Jay W

You may have seen some of my posts about the anti-drainback valve being clogged on my S. When that was happening I was waiting the 10 minutes for the lifters to quiet down but they never did. I did have the valve cover off and should have realized there wasnt nearly enough oil gettting pumped up to the top. Also while idleing the engine did stop on its own once. I think the cam locked up slightly and it killed the engine. Since I had the cover off I was able to use an oil squirt can to put oil around the cam bridges. I did see some of those chips come out from between the cam and the bridges so it was wearing very quickly. After I put the oil on it did start back up but the lifter noise stayed. I then did a search and found reference to the oil drainback valve in my 944 PDF files. I took out the valve, cleaned it and put it back in and had a gusher of oil up there. Apparently I lucked out on the damage to the head and cams because I have put at least 10,000 miles on the car since then.

CarbonRevo

So how important is it to change or clean the anti-drainback on the 16v cars? You guys have me wanting to take mine out and clean it now, because of these horror stories.

I remember reading on how to do it in the FSM's, but how hard is it in reality? How do you even clean it?

Jay W

I suspect mine was partially clogged way before I had the head work done simply because the chain tensioner pad that had less than 10,000 miles had deep grooves in it. Also the tops of the cam followers had noticeable wear as well as the cam lobes.
On the S there is an allen screw in the side of the head that you just loosen a few turns, then pull the valve out of the head. It was a bit hard to pull out. I cranked over the engine a few times with the valve removed and oil shot about 5 feet beyond the side of the car, all over the garage door. I did that because I was afraid there was more gunk in the oil passage just before the valve that would clog it back up. Then I rigged up a way to connect the valve to my air compressor so I could see if it opened. It did open just fine under the air pressure so I sprayed in some carb cleaner and put it back on the air hose. Blew that out and hoped I had it clean enough. Put on a couple new o-rings and reinstalled. Not a complex job and it made all the difference.

I really do think it was partially clogged for a long time and that contributed to premature wear on the cams and followers and chain tensioner.

pjburges

So from what it sounds like, perhaps you could try these things and get it running again.

Do as Jay W says and clean out that valve.

Remove the suspect cam and re-install the caps and then get yourself a small fine grit centerless hone with a flexible neck and lightly hone all the surfaces out to remove any scarring.

Try to re-assemble it using lots of assembly lube/grease this time and maybe it'll still live on!

However, I am suprised that it developed enough resistance that it killed the motor, yet it didnt break the chain or the belt, or cause the cam sprocket to jump a few degrees off. I have a friend who is having troubles with his S motor too, its really a learn as you go thing for us as well.

Charlie944

jay W, What was clogging it up...carbon deposits?

I just bought a 89' 944S2 and I have been trying to familiarize myself with the 16V quirks.

Thanks!

CarbonRevo

I wonder how much a new valve would run me? I might as well put it on the tab for this winters repair project of various things here and there.

My pads only had slight grooves on them at 78k miles. Cam lobes looked to be in great shape. All cam journals were also in excellent shape. Couldn't catch a fingernail on anything or see anything wrong.

You'd be suprised how little it takes to stop that motor from turning. A cam that barely locks up could easily stop it. Kind of like how easily a locked up wheel bearing can stop a moving car.

Jay W

Yes it was just idleing in the driveway, I walked out into the yard to pick something up and when I came back it had stopped. When I turned the starter, it turned slow for a second, then I guess the cam broke loose and it started back up. I dont remember if I squirted the oil onto the cam bridges before I tried to restart it. I was pretty confused about what was going on at the time.

I think a non-scientific test to see if there is enough oil is to take off the valve cover and start it up for a few seconds. If the top of the engine gets showered with oil and you are ducking from splashing oil then there is plenty getting up to the top. When I had the clog I was running it with the cover off and barely any oil was coming out around the cam bridges and none got outside the top of the head. My chain tensioner wore badly in 10,000 miles. If yours went 78,000 then if it is clogging, it is just starting to clog now.

I am pretty sure that shavings from decking the head and other machine work did the final clog on my valve, but I think metal particles and other bits and pieces in the oil building up in the valve had that thing partially clogged for a while. The opening of the valve is pretty small

I have heard that the valve is not cheap to buy, and I was able to see that it was opening and shutting with the air pressure. So I cleaned it a bit and put it back in. Its not a complex piece so if it looks like it is working then it probably will.

lucifer_sam

Thanks guys, this is definitely encouraging. Very brave of you to crank it until it started again, Jay W! I had put that sort of idea out of my mind when I put the 1/2 socket driver on the crank bolt and couldn't get the cams to turn even when leaning my weight on it . . . but maybe that starter torque combined with generous pre-lubrication is just the key to getting it unstuck.

Anyway, I'll take that exhaust cam out and if it's the bearing journal binding, then I'll know right away. If it's the lifter binding, then I'll have to work some craziness to get it loose, or else take the head off and make the shop do it.

hosrom_951

You are doing a good job, keeping debris out while cleaning and marking hoses and such, don't worry about anything, keep going in that direction and you will be fine.

Few things to say:

- If you really wish to get the pistons and block surface clean, get a scouring pad from the local super market, spray on some WD-40 and (with light pressure) go over everything. You will leave behind a black residue, which is the dirt that was caught by the WD-40, it is like wet sanding, only the scouring pad does NOT remove ANY metal.

-About the heat studs, there is no need to replace them, i reused mine twice, and it was re-used before me (so that's three so far). Just get a tap and die kit an go over ALL threads, i would recommend new cylinder head hardware (nuts and washers), for a peace of mind.

Looks good though!

lucifer_sam

Don't run without oil in the head, kids.

