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Mark

  • Karma: +0/-0
Plastigage accuracy?
« on: July 26, 2008, 07:54:13 AM »
Started putting the motor (468" BBC) together last night for the kid's boat.  The main journal clearances checked out at 0.0015" - 0.0017" which is tight.  Who has used Plasigage recently, is it reliable, or is it now made offshore and is crap?

Rely on the machine shop to have done their job right?  Close my eyes and go forward?

A set of inside/outside micrometers is around $1,000.00 through MSC or McMaster-Carr, that's kinda out for a once every four or five year activity.

Thanks, Mark
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2009 28' Magic Deckboat, 540 Pfaff
1974 20' Spectra, blown/EFI 468 BBC, 12JC
1979 19' Spectra, twin turbo/EFI 468 BBC, 12JC

GT Jets

  • Karma: +192/-0
Re: Plastigage accuracy?
« Reply #1 on: July 26, 2008, 08:15:48 AM »
Hey Mark, This post popped up as I sat down do do some work :banghead: I like plastiguage, but only for double checks, if its showing .0015 at all, I would suspect a little tight, what was the temperature of the plastigauge? Too warm and the stuff gets "loose" and will give you a tight #, too cold and it will read loose (try to keep it at about 70-75*F)

You can buy an inexpensive set of mics at like Harbor Freight, I think I recently paid about $60 for a set of three (1", 2", 3" and the standards for checking accuracy, then you buy the snap guages for another $20 for inside, they even have Mitutoyo mics at a pretty good deal, I've used them for years and buy a new set every couple of years because I keep them on my service truck and they get pretty beat up (I am an HVAC/Mechanical technician). If anything I would grab the crank and head to the machinist with your concerns, it should be even a little loose if its going into a jetboat without thermostat contol, (its difficult to control the oil temp) I would look for about .0022"-.0024" on the mains and similar on the rods, but I err. on the side of stock on the rods (.0021"-.0022").  Had you come up with a # of .0022" I would have said "run it", but definately sounds a little tight to me (the .0015" has me spooked)

I hope this was helpful, I know someone else will pipe in, Good Luck, GT.
« Last Edit: July 26, 2008, 09:22:48 AM by GT Jets »
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

Ralph Brunt

  • Karma: +51/-0
Re: Plastigage accuracy?
« Reply #2 on: July 26, 2008, 08:43:35 AM »
i dont like plastigauge and like gt said you can get a decent mic for a 100 bucks. general rule of thumb for jet boat motors is .001 for every inch of journal.
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CHEAP, FAST, RELIABLE...PICK 2 CANT HAVE ALL 3
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They are all fukin tasty. My long time favorite, "Dirty Dicks -beerjet-
Glasscutter, Skip, OC2  Nordie and many more nail me good every time, relentlessly, I love those guys!

Mark

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #3 on: July 26, 2008, 09:36:32 AM »
Thanks guys, and I just noticed I posted in the wrong category   :screwy:

Temp would have been in the 75F range here in the shop last night. 

The other thing I did that may have screwed up the reading was smearing some assembly lube in the upper bearing shell before setting the crank in place.  Is it possible that this could be keeping the crank from being centered?

Harbor Freight is less than a mile away.  I bought my digital 6" calipers there, but those are only good for + 5 mil accuracy.  I never considered looking to HF for a precision device but I'm running down there in a few minutes.  I'll buy the suggested snap gauge (even though I have no clue what that is right now).

Thanks again, Mark
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2009 28' Magic Deckboat, 540 Pfaff
1974 20' Spectra, blown/EFI 468 BBC, 12JC
1979 19' Spectra, twin turbo/EFI 468 BBC, 12JC

GT Jets

  • Karma: +192/-0
Re: Plastigage accuracy?
« Reply #4 on: July 26, 2008, 09:44:33 AM »
Hey Mark, definatley use plastiguage on a "dry" assembly, I only spray the crank with Amsoils MP spray (metal protector) its dry and keeps thing from rusting while your out making money to go and spend said money on something that is going to break so you can do it all over again. :screwy: The oil could have definately made up for the .0005" IMO, let us know how things turn out....

