Mike Lindsey

We are familiar with the companies that did Fluidplays machine work, engine build and where the pistons were purchased, neither of which was Lindsey Racing although we are happy to offer up some ideas.

Here are some things to think about or different possible scenarios.

Fuel Rail/Line Knock:
There has been reports of this on stock rails, and billet rails, regardless of injector size, brand and fuel line type. Should not worsen.

Cam bolt working loose:
We have seen this and it will cause the motor to loose power, and eventually the valves will collide with the pistons. Pull the front clam housing and check the gear for play (wiggle around). Check the torque on the bolt. We have seen this on solid and hydraulic lifter engines. We now "always" loctite the cam bolt as a preventative measure.

Loose Flywheel:
Will be a knocking sound, but don't think you would of made it 600 miles. Look straight up where the crank meets the flywheel and see if it's tight together. Pry on the flywheel so see if it moves.

Loosing a main or rod bearing:
May have a bearing issue. Could be a faulty line bore, mis-matched girdle, or inadequate cleaning of the crank or block prior to assembly. Drain the oil and run it through a paint filter. Get one from an auto body shop. If you are loosing a bearing, main or rod, you WILL see evidence in the oil. Even if you don't think you see anything, take the oil out in the sunlight and tilt it back and forth and look for sparkling material. Cut the oil filter apart and inspect for debris in the filter
material.

What happened to the previous motor? Spun bearing? Was everything cleaned or replaced that should of been? Oil cooler lines, oil cooler etc... That trash can go right back into a new engine if not and kill it.

Noisy or failing pistons:
When purchasing a piston from Mahle, unless you clearly specify what material you want them to make it out of, it could either be 2618 or 124 (their version of 4032). Did the shop(s) know what they were made of, and bore appropriately? The Mahle spec sheet will "not" say which forging they used. One not knowing would probably assume 4032, just because it's a Porsche 944, and the tight clearance used. Result will not be pretty. Mahle keeps a production number which they can look up and see.

1) Piston is 124 which will allow for a tighter clearance, and the shop bored the block for 2618. Since the piston isn't going to grow like a 2618, it's noisy all the time rather then just on warm up. Wouldn't expect it to worsen over time though.

2) Piston is 2618 which requires a looser clearance, and the shop bored the block for 124. Since the piston is going to grow, and there isn't the proper clearance, it starts to gaul the cylinder and possibly stick. Not sure if there is a situation where it starts to get noisy first before major failure.

Having learned your loosing power, this unfortunaly sounds like the more possible scenario if a piston issue.

3) Piston is either 2618 or 124 and was bored to loose and it's just plain noisy.

Pull the spark plugs and bore scope the cylinders, with pistons down. If you see scoring, then probably scenario 2. If clean, then 1 or 3.

Other things to think about...

The standasrd Mahle piston is symmetrical. You would have to specify a offset piston pin to get one. They put orientation arrows on the piston, even though it doesn't matter unless offset.

What oil are you running. We found RedLine for example to make engines sound looser. Very loose a matter of fact when cold or warm. Changing to Joe Gibbs or Valvoline 20/50 VR1 with our ZDDPlus ran much quieter on startup and as well as after warm up even running a 2618 piston.

Good luck Dennis!

Fluidplay

Mike, first off thanks for taking the time to jump into my nightmare...certainly appreciate the time you took to outline possible scenarios of my problem. Definitely going to check such things as; cam & crank bolts, flywheel etc... I had changed the oil & filer (VR1 20/50) at 300 miles, opened up the filter and found nothing...clean as a whistle, but to just to eliminate that possibility, I'll do it again this weekend.

I truly believe all the machine work was done very well...I may not have a great mechanical background, but I grew up in a machine shop (family owned) and know good work when I see it. I will say though I did not know about the differences in piston materials. I (excuse my ignorance) assumed the individuals I was working with would know what they had and knew how to handle it or at the very least question the application. I relied on they're expertise.

At this point, I don't really know how I could find out what these pistons are made of. I will inquire...As I mentioned the pistons used have a centered wrist pin connection to the head, where as the stock piston has an offset. This was bought up early in the game and was informed they would work and provided guidelines to boring, which were passed along to the machinist.

Again, thanks for your suggestions and support. I will let you know what I find over the next few days.
Dennis

TurboTommy

Crazy, off-the-wall suggestion:
Sometimes pulling away (and you can hear this in first gear) the twisting of the engine in the engine bay causes contact of metal parts, like exhaust hitting somewhere. Especially true if motor mounts are worn.

Fluidplay

TurboTommy- new oem mounts...figured while the engine was out it was a good time, but thanks for the idea.

Ski

When the engine was built, was the crank checked for play after the main bearings were installed? How was the head, had it been milled or did it meet spec, same for the top of the block if it had a cleaning pass.

