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CSEBug
Samba Member
Joined: August 26, 2013
Posts: 63
Location: Pennsylvania
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 Posted: Tue Apr 21, 2015 1:40 pm Post subject: Connecting Rods Tight. What gives? |
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Hey guys started to do a mock up/ checking clearances and already ran into a problem. When installing my rods on the crank they are tight on every journal, meaning they will not spin freely at all. The #3 journal is the worst while #2 seems to be the closest to normal but still has a tight spot.
Specs:
69mm DPR c/w crank .010 under
Scat 5.394 I Beam rods w/ .25mm rod bearings Torqued to 50ft/lbs per scats instructions
Heres what I have tried/checked
1) Switching rods to other journals- Didn't seem to help
2) Using an old rod from the original crank - Still hangs up the same
3) Side clearance is within spec.
4 Plasti-gauged each journal - 3 were about .0015 with one being closer to .001 Too tight?
I have an old micrometer but I have no way to calibrate it (gonna buy a new one). Checked with my caliper to get a ballpark measurement and its at least .010 under. Got pretty frustrated and stopped working after all this.
Anything else I can do or should I take it over to the machine shop and forget about it?
Ive rebuilt my fair share of 2 stroke dirtbikes but this is my first time in the VW ring.
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mcmscott
Samba Member
Joined: March 12, 2010
Posts: 4856
Location: sanger ca
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| Posted: Tue Apr 21, 2015 1:51 pm Post subject: |
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I had the same problem recently with silverline rod bearings, switched them to Mahles and all is good
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Tue Apr 21, 2015 1:53 pm Post subject: |
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torque the rods without bearings in them, and bring them. Bring the crank, and bearings too.
Rod ID should be 2.2758-2.2764 |
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CSEBug
Samba Member
Joined: August 26, 2013
Posts: 63
Location: Pennsylvania
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| Posted: Tue Apr 21, 2015 2:22 pm Post subject: |
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| mcmscott wrote: |
| I had the same problem recently with silverline rod bearings, switched them to Mahles and all is good |
Yea I am using silverline rod, bearings. Hmmm. Maybe ill buy a different set. |
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CSEBug
Samba Member
Joined: August 26, 2013
Posts: 63
Location: Pennsylvania
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| Posted: Tue Apr 21, 2015 2:29 pm Post subject: |
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| modok wrote: |
torque the rods without bearings in them, and bring them. Bring the crank, and bearings too.
Rod ID should be 2.2758-2.2764 |
Modok, thanks again for the help. If a different set of bearings doesnt help I assume any machine shop would be ok right? Closest VW place is over an hour away. Do I just give them everything with the clearences I need and say make it work? |
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mark tucker
Samba Member
Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Tue Apr 21, 2015 2:46 pm Post subject: |
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| look to be sure the tang on the bearing isnt hanging up in the rod tang slot,if it does it will pinch and grab the crank.(as in the bearing tang is wider than the rod,or the forming of the tang leaves a portion raised so it dosent seat in the rod.mightneed to file a little in the coprrner of the rod. |
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michla
Samba Member
Joined: January 17, 2003
Posts: 331
Location: Wasilla, AK (yes, there's drag racing up here !)
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| Posted: Tue Apr 21, 2015 3:05 pm Post subject: |
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| mark tucker wrote: |
| look to be sure the tang on the bearing isnt hanging up in the rod tang slot,if it does it will pinch and grab the crank. |
I was going to elude to the orientation of the rod caps to the rod itself--you're sure you have them oriented correctly, right? Some rod manufacturers stipulate the tangs of each rod half be mated together on the same side of the rod as assembled, some stipulate opposing sides of the rod.
That can have a great deal of affect on the resulting bearing clearances you're seeing.
I agree with trying a different brand of bearings too. They are pricey, but Silverline is NOT known for being consistent with their bearings. You didn't mention what type of rod journals you have (VW size, Porsche, Chevy, Buick, etc) but here's a tip: those rod journals look like they could REALLY use some polishing with emory cloth to smooth them down. Rough journal surfaces spell earlier demise for bearings. You can find instructions how to polish the journals properly on the Internet, but suffice it to say, polishing the journals thoroughly will buy you maybe another .0005" clearance resulting in .200" clearance-closer to what you should really have. The machine shop can do this for you with a machine, but it will cost because machine shop labor is usually pricey with minimums.
You really do need a decent micrometer to be messing with crank journals. Too easy to err on the readings from deflection of a caliper beam and how worn it is. And there's a need to check all the crank journals for being ground properly to specification with a micrometer (0.25mm under) and you should be checking that too since it sounds like this crank is new to you. |
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CSEBug
Samba Member
Joined: August 26, 2013
Posts: 63
Location: Pennsylvania
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| Posted: Tue Apr 21, 2015 4:36 pm Post subject: |
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| Yes I kept the the caps in the same orientation, and the bolts in the same location as I received the. VW journals. |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Tue Apr 21, 2015 4:53 pm Post subject: |
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I trust DPR crank to be within tolerance, rods and bearings Do vary.
If I had the rods and bearings in hand I could size up the situation quick.
generally, I end up going with clevite rod bearings and the rods honed toward the high end of the specification, and that gives around .002" clearance. never tried silverline......, but KS and mahle and clevite all run about the same thickness, tho clevites have a bit more crush and eccentricity.
There isn't anything special about VW rods, they are made of steel and have two holes just like any rod. a well equipt machine shop can do any rods.
