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#86051 - 06/23/15 11:15 AM Re: Chamfering rod bearings [Re: Beater of the Pack]
mdonohue05 Offline
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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.


Edited by mdonohue05 (06/23/15 11:52 AM)

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#86096 - 06/26/15 04:12 AM Re: Chamfering rod bearings [Re: mdonohue05]
intergrated j 78 Offline
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Which head did finally go on the 261? The 848? How many cc's? Thanks for keeping us informed. Jay6155

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#86103 - 06/26/15 08:39 AM Re: Chamfering rod bearings [Re: intergrated j 78]
mdonohue05 Offline
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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.


Edited by mdonohue05 (06/26/15 10:57 AM)

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#86107 - 06/26/15 11:09 AM Re: Chamfering rod bearings [Re: mdonohue05]
CNC-Dude #5585 Offline
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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.
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#86109 - 06/26/15 11:19 AM Re: Chamfering rod bearings [Re: CNC-Dude #5585]
mdonohue05 Offline
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Is your book on the market? I am always looking to learn more!

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#86113 - 06/26/15 05:37 PM Re: Chamfering rod bearings [Re: mdonohue05]
CNC-Dude #5585 Offline
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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
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#86131 - 06/27/15 05:27 PM Re: Chamfering rod bearings [Re: CNC-Dude #5585]
intergrated j 78 Offline
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I can't wait to get a copy. Jay6155

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#90677 - 09/19/16 06:15 PM Re: Chamfering rod bearings [Re: intergrated j 78]
mdonohue05 Offline
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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

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#90681 - 09/20/16 10:58 AM Re: Chamfering rod bearings [Re: mdonohue05]
stock49 Online   content

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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.

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