Does anybody know if the rings on a 928 engine can be replaced without removal of the block? I have never torn one down, so this is new territory for me. I successfully accomplished this on my 79 VW 1.6 liter, but I wasn't sure of the construction of the lower crankcase casting on the 928 and if it allows accesss to the rod bolts when the oil pan is removed.

Thanks

 

A 928 engine rarely requires new rings.

It would probably be more trouble to do it in the car than to pull the engine.

 

I'm going to do a leak down on the engine before I pull the heads to see where the problem might be residing...

I have one cylinder which only returned 135 psi to the crank up type gauge, while the others returned 150+ With any luck it will be the head gaskets. I hope I don't have a valve or piston problem...

 

if you go for a re ring, it would be worth it to just up grade to a 85 5 liter short block and re-ring that. I agree with wally, much more effort that it would be worth. even head gaskets would be worth pulling the motor and starting over.

Let me know if you want the details of the 5 liter conversion. pretty straight forward, except for the 2 valve reliefs in the 4 valve pistons. that is a little tricky, but very doable.

Mk

 

John as Mark Kebort points out you could make it a five liter ! But since you use boost you would be a candidate for using the 1987 > pistons which as Lucky Echman will confirm when fitted with two valve heads gives you a compression ratio of perhaps 7.5 or 8 to one . That is so much better than trying to boost a 10-1 compression engine . You really should pull the engine to remove both heads especially if there is a possibility you might need to go deeper into the engine . Working leaning over the fenders just kills your lower back !

 

My compression ratio today is 8.5:1 and just about ripe for a moderate boost application. I am going to build a bleed down pressure tester and see where some of the leaks are occurring. I have heard the horror stories of the crushed ring lands, so let's hope I am not a casualty here as well.

It is not like the bottom end is gone, but I thought I might be able to freshen it up while I am in there. I want to avoid changing too much stuff, because right now I don't really want to pull the engine out and I am already dropping enough coin in just the fuel system mods and turbocharger rebuilding, not to mention that I need a new steering rack. I can feed enough air into the 4.5 liter to make good power, so that is the goal. Unfortunalely, the 944 turbo pistons are larger at 100 mm bore as compared to the 95 mm bore on the stock M28/15 engine. I had a brain fart that I might be able to put some forged 944 turbo pistons in, but that obviously won't work.

My back is already bitching but it will get used to it.

Maybe I should just follow George's lead and drop the small block in?

 

Mark - PLease post your experiences here regarding the 5.0 switch for the early 4.5 liter heads....

I have a 4.5L 81 that now has a 4spd is is just screaming for a 5.0 switch.

This is something you should share with everybody.

 

Kibort?

Heeellllloooo?

 

Im here!@!!

Yes, the Guys at 928 Intl helped by supplying a low cost 5 liter (85-86) short block. Devek helped me a great deal, in re-ringing it and cleaning it up, as well as re-assembly.

Not too difficult. I took the block apart, cleaned it up, took the pistons to a well known engine machine shop and gave them a euro 2 valve piston and had them cut shallow 2 valve cuts in all of them. I got pretty close with that, but as luck would have it, we assemble the engine, and the valves were just barely hitting the valve cuts. So, we sealed off the cylinder holes and I just used a air grinder and went to town on all of the valve reliefs to be sure. (only one was hitting , but there is no down side to grinding more off than is really needed.)

My advice is to use the euro piston, and then have the machine shop make the cuts 1mm deeper and wider than is scribed out.

after that, its pretty straight forward:

put euro heads on with new head gasket from an 85.

re route US cold start injection from going to heads on euro heads to going to intake plennm (already an un-used fitting on euro plenum). (very easy)

there is a small mod to the alternator on how it bolts to the block, and a dip stick difference, both being kind of minor in my opinion.

Result is that you just bolted on 300-500ccs and everything fits perfect and you get some big HP gains, even if you are bolting to a ole US AFM system.

Jim's right John, if you use a 87 short block, then the compression is much lower for your supercharged set up. I calculated around 8:1. The US euro turned out to be around 10:1. (this one is a no brainer) even US heads on the 5 litre 85 would be around 9-9.3:1.

Jim's also right about doing head gaskets or rings in the car. trust me, it aint worth it. just yank it, and re-ring a 5 liter short block. heck, I think they are only around $1500. when you are done, you will really have something!!
rings are pretty cheap, and so are the bearings, and you would be doing them anyway.

MK