Not sure if they are qualified? Ask them how they check alignment of a connecting rod. if the answer is: huh??? then go somewhere else  |
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satterley_sr
Samba Member
Joined: March 31, 2005
Posts: 650
Location: Belleville,MI
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| Posted: Tue Apr 21, 2015 5:13 pm Post subject: |
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Sometimes you have to whack the side of the rod with a hammer to relieve the stress. Crude but effective.
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fastfil
Samba Member
Joined: November 25, 2006
Posts: 356
Location: Sunshine Coast, AUS
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| Posted: Tue Apr 21, 2015 5:19 pm Post subject: |
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^^ When in doubt...
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mark tucker
Samba Member
Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Tue Apr 21, 2015 5:54 pm Post subject: |
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| satterley_sr wrote: |
| Sometimes you have to whack the side of the rod with a hammer to relieve the stress. Crude but effective. |
whacking your rod to re-leave stress  you can also look at the bearing to see the portion that is tight A shiney spot will usualy be there, if it's at the tang there is you issue. if it's in 2 places on the bearing with the pin at 12 oclock and a rub at 5&11 or2&8 your cap isant aligined. if you look at it you should be able to see what is rong.I have had many bearings with crap on the outer shell and that will also do this(coating,cosmoline whatever)Ive also seen new rods that were honed by a machine too fast,or with old or rong honing oil, and the steel was torn&layed over,never fine honed or inspected.my sunnen rod hone is not automated....kinda wish it was though. |
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raul arrese
Samba Member
Joined: July 23, 2006
Posts: 1329
Location: miami florida
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| Posted: Tue Apr 21, 2015 6:01 pm Post subject: |
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| mark tucker wrote: |
| satterley_sr wrote: |
| Sometimes you have to whack the side of the rod with a hammer to relieve the stress. Crude but effective. |
whacking your rod to re-leave stress you can also look at the bearing to see the portion that is tight A shiney spot will usualy be there, if it's at the tang there is you issue. if it's in 2 places on the bearing with the pin at 12 oclock and a rub at 5&11 or2&8 your cap isant aligined. if you look at it you should be able to see what is rong.I have had many bearings with crap on the outer shell and that will also do this(coating,cosmoline whatever)Ive also seen new rods that were honed by a machine too fast,or with old or rong honing oil, and the steel was torn&layed over,never fine honed or inspected.my sunnen rod hone is not automated....kinda wish it was though. |
At least you have a rod hone ... I don't : (
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[email protected]
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Location: Brew City
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Northof49
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Joined: July 22, 2013
Posts: 1759
Location: Winnipeg, Manitoba, Canada
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| Posted: Wed Apr 22, 2015 2:06 pm Post subject: |
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What is the maximum that you would hone the big end of a vw rod to, to maximize clearance? 2.2764?
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CSEBug
Samba Member
Joined: August 26, 2013
Posts: 63
Location: Pennsylvania
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| Posted: Wed Apr 22, 2015 3:33 pm Post subject: |
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| Damn roy that sucks, looks like im not the only one with this problem! Picked up a new mic today and new bearings should be here by the weekend. Ill see what that gets me. |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Wed Apr 22, 2015 4:22 pm Post subject: |
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| Northof49 wrote: |
| What is the maximum that you would hone the big end of a vw rod to, to maximize clearance? 2.2764? |
IMO, yes.
It's been like this for at least ten years, probably longer, the rod bearings tend to be tighter rather than looser.
Eagle rods, for instance, always came on the low side, so the engine builder can have the option to hone them larger or not, depending on personal preference, Cool! But with the DIY crowd I think this mainly resulted in more thrown rods, which was good for them as they sold even more.
CB's h-beams rods come honed out to about 2.276, I'm not sure about scat. |
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Bajaman65
Samba Member
Joined: January 16, 2007
Posts: 469
Location: Borrego Springs
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| Posted: Wed Apr 22, 2015 7:12 pm Post subject: |
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| modok wrote: |
| Northof49 wrote: |
| What is the maximum that you would hone the big end of a vw rod to, to maximize clearance? 2.2764? |
Eagle rods, for instance, always came on the low side, so the engine builder can have the option to hone them larger or not, depending on personal preference, Cool! But with the DIY crowd I think this mainly resulted in more thrown rods, which was good for them as they sold even more.
CB's h-beams rods come honed out to about 2.276, I'm not sure about scat. |
I bought (4) H- Beam rod sets in the last couple of months, 2 CB and 2 Scat, all four are on the big side 2.2760 - 2.2764. I am getting around .0025 oil clearance average. |
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mark tucker
Samba Member
Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Wed Apr 22, 2015 7:24 pm Post subject: |
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| he had good clearancem, witch means the bore is the right size .there is another issue. use you eyes. |
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CSEBug
Samba Member
Joined: August 26, 2013
Posts: 63
Location: Pennsylvania
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| Posted: Sat Apr 25, 2015 5:44 pm Post subject: |
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Alright guys I changed to a set of Mahle bearings. I can't beleive how tight the silverlines were. They made a huge difference. There are no more tight spots, but I still don't think they are free enough. The rod for cylinder #1 seems spot on, the rest still seem to drag a bit. Clearencas are now in between .015-.02 (closer to .015")
I made a video. The first part shows the silverlines installed. The second half is with the mahles. Let me know what you guys think.
https://www.youtube.com/watch?v=8JBCZs-e6KA&feature=youtu.be |
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