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Tractor Pulling Discussion Forum

what rod up grades to think about

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Howard

07-14-2004 08:19:41




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are JD 70 rods the same length as JD G rods or can you get some cheap stroke by changing them.
do you lose any lug when switching from cast piston to alumnim piston becouse of less mass wheigt or does the flywheel take care of that just wondering if the new G motor is toast for what mild up grades to consider if it has to be torn down ( water in the oil )thanks for any thoughts Howard




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JDGnut

07-14-2004 15:47:38




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 Re: what rod up grades to think about in reply to Howard, 07-14-2004 08:19:41  
You can get a cheap stroke by using an A or 60 rod... they are the same length as the 70 or G rods (13in.) and have the same piston pin dia... but they have a smaller crank journal..



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what can you stroke?

07-14-2004 22:34:38




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 Re: Re: what rod up grades to think about in reply to JDGnut, 07-14-2004 15:47:38  
what is the average stroke on a G....8?...have heard alot go with a 9.25"..but i'm assuming its not an A/60 rod...is it you that has the B weights in the G? thanks alot



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JDGnut

07-16-2004 15:05:10




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 Re: Re: Re: what rod up grades to think about in reply to what can you stroke?, 07-14-2004 22:34:38  
Using the A rod... 8.5 is about it.. ( maybe 8.75.) but the rod bolts cause problems with the cam and the top cover... If you are going to stroke it.. Just use the diesel rods.. 8.5 you will not have to cut the back wall out.. but you will have to grind on it.. and a little on the rod bolts and nuts... the top of the case.. and a lot on the cam..... JDGnut



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G-MAN

07-15-2004 09:55:41




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 Re: Re: Re: what rod up grades to think about in reply to what can you stroke?, 07-14-2004 22:34:38  
You get a cheap stroke using and "A" or "60" rod because the rod journal is smaller - 3.000" instead of the 3.375" on a "G" rod/crank. You have the "G" crank journals offset-ground down to 3.000" and gain a little stroke. Not much, but some - probably around 20 cubes or so on a .125" over "G" engine. The "A"/"60" rods are the same length and have the same wrist-pin diameter as the "G" rods, and a lot of guys do that simple procedure in order to gain the benefits of an inserted rod and a little stroke at the same time. Late "A"/"60" (with factory bearing inserts) are cheaper than late "G"/"70" rods and more plentiful.

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i know that, but what abo

07-15-2004 10:25:31




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 Re: Re: Re: Re: what rod up grades to think about in reply to G-MAN, 07-15-2004 09:55:41  
i know that there smaller journal size picks up stroke..but what is the max with welding up the crank and grinding it back with an A rod?....can you get 8"? or bigger? including the offset grind from the rod journal differances....thanks



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G-MAN

07-15-2004 10:43:42




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 Re: Re: Re: Re: Re: what rod up grades to think ab in reply to i know that, but what abo, 07-15-2004 10:25:31  
That's territory I know nothing about - I'm not into big-time cutting, welding and all that, although I think 8" is a pretty common stroke and not too expensive - I was quoted something like $400 to put an inch in a "G" crank. I believe that in the bigger strokes, they're using 4020 rod bottom ends for even more offset. Obviously the smaller journal you can get the more stroke you're going to get for a given amount of welding.

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wow..thas a good deal...

07-15-2004 10:59:51




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 Re: Re: Re: Re: Re: Re: what rod up grades to thin in reply to G-MAN, 07-15-2004 10:43:42  
an inch on a G as in half each way like 7.5 or 8" crank? if it was an 8" thas cheap..i was quoted $900 for an 8"....but i think i want to go bigger if i want to pay that much i might just as well go bigger. got an A at 7.25 " stroke and a 6.125" bore and a 60 head. i dynoed it once with like a half hour on the engine...58hp..its broke in ALOT more now and everytime i've tried to dyno it since we've blowed a head gasket at 55hp and stil had a ways to go....do maybe its got 60 -65? i dunno..i'd like to find out though..lol..what do you think it has? thanks alot

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G-MAN

07-15-2004 13:48:14




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 Re: Re: Re: Re: Re: Re: Re: what rod up grades to in reply to wow..thas a good deal..., 07-15-2004 10:59:51  
That $400 figure was in addition to some other money to build up and regrind the mains down to standard etc, not for the whole job. It would have ended up being in that $800 range or a little more altogether. Sounds like you need to find better head gaskets and see what she's got, lol. Are the block and head both good and flat? Are you retorquing the head studs after the engine is good and hot?

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well....i have'nt retorqu

07-15-2004 21:02:26




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 Re: Re: Re: Re: Re: Re: Re: Re: what rod up grades in reply to G-MAN, 07-15-2004 13:48:14  
ya..that sounds more like it..lol.ya....i need to...the head was surface ground..but the block was done a while ago so it could be a little unflat...but it has the wire in it..so.....i shouldn't matter....and its torqed down to 205...lol...and it still blew...tyhat was the deere fiber mesh gasket..now i have the steel automotive store style gasket..and haven't been brave enough to put her on the dyno again..lol..i guess i should re torqe it..what do ya think it should run?

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buickanddeere

07-14-2004 10:40:53




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 Re: what rod up grades to think about in reply to Howard, 07-14-2004 08:19:41  
Stroke length does not change with rod length, it's the throw on the crank. Rod angle improves and cylinder wall side loading decreases with longer rods. If there is room to swing it all. The 70 rods use inserts. There is no lugging difference between identical shapped pistons cast or aluminium. The lighter pistons cause less bottom end stress if balanced. The stove oil burner "G" engine needs the compression bumped from 4.15 to 8 to 1. Gasoline manifold and blend all the rough edges and mismatches out of the ports/mainfolds,valve bowls,valves and combustion chambers. A cam from Roberts and she'll pull 6500 or 8000 lbs in 1st gear on the stickiest clay track with 15.5x38's.

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not the 8000....6000-7500

07-14-2004 20:44:03




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 Re: Re: what rod up grades to think about in reply to buickanddeere, 07-14-2004 10:40:53  
the 8000 is gettin up there...got a G with 70hp that won't handle low in the 8000 at a track up here..... so it will take a lil work to get ANY 8000 class..... 80hp limit..



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Ironman

07-15-2004 11:20:29




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 Re: Re: Re: what rod up grades to think about in reply to not the 8000....6000-7500, 07-14-2004 20:44:03  
What horsepower it takes for a tractor to compete in a certian weight class is totally dependent on sled and track. A 50 horsepower G may pull fine in the 6,500 lb. class one place and another place 50 horsepower wouldn't cut it at 5,000 lbs. Just depends on how sticky your track is and how the sled works (does it spin you out or load you down hard).
JD A rods are good to about 8.75" stroke. They give you more clearance in the back but not much up top. Past that you need 4020 rods to get the clearance up top and you just cut the back out. In the highly competitive areas 9.25" or 9.375" is a pretty common stroke. Other areas is a lot smaller. 10.5" is as big as I've heard of.

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