4drgl

Ok...

car is an 80 U.S. 4.5 automatic

When I purchased.. it was not running... I ended up draining the fuel out of the tank and replacing the fuel. Once I replaced the fuel with fresh and replaced the fuel pump. Motor started and idled well...

I took it around the block for the first time, at 2500 rpm it seemed to not be able to rev any higher. I attributed to possibly a vac problem...

So I pulled the motor, because I noticed coolant weeping on the outside of the motor between cylinders 2/3, 5/6 on both sides... Bought a seal kit, and while the heads were off, decided to get it a valve job.

The machine shop is telling me that there are 6 bent exhaust valves, and 1 bent intake valve.... Not sure which cylinders the valves are bent on.

Anyway. The 4.5 16v is a non-interference motor... and I asked what could possibly cause it to have bent valves?? Because it was running when I tore it apart, and did not attempt to pull valves myself. He suggested either it was over-revved or that the bad fuel caused the valves to get stuck...



Any suggestions??

Oh and by the way I need valves like yesterday!!!

I'm gonna get it running, I'm not giving up... but DAMN...

Thanks

WallyP

I would want to see the bent valves, but that is just me.

Sounds unlikely that an engine that idles well would have bent valves...

hacker-pschorr

Friend of mine had an Audi 5-cylinder in his shop last year, idled and cruised perfect, no power above a certain RPM.

Compression test was perfect compared to other cars with the same motor, leakdown told a different story. He pulled the head, most of the valves were bent.
In his 30+ years of fixing foreign cars this was a first.

WallyP

A bent valve leaks at a certain rate. At cranking and idle speeds, the time available for leakage is three or four times that available at higher speeds, so there is much more leakage. The loss of compression is a much bigger portion of the usable mixture at cranking/idle than it is at high speed.

The combination of these factors should make the negative effect of bent valves much more noticeable at cranking/idle than at high speed.

Odd.

4drgl

The local havana machine shop is pretty good, I've had work done there before, and they've dealt with lots of 944 heads... so I know they're not jerking my chain...

I will get the bent valves from them for my "How not to buy a 928" memories in the future...

As Hacker said it, I've heard of this problem too with some other vw's, but just shocked.... that it was my heads!! DAMNIT... Anything that can go wrong does go wrong!!

hacker-pschorr

It was a very odd situation. It's the rare 20V 5-cylinder with Hitachi fuel injection, I have the same car.
He was using my car to swap parts since the good compression numbers pointed away from bent valves (didn't do the leakdown right away). After we swapped everything within reason (MAF, computers, sensors etc...) he did a leakdown. We were both a bit surprised by the results.

ptuomov

Bent valves and high rpm problems? How about the possibility that high-rpm problems and bent valves are both symptoms of some other problem. For example, say valve springs are f'd up. Fouled valve springs might cause valve float which takes out the high-rpm power and this might also man-handle the valves to the point that they get bent. If the valves are bent slightly enough, they are not causing obvious problems on their own and the car runs at low rpm.

piperporsche180944

Bent valves? Thats not good! I have cylinder heads off of a 1981 928 you can have for $200+shipping.

dcrasta

Maybe it overheated. Bent valves usually wont 'leak coolant'. A severe overheat could weaken the valvesprings, causing a float that would bend valves.

Check your valvespring pressure also I would wager a cold one that they are weaker than spec..

4drgl

How do you check the valve springs for problems?? The machine shop is supposed to pull everything apart and check for problems...

I just talked to the shop, and he checked the height on the springs/compression and they were all very close... He didn't have the spec sheet handy so I couldn't get the #'s from him

Anybody know what the specs should be?? I don't have the manual handy it's at home!

4drgl

A severe overheat would have also warped the heads... and most likely ruined the headgaskets... allowing coolant into the chambers there was only a weep causing crusty things on the side of the block, no drips, and no coolant in the exhaust..

I also asked about the heads, and they are in excellent shape, they were square and flat. They replaced all 16 guides, and are now awaiting new valves... WEIRD...

What's the compression on the spring supposed to be?

dcrasta

Hey 4drgl,

Check this out - http://www.ehow.com/how_5143166_check-valve-spring.html

Your machine shop should be able to confirm if the springs are within spec. I would contact Roger or Mark for specs on spring seat pressure.

Landseer

You can refer to CD tech specs and WSM for the technical information needed.

4drgl

I have them.... just not here at work... I'm trying to get the info to double check the machine shops numbers.

dcrasta

From 10-1 of the WSM

Valve guide/valve stem
lntake
Exhaust
Compression
Clearance
When lnstalled new Wear Limit l
Intake 0.80
Exhaust 0.80
Compression 8 bar and more 6. 5 bar
(8 bars = 116.03019)PSI (6 bars = 87.0226426)PSI