Another 944 Turbo Engine Rebuild Thread

dlknight · Mar 7, 2024

So I resumed the engine rebuild pretty much as soon as I returned home.

First job was to split the rods and pistons and remove the rod bearings.

Rod #1 (left) Rod #2 (right)

Rod 3# (left) Rod #4 (right)

Then a lot of RP90, heat from my propane torch was used and a pair of stilsons to remove the old head studs. I was lucky none of them snapped, a few came out easy and the others were quite tight. At the same time I also removed the water pump studs using the double nut method and got them out without any snapping.

Finally the block was ready for the machine shop.

A very kind person donated some parts to me early in January and I got 2 spare 944 crankshafts, one is very good and the other has some surface rust on the journals.

Original on far right, good spare in centre.

On Monday I took the following parts over to Knight Engine Services near Daventry, spookily the owner has the same name as me...

Complete Cylinder Head
Engine Block
Flywheel & Clutch Kit
Crankshaft (original and a spare)
New Valve Springs
Connecting Rods

Currently looking at 4 weeks or so before they can start on this, I'm getting the following jobs done:

Port and Polish inlets on Cylinder Head
Machining Cylinder Bores to 1st oversize retaining alusil
Check original crankshaft wear with the option of using the spare if badly worn (thrust bearing was toast)
New Valve Guides
Skim Cylinder Head and Block as required
Rebuild head
Balance Crankshaft
Balance Flywheel
Block and Cylinder Head Vapour Blasted (baked and thoroughly cleaned of blast residue)

Hopefully I will have some pictures of lovely new shiny bits to show you soon!

scam75 · Mar 7, 2024

De...ja....vu!!

Will all be worth it!

blade7 · Mar 9, 2024

I know there are different requirements and budgets, and my engine has very likely got the same rods in it. But as the engine is apart, I'd chuck a set of forged rods in it. I think you can buy them for under £500 now.

dlknight · Mar 9, 2024

blade7 said:
I know there are different requirements and budgets, and my engine has very likely got the same rods in it. But as the engine is apart, I'd chuck a set of forged rods in it. I think you can buy them for under £500 now.

Good shout, I went through the same thought myself. Also, David at Knight Engine Services said it's up to you but by the time you've had the original rods checked and new bushes fitted (if required), then you are almost at the price of a set of those Bridgeway rods (although I will have him check over them to make sure all good before fitting). So, I made the decision, and they are already on order from Part Box along with some other goodies!

He did say though that the original rods are well made and perfectly usable for my build.

BTW if anyone is interested in the Bridgeway rods, they are currently on clearance sale at Part Box, get them while you can!

dlknight · Mar 15, 2024

So a few more jobs done last weekend and in the evenings, whilst I waiting for orders to be fulfilled and my place in the queue at the machine shop.

First off, I started to reseal the gearbox with the reseal kit from Porsche.

I change the left side output shaft seal, according to the manual there is a stop, but posts on rennlist and elsewhere suggest there isn't and to push the seal in to a depth of 6/7mm. My seal would only go to a depth of 6/7mm, I then put some general purpose grease on the inside of the seal as instructed in the WSM.

Next up was the selector shaft seal (although I don't think it was leaking and probably could have left it). First off you need to remove the reverse lockout spring from the top of the gearbox. Then you can remove the selector shaft cover and slide the entire assembly out. The seal was quite hard to pry out but did eventually succumb.

New seal inserted, shaft lubed up with gearbox oil, new paper gaskets for the cover and lockout bolt.

Next up remove the diff cover and inspect for damage, will also be cleaning the magnets on the cover, pump strainer, and possibly dismantling and cleaning the pump itself (think I may have to do so to clean the strainer anyway). I will then need to measure the drive with a dial indicator to select the correct thickness gasket for the oil pump cover (there are 2 thicknesses available). Diff looked OK to my untrained eye, lots of furry metal bits on the magnets which I guess is to be expected at over 200k miles. No debris at the bottom of the box thankfully.

I've parked the gearbox work for a few days whilst I measure the play in my turbocharger before I send it down to Turbo Dynamics.

End play was within spec (0.08-0.105mm vs 0.16 max) but the radial play was about twice what is allowed in the WSM (0.73mm vs 0.42mm max).

You may have noticed my fancy dial indicator stand, it is a copy of the VW 387 tool which I was able to obtain from Bartek Motorsport in Germany.

