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Discussion in 'The Garage' started by Tshane, Jan 23, 2003.
What would u recommend for a 383 connecting rods?? /forums/images/graemlins/truck.gif
go with at least a 5.7 inch rod from a 350. The stock 400 5.565 rods will wear out the piston skirts/block quicker be cause of sideloading from a bad rod/stroke ratio. When i build my 406 im going to use 6 inch rods for a hair more torque and hopefully more longevity.
I have used eagle rods. great quality for price. same for oliver rods. but eagle seem to be easier to get.
I would use a 5.7" rod. The stumpy 400 rods do load the walls more than a 5.7 and a 5.7 puts the wrist pin up higher. There are lots of off the shelf pistons for the 5.7 rod too and alot of aftermarket rods dont require much if any clearancing(caps screws help out quite a bit in that aspect) Egal makes some deccent stuff for cheap. Good factory 5.7's would work too unless you are getting nuts. For real beef and fairly cheap made in /forums/images/graemlins/usaflag.gif rods, go crower sportsmans. Egals are china.
Using a 6" rod is ok for a race motor but using a rod length that puts the wrist pin in the ring lands is a bad idea on a motor that will see more use IMO. also the long vers short rod debate is one that will likely go on for awhile. Some people believe long rods make power. rheir morrison(you can read up on thier site, I would highly recomend it since there is lotsa interesting stuff on there as well as some bad assed motors) claims that in there testing they have seen 0 difference in power between rod lenghts. They even showed the gm engineering boys this.
Bottom line is that lots of people claim that there is power to be made with long rods but no one to my knowledge can come up with much proof that they make an apriable difference in power. There was some testing done in the 60's and such by guys like Smokey but the gains reported back then seem to be nulled by todays technology. They seem to help a bad flowing head intake combo basicly, but dont make much differnce either way with todays stuff. I dont have any personal dyno stuff or back to back testing to pass along this is just some views from the other side of the fence of the longer is better argument that I have heard from some very smart people.
Even if there was power or torque to be had with a .3" longer rod I dont think it would be noticeable enough on a dyno let alone enough to justify sticking the pin in the ringlands for a motor that will get much time on it. I'm not taking shots, thats JMO /forums/images/graemlins/smile.gif
If you are making a motor that is needing to be strong down low , than by all means use a 5.7 rod. Just deal with the piston side load , it's better than the high wrist pin w/ the long rod combo in a 4X4 motor.
Everone has an opinion on the L/R ratio but I will put a vote in for the short rod in a motor that makes good power down low ....... Tom
Yeah my motor is slowly turning into a pretty wild beast. 406 with a forged steel crank, 6" H beam rods(dads old race car parts)forged pistons, XR282 rollercam, fully ported 461X heads, roller rockers, performer RPM air gap intake. It was just gonna be a 300 hp 400, but as i gathered parts it got pretty wild. Its mainly a mud truck anyways so it can use some mid and top end too. /forums/images/graemlins/thumb.gif
The best argument I've seen for a long rod is that they tend to have much flatter torque curves than short rods do, all else being equal. That makes for an engine that is easy to drive.
The best argument I've seen against long rods is that they increase the piston's dwell time at/near TDC. This makes for an engine that is easy to detonate if fuel quality can be questionable.
I'd go with the 5.7's. The point made above about not having the wrist pin up in the ring lands is a good one.
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