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Discussion Starter #1
I had the motor out to deal with a spun rod bearing. I replaced the crankshaft with the same Scat 331 striker crank that came out. I noticed that my original poly mounts from Summit Racing(their in house brand) had literally melted due to to how close my shorty headers were to them. I spent more money on new Prothane poly mounts. Now I feel more engine vibration from 2k rpm's to 3k where it smooths out. The crank, harmonic balancer and flywheel have the same balancer factor(28oz) as before. Rear diff angle is the came. I can feel the vibration even when the car is in neutral. I'm thinking and hoping it's because of having stiffer motor mounts than before. Have other people noticed this? It's really kind of annoying. I originally had rubber mounts but over time they collapsed allowing the oil pan to extend below the frame rail. I found that out because I was out having fun on some rough roads where I bottomed out the suspension just right to knock the oil drain plug loose where upon all the oil leaked out causing the motor to seize. I'd really not have to go back to rubber mounts but?
 

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Senior Charter Member
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1,752 Posts
If you really think the hedder heat is causing your problem, how about finding or fabbing some heat shields to protect the mounts??? Then you could go back to some softer mounts to absorb the vibration.
Over the years I've found that most motors have an rpm range where they put out some vibration.
 

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886 Posts
Did you have the crank balanced with your other components?
 

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Marty, I have solid steel motor and tranny mounts! Love them! Yes your going to feel the engine running and such but put rubber washers in the seat mounts and a good rubberized matt under the carpeting and nobody complains. It still doesn't vibrate as much as a Harley Lol... Again though it is my preference and I have stock in Blue Locktite. That being said I don't know why you would have a vibration at the RPM range you mentioned.. My engine smooths out off idle and with the wind in your hair you wouldn't know I had steel mounts unless I told you. I would wrap your headers near your mounts or fab some heat shields as mentioned and have an engine guy look into the vibration. I have a bad feeling you might be taking this engine down again to have the assembly balanced and the block checked. running out of oil can do a lot of unseen damage that only a machine shop can find. Hope I'm WRONG. Mike
 
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