Kano808 Posted May 6, 2015 Share Posted May 6, 2015 So I dropped my 1986 jeep comanche flywheel off at a machine shop which is externally balanced. I told them I needed it neutrally balanced for a 3.4 engine. My problem is the guy told me he needs the crankshaft also to do it from the engine it's going to be paired with, I'm just wondering if that's normal? Never heard of that before. Link to comment Share on other sites More sharing options...
Jeep Driver Posted May 6, 2015 Share Posted May 6, 2015 Yes, he's going to balance the crank and the fly wheel. Link to comment Share on other sites More sharing options...
Kano808 Posted May 6, 2015 Author Share Posted May 6, 2015 Ok sounds good thanks for clearing that up! Link to comment Share on other sites More sharing options...
Pete M Posted May 6, 2015 Share Posted May 6, 2015 I still don't understand. why does he need to balance the thing that's already balanced? Does he understand the 3.4 is already balanced? Link to comment Share on other sites More sharing options...
Kano808 Posted May 6, 2015 Author Share Posted May 6, 2015 He said something about having to balance it to avoid off-weight rough vibrations between the crank and the flywheel. I honestly am not to sure what he is talking about because I have never had to do this before. Link to comment Share on other sites More sharing options...
Pete M Posted May 6, 2015 Share Posted May 6, 2015 I don't remember ever reading such a thing for this swap. :dunno: not once. Link to comment Share on other sites More sharing options...
shelbyluvv Posted May 6, 2015 Share Posted May 6, 2015 Me either Link to comment Share on other sites More sharing options...
Eagle Posted May 7, 2015 Share Posted May 7, 2015 Does this guy know the difference between a counter-weighted flywheel and a neutrally balanced flywheel? I have alo never heard of anyone trying to balance the flywheel with the crank when doing this swap. IMHO it's not necessary and it's an invitation to screw something up. Tell him to balance the flywheel. What will cause those vibrations he's talking about would be using the counter-weighted 2.8L flywheel on the 3.4L crank. I've been through that many years ago, in a different vehicle with a different engine combination. Some previous owner tossed in a junkyard engine of a different displacement than the original, but he used the original flywheel -- which was (like the 2.8L) counterweighted. The junkyard engine needed a neutral-balanced flywheel. Once I got the thing running it had a nasty vibration. Took a bit of detective work to figure out what had happened. Bought a used flywheel that was correct for the engine, bolted it in, and it ran as smooth as silk. Leave the crankshaft alone. Link to comment Share on other sites More sharing options...
Jeep Driver Posted May 7, 2015 Share Posted May 7, 2015 I assumed the crank was loose since the OP stated that the machinist asked for it. Would not surprise me if he wanted to check the crank and fly wheel for balance together if the crank was loose...........apparently it's not. Link to comment Share on other sites More sharing options...
86FUBAR Posted May 7, 2015 Share Posted May 7, 2015 That's absurd ! I just told the guy at the machine shop what I was doing and asked to have it balanced and all he said is it was going to be a couple bucks more than normal as he had to grind off the majority of the weight before starting the balancing process as that is not a standerd step included . Sounded fair to me , and has worked perfect since. There is the possibility of using a neutrally balanced flywheel from a later s10 as those were already balanced , though I don't have a part # for ya I do know they are available . Link to comment Share on other sites More sharing options...
jimoshel Posted May 7, 2015 Share Posted May 7, 2015 Say 'adios' to the guy and find yerself another shop. Link to comment Share on other sites More sharing options...
Kano808 Posted May 11, 2015 Author Share Posted May 11, 2015 Right on for the replies, I was feeling all confused on that. Yeah and get this I take the crank shaft over and he tells me he needs the pistons and the rods also. It was then that I knew, this guy is ridiculous so I told him just balance the flywheel and that's all. Link to comment Share on other sites More sharing options...
Eagle Posted May 11, 2015 Share Posted May 11, 2015 Right on for the replies, I was feeling all confused on that. Yeah and get this I take the crank shaft over and he tells me he needs the pistons and the rods also. It was then that I knew, this guy is ridiculous so I told him just balance the flywheel and that's all. He's trying to do a complete engine balance. That's only for "real" race cars that are going to be run hard and long at sustained high RPM (like 7500 RPM and higher). That level of balancing is completely unnecessary for a street vehicle. Link to comment Share on other sites More sharing options...
gogmorgo Posted May 11, 2015 Share Posted May 11, 2015 Although if you let him do it, you'll end up with a very smooth running engine... Link to comment Share on other sites More sharing options...
Eagle Posted May 12, 2015 Share Posted May 12, 2015 Although if you let him do it, you'll end up with a very smooth running engine... True. You'll also spend a boatload of money that doesn't need to be spent. Link to comment Share on other sites More sharing options...
gogmorgo Posted May 12, 2015 Share Posted May 12, 2015 Also true. Link to comment Share on other sites More sharing options...
Kano808 Posted May 12, 2015 Author Share Posted May 12, 2015 Could I instead just use a a flywheel from a newer comanche that is already neutrally balanced? Say like a 92 flywheel? Or are the dimensions different? Link to comment Share on other sites More sharing options...
Jeep Driver Posted May 12, 2015 Share Posted May 12, 2015 From what I have read you can buy a new fly wheel that is already NB. Bolt pattern for the crank will be different........no, a '92 will not fit. Might check a S10 fly wheel........I have read that the S10 and Camaro wheels are different.....might be that S10 is similar to yours. Link to comment Share on other sites More sharing options...
Jeep Driver Posted May 12, 2015 Share Posted May 12, 2015 Do you have a fly wheel or a flex plate? Link to comment Share on other sites More sharing options...
Kano808 Posted May 13, 2015 Author Share Posted May 13, 2015 I have a fly wheel and shoot thanks for letting me know, that's a bummer the 92 flywheel would be cheaper than NB my current one. Link to comment Share on other sites More sharing options...
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