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petrol punk Samba Member
Joined: August 21, 2007 Posts: 973 Location: Las Vegas, NV
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Posted: Sun Apr 24, 2011 7:34 pm Post subject: Rod is Tight on the Crank |
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I've started assembling the bottom end of my stock 36hp, and I've run into a problem of one of the rods binding up once I torque it down. I double checked the oil clearance and it comes out to .0015" and tried swapping rod bearings and switching it between rod journals and the problem persists. I'm trying to think of how to solve this problem. Anybody got any ideas on how to alleviate this problem? My only idea is to hone the rod big end to open it up but then I think my oil clearance would open. Maybe I just need a new rod? |
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Bashr52 Samba Member
Joined: July 16, 2006 Posts: 5666 Location: On an island in VA
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Posted: Sun Apr 24, 2011 8:43 pm Post subject: |
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Its just the one? Could the rod or crank be slightly our of round? |
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petrol punk Samba Member
Joined: August 21, 2007 Posts: 973 Location: Las Vegas, NV
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Posted: Sun Apr 24, 2011 10:51 pm Post subject: |
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Yeah, just one. I tried swapping the rods around the different journals and the journals seems fine, the problem only follows the one rod. I tried bolting up one of my brother's rods and it felt alright. |
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Snort Samba Member
Joined: April 02, 2005 Posts: 1957 Location: Seattle, WA
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Posted: Mon Apr 25, 2011 6:39 am Post subject: |
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I had to re-size my rods on my 36hp after they came back from balancing. There's just not a lot of metal there on the rod cap and they can distort quite easily apparently. |
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avus Samba Member
Joined: November 11, 2005 Posts: 268 Location: Drain, Oregon
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Posted: Mon Apr 25, 2011 5:06 pm Post subject: Re: Rod is Tight on the Crank |
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petrol punk wrote: |
I've started assembling the bottom end of my stock 36hp, and I've run into a problem of one of the rods binding up once I torque it down. I double checked the oil clearance and it comes out to .0015" and tried swapping rod bearings and switching it between rod journals and the problem persists. I'm trying to think of how to solve this problem. Anybody got any ideas on how to alleviate this problem? My only idea is to hone the rod big end to open it up but then I think my oil clearance would open. Maybe I just need a new rod? |
I'll probably catch some crap for this, but it's worked for me: The rod bolts align the rod and cap on 36 and 40 hp VW's. There can be slop in the fit of the threads and between the bolt and the hole in the cap--sometimes enough to cause the bearing halves to misalign.
Try this: 1 snug the rod bolts evenly to where the rod just starts to bind on the crank. 2 With a small hammer, smack the connecting rod on the parting line, perpendicular to the rod bolt, toward the crank pin, from each side. 3. If this loosens up the bearing, torque the cap to spec and spin it around a few times to see if anything changes. If it's still sticky, admit it--you need to replace or resize the connecting rod. If it turns freely, it's a good idea to take it back apart and check for serious shiny spots on the bearing. If it's cool repeat steps.
Fire away! |
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hazetguy Samba Member
Joined: April 06, 2001 Posts: 10773 Location: iT StiNgeD iTseLf tO dEAd
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Posted: Mon Apr 25, 2011 7:04 pm Post subject: |
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i've done the above method with success. also, I forget who told me or where I read that a trick to do when assembling 25hp, 36hp, and early 40hp rods (non self aligining), is to fit feeler gauges between the rod and crank. It takes away the "wiggle" space of the rod and cap, so that the rod stays in alignment while torquing the rod bolts. It seems to work very well.
_________________ thebucket: I invested in hoodride, now DBD won't return my call?
hazetguy: invested?
thebucket: Yeah Haze, its where people put money into a company in hopes of a return on their money |
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avus Samba Member
Joined: November 11, 2005 Posts: 268 Location: Drain, Oregon
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Posted: Tue Apr 26, 2011 7:52 am Post subject: rod cap alignment |
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hazetguy wrote: |
i've done the above method with success. also, I forget who told me or where I read that a trick to do when assembling 25hp, 36hp, and early 40hp rods (non self aligining), is to fit feeler gauges between the rod and crank. It takes away the "wiggle" space of the rod and cap, so that the rod stays in alignment while torquing the rod bolts. It seems to work very well. |
I like. This would minimize axial misalignment that could affect side clearance binding. Good trick. |
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Bart Dunn Samba Consiglieri
Joined: May 09, 2004 Posts: 2354 Location: Sea level (Mid Atlantic)
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Posted: Tue Apr 26, 2011 3:22 pm Post subject: |
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Make sure there are no burrs under the rod bearings, too. They can hide close to the edges where the machining is done, or there can also be a burr between the rod and the cap--same thing, sort of hiding along the edge. _________________ Not enough car seats fit into my:
'58 Beetle convertible
'58 Beetle sedan |
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Matthew Tolbert Samba Member
Joined: March 27, 2004 Posts: 706 Location: Georgia
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Posted: Thu Aug 06, 2015 7:55 am Post subject: |
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Bringing back this old thread because I had the same issue with one of my rebuilt rods I got from rimco. When I first torqued it down it would bind in a couple of places so I took it apart and there are some shiny spots on the bearings only on the NON tang end of each. I found this thread and was able to get it moving freely by tapping the rod like mentioned and I also found some very small burrs at the parting line that I sanded down. My question is are the bearings on that rod ruined and need replacing? I'd hate to have to buy another set and wait for them but will if necessary. _________________ Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S |
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Mr. Motorhead Mad Scientist
Joined: January 06, 2004 Posts: 717 Location: Practitioner of 36hp alchemy
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Matthew Tolbert Samba Member
Joined: March 27, 2004 Posts: 706 Location: Georgia
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Posted: Thu Aug 06, 2015 3:28 pm Post subject: |
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Yes the rod moves perfectly now. That's good to here about the bearings. _________________ Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S |
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akomjathy Samba Member
Joined: October 15, 2004 Posts: 208
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Posted: Thu Aug 20, 2015 2:15 pm Post subject: |
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I have a problem with one of my stock rods in my freshly rebuilt 40 HP engine. It seems the rod hits the crankshaft when turning around the engine. It knocks and has an ugly noise. It makes in one point on the 3rd cylinder, when it goes to the top direction. The piston doesn't touch the head. Here is a video:
http://youtu.be/kJkbwYni4Uc
What do you think? The cranshaft is a standard size one, with very low mile. I put NOS vw bearings and NOS Kolbenschmidt rod bearings. The case is perfect. |
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Matthew Tolbert Samba Member
Joined: March 27, 2004 Posts: 706 Location: Georgia
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Posted: Thu Aug 20, 2015 5:19 pm Post subject: |
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Did it turn free when it was just a short block? Is the cam indexed correctly? Take the rockers off and try to turn it. May be hitting a valve. _________________ Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S |
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akomjathy Samba Member
Joined: October 15, 2004 Posts: 208
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Posted: Sat Aug 22, 2015 1:36 pm Post subject: |
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I took off the rockers already. The knocking is on, when there are no lifters in the engine case, too. For sure the rod hits the crankshaft. I stressed the back side of the rod to the crankshaft side with a big screwdriver and there is no knock!! Here is a pic:
Matthew Tolbert wrote: |
Did it turn free when it was just a short block? Is the cam indexed correctly? Take the rockers off and try to turn it. May be hitting a valve. |
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