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Discussion Starter #1
Buddy of mine has a very nice 66 Chevelle SS. Car had the original motor and trans. He ended up buying a 502 with a roots style supercharger installed off of a guy. He bought a new trans and then installed into his car. Well he got about 300 miles on her and literally drove one of the lobes of the supercharger out the back of the housing breaking the rear plate on the supercharger and destroying the lobe. Come to found out that the motor was in a boat before he bought it. I went over and looked at it and noticed the size of the blower pulleys. I had him call the guy he got it from and asked him at what RPM was he running the boat at. The guy stated he used to run it at 4500 to 5000. Well that answered the question of what happened. My buddy has had this motor up to 6500 rpms a few times and he over revved the supercharger and thats what blew it up. Lesson here, Boat motors are designed for Boats, Not cars. Hopefully none of the supercharger debris hurt the motor. Now he is pulling the motor to check for any internal damage.
 

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Actually a boat engine can make a wonderful street car engine. Lots of torque, great valves, broad torque band, lower rpm engine. Now if the blower had "gas" end plate and bearings on it (which it had to have), 6500 rpm is not an issue with it. A broken plate, bad bearing, problem with a rotor, etc., is more likely the problem.
 

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Discussion Starter #4
Well the pulley set up was set up for the blower to run its max rpm at 5000 rpms so just putting it into a car and running it up to 6500 is a bad thing. The blower was overspinning and fried the bearings and then welded to the lobe. Called the supercharger manafacture on it and as soon as we told them the pulley sizes, the tech guy said it was way over its max revolutions. The pulley set up when it was in the boat was already pushing the blower to a dangerous max revolution.
 

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That's why when you buy used parts you have to be sure of what you have before oyu use them. If he would of checked the pulley numbers, then he wouldn't of had the problem. Plus he should of checked them anyhow to know what kind of boost level he had.
 

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Discussion Starter #6 (Edited)
That's why when you buy used parts you have to be sure of what you have before oyu use them. If he would of checked the pulley numbers, then he wouldn't of had the problem. Plus he should of checked them anyhow to know what kind of boost level he had.
I agree 100%. I told my buddy he better look into the cam as well. Boat Cams and Car cams are of a different breed. Boat motors are good motors. I never said a Boat motor was a bad thing. I Have had a 350 out of a boat and it was an excellent motor. But I changed the cam and valve springs in it before putting into the car. I told my buddy that the Boat motor he got was set up for a completely different RPM. To be honest I dont think this 502 was originally built for marine use. Has normal freeze plugs and it also has Normal gaskets on it. Every marine motor I have worked on had brass freeze plugs. I really think the guy who he got the motor off of kinda screwed him. Buddy told me it had aluminum heads and when I went over and looked at it, The heads are painted silver to look like aluminum.

Edit: One more thing I forgot to add is he is running a 4.56 gear ratio in the rear. I told him he better drop the gear down to a 3.42 or 3.55. Blowers tend to like the lower numbers in gear ratios as for the amount of torque created from the blower.
 

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Rear end ratio should be based on the use of the car, and the size of the tire. I ran 4:56's on my blown pro-street and they were great. But, I was running a 33" tall tire.
 

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Rear end ratio should be based on the use of the car, and the size of the tire. I ran 4:56's on my blown pro-street and they were great. But, I was running a 33" tall tire.
True, but I interpreted his statements as being the blown 502 has massive amounts of torque down low and you can push a smaller rear ratio while still having alot of performance. And ummm? The 33s VS a street 26 will kinda go in that direction. :) JR
 

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Discussion Starter #10 (Edited)
True, but I interpreted his statements as being the blown 502 has massive amounts of torque down low and you can push a smaller rear ratio while still having alot of performance. And ummm? The 33s VS a street 26 will kinda go in that direction. :) JR
He is running a 26" tire. He swapped the 12 bolt rear from his 68 which had a 3:55 gear into the 66.

Sounds more like he ran it dry of oil.
It had oil in it as the oil ended up all over the engine and firewall and proceeded under the car.

He got the supercharger rebuilt and went through the motor to make sure nothing internally was damaged. He did end up changing cams, valve springs and the pulleys. Got it fired up last night and it sounds and runs alot better. Pulls extremely hard and doesnt wind though the RPM range to quickly now. This isnt built to be a full out drag car. More of a street and weekend racer. He had some garbage electric fans so I gave him a set off of a 2002 T/A. The T/A Fan assy. actually look right at home on the Radiator. Cool thing is he had changed the Th400 for a built one he bought new. so for giving him a hand he gave me the original one out of his car and the cool thing is its a working trans. will make a nice rebuild for myself.
 

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I doubt the supercharger failure was from RPMs...perhaps lubrication or bearing failure. I think the engine would've failed first if all things were equal. I overdrive the crap out of my blower, making almost 40 pounds of boost on our blown altered...I've blown the crank out of a block before, but never hurt the supercharger.
 
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