Chamfering rod bearings

Posted by: mdonohue05

Chamfering rod bearings - 07/15/12 03:34 PM

Putting 302 rod bearings in 261 chevy. Looks like the rod bearings need to be chambered to clear the crank pin filet. Has anyone done this by hand and if so what is the procedure and tools. Thanks!
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 07/15/12 03:50 PM

It needs to be done in a lathe. You will need to make a fixture from an old connecting rod. Done it many times on 250's and 292's. You also need to make sure the GMC rods also were machined with a radius back in them after they were narrowed or that will also cause you problems as well. You may also have to narrow the bearings since the GMC bearing is wider than the Stovebolts. That conversion is a little more involved than is realized.
Posted by: mdonohue05

Re: Chamfering rod bearings - 07/15/12 04:18 PM

Charlie baker did these rods for me many years ago. Just now trying to use them. I don't have access to a lathe so I guess the question is there no other method? Anyone know of someone who can do this procedure?
Posted by: Armond, II#298

Re: Chamfering rod bearings - 07/15/12 04:47 PM

Lay the bearing shell in the crank throw and visually see if in fact it is touching the radius. Another way is to actually bolt the rod and bearing to the crank, then see if it can be rotated easily. Even with the wider GMC bearing, it's not that much!
Posted by: mdonohue05

Re: Chamfering rod bearings - 07/15/12 04:54 PM

I could turn the crank by hand after I put three of the piston rods in. Put the fourth and fifth in and more resistance but could turn using a crank turning socket on the snout. Put the sixth in and would not budge. Took cap off and you can see where it was compressing on the filet. Armond, are you saying that the bearings may only need a little chamfering?
Posted by: mdonohue05

Re: Chamfering rod bearings - 07/15/12 08:03 PM

Anyone know of a machinist or machine shop that could narrow my bearings? I do not have the ability to do this myself so will need help.
Posted by: THE FRENCHTOWN FLYER

Re: Chamfering rod bearings - 07/16/12 08:04 PM

I'd do this procedure using a rotary milling table in a mill. You cau use an old rod to center up the insert, and a 45 degree cutter to take off as much as you need. Worked for me.
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 07/16/12 11:46 PM

Here are a few pics from a Stovebolt Performance book showing a GMC rod having the chamfer re-machined in it after it has been narrowed to fit the Stovebolt engine.



Photos are the copyrighted property of the author, and are not for distribution in any shape or form by anyone!
Posted by: Curt B #5628

Re: Chamfering rod bearings - 07/17/12 09:52 AM

If you only need a radius/chamfer and not a width decrease try the following:

1. clamp bearing shells around a block of wood or plastic that is narrower than the bearing.
2. locate a pc. of 1/4 cold rolled bar.
3. using a hacksaw, carefully cut a slit in one end about 3/4 long.
4. fold a 1 X 2 pc. of emery cloth lengthwise and insert in slit.
5. mount rod in a die grinder.
6. hold die grinder parallel to bearing centerline and bump the paper against the ends until desired radius is generated. Coarser paper will take off material more rapidly so use caution and start with 220 grit or finer.
Posted by: mdonohue05

Re: Chamfering rod bearings - 07/17/12 06:54 PM

Thanks everyone. Thanks CNC for the photos. Turns out a really good friend of mine who use to crew on an alcohol funny car says he can do it. I have to locate a 302 rod to make a fixture out of to hold the bearing and then be able to chuck it in a lathe and narrow the bearings. Looks like the procedure will be to cut the small end and beam off, narrow the wide end sufficiently for the narrowing and to be able to chuck it in a lathe. CNC I just looked at my rods and they don't have much of a chamfer so I will show my friend the pictures and see if we can put a little more of a chamfer.
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 07/17/12 11:08 PM

Sure, glad it helped you out. If he looks at the pics, he should be able to fix you up with no problems. Make sure he chamfers both sides of your rods also.
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 07/24/12 10:29 AM

Any luck finding a GMC rod? There were two different forgings so make sure you get the right one that has the same width bearing tangs as the bearings you will be using.
Posted by: mdonohue05

Re: Chamfering rod bearings - 08/02/12 06:47 PM

I did find a rod with the correct tang. The rods I have use the 1/4 inch tang so that is what I got. Probably start this week on the fixture.
Posted by: jimmy six #35

Re: Chamfering rod bearings - 08/13/12 02:31 PM

If I'm reading you correctly are yours hitting on the side edge of the bearing or the angle in the radius of the crank? I've "hand" chamfered my 302 bearings for years to make sure the oil would flow out properly. I have more side clearance than stock so it's always one of my checks and I do it by putting the bearing in the rod and use a bearing "knife" to add more clearance for the oil.(about a 45 degree angle)

The GMC has a lot of bearing surface so this has never been a problem. My side clearance is a minimum of .015"+ The side clearance comes from using a surface grinder at work.

