Cam and valvetrain longevity....??? low duration high lift...
10-02-2016, 10:41 AM
#931
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Perhaps another thread in the spring. Yours specs are very similar to ones out there running around all over and haven't necessarily had problems. I'd be questioning the hardening process and if he's still with CM etc. see if it's 8620 core. Also ask Bob if your gonna get more than 60 hours out of them?
10-02-2016, 10:43 AM
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Tks
John
10-02-2016, 11:13 AM
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Did you take the marine ready heads apart and check or open guides? They are custom made for him by just sliding in exhaust valves... I'd inwere you I would not run them if you didn't...
after reading this post I am not feeling too good with my MK cams. I just got a heads and cams package specked from MK 2 months ago and numbers are not than much off of Tim's. thought I was doing the right thing going to MK spent to me was a lot of money building my 540's. my motors are almost finished and I may end up with a couple of 540 stones for the money I spent. that sucks. my grind # is XA242-390/247-385/112+4 core# 315629 actual on cam card reads 242.2 .664 247.1 .656 325 AFR heads
10-02-2016, 11:14 AM
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Many have stressed with a wet exhaust of any sort, a 5 degree split is nowhere near enough, that's why...
Can you explain why? I've read up on and expermitted with different splits over the years on stock heads vs aftermarket good flowing heads but am curious as to what you input is. And perhaps jsand117 can have some input when he contacts Bob this week. The numbers very similar to his make decent power but long jevity is a huge concern here.
Tks
John
Tks
John
10-02-2016, 11:16 AM
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Send Bob the pic of mine at 65 hours let's hear how it's my fault again... That's what he would say...
Perhaps another thread in the spring. Yours specs are very similar to ones out there running around all over and haven't necessarily had problems. I'd be questioning the hardening process and if he's still with CM etc. see if it's 8620 core. Also ask Bob if your gonna get more than 60 hours out of them?
10-02-2016, 11:22 AM
#939
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Whats interesting to me, is how similar, all these custom cams are from MK.
BCK has a 548ci. Tim has a 540ci. Both have intake durations around 241 if i recall and 9.5-10:1 range?.
This last pic, guy has a 502ci 9:1 deal, he gets a 237* intake lobe.
MER had a 502ci 525 merc, inital cam was like 238 or 239 intake lobe.
Some other 540-548 builds getting the 241 ish intake lobe.
I mean, what RPM are these engines supposed to be spinning? A 548ci turning 6k peak, is gonna need a significant different intake lobe, than a 502ci turning 6k rpm, and a hell of a lot different than a 502ci turning 5500.
While head flow plays a part, its not like going from a head that flows 400cfm at 600 lift, is going to require a grossly smaller intake lobe, than one that flows 350 at 600 lift. We are talking a couple two three degree change in duration to compensate for a better flowing head. Main factor is CID x RPM. You have to at least be in the ballpark .
BCK has a 548ci. Tim has a 540ci. Both have intake durations around 241 if i recall and 9.5-10:1 range?.
This last pic, guy has a 502ci 9:1 deal, he gets a 237* intake lobe.
MER had a 502ci 525 merc, inital cam was like 238 or 239 intake lobe.
Some other 540-548 builds getting the 241 ish intake lobe.
I mean, what RPM are these engines supposed to be spinning? A 548ci turning 6k peak, is gonna need a significant different intake lobe, than a 502ci turning 6k rpm, and a hell of a lot different than a 502ci turning 5500.
While head flow plays a part, its not like going from a head that flows 400cfm at 600 lift, is going to require a grossly smaller intake lobe, than one that flows 350 at 600 lift. We are talking a couple two three degree change in duration to compensate for a better flowing head. Main factor is CID x RPM. You have to at least be in the ballpark .
10-02-2016, 11:53 AM
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I get another text from an oso guy just now.
His 540, gets a 239/246 cam. He is running GM IRON HEADS. So, whether you have 325 afrs, or 305 afrs, or GM iron heads, you pretty much get the same exhaust duration, and within a deg or two of intake duration.
Sounds awesome. I need custom cams for my tailored application.
His 540, gets a 239/246 cam. He is running GM IRON HEADS. So, whether you have 325 afrs, or 305 afrs, or GM iron heads, you pretty much get the same exhaust duration, and within a deg or two of intake duration.
Sounds awesome. I need custom cams for my tailored application.