Finally I made an error late one evening, thinking I had found the deal of the century on a full set of crankshaft bearings from Autodoc for around £70

When they arrived the packet looked right with a picture of crankshaft bearings, but the part number and contents gave the game away! I've ordered some ACL Race Rod Bearings so I will hang on to these for now (just in case) and have the extended return period (200 days).

Lastly a new standard (2.5 bar) fuel pressure regulator from URO with the slip on hose fitting (my existing one has the threaded fitting) and a full set of seals for my front brembos.

scam75 · Mar 15, 2024

Busy boy! Great work.

dlknight · Apr 22, 2024

Time to update!

Pistons arrived from Mahle Motorsport (via Design 911 - with the 10% PCGB discount), production date is 23rd January 2003! I hadn't even purchased my 944 Turbo then, was still on my first Porsche 944, a 1988 2.5 NA (also black).

They have a black phosphate coating (supposedly to control heat) and the Mahle Ferroprint skirt coating for alusil applications.

I finally got the right set of crankshaft bearings from Kfz-Kauert in Germany (they sell on ebay and have their own webshop) for a bargain price of 176 euros. This was way cheaper than I'd seen them anywhere else. I still *might* have to get the different size thrust bearing depending on the analysis of my crankshafts by the machine shop (they are only available from Porsche and silly money).

Collected a bag full of nuts, bolts, washers, and other larger items from the electroplater! Then I spent several hours, split over consecutive days, sorting through them with the notes I'd made and putting them into labelled bags ready for reassembly.

Progressing along nicely with the gearbox reseal, I replaced the input shaft seal (again) this time using a piece of plastic waste pipe of the correct diameter (30mm?) to gently tap the seal into place.

The oil pump has been thoroughly cleaned and reassembled with a fresh 0.20mm gasket. Next job was to measure the end play of the pump, the WSM gives a figure of 0.05mm + 0.1mm. I got a repeatable figure of 0.09mm so well within spec. Gaskets are available in 0.15mm and 0.20mm, the 0.15mm would have been too small taking the end play down to 0.04mm.

Used some Permatex Form a Gasket No.3 on both sides of the paper gasket (we don't want any leaks). All torqued up to 8Nm.

A new output shaft seal is already installed, just need to reinstall the magnet and seal the side cover back in place with Loctite 574.

Whilst waiting on other bits I've taken the time to remove the intercooler (see the other thread in this forum) and also clean the engine bay.

BEFORE

AFTER

Will get the cross member and steering rack cleaned up separately. Couple of patches of surface rust to attend to, on the wheel arch where the coolant tank has rubbed on the paint and at the front under the intercooler. Will deal with those when the car is back in the garage, and I can properly mask it up to avoid overspray.

scam75 · Apr 22, 2024

Awesome stuff as ever David! I'm getting everything under my front bumper tidied up at the moment as it has been removed for repairs and paint. Well worth doing these things when you have the chance.

dlknight · May 30, 2024

Not much of an update from me, I took the rods, pistons, and valve stem seals down to the machine shop at the end of April. They were quoting around 4 weeks to start on my engine. I had a call from them yesterday and the block is almost finished, but a bit of bad news on the cylinder head. There is a small crack between the water jacket and a head stud / bolt hole near the middle of the head. They said it isn't very bad and would probably be OK but luckily, I have a spare turbo head thanks to Andy from Promax. I will be dropping the spare head off with them for a clean and pressure test when I pick up the block. They did say the crack in the original head could be repairable, so will need to weigh up the options.

Still waiting for Ferrea to ship some oversized inlet valves to the UK, been almost 2 months waiting now... I must have the patience of a saint!

The machine shop has also resurfaced the flywheel whilst balancing the rotating assembly.

My reconditioned turbo arrived some time ago now, I took a couple of photos of it in the packaging as I didn't want to open it yet.

Over the last month Matt from MB Engineering and Vapour Blasting in Malvern has been steadily working through all of the aluminium pieces from the engine. They look amazing but I'm waiting to do a before and after photo, when I have all the pieces back. The cam tower has been vapour blasted, painted with cerakote and then the Porsche lettering has been milled. Matt has also moved my towing eye project along a little way and drilled and tapped the hole for the replacement towing eye. I just need to drill and tap the mounting bolt holes and paint.

I've also been working on the front brake calipers, stripped the paint using paint stripper gel (from a body shop), sanded any corrosion and irregularities, and repaired the aluminium under the plates with some JB weld. I've just given them the first layer of gloss black paint this afternoon. Then plan on sanding off the Porsche lettering and painting with a white enamel (possibly using the sponge method), followed by a final coat of clear.

