924Board.org

[bureau13]

I got in a hurry and got stupid.

See if you can find the missing step:

Put wrench on crank, turn to 0 TDC
Install dizzy w/ cylinder 1 wire pointed to by rotor
Put cap on
Start car

Yeah...I'm missing step 2: Remove that f*&&& wrench. I started the car, it ran for maybe a second until it unscrewed the crank bolt Car died, I got out and saw the wrench still there, and the crank pulley was loose. The belt was still on it but it had rotated some. I'm sure it died when it got out of time enough, the question is, did it also bend valves? I have to assume it did, but I'm going to put everything back together and see what happens.

Here's a question though...first, is there a dedicated tool for these cars to lock the flywheel or something when you torque down the crank bolt? Also, since the crank and cam are no longer lining up, do I just rotate each of them to the 0 TDC position and then string the belt? I've never had to deal with the scenario where they weren't already lined up properly when I took the belt off.
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1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[morghen]

The crank pulley has a positioning pin thats 4-5mm long...unless you sheared that pin(not likely), with a tensioned belt...i doubt that you slipped the crank pulley vs crank.
Double check your timing again..use the correct timing marks...take the belt off..rotate the crank by hand half a turn after TDC, then turn the cam to the mark...put a pulley on and rotate the whole thing by hand...see if anything feels jammed..i would be suprised if you managed to offset the engine and damage it.
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https://www.the924.com

[bureau13]

I hope you're right! The locator pin is intact, I just noticed when I pulled the loose pulley off the hole and the pin were not lined up, but I easily could have done that myself...I wasn't sure what the mechanism was for fixing that location so I took it off to look.

I am confused about the "half turn after TDC" thing though. Is that where all the pistons are retracted enough that nothing will hit? Then after moving the cam I would move to TDC? On the 928 I know there's a point where you can set the crank that nothign will hit, I've just never seen it spelled out where that is for this car...

[morghen]

Yeah so nothing would hit.
If you poated pictures it wouls be easier yo understand what happend.
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https://www.the924.com

[bureau13]

I carefully put the crank and cam sprockets in position, strung the belt and rotated it several times carefully. It felt like I was getting compression and I didn't notice anything making contact, but it won't start and it sounds odd. So I'm betting it's ****ed. I'm going to do an actual compression test this weekend but it's probably time to start thinking about how to deal with it.

Having it rebuilt by a professional is not something I'm going to be able to pay for. However I know someone with a shop and considerable general know-how, who has rebuilt motors. He doesn't know this particular car, but he seems to feel that this is something we can tackle.

Is there a good writeup somewhere for pulling the motor and tearing it down? I have the Haynes, but no factory manual. I haven't looked in the Haynes yet but generally I think motor rebuilds are a bit beyond where they go. I could be wrong.

If the pistons are still good, can this be done without pulling the motor? Or is that even worth trying? (FWIW my friend says we should just pull it and take the opportunity to go through it thoroughly and refresh everything).
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

Just browsing around looking for things like pistons and valves and...really not having much luck. Maybe I don't know where to look. The tech section and a few threads here mentioned EBS racing having pistons and valves, etc but I guess that was a few years ago. I don't see anything now.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[morghen]

It depends on you if you want to go "while in there" or not.
If the clutch and bottom end are in good condition i see no reason to pull the motor. You can always pull the motor at a later time...i dont understand the judgement that you're saving 1-2h of bolting/unbolting stuff but loosing 6 months of driving the car as you cant find parts or whatever unexpected reason.

Just take off the head and have it repaired or replaced with a known good one.
If you set the timing right it should start even with a bent valve or two.

How did you set the engine timing?
Did you use the mark on the crank accessories pulley and the mark on the INSIDE of the camshaft? Or did you use other marks? Dont use other marks, dont use the flywheel mark as there are different flywheels and markings and you can get confused. Use only the marks show in the two pictures below and you will properly time the engine.





In regards to the car not starting, appart from the engine timing possibly being off, i bet your spark timing is off....you probably put the distributor in the wrong way and maybe thats why its also sounding weirdly as its sparking at the wrong moment.

Oh and dont turn the engine anymore until you have set the timing belt and marks properly like described above.
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https://www.the924.com

[Fasteddie313]

I 2nd just pull the head.. (after a compression test and making sure it is timed right)
These are also super simple heads..

I wouldn't pull the bottom end apart because it probably costs just about as much to put one back together as it would to just buy another used one..

How to fix/replace the head if it is messed up is a completely different story..
And inspecting pistons, but we can get into all that if you have damage..

If you pull the head, I'm a pretty firm believer that ARP headstuds are one of the best engine upgrades you can do, and just about the only thing you need to do internally at all..