Good Luck
Posted by: mdonohue05

Re: Chamfering rod bearings - 08/19/12 06:27 PM

You read the problem correctly. What does a bearing knife look like? I am willing to try doing it by hand as I just got an extra set of bearings in. Where can I buy one of these knives?
Posted by: jimmy six #35

Re: Chamfering rod bearings - 08/22/12 12:09 PM

I use the trianglar one my dad had in his machine shop and I've has since 1963. In the McMaster-Carr book they are called bearing scrapers and I guess that's what I meant to say. Any machine shop supplier should be able to help you out....JD
Posted by: panic

Re: Chamfering rod bearings - 08/22/12 01:42 PM

The tool is less imporant than understanding the purpose: when the rod moves laterally to either CW shoulder, its bearing edge must be contoured to prevent contact with the CW cheek radius to the journal.
You could do it with a rock if you had time enough.
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 08/22/12 02:35 PM

The purpose of getting a spare rod was to make a fixture to narrow them in a lathe, you just use any number of lathe tools formed or ground to do this. You can narrow or chamfer the bearings with this method, done it hundreds of times.
Posted by: mdonohue05

Re: Chamfering rod bearings - 08/22/12 07:01 PM

Have the rod, cut the beam and small end off. Taking it to a friend who will narrow it to stock 235/261 width, and then some. The then some is where I am still figuring out. Have to carve out time to look at the rod journal and measure the width to not include the filet. Armond left me a message last month but I missed it so I just followed up with him.
Posted by: mdonohue05

Re: Chamfering rod bearings - 09/16/12 08:29 AM

So as an update. My friend and I just finished making the fixture to narrow the bearings. We cut the beam off the rod and ground down the casting on either side of the outside of the big end so the lathe tool would work a little more smoothly, if that makes any sense. We chucked it in the lathe using inside clamps and turned down both sides of the outside of the big end so that we could clamp the rod end in the lathe using outside clamps. We then measured a stock 261 rod bearing and the 302 rod bearing and decided to take about .080 from each side of the bearing. We blued the bearing, scribed .080 lines on each side of the 302 bearing, put the scribed 302 bearing in the rod end, chucked it into the lathe and cut the rod end until it had reached the .080 mark on the bearings. We then used a little tool that he had used to scrape bearing on an alcohol funny car and put a little chamfer on each side. Today I will mock up the bearing to see if we cut enough off. I have a picture of making the fixture but don't know how to post it. If someone could post it for me I can email it.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 09/24/12 11:02 AM

Here you go. I hope this works. These are mdonohue05's pictures I just posted them for him.


Machining the outside of the big end so an outside clamp can be use to hold the rod end.


This is the finished tool with another uncut bearing half installed just to see how it fits. Once both halves are installed and tightened we will cut the bearings to the tool and chamfer following the cut.


Another shot showing the turned down rim with an uncut bearing half in place.


We put a bearing in the rod after we had scribed .080 lines on each side of the bearing. Then we cut each side of the rod down until it cut the bearing at the scribed line. After we did both sides, we double checked to make sure we actually got the .080 off




Posted by: mdonohue05

Re: Chamfering rod bearings - 10/23/12 04:41 PM

Ok so this past weekend my good friend Pete "lucky" Luciano of Lucky's Race Cars in Phoenixville, PA,, machined the bearings down. The gmc bearings are now narrow enough to clear the crank radius. Narrower than stock gmc but wider than stock 235/261. Probably did not need to narrow them as much as I did but I wanted to make sure I had more than enough clearance Installed the bearings on Sunday and no more problems. Rotating assembly actually rotates now, lol. So I think the gmc swap goes like this: early gmc rods with.990 pins and 1/4 inch bearing tang, big end narrowed to 235/216 dimension. Slightly narrowed rod bearings. The testy part is you need custom pistons with the pin moved to compensate for the longer rod. I have a couple of pictures is beater would be nice enough to post for me.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 10/24/12 09:11 AM

Send them like last time and I'll get them posted. This is good stuff. I'm thinking about doing a similar thing with Hudson rods in a GMC.
Posted by: mdonohue05

