BC

Plastigauge can be used, but I think the point is that you must also properly torque the rods with the bearings in, and use the bore gauge, as well as measure the journals on each side, per each numbered rod.

ptuomov

I think it's very easy to mismeasure clearances with a micrometer as well. Wrong anvil, different temperature measurement tools and components, or just good old-fashioned inability to read a micrometer correctly. (They teach reading a micrometer in 7th grade of the Finnish school system, at least used to teach...)

Charles Parkinson

Alex,
Saying Plastigauge is completely crap is probably not fair as I think it depends on the application....it is fine for the situation anticipated in the WSM... a dealership mechanic replacing bearings on a road car as quickly as possible before the service manager bellows at him to move on to the next job.

However, when you change application to preparing a race engine, particularly one that is known to be sensitive to bearing clearance issues, then Plastigauge isn't ideal.

Also, as Tuomo pointed out, micrometers can be less than user friendly. So, there is a role for Plastigauge, just not in race engine prep.

blown 87

Every bearing in every motor gets plastigauged before the last time I put it together, after it has been miked, it will show things a mike wont in some cases if used right.

justaguy

Sorry to hear of your engine failure. I feel your pain. Good luck with your next motor. More oil and bigger quality lines on a shorter run can't hurt either. All good advice.

Mark K is a very good driver who's style tends to preserve his equipment. I think that we all agree he is Witout a doubt the exception when it comes to track 928's.

smiffypr

I've had a thought which would avoid a repeat of this failure if it was lack of oil to the pressure pump input.
If you added a connection for a vacuum gauge at the inlet to the pump, you would see what the pressure drop was when the engine was running at real temperatures and revs, and get lots of warning if the gauge started heading towards total vacuum. You would get this warning before the oil pressure gauge showed anything abnormal.

danglerb

Lack of oil doesn't always mean vacuum, could be air at normal pressure, which would be higher than oil that would have some pressure drop at the input from the flow.

smiffypr

True, I was thinking of the situation where the oil flow is to strangled. Of course the vacuum gauge would show less than normal vacuum when the oil feed was filled with air, so it might still give a noticeable indication of what is happening.

mark kibort

It proves that Im running faster and pulling more Gs, and certainly not reserving redline for special occasions. I have had no issues with motor bearing failures.
what is a GT4 over there accross the pond?

Cheburator

GT4 is GT4 every where. A 470bhp Aston Martin GT4, a 440 BHP E92 M3, Mustang GTs, GT3 Cup cars, 400 bhp E36/46 M3s

Your point that you are running faster? Faster than who? It does not make a lot of sense I am afraid. Last time I checked r888s and cups are E marked street legal tyres. The GT4 boys and you are running slicks


Or are we gonna get into the realms of ***** waving? My car pulls more G than yours and such like. Oh, the irony...

mark kibort

The point is, Im running fast enough that if there was an engine issue, I would have seen problems. I dont believe you are running faster than me, expecially with the non-stroker engine and smaller tires. I dont care, faster, slower, it doesnt matter, what I am doing is showing that the engine can survive and be run at its limit. thats all. Now, you think you are faster?

Ill take the top cup car drivers in the world in your side of the pond and compare their times to yours as a competition. Not just astons, cup cars and mustang GTs, e36/46s driven by who knows. pick a track, give me Dirk mullers time at that track in a 2010 cup car in the series on slicks.
the point there was to just compare relative speed on the track. certainly if you are running R888s and have a stock GT engine, you will be slower and for some reason, im not burning bearings, thats the only point. yes, and im ONLY on the DOT tires like the R888 and have never been on slicks in my cars, others, yes, mine, no.

now, you are running 8% of the top pro drivers in GT3 cup cars at a track near you? I would be interested to see this, and very proud of you if you were on R888s and a stock engined powered GT racer.

mk

Cheburator

Mark if you actually read in depth what I posted before I am not running a stock GT engine. Far from it - I run a hot roded GTS lump with all the tricks sans ITBs. It makes enough power that the car walks away from 400bhp E92M3s and stays with the 505Bhp E60 M5s. Make of that what you want.

I give up arguing simple stats with you. Basically we cannot build engines, we cannot drive them either and we are slow. And the 928 engine is ultra bulletproof even if taken to thr red line provided you put Amsoil in it.

slate blue

Given this some thought, what is known is the capacity of the 928 oil pump is 3 times optimal in terms of volume, i.e the supply side supplies 3 times the "optimal' required oil. Then the oil tank in your car is half what is optimal according to Joe Gibbs Racing (JGR). They say that their oil in the tank circulates every thirty seconds. Yours Alex circulates every 6 to 7 seconds. You only need to be in the 6,500 to 7,000 rpm for maybe 5 to 10 seconds and there could be trouble. JGR says you need the oil in the tank as long as possible. Maybe this explains some of the cavitation issues and there wont be enough time for the air to get out. Here's their take on lubrication.

http://www.joegibbsdriven.com/traini...ch/JGR_RET.pdf

Greg

928mac

Hello gentleman,

I am starting to see some reoccurring engine failures happen on Rennlist.

Everyone seems to have different ideas on how to stop their problem from happening again including one poster saying that he changes his bearing once a year.

Now I drive my relatively stock 89 on the street but I drive it hard.
I slowly warm it up before it revs over 3g but then it normally will see 6300 in every 1st and 2nd gear shift.
I will drive down the street revving 4 or 5000 in 1st or 2nd just because (exh tone and attention)

should I be looking at the con rod bearings every year?

Brad

James Bailey

Brad you are not anywhere near as hard on the engine as if you were racing, Lateral g forces high engine temps ...your trans on the other hand might like you to give it a break before it gives you one Roaring around in 1 , 2nd at 4,000-5,000 will easily wear out the engine in 1/3 the time not to mention fuel economy. Perhaps you can find some other way to get attention.