I found that standard basin and bath drain plugs were a great fit for the piston bores on the calipers (to prevent paint getting in them).

Looking forward to getting the block back and starting to begin the build process.

blade7 · May 30, 2024

When did Ferroprint replace Ferrostan?

dlknight · May 30, 2024

blade7 said:
When did Ferroprint replace Ferrostan?

Late 1990s (1999) I believe - I did find out the approximate year when I was doing my research, there is a press release somewhere on Mahle's website.

MAHLE chronicle - MAHLE Group

Chronicle of the MAHLE Group

www.mahle.com

dlknight · Jul 7, 2024

I've been busy, apologies for not updating the thread recently! Also have been feeling a bit drained from my regular work and then trying to keep up with the restoration, so kind of let things slide for a little while and try and keep my mind elsewhere.

As in the last post I'd started to restore the front brake calipers, some corrosion under the guide plates needed treating, so I used some JB Weld after removing as much of the corroded material as I dare.

I then setup my temporary spray booth in the utility room (bad idea as the black paint leaves black dust everywhere)

First few coats of VHT gloss black caliper paint, then painting the lettering using a sponge brush and some VHT white engine enamel (didn't have the brake caliper paint in white!). Made a few mistakes but found that a cocktail stick with the gloss black paint sorted those issues out without it being really obvious.

Then a final coat of VHT gloss clear caliper paint, looking better than new!

Back to engine stuff and I collected the finished block in June and gave it a rigorous cleaning, using various bottle brushes to get into the oil passageways, hose pipe and car shampoo. I then used brake cleaner and an air duster can to clean out the passageways again and all of the bolt holes.

Then some more shiny bits back from electroplating -

Got the rods out and weighed them all (possibly need to do so again with a more accurate set of scales as mine only read within 1g), all weighed the same to the g. I also weighed the pistons and gudgeon pins which also weighed the same to the g.

Yesterday I spent a couple of hours with a cheap hand crank piston ring filer and gapped all the rings, also cleaned up the crankshaft with some brake cleaner, microfibre towel and a bottle brush to get into the oil passageways.

Top ring = 0.60mm (0.0237 inches)
Second ring = 0.60mm (0.0237 inches)
Oil ring = 0.70mm (factory gap not modified)

Used my new total seal ring setting tool to set the ring in the cylinder for measuring, I also picked up a tapered ring compressor to use when installing the assembled pistons.

Just waiting on some tools now including a stretch gauge before checking final clearances and beginning to assemble the bottom end.

dlknight · Jul 15, 2024

Finally got chance to inspect the 944 in the dry, been meaning to take the cover off for a few weeks but every chance I have it has been wet. So Friday evening I removed the cover, made sure no rodents were home inside, and gave the car a quick wash and dry. I also removed the front brake discs so I can either clean up and paint the hubs / bells silver like the rears or replace with a new pair. The vents are quite rusty, but the discs haven't had much use, with hardly any sign of a lip forming yet on the edge.

Next I spent the evening with my new set of electronic scales from the hydrophonics supply shop (on Amazon)

and measured the weights of the connecting rods, pistons, pins, rings, and circlips to 0.1g. It really does show the quality of the components as they were all very close within 0.3g at most! After I juggled the pistons and rod pairings around (and erased my previous markings from the rods) I got some extremely close weights for the complete assemblies.

I checked my scales with a selection of UK coins and details of weights from the royal mint website, with the coins the scales checked out as extremely accurate. The weight of the connecting rods recorded on the box was a total of 670.5g (I assume this is before the ARP lubricant has been added to the bolts). The pistons didn't have a recorded weight on the box, but there was a measurement for the pins at 125.0g.

You can see from my results below that the scales were pretty close to the manufacturers measurements.

