Connection Rod - 401 Stroker

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   Hi everyone

I've started on my 401 block, 3.900 stroke, 2"mains stroker project. What I have is SCAT H-beam rods pn 2-350-6125-2000. Crank is standard AMC width for the rods.
Scat GM rods have approx. .040 beam offset.

I've done a mockup with the SCAT rod fitted on the crank in order to measure the relative position for the smal end of the rod in respect to the bore. I did it with the crank pushed towards the rear of the block (.010 crank end play). 

Cylinder 1,3,5 and 7 have a average of .080 offset towards the back of the block (away from the crank cheek). Cylinder 2,4,6 and 8 have a average of .135 towards the front of the block (away from the crank cheek).

I've read about chamfer the other side and turn the rods around plus removing some material on the "new" side that goes towards the crank cheek. 

How centered are the original rods in a AMC 401 block?
What is the feeling of how close to center is OK, and how much off center is not so good for a 430 cui  7000rpm engine.
Any suggestions on how you would install these rods?
How do I solve the width of the bearing? Sand down to correct width? Fine sandpaper on a piece of glass. Figure of 8?

Rune, 
Norway

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turvlo Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: May/02/2010 Location: Norway Status: Offline Points: 28	Post Options Post Reply Quote turvlo Report Post Thanks(0) Quote Reply Topic: Connection Rod - 401 Stroker Posted: Nov/07/2014 at 6:13am
	Hi everyone I've started on my 401 block, 3.900 stroke, 2"mains stroker project. What I have is SCAT H-beam rods pn 2-350-6125-2000. Crank is standard AMC width for the rods. Scat GM rods have approx. .040 beam offset. I've done a mockup with the SCAT rod fitted on the crank in order to measure the relative position for the smal end of the rod in respect to the bore. I did it with the crank pushed towards the rear of the block (.010 crank end play). Cylinder 1,3,5 and 7 have a average of .080 offset towards the back of the block (away from the crank cheek). Cylinder 2,4,6 and 8 have a average of .135 towards the front of the block (away from the crank cheek). I've read about chamfer the other side and turn the rods around plus removing some material on the "new" side that goes towards the crank cheek. How centered are the original rods in a AMC 401 block? What is the feeling of how close to center is OK, and how much off center is not so good for a 430 cui 7000rpm engine. Any suggestions on how you would install these rods? How do I solve the width of the bearing? Sand down to correct width? Fine sandpaper on a piece of glass. Figure of 8? Rune, Norway

SKeown Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/30/2009 Location: Texas Status: Offline Points: 3085	Post Options Post Reply Quote SKeown Report Post Thanks(0) Quote Reply Posted: Nov/07/2014 at 6:08pm
	I've done a number of AMC strokers, I currently run a stroke of 3.925". I assume when you said 2" mains you mean 2" rod pins. With you're current selection of rods you'll be fighting an additional problem beyond centering the rods on the wrist pins. With that long of a stroke in an AMC block with a 3.900 stroke you'll have a very short piston pin height with a 6.125 length rod. The way I did mine was to use Carrillo 6" rods for 2" journals that were designed for Chevy LS engines with centered beams (no bearing offset). By using a 6" rod it required a piston with a 1.240 compression height. With a 3.900 stroke and a 6.125 rod length the piston pin height would be reduced to 1.1275". That's too short and won't allow room to correctly fit you're ring pack even with the narrowest rings. Sacrificing ring seal will more than offset the benefit of the additional displacement. To center the LS style rods I had .010 removed from the crank side of the rods and used the off shelf narrow bearings designed to clear large radius cranks. By my using .047 compression rings the oil ring still intersected the pin bores and required using ring supports. There is a Ford rod that can be used, If you want to know the details I will provide them. SKeown Edited by SKeown - Nov/07/2014 at 6:19pm

Boris Badanov Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209	Post Options Post Reply Quote Boris Badanov Report Post Thanks(0) Quote Reply Posted: Nov/07/2014 at 7:51pm
	As i remember (I am not at the shop and can not verify this) AMC rods have a CL of .930~ and a cylinder bank stagger of exactly 1" They are in effect not centered. If all things are perfect that means a minimum off center condition of .035. I feel this is a DMS thing. I will soon be dummying up my 430 stroker with Carrillo 2" journal SBC rods. I will post the results.
	Gremlin Dreams

