body. I think this was probably a useful move, as the old seals and O-rings came out in pieces!
All rubber (vacuum, fuel lines etc.) as well the fuel damper and regulator were all replaced.

Most of the ancillary metal bits were either replaced with new, or re-plated. This was pretty much the state of the engine by mid-2018, at which point I “set it aside” as I was neck deep in rear suspension, transaxle etc. at that time.

Rewinding back in time, I will pick up the story of the rear suspension and torque tube. The first portion of this work happened before any of the engine build(s).

Early on in the project, I had cleared all of the suspension from the car and then started to figure out how I would change things. I decided to rebuild the torque tube, and renew the rear suspension with new 28 mm torsion bars to go with the stiffer front springs and new bushings. My original “build” was to use standard bearings from FAG in the original TT bearing housings and Elephant Racing monoballs for the rear semi trailing arms and polybronze bushing for the spring plates (as well as the stiffer sway bar). The TT and the torsion tube carrier were powder coated (outside) and the hardware was either renewed or replated. This work went on mostly in 2006. We were planning to move house in 2007, so I needed to get the car back to being a roller by then.

Here is the rear suspension sub-assembly when it came out:
Freshening the TT bearings:
Putting the rear sub-assembly back together:
Once the rear sub-assembly was back in the car, new wheel bearings were pressed in and the parking brakes were reassembled.
At this point, wheels could be re-attached to back end, now I had to get the front end ready.
As will be eventually explained, a good amount of this work was subsequently changed.