Piston #	Cylinder #	Weight^ (g)	Pin Weight^ (g)	Circlips^ (g) x 2	Total Weight (calculated)	Total Weight (measured)	Rings^ (g)	Weight inc Rings (g)	*Total Mass (g)**
12:21:46	1	473.9	125.1	2.2	601.2	601.3	29.0	630.3	1303.5
12:56:16	2	473.9	125.3	2.2	601.4	601.4	29.0	630.4	1303.5
13:01:52	3	473.8	125.3	2.2	601.3	601.3	29.1	630.4	1303.5
13:09:15	4	473.5	125.3	2.2	601.0	601.1	29.0	630.1	1303.4

^ weights based on an average taken from 3 different measurements
* including connecting rod

Rod #	Cylinder #	Weight^ (g)
190222	1	673.2
190226	2	673.1
190245	3	673.1
190243	4	673.3

dlknight · Jul 23, 2024

Last week I found some time to remove the rod caps and clean all the ARP bolts and then apply some fresh ARP lube as per the instructions. I also unpacked the rod bearings, cleaned and installed them into the rods (and caps). So now ready to check rod bolt stretch and bearing crush. Tested out my £20 vice purchase from FB marketplace (an old Record vice), I ordered some strips of aluminium angle in the right size to use as soft jaws to hold the rods (this worked well).

Finally, my oversize +1mm inlet valves arrived all the way from Florida, after some shaming about customer service on the manufacturer's Facebook page.

I've amassed a selection of tools for the rebuild, two new torque wrenches (one slightly used, one brand new), made by Norbar in the UK. These are lovely to use and much better than the chinese ones sold by many stores. I also picked up some old but functional micrometers and a couple of bore gauges.

This weekend I managed to get lost in the garage again and concentrated on getting the crankshaft installed in the block. Starting off by cleaning all the main bearings and then installing them.

Then using the plastigauge technique to measure the clearances as described in the Porsche WSM, I noted the following clearances -

Item	Description	Checked	Tolerance	Wear Limit	Actual Value	Date	Comment
Main #1	Clearance (mm)	No	0.020 - 0.098	0.16	N/A	22/07/2024	Unable to measure with Plastigauge
Main #2	Clearance (mm)	Yes	0.020 - 0.098	0.16	0.050 - 0.063	22/07/2024	In the middle
Main #3	Clearance (mm)	Yes	0.020 - 0.098	0.16	0.050 - 0.063	22/07/2024	Closer to 0.063
Main #4	Clearance (mm)	Yes	0.020 - 0.098	0.16	0.050 - 0.063	22/07/2024	Closer to 0.050
Main #5	Clearance (mm)	Yes	0.020 - 0.098	0.16	0.050 - 0.063	22/07/2024	Closer to 0.063

Next up I measure the crankshaft end play (or thrust bearing axial clearance).

I got a repeatable measurement of 0.28mm which is considerably better than the pre-rebuild value, which was approximately 0.84mm.

Item	Description	Checked	Tolerance	Wear Limit	Actual Value	Date
Crankshaft	End Play (mm)	Yes	0.110 - 0.312	0.40	0.28	22/07/2024

Then ready for final install of the crankshaft, prepared the bearing surfaces with some LIQUI MOLY LM 48 Installation Paste, and place the crankshaft in it's final resting position.

An important note, it is very hard to locate the #1 main bearing, owing to is being a complete diameter and having a locating hole on the top edge which locates over the dowel in the block.

TTM · Jul 23, 2024

Thanks for the pictures, especially of the gearbox cover. The first time I see how the oil pump is made.

Are those rods proven? They look like the average Carillo knock offs and some are known to break...

dlknight · Jul 23, 2024

TTM said:
Thanks for the pictures, especially of the gearbox cover. The first time I see how the oil pump is made.

Are those rods proven? They look like the average Carillo knock offs and some are known to break...

I hope so, they are made by Bridgeway who apparently supply many other "manufacturers" who appear to add their own branding and then charge more (I'm sure there is a bit more to it, possibly). Their website says they supply Molnar Technologies, and they are sold by several distributors here in the UK. I haven't found any reports of issues when searching for them.

Home - Bridgeway

Professional in Manufacturing Crankshaft and Connecting Rod manufacturer since 2005, supply over 40,000 engine components annually. Precision in Details Equipped with high precision CNC machines that specialized in Crankshaft and Connecting Rod. Passion in Race Support motorsports industry...

bwmotorsport.com

Eldavo · Jul 24, 2024

TTM said:
Are those rods proven? They look like the average Carillo knock offs and some are known to break...

Yes - I ran them in my old 2.5 8v engine and I believe that EMC use them for their race car builds.

TTM · Jul 25, 2024

Eldavo said:
Yes - I ran them in my old 2.5 8v engine and I believe that EMC use them for their race car builds.

