Project 924 S engine replacement

[HondaDustR]

I'll go ahead and start a project thread to cover the recovery from this fiasco, esp since I'll probably have lots of questions along the way.
Want to kill an engine with a few bits of paper towel? Ask me how!

So, to start things off, today was the autopsy of the top end. Got most everything stripped from the top of the block. I don't see any paper towels, but all 4 oil drain ports are full of oil, so they must be down there somewhere. Cam tower looks good, head looks good, no bent valves as the cam belt looks fine, too. The crank is welded in place near cyl 2/3 TDC, and cyls 1 and 4 look as if nothing really happened. There's a small scratch about 15mm long in cyl 1 that catches a fingernail, and another long scratch on cyl 4 that I can feel, but it's not nearly as deep as the small one, but for all I know, they've been there already. I was kind of expecting scoured aluminum showing, but apparently, it's just the bearings that seized. There was maybe 1.5 qts of oil left in the pan and looked pretty normal for how long it's been since the last oil change. Nothing out of the ordinary came out. I haven't looked inside the oil filter yet.

So, I may mess around and try to drop the short block before any money gets thrown around, just to see what kind of mess there might be inside. Anyone have any idea what a short block weighs?

Also, there seems to be alot of early blocks out there but pretty much no late blocks, which is causing a problem with OPRV compatability, since mine has the late style OPRV, and the block I'd really like right now does not have the OPRV or the oil cooler housing. Are there any differences between the early and late oil cooler housing, or will I have to hunt down an early OPRV and cooler housing as a set?


Update:
Just pulled the valves out of the head. Seats and valve faces look good. Exhaust valve guides are pretty worn. I had a new valve guide on hand, so I checked the fitment of all the valves in the new guide and they all felt good, or at least much better than they did in the old guides, so I would say it would benefit from just having the guides replaced. Do the seats really have to be re-cut after replacing valve guides?
I think I'm going to have my head measured for warpage, and if it's warped, I may try to have it milled or get ahold of a different head, but the gasket looked good and it certainly wasn't leaking when it was working, so I think it should be fine.

[HondaDustR]

Got the block stripped down to cut the weight, since I have decided I will attempt to extract it without a real engine hoist. Decided it would be easier to pull it if the torque tube was detatched from the bellhousing first, so transmission is out (MUCH easier the second time through, especially if you slide the driveshaft coupler back BEFORE you loosen any of the trans mount/bellhousing bolts! )

Now it's just the steering rack and crossmember and hopefully I'll have the engine on the ground before the day's out! Just realized doing just a clutch job wouldn't be quite as hard as I thought. Also realized I would be doing all of this even if I stopped before the engine seized...I still haven't seen any sign of paper towels and the oil drains have been full of oil for days! At least I'll get an engine rebuild out of it this way...

[Slam]

Oh boy... I'll be very interested in the condition of your crank. The late OPRV will fit the early block. It's a recommended upgrade anyway, so you shouldn't have trouble there. Dude, that's a LOT of work you're doing. Good luck with it!

[fast924S]

SOrry but can I ask, what Happened???? Your hinting on no oil?, Did you rebuild it and leave paper towels in??

[onZedge]

FAST924S: "he acted stupidly"

(no offense DustR)

[HondaDustR]

Originally Posted by Slam

Oh boy... I'll be very interested in the condition of your crank. The late OPRV will fit the early block. It's a recommended upgrade anyway, so you shouldn't have trouble there. Dude, that's a LOT of work you're doing. Good luck with it!

The thing is, I don't think the late 1 piece OPRV will fit, but the retrofit part for the earlys will.
http://www.clarks-garage.com/shop-manual/lube-02.htm
going by this, my engine number falls into the late designation. I don't know what the early retrofit 1 piece OPRV looks like compared to the late, so I really don't know. They say the late is longer.


Yeah, it was stupid (check the link at the beginning for the story)... I have gotten the engine out (without an engine lift) and have gotten the oil pan off. Still no sign of any paper towels! So I costed myself $500+ just by starting the thing! , and I will probably have to disassemble the crank girdle just to find them!