(Yeah, I'm just getting back to this now. Got married in the interim )



--
LS
89 S2

lucifer_sam

This thread needs a conclusion!

Ok, here's the end of the story:

The scored head and camshaft shown above had to be replaced. I contacted the Milwaukee PCA, and they put me in contact with Chris Shuh at CS Motorsports. Chris is a stand-up guy (with a bit of a 944 building reputation in the racing world), and he had a '91 head and associated intake cam lying around the shop that he gave me for a very reasonable price. I took the head back to my guys at SPR in Port Washington, and they cleaned, welded and decked the head, and installed new valve guide seals. It was a thing of beauty when it came back. Now for the important part - I carefully installed the brand new, $300, Oil Pressure Anti-drainback Valve. The failure of the stock valve was what had caused the previous head to scrape itself to death.

Now for the interesting part (at least for anyone who's looking at a 944 head rebuild): My stock lifters were all shot. After soaking them in oil for days, they still had no resistance - I could squeeze them all the way with my fingers. But new Porsche lifters are stupid expensive, and I just paid for a $300 anti-drainback valve! Well, it turns out that Jeff at SPR used to build VW race engines, and he had a shelf of VW lifters that were more than 10 years old and still holding their oil pressure perfectly. And, yes, one of those lifters measured out to exactly the same size as the Porsche units. Turns out to be about $10/lifter cheaper, too. Multiply that by 16, mm-hmm. So I spoke to Chris Shuh about this, and he was more than interested to know if this would work or not. He said that the lifters that you can get from Porsche today are not of the same quality as the original units from the 80's and his race cars were eating them up, regularly. So he ordered me a full set of the VW lifters, and they dropped into the head without a hitch.

After installing the new head back in the car and buttoning everything up (set timing, new battery, new coolant, new oil, etc), it was time to turn the key. Now, just to set the stage, note that last time I had turned this key was more than a year prior, and that particular event had ended quickly and brutally. Since that time, due to lack of funds, marriage, buying a house and other life events, I hadn't been able to get back to the car, but I had been haunted by dreams of it - in some I install a new engine and it too breaks shortly after starting, and in others I drive up a twisty mountain road in my recently repaired 944, giant smile plastered on my face. Suffice to say, there was a bit of tension.

I turned the key and after few short seconds of pumping, it chugs to life. The lifters are clacking. I rush from the driver's seat to the engine bay and back again, checking the oil pressure, listening to the cam cover with a long screwdriver to my ear, and fretting. Let it idle. Let it idle. It's approaching the deadly 10-minute mark, the danger zone. I chicken out and shut it off. I undo all the cam cover bolts and thoroughly inspect the cams and lifters. No damage! A nice coat of oil gleaming on everything. Good, the new anti-drainback valve is working. I put the cover back on and start it again. It runs. The lifters are quieting down! My screwdriver stethoscope communicates that sweet sewing machine "shuch shuch shuch" sound. The injectors make the only clicking now. I'm still scared, so I shut it off again. I take off the cam cover again. Everything looks fine, I can't see any issues. I put it back on and start the car again. I can finally breathe easy - IT RUNS!

Now I've put 1700 miles on the new head, and it still runs like a top. It's amazing to drive because right before this whole saga began I had brought all the mechanicals up to snuff - new clutch, rebuilt ball joints, new tranny fluid, new water pump and belts, resealed AOS - this car runs and feels like new!

So if any one's interested, the VW lifter P/N is 050.109.309.J. These are nearly identical to the porsche lifter P/N 928.105.312.02 - the only difference is a circumferential grove at the oil inlet hole (the porsche head has this groove cut in it, so the Porsche lifters don't have it), but it doesn't change anything about the fit or operation of the lifter. It remains to be seen how the VW lifters wear compared to the Porsche units.

One more statement on the original cause of all this - I believe what happened to the belt originally was that it snapped because it was tensioned too tightly. I've always used Bruce Arnn's tensioner to tension my belts, but after the guys at CS Motorsports took one look at my belts and loosened them WAY up, I have been very suspicious my ability to tension a belt. I believe Bruce's AWX design is solid, but since the 1/4" torque wrench is user supplied, there is a large margin for error, depending on the accuracy of the torque wrench used. Since I got my torque wrench at Harbor Freight and it's a couple of years old, it is likely way out of spec, which means the tensions readings I am getting from my AWX are meaningless. I need to calibrate that torque wrench before I use it again. However, now that I've seen a belt tensioned by hand, and had it explained to me, I'm almost more inclined to start tensioning by hand. I always thought my tensioner spring was old and soft, because I was pushing the tensioner into the belt and then tightening the lock nuts. At CS Motorsports, they pretty much left it just resting on the belt, with no additional tension added. Ah the joys of learning to be your own mechanic!

Thanks again, Rennlist - this wouldn't have been possible without you!


--
LS
89 S2

lucifer_sam

P.S.

Yeah, it's for sale now. I love it, I own it free and clear, it's been very reliable, and it's been a joy to work on. But I'm forcing myself to move on - keep discovering, keep learning:

https://rennlist.com/forums/924-931-...condition.html

ArcticSteve

Very informative. Thanks!

Charlie944

Hi LS,

I am glad to hear you got the S2 all back together. I shared in your suspense while reading of the first few starts with the new head.

I miss my 944S2, I had the car far to short of time before it was claimed by an engine fire.
Also, I will have to keep CS motorsports in mind as I am relocating to the Waukesha, WI area.
Best of luck with the sale!

lucifer_sam

Heh, thanks. Yeah, the guys at CS are very cool - ask for Chris or Joe. (The other guys are probably cool too, I just haven't met them all yet!)

http://www.csmotorsports.net/