1997 3.6 L varioram in the Engine Hospital - needing Diagnosis

[betterair]

here are the leak down and comp nos on the engine.

1 2 3 4 5 6

Leakdown 79 79 79 79 72 79
(put 80 lbs in)

Compression 180 180 205 195 190 195
Backround :

This leak down and comp data was taken after the car was blackflaggedexhibited heavy white smoke at the end of a weekend DE track session
Car was brought off track and into the pits.No motor noises or noticeable decline in power.
Engine was restarted,and exhibited the same heavy white/bluish Color smoke. Again Engine had no apparent mechanical noises ,valve train noises and was driven onto the trailer with no issues.

Engine History:
This street transplant motor was rebuilt (top end) @ 60 K mi.it now has approx 75K .approx( 60K mi.on and reportedly has been running very strong during these 15 K miles., It is a track car.
Engine is also running PMO's , and short geared 915 drive train,which I don't think weigh into this problem.The 60K rRebuild was done by a 4 star shop.

Plan is to confirm leak down and compression data above, when we dig into it but I wanted to ask your opinions, as I am pretty sure someone out there has seen this same issue.

The leak down and compression numbers above, seem NOT to indicate a major problem, but obviously there is due to the volume of smoke.

Any ideas?Thanks !!

[Steve@Rennsport]

Leakdown numbers look excellent.

Make sure the ignition system is working correctly on all 12 plugs.

Then,......

You need to check fuel pressure and make sure its 4 psi,....then measure the float levels so they are PERFECT,...not just "close", but spot on!!

[txhokie4life]

Leaky valve guide?

Not necessarily "visible" with leak down test?

What do the plugs look like?

Mike

[betterair]

I Haven't pulled the engine yet. Just gathering the input before the main event, which may be later next mo.

If Steve is right and it is a fuel issue, it would be putting a huge smile on my face

[Trackrash]

Originally Posted by txhokie4life

Leaky valve guide?

Not necessarily "visible" with leak down test?

What do the plugs look like?

Mike

+1

Is there oil or gas on the plugs? That will tell you a lot.

White smoke = oil. Gas = black or gray?

[betterair]

Thanks guys,
I will report back, once the engine on the engine stand.
appreciate the input very much.

[betterair]

Very slow progress here , but I have learned that the cause of the white/blue smoke was a faulty O2 sensor that resulted the cylinders flooding with fuel while the car was on the track. And then in the garage upon restarting it.
The O2 sensor has been disabled. And I am getting a recommendation that it's most likely the rings will be Will need to be replaced and a light hone in on the cylinders.

Has anyone seen this before when a O 2 sensor fails causing the engine to think it's running lean and do a fuel dump via the KMS ecu?

[Steve@Rennsport]

Too much fuel, as I suspected. I didn't know you were running EFI as your original post indicated PMO's without any reference to Engine Management.

We always run our Motec engines open-loop for this and other reasons, however the default base map must be correct to prevent excessive richness if the O2 sensor fails. I suspect this is the root of your current issue.

Although your leakdown numbers is damned good, I would inspect all the rings VERY VERY closely and if they are damaged in any way, I would replace them. Same goes for the cylinder walls as they may need a very light hone and a thorough cleaning.

[betterair]

My mistake on the reference to PMO's, incorect info.

The ECU is from KMS (MP25)as are the ITB's .
Your comment on running it open loop would have prevented this mess,thats for sure.
Now you have peaked my curiosity.

I hope to have the dbl check of the leakdowwn and comp. nos within the next week or so, since everyone is busy prepping for our Pocono DE on Aug 9.

Steve ,Your diagnosis seems to be echoed by a few east coast gurus as well.

Ps : Are you aware of KMS ECU's , the are pretty visible with the BMW guys ,but not so much with the Porsche Marque that I can tell.
The PO advised excellent ecu reliability over his five – six year ownership, so I'm hoping to continue the string with it .

More to follow.