Ok, the verdict is...
Rod bearings were practically melted shut (the crank would not move, not even with my big breaker bar...the crank bolt was loosening!). I smelled a definite burning smell as soon as the oil pan came off. The #4 bearing shells looked a bit scoured, but the crank looked ok. #1 had torn away most of the chrome coating (or whatever they put on there), scouring up the crank in the process. #3 had ground up badly enough that the copper (or brass...it looks like copper to me) was beginning to show though and the crank looked just as bad. Now #2...the other bearings looked pretty good compared to #2! Most of the silver bearing material was completely gone...and there is a cone shaped mound of bearing shell backing material that is now part of the bearing from building up into the oil feed hole on the crank! I guess it melted itself to the bearing shell once the crank stopped. I had to hammer the bearing shells and rod caps off of #2 and 3. The journal areas look blued from overheating, and the big ends of the rods look blued as well, especially #2...blue about an inch up the rod from the bearing...and there was no oil residue anywhere near #2 and 3 rod bearings...bone dry. It burned off what oil was left on them!
The crank does spin smoothly on the main bearings. Didn't have time to dismount the crank girdle yet, so I don't know what they actually look like. It's definitely cheaper to find a good block then try to salvage this one. I have some deals I've been talking about, so I'll have another block fairly soon. At least I've had a primer on bottom end disassembly, since I'm planning to do rings and rod bearings on whatever block I get.

[HondaDustR]

Ok, update.
I'm supposed to be getting my used engine tomorrow. I was going to go with a shortblock, but I got a really good deal on a whole engine out of a previously running car, and it's an 87.

I've pretty much torn down the entire old block. The main bearings looked more or less fine. The silver coating on the front side of the thrust bearing surface was mostly worn out, but I didn't have my feeler guage to get a idea of how worn it was.
Piston to bore clearance seemed within spec...I couldn't fit my now newly aquired 0.04mm feeler guage in any way shape or form between the piston and the wall, and the range is 0.008-0.032 with the limit at 0.08, so the pistons and bores probably have some life left. Piston ring groove clearance was nice and tight. Piston ring end gap was way out of spec just by looking at it. Looked like nearly a full mm (spec is 0.2-0.45mm), even near the bottom on fresh cylinder. The only thing driving me nuts about this is how much was worn out already and how much is because it ran at 5000 rpms with no oil for 15 seconds before the rod bearings melted.

Otherwise, the project's been mostly cleaning, planning, and waiting. I had some trouble getting the clutch release pivot pin out, but that's out now. The throwout bearing was reasonably tight and smooth, but a little dry feeling, so I popped it apart and injected a little grease into it. Feels good as new now. Pressure plate looks good. Pivot shaft has needle bearing marks etched into it, so i'll be replacing it, plus bearings. Clutch disk turned out much to my surprise to be the old rubber centered disk (PO said it got a new clutch...yeah right! ), and the friction material is looking pretty close to the backsides of the rivets. Rubber damper looks fine, though. If anyone has a good low mileage used spring centered disk please drop me a PM. I don't really want to throw $350 away unless it's pretty much my only option, and esp in that case, I'll be going back in later to replace it, 'cause I don't have that extra money.

I seariously need to hunt down a camera to borrow!

BTW: is a 2.5L crank with spun rod bearing journals worth anything to anyone besides for scrap value? How about a block with not so usable cylinders (one had a small scratch that catches a fingernail and another has a small dent in it 'cause I wasn't being too careful pulling it apart, assuming it was pretty much scrap anyway). The crank's kinda cool as a desk ornament but the block has to go one way or another.

[Schumi]

I've worked on other engines where there was a spun rod bearing and the crank stayed perfectly in tolerance. It is possible it is still good... but most likely not worth too much. Entire short blocks are pretty cheap thesedays.

[HondaDustR]

Just got the engine delivered this afternoon. Looks good so far. Turns over smoothly and I can feel compression in every cylinder. It was relatively clean, except for the front, where it looks like the front seals have been bad for some time. The head looks nice and clean as if it was rebuilt/replaced at a later time in the engine's life, and even has a little badge glued to the front freeze plug saying warranty void if removed. The intake gasket surfaces are perfect, intake ports are clean, the exhaust studs look like they are not original (i.e. not very rusty), but the exhaust has a good layer of carbon in it, so it definitely has been a few miles since the head was put on. The water pump looks fairly new, and the bearing spins smoothly with just a tick of play, so I'll keep it as an emergency spare. Oil cooler housing was pretty clean as if the oil cooler seals have been done recently. RMS area looks dry. The rest of the block is actually pretty clean. I did give it a cleanup with some engine cleaner to get it looking good and to remove as much dirt so I don't get any in it when I start pulling stuff apart.