And don't worry about the section, at least we didn't thread jack someone racing or something :screwy:
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

realHawaiianJet

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #5 on: July 26, 2008, 10:15:46 AM »
I bought some mics on eBay, and they are very nice, carbide faces, 0.0001" accuracy and everything. First thing I did was check them with the gauges that came with em', then checked the gauges with a buddy's Mitutoyo mics. And everything checked out. I paid around $300 for the full range, 0"-6" and 6"-12" in mahogany plywood boxes. One of the best purchases I ever made on eBay. But, for my calipers, that I use everyday, I went with some really nice Mitutoyos w/ TiN slide surfaces, I never have to worry about whether or not they giving me a precise dimension. And if I used my mics everyday, I would have splurged on a nice set of Mitutoyo or Starrett ones.

Good luck.
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Mark

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #6 on: July 26, 2008, 09:21:58 PM »
Bought the micrometer set from Harbor Freight today, $43.95 + tax.  Double checked them and the included reference blocks against a friends Starrett.  I was amazed, they matched perfectly. 

The crank measures out at 2.740, which is perfect for a 0.010 cut.

Bolted down a main cap and torqued it to #105.  Tried to use the telescoping inside gauge that I also picked up from Harbor Freight.  It's supposed to expand to the inside diameter, then you use the outside calipers to measure it.  It's a POS that has at least 10 mils of slop in it, no way to get a reliable measurement.

Wiped all the assembly lube off the crank and repeated my earlier measurements with the Plasigage.  Still reading 0.0015.

So I've got a crank that's spot on and :

1)  A bad set of Clevite 77 bearing shells,
2)  A bad line bore,
3)  ?

Thanks, Mark
« Last Edit: July 26, 2008, 09:36:08 PM by Mark »
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2009 28' Magic Deckboat, 540 Pfaff
1974 20' Spectra, blown/EFI 468 BBC, 12JC
1979 19' Spectra, twin turbo/EFI 468 BBC, 12JC

Ralph Brunt

  • Karma: +51/-0
Re: Plastigage accuracy?
« Reply #7 on: July 26, 2008, 09:46:08 PM »
you can get .001 over or under, from king bearing i think ;)
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CHEAP, FAST, RELIABLE...PICK 2 CANT HAVE ALL 3
Quote
They are all fukin tasty. My long time favorite, "Dirty Dicks -beerjet-
Glasscutter, Skip, OC2  Nordie and many more nail me good every time, relentlessly, I love those guys!

GT Jets

  • Karma: +192/-0
Re: Plastigage accuracy?
« Reply #8 on: July 26, 2008, 09:57:50 PM »
Was the block line honed?, should not make any difference, but if the bores are out of round, woukd do some intersting stuff.

What bearing are you gauging (1,2,3 and so on) and rods and mains and are you 100% you have the right caps in the right positions? (I know, dumb question) Done that before damn did I feel slow...

There is no reason to think Clevite didn't screw up, but would be more than a little surprised.

One more, did you torque all of the main bolts, or just the one? and also, you absolutely cannot move the crank, it will leave you chasing your own ass for days.

BTW those inside gauges are a little finiky but I've had some pretty good success with them, may have gotten a bad set.
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

Mark

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #9 on: July 27, 2008, 09:29:31 AM »
The block was line honed.  For some reason the machinist reversed the #1-4 caps, but he restamped them with the new assembly order.  Cast arrow is pointing forward on caps #1-4.

I'm checking all caps including the rear main.  On #1 I also measured at 30* and 150* (90* being at the bottom of the cap).  Appears to be in round.

I'm using a 1" piece of Plastigage so I can check taper on the journals, but all are consistent.

Checked the bearing shells and they're stamped Clevite 77, A-1, .010, MB2403P

Been torquing all 4 bolts per cap to #105.

I think the block needs to go back to the machine shop on Monday unless I figure out something this morning.

Thanks for all the suggestions!