[Steve@Rennsport]

Originally Posted by betterair

Ps : Are you aware of KMS ECU's , the are pretty visible with the BMW guys ,but not so much with the Porsche Marque that I can tell.
The PO advised excellent ecu reliability over his five – six year ownership, so I'm hoping to continue the string with it .

More to follow.

I'm aware of KMS, but we do not use those.

We use Motec exclusively for its features, quality, reliability and tuneability. M84 is our preferred one except for special apps which get M600.

[betterair]

Well,here's the problem...... no. 3 intake head fracture and dropped valve guide.

To recap ,engine had maybe 5 k track miles when this happened .At that time,heads were rebuilt w ti caps and hd springs ,rs spec cams and redline bumped to 6800 with the new KMS itb/ecu upgrade.

So,was guide cocked when it was rebuilt 5K mi ago,or is this just an isolated stress fracture on a bad head casting.Another contributing factor may be in part , a O2 sensor failure and resultant flooded cyl, temperature shock ,when the ecu sensed a lean condition.
Make Sense?
The Symptom was a volumes of white exhaust smoke all over the track when it let loose.Now my car is known as ZIKA THE MOSKITO KILLER. fortunately all the oil stayed in IT.

[txhokie4life]

how did it hold leak down and compression with that?

[faapgar]

Obviously the valve was closed & leakdown will never show a guide issue.Fred

[betterair]

leakdown/comp numbers were given to me when i bought the car.
I did not confirm them before teardown.

[Steve@Rennsport]

Whoever did the heads didn't know how to properly remove and replace the guides, hence the damage. This doesn't affect leakdown numbers unless the guide is not centered correctly.

[m42racer]

The amount of guide shown in the port does seem to indicate it has dropped downwards towards the valve head. If the guide is low enough it could hold the valve off the seat and lower the comp numbers and give poor leak down numbers.

How this happened is hard to say. Typically to break the flared part that protrudes into the port requires the guide OD size to be wrong. A lot of the guide is already in the bore before it reaches this part of the head. Guides are typically 0.3150" std size with some +0.0020" as an oversize. This could have been the cause, but measuring the guide would tell.

Is then head Ok? Have it crack checked to see. Crack check them all. In fact, probably be good call to remove all of the guides to make sure they are all OK. Removing this part of the head will not cause an issue. The guide is supported with enough material. This is more of a deflector to help guide the air around the valve stem.

Make sure you know who is doing the work and they know how to do this work. This is the difference between production level machine work and high end, low tolerance work. Production shops will hammer the guides out and hammer them back in. Most of the time you get away with short cuts, but when you don't, it comes back and bites hard.

[Trackrash]

A cheap mechanic will cost you money.

[betterair]

"A cheap mechanic will cost you money".

Amen to that, except I am the cheap mechanic .... (who very well knows his limitations)

M42,the valve guide did drop to the base of the valve backside. The peculiar thing is that it ran like a top for the last 5 yrs (which was the last top end rebuild ).So,If the guide o.d. was to the high side of tolerance,you would think it would have failed quicker.
On the other hand, the heat/lean condition from the failed o2 sensor ,could have been (probably was )the last straw.
Great input -thanks.
Without a doubt ,I will use the best technical resources I know of to bring this engine back to spec.
Great advise on evaluating ALL 6 head assys.It will be done,since I do not wan to tear this engine down again in another 5 yrs.

[Trackrash]

So The guide was moving? That's interesting....

I just replaced the guides in my motor and found that the new guides were not consistent in diameter. I mic'ed one and it was in spec. I mistakenly assumed they were all the same.

It wasn't until on the second guide not going in all the way did I notice the problem.

I realized some were a little (1 to 2 thou) larger than spec. I then needed to machine them to size to match each bore in the heads. Never had to do that before with "standard" size guides.

Let us know what you find out when you get your heads apart.

[Trackrash]

BTW. The guides I used have a lip that at prevents them from being installed too deep. Maybe the 3,6 guides don't have that feature?