 Plastigauge mains?, how to? |
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| goose2 |
 Feb 13 2006, 05:33 PM
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#1
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Senior Member  Group: Members Posts: 976 Joined: 30-March 05 From: Eugene, Oregon Member No.: 3,847 Region Association: Pacific Northwest  |
I'd like to do a dry run on my lower end assembly to check main bearing clearances with Plastigauge. I assume I can just bolt it up and torque it down using only the main bearing saddle bolts, with no sealant, to get a reading. It's a 3.0 six. Is this correct?
Thanks, Randy |
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| Cap'n Krusty |
Feb 13 2006, 05:44 PM
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#2
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Case been align bored? Crank been turned? Measured? I see no reason to plastigauge the mains unless you reasonably suspect a problem. If you do decide to measure it that way, remember not to turn the crank when you're doing it. The Cap'n
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| goose2 |
Feb 13 2006, 11:49 PM
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#3
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Senior Member Group: Members Posts: 976 Joined: 30-March 05 From: Eugene, Oregon Member No.: 3,847 Region Association: Pacific Northwest |
Thanks for the reply. Everything measures good Cap'n...just obsessing...and want to make sure everything draws up properly before final assembly. Also want to eliminate any possibility of a bearing shell out of spec.
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| Jake Raby |
Feb 14 2006, 08:34 AM
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#4
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Plasticgage is near impossible to use on mains....
If you want to know the true running clearances, install the mains and torque the case up. drag up a dial indicating bore gauge and measure the ID of the installed bearings. Then mike the crank and subtract the crank sizes from the main bore sizes and thats the true running clearance.. Yes it takes hours and yes every engine I build gets it done- BUT I'm with the Capn' and don't think most enthusiast need to worry about it..... A good test is to plop the crank into the case with all the bearings installed and lube the crank with 20 wt oil ONLY, none of that BS assembly lube... Then torque the case up and then rotate the crank using an inch pound dial indicating torque wrench. If it takes more tha 10" pounds to rotate the crank in the case, the clearances are too tight.. If it takes less than 5" pounds to rotate it, more than likely they are loose... Thats what doing it a few thousand times will teach you.. |
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| Joe Ricard |
Feb 14 2006, 10:10 AM
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#5
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
Hey that's cool tid bit of info.
Jake are you back to regular routine now that the Magazine guys are gone. Better get to work you got some catching up to do (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) |
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| Jake Raby |
Feb 14 2006, 10:51 AM
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#6
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
I'm pretty much caught up now... magazine guys are gone and I have the baddest 2270 ever built on pump gas still sitting on the dyno as a result of the article..
You guys ALL have to get a subscription to Hot VWs, this article will be a span of 5 months and has tons of info! |
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| type47 |
Feb 14 2006, 11:55 AM
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#7
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
then do you just adjust the torque on the case bolts accordingly ? .... then the factory specs become guidelines? maybe hot vw's mag has a web site for subscriptions. i'd like to make sure i get your article. |
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| restore2seater |
Feb 14 2006, 12:57 PM
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#8
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Future 914 copilot. Group: Members Posts: 311 Joined: 30-October 04 From: Dunlap,IL Member No.: 3,037 Region Association: None |
Hot VWs |
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| Jake Raby |
Feb 14 2006, 01:06 PM
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#9
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
No! You find the issues that are creating the tightness or looseness and you measure and adjust clearances until the issue is ironed out- at this point seek the aid of a professional. Or slap it together and hope for the best! |
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| LvSteveH |
Feb 14 2006, 01:22 PM
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#10
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I put the Poor in Porsche Group: Members Posts: 1,080 Joined: 22-April 03 From: Las Vegas, Nevada Member No.: 600 |
With regard to the plastiguage issue, some of the best 911 engine builders prefer to rely on measurements instead of plastigauge. Apparently it is almost unheard of to find a quality bearing out of spec for a 911, and there was some concern about torquing the bearings then pulling it all apart again. I like Jake's idea of measuring the rotating resistance, although I don't know if a 911 would be the same as a type 4.
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| goose2 |
Feb 14 2006, 01:58 PM
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#11
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Senior Member Group: Members Posts: 976 Joined: 30-March 05 From: Eugene, Oregon Member No.: 3,847 Region Association: Pacific Northwest |
Thanks for all the good advice. I've built perhaps 100 motors over the years and always used Plastigauge as a final check on clearance. I'll admit to two facts...this is my first Porsche 6 (done some 356's though)...and I can only remember one time when Plastigauge revealed an unforseen problem. I like Jake's suggestion but wonder why it would be so difficult on a six to use the plastigauge. Obsessive as I am about motor building I'll probably do both (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)
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| Jake Raby |
Feb 14 2006, 05:20 PM
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#12
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
I would like to add that the specs I gave were for my parts with 20WT oil used as assembly lube, many things can make these vary and my numbers are only to be used as reference...
BTW- I have not used plastigage in 5+ years, "its as worthless as tits on a boar hog" with the TIV engine.... Last week time didn't allow the Hot VWs engine to be mikked upon final assembly, only mock up clearances were checked 100%, so I did the entire build "By feel" and that engine made MORE POWER than ANY 2270 ever before! People that go crazy with numbers generally get so caught up in the moment they forget the most important stuff... I have even done that! Hell, I have built an engine from used parts while being blindfolded in front of 500m people at a VW show- that was done "By feel" and the engine ran @ WOT for 5 minutes before the cam snapped in half- we killed it for fun! Here is the proof! (IMG:http://www.aircooledtechnology.com/pics/circlewagen17.jpg) |
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| Mark Henry |
Feb 14 2006, 05:24 PM
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#13
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
I've only ever used it once in 20 years of building engines
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