Re: Chamfering rod bearings - 10/24/12 04:54 PM

You are too cool Beater! Pictures are on the way.
Posted by: mdonohue05

Re: Chamfering rod bearings - 10/24/12 05:05 PM

So here is what I discovered. Federal mogul bearings come with a small chamfer on the bearings. You can get them in as is and the motor will spin, but they are really too close as after a couple of rotations, you can see a little distortion on the edges of the bearing. The sealednpower bearings do not have a chamfer and absolutely hit the crank filet radius, distorted the bearing, and locked the motor. The bearings I got from egge were gm bearings but apparently from a couple of different sets. There is no question that the bearings need to be cut down a little bit. We used a standard lathe tool and cut slowly until we got to the desired size. Chamfered with same tool just higher. Touched up the edges with some fine abrasive paper, polished with even finer paper. The tool needs to go slow or else it may chatter and make the edges a little rougher. The sealed power and federal mogul bearings were softer and easier to machine, the steel in the gm bearings was noticeably harder and we had to be more careful machining them
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 10/25/12 10:16 PM

Here you go Mike.
Stock size 302 bearings on the 235/261 crank
Comparing the stock 302 bearing with the cut down 302 bearing
This is the cut down bearing installed in the narrowed 302 rod. You can see that there is more than enough clearance now for the crank
Same view you can see just how close
These bearings came from Patrick's who got them from egge. I am not particularly happy with the bearings but they will work. Egge apparently sprayed them with some sort of coating. Put like a thousandth on the clearance. Came off with lacquer thinner and then the clearances came in to spec
Posted by: junkrodder

Re: Chamfering rod bearings - 10/26/12 02:02 AM

Stuff like this makes my day! Thanks for sharing.
Posted by: mdonohue05

Re: Chamfering rod bearings - 10/26/12 12:31 PM

oh believe me its my pleasure. I know that some folks are not so generous but to be sure, i love playing with these motors and am happy to help anyone with what limited knowledge I have. What fun would it be otherwise! Besides, when I first became an inliner, i was in my early 20s and did not know all that much. Lots of the early members were very gracious and generous with me and i think a lot of that was just their simple enthusiasm for the club and the motors we were all playing with. I come from that same background!
Posted by: mdonohue05

Re: Chamfering rod bearings - 10/28/12 01:32 PM

So the last piece to this is that when I installed the cam, I was checking the rod to cam clearance and what do you know, 030 on two of the rods, not nearly enough, sooooooooooo, out came the cam three different times so I could use the die grinder and grind some clearance. I ground a little more than I intended so I am a little concerned that I weakened the cam a bit but it is what it is. So that looks like the last piece for the 302 gmc swap. Clearance the cam for the rods. I will take a few final pics this week or so, right now, buttoning down the hatch for the hurricane.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 11/08/12 10:37 PM

 Originally Posted By: mdonohue05
So the last piece to this is that when I installed the cam, I was checking the rod to cam clearance and what do you know, 030 on two of the rods, not nearly enough, sooooooooooo, out came the cam three different times so I could use the die grinder and grind some clearance. I ground a little more than I intended so I am a little concerned that I weakened the cam a bit but it is what it is. So that looks like the last piece for the 302 gmc swap. Clearance the cam for the rods. I will take a few final pics this week or so, right now, buttoning down the hatch for the hurricane.

Here's the picture for that.
Posted by: mdonohue05

Re: Chamfering rod bearings - 11/24/12 06:48 PM

Finished up the bottom end and went to bolt on the head and it would not go on. Seems the pop up venolia pistons are not machined correctly and are hitting the head. I bought these pistons from themnover 20 years ago so I am stuck figuring out what has to me modified, short of machining off the lump, and that would be a shame so the project is done as far as I can go for this year. Too cold to work out in the garage now. Beater has graciously agreed to post the last few pictures for me. Going to start aanother block as I need a motor by spring and no time to sort out the piston thing on this motor. Soon as I get it sorted out I will post.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 12/03/12 07:47 PM

Here they are Mike. Sorry for the delay. Remember to send photos of the piston fix.




Posted by: Just Me

Re: Chamfering rod bearings - 12/06/12 01:14 PM

I used to be a factory rep. for a production engine rebuilding company. When we built a 261 chev. egine we always used a crank that had ben chrome plated on the rod and main journals. We then used copper alloy bearings. We never had a bearing problem in this engine. One or two thousands of an inch of chrome is a wonderful thing on bearing journals. I once seen a 327 chev that was in a drag rail that run a .010 chrome plated crank. This engine would naturally burn out bearing on a regular basis. We would only polish the crank back to std. and he would run again. Some times we had to put the crank in a grinder to get the excess bearing material off from it so we could polish it to finish.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 12/06/12 07:03 PM

