Thorwon Posted February 23 Share Posted February 23 I've built a 4.6L short rod stroker. I used a 1988 Comanche block, the light crankshaft and rods from a 4.2L. SPEED PRO Hyper H802CP40 pistons. The camshaft is a Crane Cam H-260-2, .456 intake .484 exhaust. And a 7120 head. I put a new Dorman 594-018 Harmonic Balancer on it. It starts and runs great, but at about 2500 RPM there's a vibration and the higher the RPM the worse it gets. Idling it's as smooth as it should be. Everything I can think of is right. Anyone have any ideas what it could be? Link to comment Share on other sites More sharing options...
ratrapp Posted February 23 Share Posted February 23 did you have the rotating assembly balanced?i bought a stroker kit once that said it was balanced and ready to go.it was not and it had to come back out again and taken to a machine shop to be balanced properly. Link to comment Share on other sites More sharing options...
Thorwon Posted February 23 Author Share Posted February 23 The crankshaft was not spin balanced but all the other components were balanced. I checked every thing. Link to comment Share on other sites More sharing options...
Eagle_SX4 Posted February 24 Share Posted February 24 Does the vibration happen when your driving or when parked and just revving the engine? Link to comment Share on other sites More sharing options...
ghetdjc320 Posted February 24 Share Posted February 24 How may counterweights on the crank? I’m assuming you’re positive this is an engine vibe and not a tranny, flywheel or drivetrain vibe? Link to comment Share on other sites More sharing options...
Thorwon Posted February 24 Author Share Posted February 24 Yes it makes it when parked and revving the engine. It's the non weighted crank. I've always just called it the light weight crank. I am positive the vibration get bad as the RPM goes up. Question for ya'll. I'm running a AW4 behind the 4.6, can anyone tell me what the pilot hole in the rear of the crankshaft is? I never checked to make sure the torque converter fit the crank. Link to comment Share on other sites More sharing options...
Eagle_SX4 Posted February 24 Share Posted February 24 1 hour ago, Thorwon said: It's the non weighted crank. I've always just called it the light weight crank. As far as I know there is not a non weighted crank shaft it should have either 12 or 4 counter weights. Do you have any pics of the crankshaft you installed in you motor? Link to comment Share on other sites More sharing options...
Thorwon Posted February 24 Author Share Posted February 24 It's the 4 weight crank. I have no pics of it. I'm going to change the balancer, if I can find the old one, to be able to rule that out. Can anyone answer this? Question for ya'll. I'm running a AW4 behind the 4.6, can anyone tell me what the pilot hole in the rear of the crankshaft is? I never checked to make sure the torque converter fit the crank. Link to comment Share on other sites More sharing options...
Eagle_SX4 Posted February 24 Share Posted February 24 53 minutes ago, Thorwon said: I'm going to change the balancer, if I can find the old one, to be able to rule that out. Both the 4.2 and the 4.0 are internally balanced. Changing the harmonic damper should not change the balance of the engine. 1 hour ago, Thorwon said: Can anyone answer this? Question for ya'll. I'm running a AW4 behind the 4.6, can anyone tell me what the pilot hole in the rear of the crankshaft is? I never checked to make sure the torque converter fit the crank. According to the parts listed on rockauto for a CJ7 and a Comanche the 4.2 and 4.0 share the same pilot hole diameter in the back of the crank. As long as there was not a manual transmission pilot bearing in the crank you shouldn't have any issues with the torque converter bolting up to the engine. Link to comment Share on other sites More sharing options...
Thorwon Posted February 24 Author Share Posted February 24 1 hour ago, Eagle_SX4 said: Both the 4.2 and the 4.0 are internally balanced. Changing the harmonic damper should not change the balance of the engine. I understand they are internally balanced. But if the new balancer is not right changing it should tell me. 1 hour ago, Eagle_SX4 said: According to the parts listed on rockauto for a CJ7 and a Comanche the 4.2 and 4.0 share the same pilot hole diameter in the back of the crank. As long as there was not a manual transmission pilot bearing in the crank you shouldn't have any issues with the torque converter bolting up to the engine. The torque converter bolted up with no issues. I was just wondering if the crank pilot bore may need a bushing for the AW4 torque converter. I don't think the AW4 was ever put behind the 4.2L. Link to comment Share on other sites More sharing options...
