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Thread: Turbo Engine Re-Build
02-07-2020, 12:40 PM #106
Let see now, what was it that Forrest Gump said,??
Oh yea, "Engine building (sic) is like a box of chocolates, you never know what you will get"
02-07-2020, 02:20 PM #107
On a side note, is anyone still using plasti-gage to check bearing tolerances? By using math on the crank and rod journals and bearings it seems obsolete, but I just wasn’t sure this old school trick is still being used.
02-07-2020, 07:47 PM #108
02-07-2020, 08:26 PM #109
02-07-2020, 09:13 PM #110
02-07-2020, 09:49 PM #111
I used the red on the mains since it had the tightest tolerance I have red and green. the 4 outside measured in at .002 and the very center was closer to .003.
02-08-2020, 03:02 AM #112
To show that I actual read other threads and am not the only star in the universe, I recall others with similar questions and can state these facts.
I believe the called out tolerance from one thread, quoting Mr. Mihovetz “keep that sh*t tight” .001-.0015. While I have no experience with the aluminum blocks, the cast blocks called out a different tolerance. I also used a slight film of 30w motor oil, as per the Hypand rebuild book during the tolerance process.
At this point, I know I’m having to loosen all the main studs to gain more thread under the nut. I also have another plastigage set that reads lower tolerances. The red I used is .002 to .006 and the green is .001-.003.
I think this would be a good opportunity to pull the crank back out of the block, clean off all oil on the bearing surfaces, and re-check tolerance using the finer plastigage. I feel like I had 2 fatal flaws this past time.
1. Thin film of oil on bearing tolerances while checking, there is an opportunity for it to skew results.
2. Because I was unaware of the tighter aluminum tolerances, I used the cast specs to select the plastigage.
My only fears now are these studs have been torqued twice now, this will be the third time to re-check, and 4th time to final reassemble. I have a fear that there will be an amount of stretch that plays in a factor.
My other fear is the use of assembly lube versus straight weight oil, there will be an amount of turning to be done with the crank in terms of timing and torquing rods, and it may be a few weeks before is time to crank and fire, so I want the insurance of the assembly lube. At the same time, I don’t want a quart of it clogging everything up when it’s time to break in.
Sorry for the novel, but although I have experience with building engines, I’ve never built one to the high precision and tolerances of this caliber (if that’s not already obvious) I hope these questions aren’t redundant and I’ve been searching all the build threads to answer what I can! I hope erring on the side of caution will do me better in the long run!
02-08-2020, 03:40 AM #113
You want to shoot for a 0.0018" to 0.0025" clearance, Matt. While you can run up to 0.003" relatively safely you begin to change the delivery of lubricant to different parts of the engine.
Think of the oil system as a controlled leak. Whenever you increase clearance at one of the leak points you increase oil flow at that point at the expense of oil flow elsewhere in the engine. This can be mitigated by the use of something like a GT500 pump (which I would recommend no matter what) because the pump has such a significant capacity reserve that a small increase in flow at one location will not impact others, the pump just flows that much oil.
Here is a pretty good video from Melling on the effect of bearing clearances on oil flow, click here=> https://www.youtube.com/watch?v=tjCIuJwnVqU
Once the rings are seated be sure to use Prolong. When you assemble the engine put a drop, no more, of Prolong on each cam bearing journal and smear it around the journal.
Last edited by eschaider; 02-08-2020 at 03:43 AM. Reason: Spelling and Grammar
02-08-2020, 08:27 AM #114
Ed, I’ve got that pump from boundary already as per your advice, just wanted to see if my game plan seems good or unnecessary.
02-08-2020, 11:52 AM #115
I had forgotten you were using that pump, Matt. You are good to go. The extra clearance on #3 won't make a difference with that pump. A good place to be is over 0.002" and under 0.003". The rule of thumb is 0.001" per inch of journal diameter. Our mains are 2.650 diameter journals.
02-08-2020, 07:42 PM #116
Re-torqued studs today with at least 2 threads showing, trust me I was holding my breath the whole time!
So not the mains are tackled, until I have to do the pickup tube. I’m going to attempt to brake clean, and atf wipe a cylinder, apply total seal quick seal and try my hand at installing rods. I plan on using the green plastigage dry first, then cleaning off and assembly lube and install. Wish me luck!
02-09-2020, 12:18 AM #117
Looking good, Matt. Make sure you have two threads above the top of each nut.
02-09-2020, 07:48 AM #118
Ed, I know you said one end of the rod should have a heavier chamfer on the big end. I just can’t differentiate. I’m going to go with implicitly sake and make sure all the labeled numbers on the rod facing forwards.
Also like you stated, I plan on putting top ring at 12, second ring at six, the top oil rail at 10 expander 7 bottom rail at 4 and support rain at 2. Should give me even space between all rings.
02-09-2020, 08:13 AM #119
Crank end play measured at .006 so I believe I am well within spec there.
02-09-2020, 09:12 AM #120
With the bearings installed, still can’t deduce a side...