You say that like it's a good thing? It eats bearings but you can fix it?
Posted by: mdonohue05

Re: Chamfering rod bearings - 02/10/13 11:26 AM

The weather was fairly decent today so I decided to talkie the piston Lump to head interference issue. Last week I had made a tracing of a pristine 57 235 head using pressure sensitive rubbing paper and made a cardboard template to duplicate the combustion chamber of the 235 head. Put it on the 261 motor and confirmed that the pop ups were hitting the exhaust valve combustion chamber. So did you ever have a duh-lightbulb moment? Week I did and realized that a 261 head at 95 cc Was going to be physically bigger and that notwithstanding my specifically ordering the pistons for a 261 block with a 235 head, it was possible the pop ups were cut for a 261 head. So I checked a 56 261 head and sure enough,I had clearance on the 261 head where there is none on the 235 head. I checked the casting number of the 261 head that I had with the cc numbers that Tom Langdon had gotten for me before he retired from gm and I had a somewhat nice surprise in that rather than the 95.5 cc Head, I have a 86.2 cc head, so not as bad as I feared. About 7.1 cc larger than the 848 head. Hopefully between the pop ups and a small cut on the head and can keep a little compression in the motor. So if you are going to order pop up pistons, make sure you specify which head you are using and make sure that specification appears on you order form. now off to build a new new head.
Posted by: mdonohue05

Re: Chamfering rod bearings - 02/27/13 04:30 PM

So many have viewed this thread I thought I would provide an update. I tried a 261 head, a 55-56 5913 head, a 57 848 head and a 59-62 848 head, and the lumps hit all of the heads. Made a template up and figured about where the lumps were hitting and thought that there is no way, short of me buying a mill and learning how to use it, that I could fix these pistons. On a whim, I went into my files and miraculously found my reciept and job number from 1992 when I purchased the pistons. So I called Venolia and spoke to a gentleman named Tom Prock (more on that in a bit). Turns out Venolia keeps excellent records for their custom piston orders and he still had mine! Told me that Bob Toros who made my pistons, probably forgot to tell me that one end of the lump was only semi finished and was supposed to be hand fitted to the head for maximum compression. Mr. Toros apparently passed away a couple of years ago. Mr. Prock asked me to send him the pistons to get the end cut back so they won't hit the head. He was very cool to deal with. Now, when I got off the phone, I kept thinking that I recognized his name for some reason. So I plugged his name in on a Google search and I was right. Mr. Prock ran a number of cars here on the east coast, particularly when I was a boy. The one I really remembered was a Willys, the Prock and Howell F Troop car. That car has either been restored or recreated as one was on display at the Englishtown Funny Car reunion a couple of years ago. Ran a couplenof other cars over the years and was tom mcewen's crew chief for a time. Anyway, I just thought that Mr Prock was very cool to talk to me and help me get the piston issue sorted out. Props to Venolia!
Posted by: mdonohue05

Re: Chamfering rod bearings - 05/19/13 12:46 PM

So after I sent my pistons to venolia, they could not figure out what was wrong with them. Turns out mine were fully machined. They asked if I could makenthem a cast of the combustion chamber, which I did. They figured out what was wrong. Here, in the 90s before cnc computer machining, they used a plexiglass template. When mynpistons were made, the template was put on upside down so the lumps were correctly positioned but the shape was backwards. So in deference ton the fact that my pistons were in fact 20 years old and long out of any warranty, they worked it out with me. I paid the cost of new raw forgings, they handled the rest and made me up a brand new new set of pistons. They also machined the lumps off the original pistons for near zero deck flattops. Hats off to Tom Prock at venolia!
Posted by: mdonohue05

Re: Chamfering rod bearings - 05/19/13 12:47 PM

I have a picture or two if someone will help me post them.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 05/19/13 02:49 PM

Send them like you did the last ones and I'll try and post them for you.
Posted by: Beater of the Pack

Re: Chamfering rod bearings - 05/23/13 09:47 AM

Here are Mike's pictures. \:\)

This is the piston that I purchased 20 some years ago. If you look closely you can see the lumps were placed correctly but the shape was backward


This is the new venolia pop up
Posted by: mdonohue05

Re: Chamfering rod bearings - 06/23/15 11:15 AM

Just thought I would post an update, the 261 with 302 rods from this post has been started (two weekends ago), broken in and is running great. These were rods that Charlie Baker made up for me in the late 80s before he passed away that I just this year got around to using (life, children, jobs, education, lol you know the drill). A lot more work than I expected to get those GMC rods in but they are in and the motor is running. With the higher compression, bigger bore, and tighter center line of the Schneider cam, the motor sounds a lot different than my 235 motors, more throat to the sound. I would post a video if I knew how, lol.
Posted by: intergrated j 78