Taking off in first gear you're getting a knock, so when you're loading the engine up?

Fluidplay

Bret- after the short block was all together the guy doing the work commented that it spun very easy. No comment regarding any concerns of having too much play. The head was rebuilt by LR. There was no mention of any machine work done, other than servicing and rebuilding it. The block deck was not touch as requested by the P-shop owner doing the work. He spec it and felt it wasn't necessary.

Yes, I only hear it when I'm just letting out the clutch in first and beginning to accelerate. There are maybe 6-8 knocks before it stops. I can't hear it in subsequent gears, but doesn't mean it's not here.

Thanks

Ski

Have you put the car on jackstands to see if it does it; maybe you or someone can isolate it from there.

Fluidplay

Not sure how I feel about crawing under the car while its running...my only other option would be to take to a local P-mechanic and have them source it out. Only problem there is they'll charge $110hr to do so. Can't afford that at this time. I may just have to get under it and probe around.

Mike Lindsey

Doing some research, with some help from others, your particular Mahle's were 124 material. Those can take factory tolerences on the skirt clearance.

Fluidplay

Mike, thanks for doing some detective work...that's some positive and hopeful news. What does that mean in the scope of things taking into account the machine work had been done correctly, I shouldn't be having any issues then. Maybe it is something as simple as a loose cam gear or worn woodruff key. I haven't had time over the last few days to get into anything due to work, but will this weekend. I'm thinking about doing a compression test on it as well. On a rebuilt motor what kind of numbers would you expect?
Thanks again.

Ballistic-Chapman

Let me know if you need some help. I am availible on Sunday. My knowledge is pretty limited but a 2nd set of hands might come in useful. Driving up won't be a problem for me.

Fluidplay

Ballistic-I may just take you up on that offer...I'll let you know. Thanks

Ski

Putting the car on jack stands and getting under it - you remove the hazards and put up some barriers - ie, take the rear wheels off and place something on the floor that is a go-no go area, like a 2x4 before you get to the CV joints, it can be done safely.

You say it gets louder when you load it up in first gear, have you listened by the bell housing with the mechanics scope? Put the scope on the S and R sensors? Have you pulled the starter and checked the PP bolts, that's pretty easy to do...just sort of baffling that it does it when you load it up. good luck

Fluidplay

well this afternoon I got a chance to work on the car...here's what we got accomplished:
First with the rear end jacked up, we started it...climbed under to listen if I could detect where the knock is coming from. From the bell housing back all sounded pretty normal. Next I put it in gear and let out the clutch, it didn't make the knocking noise!! interesting, why?

Took a stethoscope to all peripheral components i.e. alternator, PS pump, oil & H2o pump...all sounded good with no unusual bangs, bumps or "knocks". Next I listened to the cam tower, it's definitely noisier than I'd like, but not knocking. Then the head, back of the engine, oil pan, turbo area etc... No knocking at idle or throttling a little.

So we put the car down and took it for a drive...first gear take off...knock, knock, knock! W -T-F is it!!! Drove around enough to warm up the oil and did an oil & filter change straining the oil through a paint filter...absolutely nothing, filter was perfectly clean. I'll cut the filter open tomorrow at work and check it out.

Last thing we did was a compression test, I wasn't thrilled with the results... compression was low across all cylinders. #1 - 90-130, #2 - 92-134, #3 - 88 -126, #4 - 86 - 126. I blew it by not running the test again with a squirt of oil in the cylinders.

Guys, this is absolutely driving me insane. I just don't know what to do. Not having a solid background in this stuff, I'm running out of ideas/things I can do to source this knock out. Does any one have a contact for a shop that enjoys(at least willing) to work on these cars in Southern Cal? Very few Independent P-shops around here will touch a modded 951. Those that do seem to look down their noses at just about any aftermarket product out there (if it's not "Porsche OEM"...)

Thanks for any and all suggestions...

Ski

My take:

Engine is fine, compression gauges differ,car should be normal operating temp and did someone hold open the TB while you turned the car over, at least 5 times per cylinder? Oil is clean so I'd guess internals are all good.

If this was my car, was up and no noise when I placed it in gear, I think I would lean to something in the rear(making a noise with it down and loaded) but that's just a SWAG(scientific wild *** guess) not being there. Check all the CV joint bolts, check the oil cooler, if you have one, make sure it's not hitting an axle...if it was me, I'd pull the axles off and go through the process again. Was there a short shift kit or anything done to the transaxle? Did you repack/rebuild the CV joints while they were out? One other thing that's pretty easy to do is to loosen up the tranny coupler, slide it forward to disconnect the tranny and try the test again - unfortunately, process of elimination.

It's seems to be something in the driveline, when you load the car up.

Vision Motorsports, Andial, Speed Force - southern CA is a big place.