OK we're into semantics at this point. Hone, bore...whatever you want to call it...the bore is round again and within a standard bearing spec. I picked up some plastigauge and will dry assemble the case and measure the clearances as well. That should speak to any runout end to end and clear up any remaining doubts in our minds about the oiling clearances. Let's get this thread back on topic and stick to oiling - start a new thread or revive one of the many old ones if you wish to beat the magnesium horse.

David
Check the plugs in the crank. Sometinmes people remove the plugs, where the crank was drilled for oil passages, to clean the oil passages and forget to replace them. Seems silly but I have seen it done.
Hope that helps,
neil

I happen to notice that at least a few of the plugs were in last night but I didn't actually do a concerted effor to make sure they were all in

T - 42 hours and counting.........

Hello, Dave.

The oiling pressure is in fact the main problem if the bearing housing is oversize, and also there is a problem with oil feed into the crank pins, especially at the back end of the crank of course.

The pressure just leaks away with oil literally spurting out between the shell and housing.

Because the only thing that seals this is bearing crush.

I would not be at all confident that plastigage would pick this up at all.. this is not what it was designed to do..


There is much more than a sematic difference between boring and honing...

Are you saying your wrench actually used a line boring tool?

If so, I'd be interested to know what the least amount of metal he thinks he can remove with the lightest possible cut with such a tool...I'd say just a clean up cut would be a half of a thou.. ie one thou on diameter..

Kind regards
David

David I have to respectfully disagree to that..

My old motor (different EVERYTHING) was soo far out of wack that both the case and crank are trash and they still showed nominal oil pressure right up until it died (from metal in the oil).

Second the EXACT reason plastigauge is made is just for this reason, to measure the clearances of bearings.

Hello, Tim.

Platigage is made to give the bearing clearance, not the housing clearance.

That is exactly the point.

I am suggesting, respectfully, that if a boring tool has been used, then the diameter of the housing is over spec.

Kind regards
David

I guess my points are not being clearly expressed. A shame, as I usually get high marks on communication skills.

The bearing housings are in spec- I've said this several times. We've triple-checked this quantitatively, and qualitatively the shells are a good tight fit in the webs. We have ruled out the loss of pressure from between the shells and housing - yes, this was specifically considered, examined, and cleared, by a professional with 20+ years of experience. I do not know the specifics of how much material he removed, what specific tool he used, etc. etc. I know he stands behind the work and the case.

As noted in the previous posts, we identified three good strong contenders for causes to our problem. All three have been addressed and we are assembling.

Neil- good call on the plugs! I'm in the middle of working on the crank now - will check immediately...

Hello, Dave.

How do you check the shell fit, please?

Kind regards
David

Purely qualitatively, ie, the shells are a nice light press fit and don't simply fall out of the case.

But, as I may have mentioned once or twice, we also ran a dial bore gauge down the case and saw it was in spec.

Right, Dave.

If the shells were simple circular rings, this would be useful.

I do it on VW engines for example.

But as you know, they have tabs.

And they are not made as semicircles at all..they are designed to crush into a circle.

I have plug bore guages which are made to the size of the bore, and this will give a useful indication of likely crush.

I stand by my opinion that any machining of an oval bore will leave it oversize and out of spec... why not ask the questions I have posed and see his response?

I have seen too many instances where I have been told the case is on size to be trusting of Anyone!

Where I agree with you is that the shell slop is not likely to be the only problem, and I note in particular the relief valve problem.

Was this case looked at by the wrench and this missed?

I run a purpose-made lapping tool down the valve holes as routine..they are often corroded or scored and will cause the valve to stick...



Kind regards
David

Not sure that repeating it a fifth time is going to cause you to pay attention, but the bore has been measured 3 times and is in spec. Cheers!

Sorry, Dave.

It's never easy being the bearer of probably bad news...even when it saves money!

I have heard that "well in spec" SOOO many times before, and my plug guage just rattles round the bores..

Guess I'm just getting old..

Kind regards
David

Just a suggestion.

If you have access to a very basic lathe, it will take you less than 30 minutes to make a nicely finished tapered plug guage of 62mm OD...

And Ifin I'm right, you will have the dubious pleasure of putting your wrench straight..

Kind regards
david

david,
While this is a street motor my machinist has the distinction of not just building HUNDREDS of motors but race winning ones at that including several monster motors (700+ twin turbo's), carrera 4 cam motors, 962 motors and even a 908. Unless you come out to say you're Jerry Woods or Walt @ CE I've got 1000x more trust in my machinist than a random person who I've never seen in my life

If he says my bore is STD is is STD. Period, end of story no questions asked. I'm sorry you're a total unbeliver but after checking this case THREE TIMES you can't tell me it's not STD.

As far as I'm concerned this thread is closed unless someone has something new to say about something OTHER THAN MY MAIN BORE.

Hello, Tim.

I stand to be corrected like anyone else.
I have got it wrong many many times too.

And, more relevantly, I know no-one, however exalted, who does not get it wrong.. there are just too many Murphy's Law variants in engineering..

But lets just examine what we know from the posts.
1. The bores were oval, sufficient to show up on some form of measuring device, and to need repair.
2 They have been machined to be circular.
It is likely that at least 0.5 thou would be removed to do this, probably more.
3. The maximum material that can be removed from even a standard Bore is less than 0.4 thou before it goes out of spec.
4. As far as We know, the only instrument which has been used to check is a dial type bore guage.

Any one who has never seen these go out of spec, they have just not been around long...adimttedly, these should always be calibrated using a Standard Ring before every use.. do you know if this was done?
a plug guage is much more reliable, as well as easier to use.

I'm sorry. the story just is too internally contradictory to be immediately accepted as Gospel..

And, I agree, once again, this is not likely the only problem if there was no oil pressure at all.. my money is that the relief valve bore problem was not picked up on checking...

Kind regards
David

Alrighty, we just turned the last nut on the longblock, we're firing it up again tomorrow. How about a collective crossing of fingers...thanks!

What was the outcome of this?

-Wayne

We tried to fire it up but didn't get much ignition. I haven't had time to really diagnose it yet. I did get 10 psi of oil pressure just from cranking so I think we might have it wipped.

Tim let us know how its coming along ive been xing my fingers for ya.