Dumb bearing question
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Main bearings are not round either.
Bearings are designed to crush somewhat to prevent certain types of failure. This was discovered after years of racing the sb chevy. Smokey Y. played a big part in developing bearings that crush to the correct shape and details all this in his "Power Secrets". I would only do it dis-service to try and repeat it. The point is u really can only measure bearing clearance acurrately with Plasti-Gauge as the bearing(s) have to distort under torque to yeild an accurate clearance measurement.
Yes Plasti-Gauge is the accurate way to measure main bearing clearance, but u should measure journal taper too - and with the correct tool.
Sounds like your going with your old iron - cool.
At least u know u have a good block.
Hope this helps Mr. BV,
cardo0
Yes Plasti-Gauge is the accurate way to measure main bearing clearance, but u should measure journal taper too - and with the correct tool.
Sounds like your going with your old iron - cool.
At least u know u have a good block.Hope this helps Mr. BV,
cardo0
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Add another 0 in to your wanted measurement. Those tenths up or down can give you the fluctuating psi numbers in some engines. That's 2 and 4 tenths to 2 and 7 tenths. A good crank grinder is worth what you have to pay him.
Had a guy for a while who over torqed his mic and left every journal a few tenths to bib. He also dressed his stone with a slight slope that went into the journal at the same amount of slope. He's gone now.
Had a guy for a while who over torqed his mic and left every journal a few tenths to bib. He also dressed his stone with a slight slope that went into the journal at the same amount of slope. He's gone now.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
Ok, sorry, that was probably .0024-0027.
I'll measure it with the set of standard bearings i have here and see what it comes up with.
Cardo,
Yes, i will be putting together my old block. I had my 400 checked out yesterday with a torque plate. The bores were all over the place. If they had to hone it to get it round i would have ended up with .008 clearance on the pistons.
This is not what i had in mind, but i want an engine in the car asap. The least expensive option was this. I'll have to put my old pistons and rings back in the bores. Bit dodgy as she already has slight ridge. Hopefully with the old rings she'll be fine and the rings won't hang up on the ridge.
Mean time i'll save up for the new block and build my favorite combo again.
Blockman,
I checked the main alignment best as i could, with a straight edge. Looks ok.
I'll measure it with the set of standard bearings i have here and see what it comes up with.
Cardo,
Yes, i will be putting together my old block. I had my 400 checked out yesterday with a torque plate. The bores were all over the place. If they had to hone it to get it round i would have ended up with .008 clearance on the pistons.
This is not what i had in mind, but i want an engine in the car asap. The least expensive option was this. I'll have to put my old pistons and rings back in the bores. Bit dodgy as she already has slight ridge. Hopefully with the old rings she'll be fine and the rings won't hang up on the ridge.
Mean time i'll save up for the new block and build my favorite combo again.
Blockman,
I checked the main alignment best as i could, with a straight edge. Looks ok.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
A cheap overall is where the fun really is.
A couple of suggestions. U can ridge ream to remove the ridge as is common practice for a good old overhaul. We just don't hear much of re-ringing and bearing overhauls anymore since labor has become so much more expensive than parts/engines. But in the OEM overhaul manuals they detail removing the ridge, just ball honing and reusing the pistons if clearance is something less than 0.006". I can't recall the clearance spec for TRW pistons. Yes my 1994 GEN II LT1 overhaul manual says that even for reusing the stock hypereutechtic pistons - but the clearance is a little less. OK, OK, use your bore gauge all u want (though i know a quicker method).
My next suggestion would be replace the rings - thats what they make ring land cleaning tools for. And i believe u can even purchase some larger ring sets that make up some wear clearance too but maybe not for every piston.
I do recommend replacing the rings.
TRW pistons are cheap. So if u want to change your c.r. this is the time. But we don't know what heads u plan on.
BTW u could have your 400" block sonic tested and it may be usable at 0.040" over - of course with new pistons. And a little block filler will help secure the bores at the base.
Sounds like a great plan, and u will always a spare motor too,
cardo0
But in the OEM overhaul manuals they detail removing the ridge, just ball honing and reusing the pistons if clearance is something less than 0.006". I can't recall the clearance spec for TRW pistons. Yes my 1994 GEN II LT1 overhaul manual says that even for reusing the stock hypereutechtic pistons - but the clearance is a little less. OK, OK, use your bore gauge all u want (though i know a quicker method).My next suggestion would be replace the rings - thats what they make ring land cleaning tools for. And i believe u can even purchase some larger ring sets that make up some wear clearance too but maybe not for every piston.
I do recommend replacing the rings.TRW pistons are cheap. So if u want to change your c.r. this is the time. But we don't know what heads u plan on.
BTW u could have your 400" block sonic tested and it may be usable at 0.040" over - of course with new pistons. And a little block filler will help secure the bores at the base.
Sounds like a great plan, and u will always a spare motor too,
cardo0
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Main bearings clearance is measured installed with a bore gauge. Rod bearings are measured the same way, using a rod vise. Cranks are mic'd. That's the only accurate way to measure main bearing clearance. If the correct bearing crush isn't attained, measuring the bore ID will show this quickly.
Here's an article where tested back to back, Plastigauge was off by .0016!
http://www.carcraft.com/techfaq/116_...r/viewall.html
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
Plastigauge at best is a quick check to ensure someone didn't screw up at the machine shop - that's it. If someone has no access at all to precision tools and they're doing a stock-type rebuild it's acceptable - barely. You're better off with a low-end mic and bore gauge than Plastigauge.