And yeah, make sure to time it like morghen said, and make sure to mind compression stroke/exhaust stroke when timing the ignition.. (dot on cam pulley up = compression)



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80 Turbo - Slightly Modified

[bureau13]

Thanks for the info, guys. I did time it as you said, with the marks on the crank pulley and the cam dot (backside). I also made sure the rotor was pointing at the wire for cylinder 1. Remember, it fired up perfectly right before it unthreaded itself, and I did verify this afternoon that the distributor was still firmly in place and the rotor was still pointing where it is supposed to, after setting it to cyl 1 TDC once again.

I can feel compression as I turn it by hand, too. I mean, I can't say it has compression on all cylinders, I'm going to do a real test tomorrow, but it doesn't feel wrong to me. It is odd that it won't start at all though, isn't it? That didn't strike me as odd at first, but now that you mention it, I would expect it to start and then run poorly with a few bent valves. Hmmm...

As for pulling the motor vs the head, I think you've convinced me.

I'm sad more than ever now that Ideola's Garage is closed. I do a search for rebuild kits and his site comes right up I did look for valves and didn't find much. There's a place I've bought from before that listed them for what was way more than I thought they should cost, so if I did bend some I hope it wasn't many! As for the ARP head studs, do they actually make those still? There was some ARP hardware for these motors that I was reading about and you had to do a sizable group buy to get them to make any. Maybe it was a different part though, I don't remember. That does sound like an improvement that would be good to make at this point.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[Fasteddie313]

Yeah..
ARP 251-4701

Looks like $150 on eBay right now but I think I got em for closer to $120 somewhere..
Definitely available though and reasonably inexpensive..
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80 Turbo - Slightly Modified

[MikeJinCO]

Those head studs are for a Ford Sierra Cosworth also the Cosworth DFX Indy motor. They are $140 from Summit Racing. If you get the studs make sure and save the head locating collars as you can't remove or install the head with the studs in the block.

I'm thinking the distributor is off one tooth. I've put in the race car wrong most of the time, when I get it to look right in the pictures it never runs, turn it back another tooth and it is fine.

On valves, SI used to make them but not any more. Ferrera has some blanks(unfinished) that have a 9mm stem, but they are huge and need to be cut down in size. 47mm exhaust and 53mm intake. They can be cut down. They are probably over $40 as they come, their prices have gone up a bunch. They say made for Porsche so might be old 356 or early 911 valve blanks which might be worth looking into.

I will have a set 931 valves available in a month or two as I'm converting a 931 head to NA and using 7mm stem valves. It promises to be an expensive experiment.
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Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

[bureau13]

Interesting...good to know there's still an option there. I'm surprised they don't advertise them as fitting, although I guess we're a pretty small set of potential customers. If I do have to do this, I'm going to tell everyone there are Indy car engine parts in use

Regarding the valves, I haven't been able to find anything new, so I may be very interested when you sell yours. Again, I'm hoping I don't have to do this (rained all day yesterday so I wasn't able to do any more investigating) but at this point it seems pretty likely.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

Well my compression tester isn't working. The needle doesn't budge at all when cranking in cylinder 1 and 3 (the two that I checked). That doesn't make sense at all. I've never used it before so I could be doing something wrong, but I don't think so? Screwed it into the spark plug hole, removed fuel pump relay and coil positive wire and cranked.

Anyway, it doesn't sound right to me when cranking. Take a listen, it definitely sounded more "normal" before, but I can't put my finger on exactly what is different.

https://photos.app.goo.gl/zHanotb3vRKmUzei7
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[Paul]

Check the other cylinders. You have bent valves at least. Your compression gauge is most likely fine. It is almost impossible not to bend valves when the timing slips with the motor running.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Fasteddie313]

Yeah, by the cranking it sounds like you still have compression on atleast one cylinder.. Find it with your tester..
Bent valves could be absolutely zero compression, gauge not even budge..

Also, if you pull the cam cover, you can probably tell which valves are bent because they will have massive valve lash gap between the buckets and cam, because bent valves won't close all the way..
So checking your lash will probably give you a good idea as to what all is wrong..

Bending valves may have also damaged the head/seats, so I wouldn't go buying valves until you asses the head..

Either way, I would think your best bet would to buy a used complete 931 head with or without bent valves, and make the 2 into one good one, or just a used working head to swap..
(post wanted ad here/facebook)

If in your position, I would probably try to just buy another entire 931 engine, turbo and all, because spare parts..

Pull the head first..
3 bolts off the turbo to manifold flange, pull J-pipe, comes right off..

If their aren't cracks or chunks broken off the pistons, I'd leave em alone..
If the dents made any sharp edges on your pistons, I'd file/sand them smooth so it wouldn't cause a hot spot and increase detonation..

Sorry for your loss..
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80 Turbo - Slightly Modified