What sort of power and torque do these engines make?

dlknight · Aug 6, 2024

More updates from me - day after the last update I installed the crank girdle, using the method from the Porsche Workshop Manual I used a small velour paint roller with some Loctite 574. The roller works really well, it doesn't look like there is enough Loctite on the surface but if you touch it you can see there is enough. When installing a minimal amount of Loctite was squeezed out of the edges, which was enough to confirm good adhesion but not so much that it made a mess. In order to line up the crank girdle properly to ensure a good fit for the oil pump I loosely fitted the crank girdle, tightening only the M6 and M8 hardware by hand. I then fitted the oil pump temporarily with the majority of its fasteners, and gave it a few taps with a rubber mallet. I left the oil pump in place whilst the crank girdle was torqued via the sequence in the workshop manual. Afterwards I removed the oil pump and checked the fitment, perfectly flat at the oil pump side and able to drag a fingernail across the join without catching.

I then decided to install the oil pump which I'd previously cleaned (the housing had been scrubbed in warm soapy water to remove any trace of vapour blasting media, and the pump internals cleaned with brake cleaner). I used a good amount of assembly lube inside the oil pump as I've read this can help prime the pump when turning over on the starter to get initial oil pressure. I installed the front crank seal before installing the pump as it was easy to do without the end of the crank in the way. Then some Loctite 574 on the edges of the pump insert before placing it into the housing. I used the same method as for the crank girdle and applied the Loctite 574 to the oil pump housing with the roller.

Next job was to satisfy myself that the connecting rods were within spec, so I measured the big end (with bearing installed), little end, rod bolt stretch, and big end bearing crush.

Rod #	Cylinder #	Big End Bearing Diameter (inches) 90 degrees	Big End Bearing Diameter (inches) 60 degrees	Big End Bearing Diameter (inches) 30 degrees	Bearing Crush (mm)
190222	1	2.0489	2.0490	2.0488	0.20
190226	2	2.0476	2.0484	2.0484	0.20
190245	3	2.0485	2.0487	2.0485	0.20
190243	4	2.0480	2.0482	2.0485	0.20

Rod #	Cylinder #	Little End Bush Diameter (Inches)	Little End Bush Diameter (mm)	Wrist Pin Diameter (Inches)	Wrist Pin Diameter (mm)	Wrist Pin Radial Play (mm)	Radial Play (min)	Radial Play (max)	Within Spec
190222	1	0.9456	24.01824	0.9447	23.99538	0.02286	0.018	0.032	TRUE
190226	2	0.9455	24.0157	0.9447	23.99538	0.02032	0.018	0.032	TRUE
190245	3	0.9455	24.0157	0.9447	23.99538	0.02032	0.018	0.032	TRUE
190243	4	0.9456	24.01824	0.9447	23.99538	0.02286	0.018	0.032	TRUE

Rod #	Cylinder #	Weight^ (g)	Rod Bolt	Free Length	Torqued Length	Stretch	MIN Length	MAX Length
190222	1	673.2	1	0.4490	0.4540	0.0050	0.4540	0.4545
			1a	0.4445	0.4495	0.0050	0.4495	0.4500
190226	2	673.1	2	0.4450	0.4500	0.0050	0.4500	0.4505
			2a	0.4440	0.4490	0.0050	0.4490	0.4495
190245	3	673.1	3	0.4460	0.4515	0.0055	0.4510	0.4515
			3a	0.4475	0.4520	0.0045	0.4525	0.4530
190243	4	673.3	4	0.4475	0.4525	0.0050	0.4525	0.4530
			4a	0.4455	0.4505	0.0050	0.4505	0.4510

			Bridgeway Min stretch:		0.0050
			Bridgeway Max stretch:		0.0055
			Bridgeway torque spec is 50/75 nm with ARP Fastener Lubricant
			The rod letter (i.e. A) refers to the bolt away from the number on the side of the rod
			^ weights based on an average taken from 3 different measurements

dlknight · Aug 6, 2024

Next job was to fit the pistons to the connecting rods and then the rings to the pistons. Used plenty of assembly lube on the wrist pins and little end bushings. The wrist pin circlips were easily installed by hand, and then ensured they were snapped into place by tapping each end of the wrist pin lightly with a suitably sized socket.

Rings were given a light coat of oil and installed, the oil ring was the trickiest as a couple of times the ends overlapped whilst installing the top oil ring, which then necessitated removal of all three pieces. The second ring is (or seems) slightly larger than the top ring and was quite a tight fit, however after applying a couple more drops of oil it moved smoothly in the groove.

Now I'm ready to install the pistons and rods into the block and check the rod bearing clearances.