swiftrev Posted April 13, 2016 Report Posted April 13, 2016 I was reading on another site somewhere where someone explained that using the 230 crank in the 217 engine and NOT changing the rods is also a performance upgrade that aids compression. He said that using the 230 crank with the longer rods would only slightly push the pistons to go over the deck and could be trimmed. Has anyone else ever tried this? I keep finding a lot of 218's around and not many 230's, besides my own which has a bad crank. Quote
Plymouthy Adams Posted April 13, 2016 Report Posted April 13, 2016 I believe you read a bogus entry...understanding the difference in the crank throw would tell even the most novice reader this is not true.. Quote
knuckleharley Posted April 13, 2016 Report Posted April 13, 2016 I was reading on another site somewhere where someone explained that using the 230 crank in the 217 engine and NOT changing the rods is also a performance upgrade that aids compression. He said that using the 230 crank with the longer rods would only slightly push the pistons to go over the deck and could be trimmed. Has anyone else ever tried this? I keep finding a lot of 218's around and not many 230's, besides my own which has a bad crank. I'd never do it without taking some VERY careful readings of the piston pin location in the 218 pistons as compared to the piston pin location in the 230 pistons,and then compare the height from the piston pin centelines in both pistons to the top of each piston. Even then I would have to put a couple of them together and spin the crank by hand while watching the top of the block to see how high the pistons go. Don't forget to ad some room for "stretch" under load and rpm. Basically,unless it is a direct swap using stock parts,it's just not worth the trouble in a flathead engine for street use. You would end up with a few extra ft lbs of torque that you would never be able to even notice,so why bother? I used 350 rods in a 412 SBC I built to give it more torque,but I bought special Keith Black pistons for that specific rod and crank combo,but that's a 7000+ RPM engine with over 450 hp. Yeah,I got a little carried away building a engine for my 1 ton tow van. Quote
Young Ed Posted April 13, 2016 Report Posted April 13, 2016 I believe 218 and 230 pistons are the same... Quote
knuckleharley Posted April 13, 2016 Report Posted April 13, 2016 I believe 218 and 230 pistons are the same... Including piston pin locations? Quote
Young Ed Posted April 13, 2016 Report Posted April 13, 2016 Including piston pin locations? My 1951 mopar parts book shows 1241622 for P22 P23 D41 and D42. By then Dodge had the 230 and Plymouth still had the 218 so I would say yes they are the same. Quote
dpollo Posted April 14, 2016 Report Posted April 14, 2016 (edited) They are the same pistons and a quarter of an inch difference in stroke would push the top ring almost out of the bore and the piston top , unless modified would strike the head. I have considered similar scenarios with the 25 inch blocks where strokes were 3 3/4, 4 1/16 , 4 1/4 , 4 1/2 and 4 3/4 and in each case if using any of the pistons available for these engines , rod swapping is not possible ( unless you wanted to reduce piston travel by having it not come to the top of the bore. With a special piston, it might be possible but I really cannot see any real gain. Only one piston, for the 3 7/16 engines ( P34 as I recall) had a different pin to deck height measurement. It came .050 inch short of the engine deck height thus reducing compression. It had 3 rings and a significant distance between the top ring and the piston crown so it might be possible to create a "dome top " with these and using rods from a shorter stroke engine you could create a "pop up" but one would have to wonder Why ? Edited April 14, 2016 by dpollo Quote
swiftrev Posted April 14, 2016 Author Report Posted April 14, 2016 Thanks for the perspectives, I am a novice, but I was just trying to figure out what i was reading. the poster of this information stated that it would only increase low end torque at a cost of more friction and heat. which would create cooling problems.....but the 1/4 stroke difference between the 218 and 230 would only be 1/8 at TDC and 1/8 at BTC right? In measuring my engine there is about .1 inch between the block deck and the piston at its top height. I was thinking about all of this because I have the gyromatic and need the 230 crank, but all I find around the graveyards here are 217s for rebuild. If I were to try this I would hand crank it to see where the piston meets at block height. it was just a thought. I was wondering why no one ever tried it. Quote
dpollo Posted April 14, 2016 Report Posted April 14, 2016 I have often thought about the possibilities but never tried it because I could never really afford to build a grenade. and you are correct 1/4 longer stroke really is only 1/8 at each end so maybe the pistons I have which are .050 short could have the tops machined off enough to provide clearance. I have a block which they will fit. maybe some winter's day I will do a trial. Let's see, that would be a 251 crank with 228 * rods, pistons .o5o short then should pop up .o75 of an inch. Balance may be another issue ......... no, I think I will stick with what I know will work. I have always favored reliability. * Canadian engine Quote
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