I'll definitely plan on replacing the external seals and gaskets, do the oil pan gasket and rod bearings, head gasket, valve stem seals, and lapping valves. I may or may not mess with the piston rings, depending on how the bores look, but since its exact milage is unknown, I'll probably do them anyway while it's really easy (the engine stand is by far the best $50 I've spent on tools! ). I did see that the pistons are the lower compresion versions. Clarks garage had a chart that said the 944's came with 10.2:1 CR pistons starting at 87, which is the year the car was that the engine came from. Maybe the chart is wrong, or the engine is not the original for the car. No big deal...a refreshed engine will still be a bit stronger than the one I was running before.

Tomorrow's plan will be getting a look inside the oil pan and hopefully getting the head off, plus maybe a tool/supply run if there's time.

BTW: what sealant is best to use on the oil pan gasket. Clarks said he used grey RTV on the corners without problems, which also happens to be my all time favorite RTV sealant. Paragon (I, think...) recomended red RTV, and I also have a tube of Curil-T. What's best?!? I DO NOT want to have to see oil dripping from the gasket when I get it all back together. That would be pretty demoralizing...

[HondaDustR]

Ok, big dilema here... Do I put new rings on, or leave the ones alraedy on the engine???

Foolishly thinking it would be straightforward, but smartly suspecting otherwise, I decided to poke around on the 911 engine rebuild forum, and they have a Alusil re-ringing thread that rivals our ultimate motor oil thread!
Re-ring Alusils?

Here's another thread I found that has some info.

Alusil cylinder de-glazing/plateau honing

I'm kind of afraid to make a decision, since I don't want to leave it if I can get it right and get fresh rings in there, especially if the old ones measure up worn (the ones in the fried engine had horrible end gaps), but I definitely don't want rings that never seat and have to do this project all over again to try to fix it!
Sounds like alot of people have success with a REALLY good cleaning of the cylinders with scotchbrite pads and degreaser. One said after his cyls spent some time in a parts washer, the cyls actually felt a little on the rough side, which is what they feel like when freshly etched, which is what you need to break in new rings. My plan will be to try scotchbrite and super clean on my old block and see what I get, measure the rings already in the new engine, and go from there.

Other thing that concerns me is if a set of rings gets removed from a cyl they have worn into already, will they still match the cyl if re-installed? Seems to me it would be next to impossible to get them re-installed in the exact position they originally broke in to, in which case how do you check end gaps to know whether to replace them or not if they turn up good but will not line up exactly with the cyl? For example, I had one of those small methanol powered radio controlled cars a few years ago and the pistons on those things did not use rings, but fitted very close to the cyl. Once it breaks in, you must not remove the piston, or it will re-break in and loose alot of compression, since the piston mates to the cylinder down to the microscopic crystal structure of the metals. I know from personal experience that they indead are never the same if disassembled, although the design is an extreme case compared to a large ringed water cooled 4 cycle motor that spins 1/4th the rpms.

[HondaDustR]

Ok, so I had enough with speculation and started disassembling the motor. Cam tower looks good, cam looks ok, lifters are all soft, but who knows how long it's been sitting, head looks really nice...like a fresh rebuild. Haven't taken valves out yet, but it's definitely a relatively low milage rebuild.

It took a big turn for the worse from there.
Cyl's generally look good...(wait what's that!?!) Cyl 1 has a BF gouge about 5/8" long right at the top of the piston stroke...about half of it extends into compression ring space! Turned the motor over to check the bearings (btw, the drain plug magnet was covered with metal sludge). Imediately went for the #2 rod bearing and it didn't look great...scratched and started to show copper. Crank journal was not the best I could hope for, but probably polishable at a machine shop. Other rod bearings were ok, not bad, but not great either. Also, the entire inside of the crankcase was caked in black/brown oil crap (why cheap conventional oils aren't good). The piston skirts looked more worn and definitely more scratched than my ond ones (yes...the ones that came out of the engine that seized on melted bearings at 5000 rpms!) Oh, and Piston #1 has BF gouge to match the one in the cylinder. I went to check ring end gaps on #1 and 2, both compression and scraper rings were way out of spec, about 0.95mm... Oh well, what do you expect... I don't think it's really rebuilding material, personally.

[HondaDustR]

haven't updated in awhile.

Finally finished my custom mild porting work on the cylinder head. I also cleaned up the combustion chambers, sanded a few areas, and polished. I was also able to port match the intake manifold to the head. The only one that was pretty close was the #3 runner. The others had some areas that were fairly far off, being smaller than the port in the head. Just have to clean everything up really well, lap the valves in, and it'll be ready for a short block.

