Seems to be a theme around these parts of the MK cams underperforming or causing valvetrain damage. It every one of em but more than enough. That my personal observation.

Especially if you can swap it out, make more power, and do it with an easier lobe profile, less lift, and so on.

I wonder how many Bob was able to keep quiet??

Compression tests 175 low to 178 high...

https://m.youtube.com/watch?v=uqJ_uMMh7Us

https://m.youtube.com/watch?v=ybb51-ZwhyU

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Hey SB. I know you and I have stressed this topic a bunch, but anyhow, I been playing with the pipemax program tonight.

Holy chitballs. It's amazing, what a 5200RPM 454 likes for exhaust header design, vs a 6000RPM 700HP 540.

Sorry, but until I see otherwise with some solid dyno data, I'm going with the theory, that Tims Stainless marine basic manifolds, are choking the hell out of that 540. If I had my choice, and that was to buy new intakes and dominators, vs buying a good set of headers/tails, I'd be doing the exhaust before anything.

Speaking of exhaust

At the Sprint Cup race this week-end, on Saturday I noticed alot (maybe all ?) of the Modifieds using 4-2-1 headers. Sunday for the Cup race we arrived late, blew thru the garage area, then pit stop row to see all the driver's getting up on the stage, and then going up to the suite it don'd on me...fuk ! I forgot to look at their exhaust. Oh well, will try to remember next year races.

So, talking with a few guys with the modifieds, they said the primaries are sized by the exhaust port, ie same size as port but if tubing not available that size they use size as close to exh port size as possible, then primary about 10 inches or so, stepped up to next diameter. They too, said the collector was really where they found the power. Of course, they all have merge collectors too.

That IS a good point, years ago when my baja made only 800 hp or so i had 1 7 /8 lightning headers, transom was always black, oil was always gassed up, re did motor and made 950 hp , test ran it with the lightnings in the driveway on a test stand, immediately pulled them off, found water at exhaust ports so i sold them (obvious reversion), put on stainless marine 3s w 5" tails, no reversion, and transom was never black again, oil was never gassed up again.
Talking to wags 382, he built some big blower motors, made 1200 or 1300 hp, put them in his boat, had efi, transom black, gassed up oil, screwy afr readings, 02 sensors kept telling him it was rich, cmi 1 7/8 headers, he knew they were too small but figured he would just be down 30 or 40 hp. His lbs of fuel per hour at .5 bsfc was telling him he was only using about 1000hp worth of fuel and boat was a pig and slow. He built a pair of almost identical motors for a friend, guy had stellings big tubes, boat ran fast and flawless. Last i talked to him he was upgrading the exhaust, it was screwing up his ability for motor to breathe so bad it was killing power. Im sure hes not the only one suffering from mismatched exhaust, his 02 teadings kept telling him it was still too rich and boat was down on power, fwiw, smitty

You can run 4000$ heads and a big daddy cam but air still has to get out!!

Not saying that your your wrong at at just adding to thread. May very well be right but I'd say 248/253-677-667 is in close but still cams in question not far off at all with right combo. Just my opinion. That grinds I'm testing for 5665. Give or take.