Well I had a 502 that I bought off craigslist in January. Finally I got it put in, did a cam break in, and started other testing and tuning. I was having problems with it idling and such. I had to get towed in twice. It was the second time that it locked up. Because it wasn't originally built for marine use, I was a bit skeptical about water reversion. One day after it shut down unexpectedly at the ramp, I pulled the boat out and pulled a manifold off. There was no sign of water reversion. Being quite happy about that I set out to fix some other ignition and starting issues. That took another week and I was delighted to have the boat out on the lake until it shut down at 2400 rpm. I tried to restart and heard metal slapping around so I figured I threw a rod. After that I contacted the builder and he agreed to take a look at it. I towed it down to his place 2 hrs away yesterday and he began to diagnose the issue. We pulled a manifold to get to the valve cover. Two pushrods dropped into the cam. We pulled the intake and saw the cam was grenaded. From that point I worked for a few hours to pull the drive and ultimately the motor. The builder isn't sure why it blew up. It had hardened pushrods and a hardened cam that was originally a Comp Cam and was reground. We are having more marine friendly cam ground for it now. It was at 108* LSA and we are putting the new one at 114* and going with 3/8s hardened pushrods. The heads are coming off and all the rod bearings will be checked. I'm pretty happy the guy is willing to fix it at his cost. He believes he can get the cam warrantied because it may not have hardened properly after the regrind. Fairly lucky for a craigslist purchase, but I sensed honesty in the guy while I was buying it otherwise I may not have gone through with it.
The cam was 598 lift and 296 duration at 108 LSA. We are going to keep the big lift and duration and only change the LSA. The builder is confident the rest of the valvetrain will hold up to prolonged use and that it is well built with the best parts that will take it. 1.72 roller rockers are in it. It is a solid lifter flat tappet cam in a Gen VI 502 block. Apparently it has Gen V timing parts to accommodate for the difference in Gen VI and V cams.
He will break in the cam with me and tune my carb and timing, which I am really happy about because I don't feel confident with my tuning skills.
Lots of members have been really helpful, most notably Mr. Fixx. He has taken my calls at all times of the day, even while I'm troubleshooting at the boat launch. He was the one who finally got me idling well by changing plugs and gap and an overheat ignition module. He and Madpoodle are the nicest guys who have helped me. They haven't belittled my engine or skills like lots of guys do who try to get you to buy stuff from them or have them work on your boat. Carl C advised me to call these two from the start. And JayZ has helped me while he performs almost the same project, a 502 in a King Cobra boat. So big thanks to Mr. Fixx and the others who have helped out!
It'll be a week before we get everything back together. I'll head back down and drop the motor in and go for a ride on the lake and see how it all goes.
I'm not sure if we can balance the thing with the flywheel on it. Does it need to go to a machine shop for that?
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Originally Posted by miike