I will be looking at motors this weekend, so the actual rebuilding part of the project is drawing near.

[HondaDustR]

Saw an 86 motor with very nice looking cylinders today, so it will be mine once I figure out some transportation for it. I'm considering having the crank balanced and possibly the rods and pistons balanced to each other, but I may try to match them myself if I can find an accurate enough scale.

Random fact of the day: The Victor Reinz NA head gasket set sold here on Pelican actually does have the Y-pipe to exhaust manifold flange gaskets.

[HondaDustR]

Finally got the motor and some pictures of the project so far.


Here's the #2 rod bearing from my motor. The #2 and #3 rod bearings literally melted themselves to the crank and stopped the engine dead in its tracks. Here, the bearing material started filling the oil feed hole, which welded itself back to the bearing shell once the crank stopped. I had to hammer the bearings off the crank with a screwdriver.



#2 rod journal. Who knows, it may not have actually damaged the crank too much underneath all the melted bearing material and may just pollish out without being ground undersized, but that'll be found out some other time.



The #4 rod bearing strangely eskaped almost undamaged. It didn't even show copper. The journal is still shiny with only some mild burning. The mains are in great shape.




The "new" motor. Out of an 86 944, but the block, crank girdle, and a bunch of other stuff say 84. The cylinders are very smooth, but not absolutely perfect. There's 1 or 2 scratches deep enough to feel, but they are small. At this point, I don't really care. My old motor had a couple of the same scratches and frankly I would have never known without seeing them. My old motor did have a barely detectable wear ridge at the top and this one doesn't so that's a big plus. The pistons aren't caked with ash like my old motor, so hopefully that's a good indication it wasn't a cronic oil burner like mine was for quite a while.




The thing's a freaking mess, though...and I already painstakingly cleaned one, only to find the killer scratch in cyl 1. This one has been cleaned already, but I haven't got a picture of it yet. Literally hours of PITA...




It's also cleaner inside than the first one was.




Ok, now I'm really happy. This is the #2 rod and it's practically spotless!




...and so are all the others! The thrust bearing clearance was 0.15mm on my feeler guage, which beats both of the other motors by a good margin!




So far the pistons are removed and bagged waiting to be cleaned, the updated oil pan from my old motor was cleaned and temporarily bolted up for cleaning the block, the block has been cleaned, and the deck surface has been scraped clean.

Next to do is removing the oil cooler, oil pump, balance shafts, and crank so I can flush the block out, set up the cylinders (to be covered later...with the old block being the test dummy first!), clean it to within an inch of it's life, plastigage the mains, and then the tedious process of reassembling the girdle, oil pump, and balance shafts.

[HondaDustR]

More pics of the head. It's all cleaned and ready for the valves, and has been port matched to the intake. Just have to wipe down the valves to get rid of all traces of lapping paste first, which I still haven't gotten around to yet.

[Slam]

Makes me tired just reading this. A great thread with good pics. It seems scratches on the cylinder walls are common. The spare motor I've got has them too, and like you said, if I hadn't seen them then who knows if I would have suspected or not.

[slow944s]

Good Post HondaDustR, keep us updated......Thanks

[HondaDustR]

Well, between work, school, homework, and a bad replacement motor, progress has been slow going to say the least. The big plus side is it has given me plenty of time to do a complete port and polish job on a 944 head, which I've been really wanting to try for a long time and not sure how to fit it into my schedule. It's also the first car head I've done, so I'm really itching to try it out. I finally broke down and got a cheap digital camera so I can get more pictures without worrying about getting someone else's camera greasy.

[HondaDustR]

More progress. Got the block stripped down to the bare minimum. Crank is cleaned and bagged to be checked and probably have the bearings polished at the machine shop. Main bearing girdle is cleaned and ready to go. Block still needs a good cleaning. I also need to clean the cylinders on my old block in order to do some trial runs for my cylinder preparing process I've planned out so I can see what it actually does. I also got the cylinder head fully assembled and bagged for reassembly.




Are there supposed to be any o-rings on this??




Woohoo...old school balance shaft bearing bridges!













Finally getting the cylinder head together.

A 13mm 12 point deep socket works perfectly for driving the valve stem seals.


I hate using this tool, but it can get the springs off with the head still installed.

[Schumi]

I'm sure you know this, but since you're swapping things around blocks, just to be sure-

the crank girdle and the block must stay matched together, no swapping one crank girdle to a block it wasn't for- they have tight mating tolerances and I think they are machined together. Mismatching them will cause spun main bearings.