Boatally Insane

My Marine Kinetics cam appears to be an 8620 core as well...

dunnitagain

Been following this thread. Ive talked with Bob , I know his buddies in the Nascar shop where he gets his advice , again I will tell you . There is No Magic Bullet Camshaft. Bob found a selling point
and used it to make a profit. Like MT said , look at the Lobe Masters from the big cam companies , you cant have big lift with low duration . It is too unstable for the valvetrain. You can pound on 3000lb springs to get the lifter to follow the lobe.... Then you end up with cams like Tims . I hate seeing guys dump hard earned money into there toys , and have it go to ****. Not trying to be arrogant here but
I have put literally 1000's of cams through Spintrons and Dynos , Flat Tappet and Roller. Played all kinds of games with valve loft , coil bind , slipper foot rockers , 1/2 diameter tapered .180 wall pushrods ,
even rockers with ratios over 2.3! The biggest thing you learn is , a valvetrain is nothing more than a multipiece tuning fork . If it is forced to run in the harmonic range it doesn't like , it will tear everthing to ****. That harmonic will eat cam lobes , valve seats , Pushrod tips and rocker cups , turn lifter wheel bearings to dust. Ive seen lifter wheels on a highspeed camera turn backwards on the lobe while still actuating the valve. Ive seen valves rotating on there seats in the closed position with 300lbs of spring ! All due to harmonics. Our engines run at a steady state 95% of the time , That is a perfect scenario for a resonance to set in and tear **** up. That's why MOST CAM Companies have master lobes that they have developed over millions of dollars and hours of R&D . Back to Tims Lobe wear , that is very typical of a valvetrain that was run in a very excited state harmonically . It doesn't look to be a hardness problem in the lobe itself . But it is hard to tell from just picks.
You guys with dynos , if your data AQ is fast enough , and you don't have your data over smoothed . You will see a repeat pattern of spikes throughout your pulls. That usually correlates to valvetrain
instability. You can get a better picture if your ramps are say 50 to 100 rpm per sec , or use a 300 rpm step up test profile . But all Bull**** aside , the only way you will pick up 30-50 Hp with a cam change is because the cam you took out was a piece of ****. As most of you guys proved when you removed the magic bullets and put in a proven cam lobe grind. Sorry for the resume and rant.

Full Force

Lol thx dude... See you tomorrow to help with gantry Hahahah

frickstyle

No prob, let me know. Do you want me to being the hardness tester with me? Or have you not torn them down yet?

Panther

Sucks to see this.

What springs are in it and what's the installed height?

MILD THUNDER

I just told tim last night. "Tim, I think its time to forget about the custom trickery magic camshafts, and go with a proven design from one of the major companies''.

Besides Bob, I think there is also another factor here that should be considered. Cam motion is grinding these cams for bob. They are supposed to be super awesome cam people. This isn't the first time one of bobs cams, have showed these same issues. Its not a fluke thing. Thats why I stressed tim to pull the intakes. Its not like its a common thing to see lobes looking like chit, but, being it was a Marine Kinetics deal, and what I've seen from there lately, I recommended pulling it. So, I think Cam motion should get some of the credit for this as well.

Irregardless, if this is a 8620, or 8660 steel core, that shouldnt happen. I have a feeling what we have here, is a cam that has poor heat treatment/grinding process, combined with a chitty lobe design, that simply eating itself up.

Dunnitagain, your post is spot on imo.You mention the dyno stuff to. I told Tim, to basically forget what some of the guys here have posted for dyno data. I've seen sheets with correction factors upwards of 12%, sweep rates so fast , a pro stock engine wouldn't accelerate that quickly lol ..

MILD THUNDER

Springs are the supplied springs, that had the upgrade, from Marine Kinetics. The AFR 8002 spring, with blue stripe, which is a PAC #1940 spring. I believe the spec on this spring, is 175 seat, and around 475 open with tims 680 lift cam

Generally, my opinion, if that is not enough spring, to keep a hyd roller pleasure boat valvetrain in check, the cam sucks. That spring should not be causing a steel cam to eat itself up, if the heat treating was done properly.

Tim, as far as magic bullets for making power, its not in aggressive lobes and simply throwing lift at it, at the price of stability and longevity. Here's a couple combos some guys on another forum, have done on a platform just like yours, with shelf camshafts.