SKeown Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/30/2009 Location: Texas Status: Offline Points: 3085	Post Options Post Reply Quote SKeown Report Post Thanks(0) Quote Reply Posted: Nov/07/2014 at 8:03pm
	Being the offset of the rods are switched from bank to bank, they become pretty near centered with OEM rods. The problem with using Chevy rods is they are offset more and in the opposite direction as AMC rods. Unless you remove .010 from the non chamfered side of the std Chevy rods and reverse them on the crank you don't need to tell me how it comes out. I already know! SKeown Edited by SKeown - Nov/07/2014 at 8:09pm

BassBoat Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1718	Post Options Post Reply Quote BassBoat Report Post Thanks(0) Quote Reply Posted: Nov/08/2014 at 8:16am
	The bearing you want to use is the N series, intended for increased clearance for cranks with big fillet radius. as described here. http://www.jegs.com/p/Clevite/Clevite-77-Ford-High-Performance-Bearings/744634/10002/-1 I had the bearing chamfer cut when the rods were re-chamferred. In my mock up (with Eagle Rods) the side of the bearing was too close to the radius with the narrow bearings. And I had the H series, juts didn't have the extra clearance desired when I reversed the rods. But, looking back, I suppose I might have had more bearing area if I simply got normal width since I ended up chamfering them anyway.

turvlo Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: May/02/2010 Location: Norway Status: Offline Points: 28	Post Options Post Reply Quote turvlo Report Post Thanks(0) Quote Reply Posted: Nov/09/2014 at 9:13am
	Many thanks for information. This being my first engine ever to look inside, there is alot to learn that's for sure. SKeown - I have Diamond pistons with 1.123 Compression Height to fit on the 6.125 Rods. Rings are Total Seal CR7560 65, 1/16 1/16 3/16. I tested with rod bearing pn CB-745HN and got only 0.0015 rod clearance. Will this be to tight, and if so what is my options? Is 0.0025 more desired rod clearance? BassBoat - how did you chamfering the bearings? Rune

turvlo Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: May/02/2010 Location: Norway Status: Offline Points: 28	Post Options Post Reply Quote turvlo Report Post Thanks(0) Quote Reply Posted: Nov/09/2014 at 10:10am
	This is my piston: http://s1355.photobucket.com/user/turvlo/media/piston_2_zpsfb04fc8b.jpg. -

SKeown Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/30/2009 Location: Texas Status: Offline Points: 3085	Post Options Post Reply Quote SKeown Report Post Thanks(0) Quote Reply Posted: Nov/09/2014 at 10:15am
	Years back when the Chevy guys tried stuffing a long stroke in their engines they had to resort to pistons that short. To avoid having the oil rings totally in the pin bores they settled on one compression ring. That created a very unstable piston and extremely short ring life, and they were running smaller bores. I hope you have better results. You must reverse the Chevy rods which will require Chamfering the opposite side of the rods as well as the bearings. Failing to do that will further destabilize the pistons due to having the rods aligned off center on the wrist pins. I have to question how deep the piston's valve pockets are? I had to go .350 in and .275 ex to clear my cam's specs. With reliefs that deep I'm curious how they got those rings in there without the lands and pocket interference? Diamond does produce an excellent product. SKeown

turvlo Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: May/02/2010 Location: Norway Status: Offline Points: 28	Post Options Post Reply Quote turvlo Report Post Thanks(0) Quote Reply Posted: Nov/09/2014 at 10:30am
	Looks like .335 http://s1355.photobucket.com/user/turvlo/media/spec_2_zpsb1aa1c63.jpg. - What about my .0015 rod bearing clearance. What would you do? Rune, Norway

SKeown Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/30/2009 Location: Texas Status: Offline Points: 3085	Post Options Post Reply Quote SKeown Report Post Thanks(0) Quote Reply Posted: Nov/09/2014 at 10:51am
	After seeing you're piston, I think they will have at lease nearly as much skirt surface as mine. That was achieved by extending the length down, and was enabled due to the longer rods getting the piston further from the crank's counterweight. Do take the steps necessary to reverse the rods. My Wiseco pistons as delivered and after further lightening.