Main bearings clearance is measured installed with a bore gauge. Rod bearings are measured the same way, using a rod vise. Cranks are mic'd. That's the only accurate way to measure main bearing clearance. If the correct bearing crush isn't attained, measuring the bore ID will show this quickly.
Here's an article where tested back to back, Plastigauge was off by .0016!
http://www.carcraft.com/techfaq/116_...r/viewall.html
Main bearings clearance is measured installed with a bore gauge. Rod bearings are measured the same way, using a rod vise. Cranks are mic'd. That's the only accurate way to measure main bearing clearance. If the correct bearing crush isn't attained, measuring the bore ID will show this quickly.
Here's an article where tested back to back, Plastigauge was off by .0016!
http://www.carcraft.com/techfaq/116_...r/viewall.html
Go back and look at the junk bore gauge they are using!! You can not measure an out of round housing bore as rod bearings have eccentricity build into them. Using a ridgid finger bore gauge is not going to give a true reading as I have proved this many times to other engine builders. Alot of guys are suprised and didn't have a clue what was really going on and why the differance between the 2 gauges!!!
Example take a ridgid finger bore gauge and slide a .0002 feeler gauge (per say) under each finger and it will change the reading on the gauge, Now take a bore gauge like a Sunnen bore with floating fingers and put the same feeler gauges under the floating fingers and you will see the gauge will not change!!!!
Those cheap bore gauges work good for round bores but not for checking bearing clearances.
Its amazing how many guys don't understand the way a bore gauge works, Just ask the guys who work at Mahle who own F/M and clevite bearings what bore gauge should be used when checking bearing clearancesHMMMMMMM
Last edited by BLOCKMAN; Sep 27, 2011 at 10:24 PM.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
I have a peacock bore measuring gauge. It's Japanese. The guys at the shop were using Mitutoya (also Japanese and high $) The bores at least when not torqued down with the plates came at the same values i had with mine. I suppose when setup correctly in the outside mic, i can rely on the gauge being correct. It will be closer than a platigage i assume.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
I have a peacock bore measuring gauge. It's Japanese. The guys at the shop were using Mitutoya (also Japanese and high $) The bores at least when not torqued down with the plates came at the same values i had with mine. I suppose when setup correctly in the outside mic, i can rely on the gauge being correct. It will be closer than a platigage i assume.
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Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
Don't know what you mean with fingers, but it's a T, with the gauge on top, then at the bottom of the T you have 2 ball type of feelers at each end that move inward and move the gauge needle. Looks just like the Mitutoya one.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
MItutoya has some good bore gauges! As long as its not like the one in the car craft article you should be fine. Like I said they are good for measuring round bores not for checking bearing clearances.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
I wouldn't buy a bearing mic just for this. They don't just give good one's away. Inside the bearing the anvil is round and the backside is flat. Just drop in a local shop, most guys I know would mic it for you for the heck of it.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
I have ball mics and they are good for measuring the shell thickness but you need to know what the housing bore of the rod is with a bearings installed and thats where a good bore gauge comes in handy.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Plasti-Gauge has a self life.
U need to use fresh Plasti-Gauge - read the shelf date on package and use fresh package only - not something opened and sitting in the tool box from last year.
Ya, i read that Car Crap article. When i saw him using the wrong type of mic to measure journal size i could tell he was an amature playing blueprinting expert. Has anyone ever meet an mag rag publisher? I have, at Pamona swap meet and car show one year and he had a nice imitation Judge GTO. But he was a journalist - not a machinist.
cardo0
Ya, i read that Car Crap article. When i saw him using the wrong type of mic to measure journal size i could tell he was an amature playing blueprinting expert. Has anyone ever meet an mag rag publisher? I have, at Pamona swap meet and car show one year and he had a nice imitation Judge GTO. But he was a journalist - not a machinist.
cardo0
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
To come back to the clearances.
With standard size bearings installed, the bore measures 2.452 (rounded off) and clearance is way to much at .0036".
With the bearings that came out of it in, the size of the bore is 62.23 mm and the clearance .0020.
I think i need a bearing that is .0012 smaller in installed diameter (oversize) to the standard one. If i would use the H-bearings which is the correct partnumber for these ?
With standard size bearings installed, the bore measures 2.452 (rounded off) and clearance is way to much at .0036".
With the bearings that came out of it in, the size of the bore is 62.23 mm and the clearance .0020.
I think i need a bearing that is .0012 smaller in installed diameter (oversize) to the standard one. If i would use the H-bearings which is the correct partnumber for these ?
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
To come back to the clearances.
With standard size bearings installed, the bore measures 2.452 (rounded off) and clearance is way to much at .0036".
With the bearings that came out of it in, the size of the bore is 62.23 mm and the clearance .0020.
I think i need a bearing that is .0012 smaller in installed diameter (oversize) to the standard one. If i would use the H-bearings which is the correct partnumber for these ?
With standard size bearings installed, the bore measures 2.452 (rounded off) and clearance is way to much at .0036".
With the bearings that came out of it in, the size of the bore is 62.23 mm and the clearance .0020.
I think i need a bearing that is .0012 smaller in installed diameter (oversize) to the standard one. If i would use the H-bearings which is the correct partnumber for these ?
What block are you talking about!!!!
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
I'm working on my old 350 (4" bore block) and putting that back together to get my ride up and running again.
