Bernie

I think, considering the number of people who have heard same, that its important we try to get to the bottom of this. I have been told on numerous occasions that pre S4 cars need not worry about TBF. Could you please post a link to the specific thread where this was discussed?

Again, I still want firsthand experience on this so if anyone can help to get to the truth here it would be appreciated. If this is a myth then I want to put it to bed now. I personally have never heard of one but have witnessed TBF's on two S4 machines.

Cheers

JE928Sx4.

I don't want to go mucking through all those posts again. Do a search on thrust bearing failure. The topic has been beaten to death over there. From personal experience, I followed Earl's recommended procedure on my 86.5 right after I purchased it and noticed movement of about 1/16th of an inch. I then buttoned it up with the locktite treatment. It'd been perfect in the 2+ years since I've had it. Most cases it moves much more than that. It all depends on if your car has been worked on improperly since it left the factory. Earl's procedure is about as difficult as changing oil. Just do it and stop worrying.

JE

Shane

My sentiments exactly. It may not be as common on pre '87 928s but I don't want my car to be one of the few that do. Especailly if you have done any HP enhancements with chip sets or forced induction.

Bernie

Well,
Thanx for solving that mystery!

Cripes, there is a 100 things I could do as preventative maintenance and a lot that are done. Still doesn't address the question. But then, you're bored so move along......

JE928Sx4.

Sometimes you have to do a bit of your own leg work. Start here: http://www.nichols.nu/tips.htm Greg Nichols boils down the good stuff from the mail list for us there. Go to the Automatic transmission section.

Some of us have to work in between f-ing off on Rennlist you know.

JE

Bernie

Thats great
Thanx JE, I will spend a couple of hours digging around to find information to support what you have said.

BTW - If you throw the 928 quickly from drive to neutral while pressing on the horn with your nose and the sprayer button with your knee, the interior lights will flash morse code to the tune of "let it be" by the Beatles. I am sure you'll find a thread out there somewhere that supports my claim.

Ahhhhh, back to the sand and my Corona.....
Zzzzzzzzzzzzz

Don Carter

I seem to remember that the parts associated with the TBF are not the same between the 85-86 cars and the S4 and later cars, and the general consensus was that it was less likely to happen on the 85-86 cars, but still possible. Just going on memory.

Why would head studs be a plus on the 86.5? I thought the later design was preferable since you can remove the heads without removing the engine, or do I have it backwards?

Steve_C

It is possible to remove heads with studs on the 86.5. Having done the passenger side, I don't understand how it's much, if even any easier, with bolts. Was told that was easier to pull the engine if you needed to remove both sides. Unless the pan gasket/baffle/mounts are required also, it seems to me to be extra work to remove the whole engine/AC/radiator etc.

Lagavulin

Head studs provide superior clamping force over head bolts, period. And studs are especially important if you have a blower on the car running lots of boost.

For a given torque/horsepower goal, it is always advantageous to use the smallest cam possible. Doing so from the factory’s point of view, the overall drivability of the car is not compromised in the name of extra high RPM horsepower, which is seldom used compared to cruise conditions.

With that said, the S4 heads flow better than the 85-86 heads. Because they do flow better, they require less cam to achieve comparable air flow, and is one reason why the S4 cams are less aggressive than their 85-86 counterparts, and is a prominent factor why the S4 has such a silky smooth idle.

Likewise, installing the more aggressive 85-86 cams in an S4 will obviously produce more horsepower, but with a slight low-end torque penalty. By the way, number-wise, the GT cams are the same as the 85-86 cams, except that the GT’s have 5 degrees more duration on the intake.

An interesting side note regarding hotter-than-stock cams is that they will lower the effective compression ratio of an engine since the valves are off their seat longer, ‘bleeding’ off cylinder volume on the compression stroke at lower RPM. This is the reason why cam manufacturers ‘require’ a higher compression ratio to offset the ‘lost’ compression caused by the hot-cam installation.

Why is that important? Well, this overlooked fact should prove interesting to anyone (..like myself) who’s supercharging their car and want to safely run higher boost with the stock 10:1 pistons. Additionally, for someone who has an otherwise perfectly healthy 10:1 engine, installing hotter cams is a whole lot cheaper than rebuilding the engine with a lower compression ratio with the intent to run higher boost.

GoRideSno

Lag,
As usual, great post. What effective CR do you think the 85-86 cars have then? Maybe this is Mark R could run the boost he did with no problems. Do you think this may change the ballance of heat equation? Maybe this would be a good thread to start.


Mspiegle,
Please remove your cams and install them in my car. Install a new T belt and water pump WYIT. Then call Whipple and get me a 2 3/8" pulley, time to turn up the boost. Youll need a shorter SC belt too.

Andy K

mspiegle

Wow Lag, VERY informative. Thank you for that info.

Andy, go get your own cams! I found your repair CDs, and I also found that your cat had an accident on your couch. I cleaned it up for the most part, but you can clean up the left-over residue.

Didn't someone say earlier that 85.6 cams need be modified to fit an S4?

Gretch

I dunno, I put more miles on my C4, because it is newer........and more easily replaced. My GT has gotten to a point where getting a hold of an exact replacement would be a real challenge................

Shane

We'll see if that still holds true after Gretch achieves SuperShark status.

Vilhuer

Currently Germans have yearly road tax system that favors newer and more cleaner cars. If this was case already 85-86 and price on 16V non-cat and 32V cat was about same, someone who didn't feel the need for extra horses might have chosen cat version. Also I think 32V was more common in Switzerland and maybe also in Sweden as they were well back then ahead of other European countries in enviromental issues.

Regards,

Erkka

1992 928 GTS 5-speed very green
Oak Green Metallic 22L
Classic Gray MX