Here is a few that I have built for power boats. 540-548 bbc's, ported Iron eagle 308 heads, not radical porting, but detail work, chamber work, ex port work, the intake received attention thru the whole runner, about 320cc ish when done. 10:1, the Dart single plane that came on the boat originaly, on the mecruiser HP 500 502, Custom comp hydraulic roller, 252-260 at .050, .640 lift, 112 lobe sep. For numerous reasons. Did like 8-10 of those, either 540's or 548's out of the original 502 blocks. THey would make 715-730 hp, and about the same for tq, peaked about 5800 for hp, in the 4500ish for tq, depending on carbs used. And they rocked. Also built similar engines, but made them 509's, using the stock crank, they would make about 680hp and about 665 for tq, but, I would pull the duration back to 248-256,to keep the same rpm range.They would actualy go 6000-6200 for peak hp, same lobe family, so the lift was the same, and the same 112 lobe sep.

The interesting part, I did a pair of 540's, with basically all the same parts, except, used a set of iron Eagle 345's, instead. The idea was to eliminate any porting. Just blended the valve job top cut into the chamber, and blended the short turns. Those were down a solid 50hp and 50 ft/lbs over the ported 308 heads. Not suprising really, more air flow thru a smaller cross section, just works better in that rpm range. The 345's moved more above .700, but less below. The 345 iron eagle 540's made about the same power as the ported 308 iron eagle 509's. The 540/345 heads still made more tq, but not much.

Have a number of similar units out and running for some time now.

Dart S/D, 540", RHS 320's, Comp retro-hyd-roller, 9.75:1 C.R., 2527 Edel, and a 4500 Holley. Bolt-together build, absolutely no HP chasing at all!

All off the dyno at/above 730 HP @ 6200 and 700 Torque @ 4500. Have many of these still in service after 15 years or more, not a single problem to date an any!

These are tested without any accessories however.

Thanks, Gary in N.Y.

P.S. With a change to a solid-roller, some very minor head work, and 10.5/10.75:1 C.R., we see above 775 HP/725 Torque, very similar RPM band. The RHS heads flow 375/275 @ .700" from the boxes. Just tested some recent "brand-X" heads we took on for a line, and still see just above 700. The cost on these heads is about 1/2 price!

mike tkach

tim,i am out of town untill next thursday but i have a few of the cam cards from some of the cam,s i used from bob at home.i think the card states the material the cores are made from.i think it is safe to say that the cam in your video is NOT an 8620 core.i will say that witness marks on lobes are normal but from the video it appears to be more than witness marks that should not have happened.it appears to me that their might be a hardness problem with that camshaft.if i installed that cam in an engine i built it would be going for a hardness check today.my guess is after all the bashing bob is not going to help you at this point but maybe you should reach out to him and see what he has to say.

HaxbySpeed

What that guy said. I've been saying the same thing for years now. I had avoided pointing out that Bob has literally zero hands on practicle experience in this field, because all his cheerleaders turn it into a chit show. After sharing info with other builders on this exact subject regarding his cam "designs" which led them to see past Bob's bs and realize what was happening, Bob began a smear campaign behind the scenes attempting to discredit me. That is why I started the cam thread earlier in the year. Unfortunately, instead of it being a learning experience, Bob's cheerleaders tried to distract from the facts. It doesn't matter what spring pressure, or how thick a pushrod you use, if the lobe isn't stable it's gonna wreck stuff. Also, when you grind through the heat treat on these cores to get your magic profile that you learned about in a seminar and tested on your laptop, its gonna look like tims. Send the core to Callies, that's who makes them. And the can test it. But I'll dave you the time and tell you it's probably been ground through the heat treat, like many others. I'm not trying to sell cams, or be the man. Just trying to save people hard earned money and time. I'm sure many of you will be receiving phone call from the con man today. Ever wonder why he won't post in public? It's much easier to lie on the phone and not get called out

Black Baja

So, are these lobes that Bob generated out of a computer program or are they Cam Motions lobes that were picked from a catalog? I also have the question in the back of my mind... Is somebody sourcing over seas cores and selling $500 custom cams on junk cores? Having bought a few cams from Bob and worked on customers engines that had MK cams installed previously before I was involved. I've noticed that some of the cams have MK stamped on the nose of the cam and some do not. Are the ones with the MK stamped the magical cams? And the ones not stamped Cam Motion lobes?