Removing/replacing cylinder heads
#1
Racer
Thread Starter
Removing/replacing cylinder heads
I’m pulling the heads on my 1982 928 S to replace all gaskets and seals. The engine is running a little rough too, which is what prompted this service. Am I an idiot for thinking I can do this with the engine in the car?
I’m cleaning and rebuilding everything else reasonable while I’m at it too, so this’ll be a big project. I’ve attached a pic of the current state of the car.
Stripping and cleaning as I go. Planning to re-plate all corroded parts, and replace the original wiring harness.
I love the Porken lift bars!!
Thanks,
Camelman
I’m cleaning and rebuilding everything else reasonable while I’m at it too, so this’ll be a big project. I’ve attached a pic of the current state of the car.
Stripping and cleaning as I go. Planning to re-plate all corroded parts, and replace the original wiring harness.
I love the Porken lift bars!!
Thanks,
Camelman
#2
Archive Gatekeeper
Rennlist Member
Rennlist Member
As Greg used to say:
1 head: Engine in car.
2 heads: Engine out of car.
1 head: Engine in car.
2 heads: Engine out of car.
#3
Racer
Thread Starter
Rob, why is that? What makes it harder to pull both heads? Or is each head just a complete pain in the butt?
Last edited by camelman; 01-12-2024 at 01:35 AM.
#4
Archive Gatekeeper
Rennlist Member
Rennlist Member
It's not any harder to pull two than one, just takes more time bent over the fender of the car, and doubles the hassle during re-installation of the cam towers and their bolts. I don't want to trivialize the process of R&R'ing the engine but since you have to disassemble the whole front of the engine anyway, it's not really all that much more time to drop the exhaust, remove the hood, disconnect the AC compressor and power steering pump, and lift the motor out and work on it on a stand with all the room and leverage in the world.
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#5
Racer
Thread Starter
Gotcha. I’ll look into it. I have a cherry picker at the warehouse already and an engine stand at home. I need to replace the oil pan gasket too, which will be a pain with the engine installed.
How tight is it to remove the engine from above? I just did this with a 944 and it was much tighter than I was expecting. I’d hate to bang up the engine bay on this car.
Thanks
How tight is it to remove the engine from above? I just did this with a 944 and it was much tighter than I was expecting. I’d hate to bang up the engine bay on this car.
Thanks
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Daniel5691 (01-13-2024)
#6
Archive Gatekeeper
Rennlist Member
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Pretty straightforward, with the accessories off you have plenty of room- the tightest dimension is the lateral edges of the timing belt covers next to the engine crossbar mounting brackets but there's something like 1-2" clearance on each side. Disconnect the AC compressor from the block, the air pump, the PS pump, and the alternator, remove the exhaust , the lower bellhousing cover/ starter, separate the flex disc from the flywheel, undo the four upper bellhousing bolts, undo the rear crossmember-to-transmission mount bolts, pry the transmission/torque tube/hellhousing case rearward, remove the four engine mount bolts, and hoist that thing out of there. The reason the trans/TT/bellhousing have to go rearward is that the engine has to be lifted straight up the first 4 inches or so to clear the motor mounts. Don't forget the engine ground strap and whatever vacuum hoses go to the transmission on automatics.
#8
Team Owner
Note on the 944 it’s easier to drop the engine out with the front suspension you do need the car on a lift to do this
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davek9 (01-14-2024)
#9
Drifting
nothing trivial about pulling the engine, especially if you have an issue with the bell housing bolts.
If I remember correctly You have to undue the tranny to body bolts in back and kick the driveline back a few inches to clear the flywheel out from the bell housing. That's a big deal!
Don't forget every time you undue a bolt you run the risk of fvcking it up, stripping the dusty aluminum. It will never be factory-snug ever again. It's OK for mechanics at a dealership they don't give a ----
If I remember correctly You have to undue the tranny to body bolts in back and kick the driveline back a few inches to clear the flywheel out from the bell housing. That's a big deal!
Don't forget every time you undue a bolt you run the risk of fvcking it up, stripping the dusty aluminum. It will never be factory-snug ever again. It's OK for mechanics at a dealership they don't give a ----
#10
Rennlist Member
There's so much WYAIT if you have the engine out but the thing that comes to mind for me is putting new engine mounts in, if you haven't already. You may also want to rebuild and firesleeve your high pressure power steering hose. The HPPSH is not the worst thing in the world to do with the engine in the car, admittedly, but since you'll have ALL THE ACCESS...
Good luck
Good luck
#11
Rennlist Member
Gotcha. I’ll look into it. I have a cherry picker at the warehouse already and an engine stand at home. I need to replace the oil pan gasket too, which will be a pain with the engine installed.
How tight is it to remove the engine from above? I just did this with a 944 and it was much tighter than I was expecting. I’d hate to bang up the engine bay on this car.
Thanks
How tight is it to remove the engine from above? I just did this with a 944 and it was much tighter than I was expecting. I’d hate to bang up the engine bay on this car.
Thanks
#12
Rennlist Member
Pretty straightforward, with the accessories off you have plenty of room- the tightest dimension is the lateral edges of the timing belt covers next to the engine crossbar mounting brackets but there's something like 1-2" clearance on each side. Disconnect the AC compressor from the block, the air pump, the PS pump, and the alternator, remove the exhaust , the lower bellhousing cover/ starter, separate the flex disc from the flywheel, undo the four upper bellhousing bolts, undo the rear crossmember-to-transmission mount bolts, pry the transmission/torque tube/hellhousing case rearward, remove the four engine mount bolts, and hoist that thing out of there. The reason the trans/TT/bellhousing have to go rearward is that the engine has to be lifted straight up the first 4 inches or so to clear the motor mounts. Don't forget the engine ground strap and whatever vacuum hoses go to the transmission on automatics.
#13
I never had to move the manual trans to pull the engine from my 1981. Doing it by myself was a 4 or 5 hour job out the top. Everything else you need to do is SO MUCH easier with the engine on a stand it is totally worth it.
#14
Rennlist Member
If you do the cylinderhead job with engine in the car you won't have that endless fun of doing other jobs while your are in there. A fairly classic pitfall I guess. I stepped into it and there seems to be no end of oddjobs to do.
#15
Racer
Thread Starter
Bores and pistons are bad
I finally got time to pull the engine and cylinder heads, and confirmed the worst. All 8 pistons are broken between the first and second rings. The landings all have a similar section broken, so it's time for a bore and rebuild. From what Greg Brown says all of these 928S Euro engines suffer from broken landings, so I don't want to just find a replacement engine since it'll likely have the exact same problems. Half of the bores need help, and one bore in particular might not even work with a 1mm overbore. Can anyone point me to a good machine shop in the SF Bay Area that can work on these engines? If not, then any other suggestions are welcome. I also need to source pistons, but don't know where to look to find quality pistons that will last. Does anyone have a suggestion for that?
Also, what does experience suggest as a repair? Bore and oversize, or replace with an iron sleeve and use stock size?
The attached pics are the worst.
Also, what does experience suggest as a repair? Bore and oversize, or replace with an iron sleeve and use stock size?
The attached pics are the worst.
Last edited by camelman; 04-14-2024 at 04:11 AM.