Re: Chamfering rod bearings - 06/26/15 04:12 AM

Which head did finally go on the 261? The 848? How many cc's? Thanks for keeping us informed. Jay6155
Posted by: mdonohue05

Re: Chamfering rod bearings - 06/26/15 08:39 AM

The short story is that even the new Venolia pistons, the lump still hit the head. I had to hand clearance every single lump. Once the lumps were clearanced properly, i bolted on a 57 848 head (the larger of the 848 combustion chambers), a 59 848 head (the smaller of the 848 combustion chambers at around 79.1 cc and the head that is on the motor now), a 59 261 head at about 86 cc, and each head passed muster, the lumps did not hit. For many years it had been suggested to me that you could fairly easily put 302 rods in a 261 motor. Ask around, and you will find that very few people have actually done it. It took a lot more messing with and some amount of frustration on occasion, to get them in, so it is not as simple or easy as some have suggested. The biggest challenges that I see are first obtaining the rods, having the big end machined down, modifying rod bolts to fit, rebuilding the rod, cut down the bearings, and I was lucky, I had a friend who helped me make up the tool and could do the job, custom pistons to deal with the 7 inch rod as opposed to teh slightly shorter 261 rod, and clearancing the cam for the rod bolts, assuming flat top pistons. With the pop up, the biggest challenge was clearancing the lumps on the pistons. I understand that Ross has a pattern that does not require any fitting so If I was to do this again, and I might, I would probably talk to Ross. That being said, the 302 rods while heavy, are pretty nice rods. Coupled with a floating 990 pin and big block rod bolts, I would think fairly strong. Moreover, there is no question that this motor sounds and feels different than any of the 235s I have built over the years (a lot). Between the cam and higher compression, larger valves (intake and exhaust) and some basic head work and smoothing and a little enlarging of the intake ports, it sounds terrific. The 57 it is in was my high school car in the middle to late 70s and has not been driven on the road for many years now. It was in need of a good bit of structural repair (rust) to make it safe, which of course lead to having to clean, paint and fix up everything else (it was all in worse shape than I expected). This weekend, hope to have the brakes finished and maybe drive it a little bit. If it runs as good as it sounds (to me anyway) ought to be fun.

On another note, I can hardly believe how many people have viewed this thread.
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 06/26/15 11:09 AM

As detailed in my book that is specific to this GMC rod swapping into the Stovebolt engines, it is a relatively easy fix to those that have a little bit higher degree of skill and machinist abilities. It was probably not intended or meant to be a complete DIY process to those that don't possess these skills or have access to certain machine tools and equipment because it does require certain knowledge and abilities that most people just don't have. But, glad to see you were able to get there with time and patience.
Posted by: mdonohue05

Re: Chamfering rod bearings - 06/26/15 11:19 AM

Is your book on the market? I am always looking to learn more!
Posted by: CNC-Dude #5585

Re: Chamfering rod bearings - 06/26/15 05:37 PM

Now that I have a lot of other distractions out of my way I can finish it up pretty quickly. I'll let you know when its available. Thanks
Posted by: intergrated j 78

Re: Chamfering rod bearings - 06/27/15 05:27 PM

I can't wait to get a copy. Jay6155
Posted by: mdonohue05

Re: Chamfering rod bearings - 09/19/16 06:15 PM

I thought I would follow up on this old thread. Got the motor finally done, installed, and running in 2015. This was just after I got the motor broken in

https://youtu.be/wm2XejDSqXg

Last year we ran the car at the 2015 trifive nationals with my old intake set up, a weiand 2x1 with a pair of pinto 5200 holly webers. Ran good but you could tell the motor had more in it but was running out of gear and carbs.

This year, put my old 4:11 rear in and installed a new Clifford 2x2 intake with a pair of 38dgev weber carbs. Ran the car at the 2016 trifive nationals. What a difference. The only problem -- I ran the carbs out of gas on every run. Here is my second run where I took it very easy off the line, shifted at 4400 rpm instead of the usual 5300-5500, and still ran the carbs out of gas when I went into third gear. So electric fuel pump and larger lines. It was a lot more work then I expected to put 302 rods in a 261 but the motor does run really well.

https://youtu.be/ov5YLeDPHiU
Posted by: stock49

Re: Chamfering rod bearings - 09/20/16 10:58 AM

Nice videos . . . exhaust note sounds awesome at WOT. Too bad the fuel bowls ran dry :-(

Can't wait to see a video once you upgrade the fuel delivery.