Mark
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2009 28' Magic Deckboat, 540 Pfaff
1974 20' Spectra, blown/EFI 468 BBC, 12JC
1979 19' Spectra, twin turbo/EFI 468 BBC, 12JC

GT Jets

  • Karma: +192/-0
Re: Plastigage accuracy?
« Reply #10 on: July 27, 2008, 09:33:44 AM »
The block was line honed.  For some reason the machinist reversed the #1-4 caps, but he restamped them with the new assembly order.  Cast arrow is pointing forward on caps #1-4.

I'm checking all caps including the rear main.  On #1 I also measured at 30* and 150* (90* being at the bottom of the cap).  Appears to be in round.

I'm using a 1" piece of Plastigage so I can check taper on the journals, but all are consistent.

Checked the bearing shells and they're stamped Clevite 77, A-1, .010, MB2403P

Been torquing all 4 bolts per cap to #105.

I think the block needs to go back to the machine shop on Monday unless I figure out something this morning.

Thanks for all the suggestions!

Mark
Machine shops will move caps around if there is an over-under size problem (not unusual), I would agree with having the shop take another look, beats building it twice, good luck and keep us posted...

GT
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

GT Jets

  • Karma: +192/-0
Re: Plastigage accuracy?
« Reply #11 on: July 27, 2008, 09:46:04 AM »
Machine shops will move caps around if there is an over-under size problem (not unusual), I would agree with having the shop take another look, beats building it twice, good luck and keep us posted...

GT

Also that number is for the one bearing half, do you have the "Set" number?
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

gregb

  • Karma: +1/-0
Re: Plastigage accuracy?
« Reply #12 on: July 27, 2008, 09:47:47 AM »
Clevite also makes the bearings in .001 oversize.
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Mark

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #13 on: July 27, 2008, 10:21:25 AM »
The same number, MB2403P, is stamped on the upper shell as well as a date code, the size at 0.010, Clevite 77, and the A1.  Date codes are different for the upper and lowers.

I don't have the package any more but the order sheet from Summit reads CLE-MS829P10    http://store.summitracing.com/partdetail.asp?part=CLE%2DMS829P10&autoview=sku

Any ideas on what the "A-1" stands for ? 

Looks like we finish off the trailer wheel bearings and wiring today and let the motor go until next weekend.

Cheers, Mark
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2009 28' Magic Deckboat, 540 Pfaff
1974 20' Spectra, blown/EFI 468 BBC, 12JC
1979 19' Spectra, twin turbo/EFI 468 BBC, 12JC

enginedoctor

  • Karma: +7/-0
Re: Plastigage accuracy?
« Reply #14 on: July 27, 2008, 12:47:35 PM »
Look into a Good "dial bore guage"....
  • Boat #1: 1970 Horizon Cheby powered Jet
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Mark

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #15 on: August 01, 2008, 05:10:36 PM »
It turned out to be a bad line bore from the machine shop, 0.0015 undersized.  Hopefully no more problems from here on   :-\.

Thanks again for all the suggestions.

Chers, Mark
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2009 28' Magic Deckboat, 540 Pfaff
1974 20' Spectra, blown/EFI 468 BBC, 12JC
1979 19' Spectra, twin turbo/EFI 468 BBC, 12JC

AA/Paul

  • Karma: +0/-0
Re: Plastigage accuracy?
« Reply #16 on: August 04, 2008, 12:21:03 PM »
Great catch!!!!
Never assume..... KNOW !!!!
 King bearings are my prefered.
A cheapie , 60 bucks or so , bore gage, set with the mics , double check.
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Redneck Punk
If illegal aliens are undocumented migrant workers.....then Drug dealers are unlicensed pharmacys

If ya can't fix it with a hammer....It's an electrical problem!

enginedoctor

  • Karma: +7/-0
Re: Plastigage accuracy?
« Reply #17 on: August 05, 2008, 06:37:44 PM »
Plastiguage is not  accurate....In my opinion :)
  • Boat #1: 1970 Horizon Cheby powered Jet
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