Off the shelf cam options for marine engines
02-19-2016 | 10:22 AM
#552
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From: Racine, Wisconsin
I would bet the lifters were bleeding down as a result of the new cam profile. On the motors I wrote about earlier that broke the rockers, etc. That customer originally purchased all hi top end components from MK, and it came with the standard morel 4603 lifters. They were doing the same thing on the dyno. They would bleed down, boost would go up, (cam essentially lost a ton of lift) and the motor would lay over. We swapped in the high revs, and the power picked up everywhere, even low end torque. Boost was still a bit high for the power, but not terrible. Unfortunately, those 4603 were acting like shock absorbers, when we put the high revs in, it transferred it all to the top end resulting in broken rockers, and eventually killing a couple of the high rev lifters too.
Thanks
Its really the only explanation that makes sense.
02-19-2016 | 12:36 PM
#553
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I would bet the lifters were bleeding down as a result of the new cam profile. On the motors I wrote about earlier that broke the rockers, etc. That customer originally purchased all hi top end components from MK, and it came with the standard morel 4603 lifters. They were doing the same thing on the dyno. They would bleed down, boost would go up, (cam essentially lost a ton of lift) and the motor would lay over. We swapped in the high revs, and the power picked up everywhere, even low end torque. Boost was still a bit high for the power, but not terrible. Unfortunately, those 4603 were acting like shock absorbers, when we put the high revs in, it transferred it all to the top end resulting in broken rockers, and eventually killing a couple of the high rev lifters too.
02-19-2016 | 12:50 PM
#554
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From: MI
1050 4150 quick fuel, matched Dart single plane, Jim Valako ported Dart heads, Solid Roller 255/265 650 or so lift, foggy on the compression but I know it was high for Marine use and was dynod with lightning headers. Motor would wind but had very little torque.
02-19-2016 | 01:00 PM
#555
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From: Vancouver BC
I've run the you-know-what out of the 4603's and never, ever had one bleed down. Blower motors, strip motors, well over 200# seat pressure and 7000rpm. Blown motor ran 6700 and made 853...489 pump gas motor w/871. I had a customer inadvertently run AFR solid roller springs for quite a few hours on a set of 4603's. They are a Pac 1224 and almost 300 on the seat. He said the motors never knew the difference. Not saying yours didn't do what you said they did, just saying...wow...!!
02-19-2016 | 01:08 PM
#556
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From: bel air, md
02-19-2016 | 02:22 PM
#560
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From: bel air, md
Wasn't about getting the whip out. Just thought you might have some insight on what you did to remedy the instability. I'm kinda in left field at this point cause I don't know anyone running larger core/ lifters in these marine engines. For myself and other readers just like to know where to turn to make it work. It's not like there are any 55/60mm shelf cams.