Eagle_SX4 Posted February 24 Share Posted February 24 2 hours ago, Thorwon said: I understand they are internally balanced. But if the new balancer is not right changing it should tell me. I know that the harmonic dampers will work on either crank. I am running a 4.2 damper on my 4.0 in my Eagle. There are long and short nose 4.2 crankshafts but either can work if you have a proper spacer to take up the extra length on the long one. As far as I know the only way they can be bad is if the rubber falls out of them or the outer pulley slips on the rubber. Check out this article it better explains the use of the harmonic damper. https://www.hotrod.com/how-to/harmonic-damper-vs-balancer-internal-external-zero-balance-tech Link to comment Share on other sites More sharing options...
Thorwon Posted February 24 Author Share Posted February 24 20 minutes ago, Eagle_SX4 said: I know that the harmonic dampers will work on either crank. I am running a 4.2 damper on my 4.0 in my Eagle. There are long and short nose 4.2 crankshafts but either can work if you have a proper spacer to take up the extra length on the long one. As far as I know the only way they can be bad is if the rubber falls out of them or the outer pulley slips on the rubber. Check out this article it better explains the use of the harmonic damper. https://www.hotrod.com/how-to/harmonic-damper-vs-balancer-internal-external-zero-balance-tech Good article. I made a spacer for the extra length. My 6 x 18 Craftsman lathe comes in handy for things like this. My concern is the new balancer may be made wrong/unbalanced. I'm going to change it with a used one off a known good running engine. Link to comment Share on other sites More sharing options...
Thorwon Posted March 4 Author Share Posted March 4 Well the balancer didn't help it. I guess I'll be pulling the engine, so I can remove the crankshaft. I've got to see if there's a shop local that can balance it. Link to comment Share on other sites More sharing options...
knever3 Posted March 4 Share Posted March 4 What flexplate did you use? They are balanced as well, but can't be installed in a different clock position. How is the water pump/clutch fan? Link to comment Share on other sites More sharing options...
Thorwon Posted March 5 Author Share Posted March 5 19 hours ago, knever3 said: What flexplate did you use? They are balanced as well, but can't be installed in a different clock position. How is the water pump/clutch fan? The power steering pump and harmonic balancer are only things that were new when I put the engine in the truck. Everything else is from the engine I took out of the truck that I built the stroker from. No fan clutch or fan. I'm running three electric fans. The flex plate is from the truck. It's original as far as I know. I have two more in the shop I'm going to compare all of them today. Link to comment Share on other sites More sharing options...
Thorwon Posted March 9 Author Share Posted March 9 What I didn't do was check the original 258 rod/piston assembly weight compared to the new rod/piston assembly weight. What I have found so far. The rod/piston assemblies are 124gr different from the original 258 rod/piston assemblies. The new rod/piston assemblies are lighter by 124gr. All new rod/piston assemblies are less than 1gr different in weight. This weight is including rod, piston, rings and bearings. The local speed/machine shop wants $375 + any heavy metal needed to check/balance the crankshaft. Link to comment Share on other sites More sharing options...
Thorwon Posted March 10 Author Share Posted March 10 I'm going to build it back to a 4.0, all I need are pistons. I have the rest of the parts. Link to comment Share on other sites More sharing options...
ratrapp Posted March 10 Share Posted March 10 thats not a bad price to balance a rotating assembly if done right.when building any kind of stroker or even using aftermarket parts it needs to be balanced.checking weights of rods/pistons doesnt tell you much.i have had enough stroker engines in my life that i don't skip that step after the first time it happened to me. Link to comment Share on other sites More sharing options...
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