• If you log in, the ads disappear in the forum and gallery. If you need help logging in or getting registered, send request to: webmaster@southernairboat.com

Cam, 489BBC, 2.68 Rot.. 3BL SW Sen, 16'


Well-known member
Still have not got a cam but looking at roller specs and their incredible lift!! :lol: I know you guys said don't buy an off the shelf cam but just looking the Solid rollers are really wild and the Hydraulic lifters are just to much money! (LIFTERS) Comp really kind of steered me to Hyd. flat tappet but just thinking. Why can't I do a little solid cam, probably 0.590 to 0.630 or so with the right numbers that could be a killer cam. I don't mind adjusting valves once in a while? Any way different for picking the numbers or would Comp be the best to contact? 8) Thanks!!
hey cold i just built a 496 bbc for a buddy if mine to go in his airboat and will put this same cam in my own when i tear it down this spring its a comp cams XM284HR-12 its not too much lift that its killing springs.i think its a good cam, thats my two cents
Cold, here's my 2 cents. I'd like a penny back if you don't mind :) .

With a gearbox you're going to want the engine to be smooth running (it'll be quieter), and because of that torque multiplier (box) you won't need to get too radical for your cam.

If I'm wrong, sue me ....... :lol: . olf
on second thought i think he is right,i run a belt drive and so does my buddy, may be a little choppy for a gear at idle, anyways you can always learn something on here all tha time,
Hey fanman, thanks! That's actually a little more duration than Comp recommended to me but that's kind of what I would be looking for. Always trying to save a buck, would the same numbers work if you did it with solid rollers. I don't want crazy lift but it wouldn't bother me to save a few hundred bucks on the roller lifters for the price of adjusting valves once in a while! Worst case is hyd flat tappet. :wink:
Cold, hydraulic flat tappets work just fine below 5000 rpm ..... think about it. Roller rockers would be a plus.
You do have a 2.68 box don't you ....... :? . olf
Yeah 2.68 box and roller rockers too but I always liked solid flat tappet cams. Lot's of the import stuff I play with are mild cams and solids. Why can't I do a mild 280 degree, .540-.560 lift solid roller and save the money on the hydraulic rollers? :?
I do plan on running at no higher than 5500. I would prefer to keep it around 4800-5000 RPM. Just solid roller followers are so much more affordable than the Hydraulics and I don't mind some of the tuning features of solids!

O,A, You don't think that just because I have a 2.68 I want to turn more RPM's do you? :lol:

Your going to have to write the "Waterthunder Rule" 100 times! :lol: :lol:
OK, I see where you're goin .......

Thunder will be on here in a few hours. I'll sit down, shut up, and defer to the Wizard. 8) olf
Cool to mix it up with you OA! I haven't done cool hotrod stuff for to many years. Comp cam's was just starting last time I built some really cool stuff so with the advent of rollers and Comp willing to do custom grinds, well :lol:

I can get .540 lift with a hyd flat tappet but I have also heard the short duration high lift -4 cams have a little higher tendency of wiping out lobes.
With out a doubt I would run a roller! If your familiar with engines and can adjust your own valves I would run a solid roller! I have built ton's of airboat motors with big solid rollers and when you get the valve train geometry right. I have ran them for a year and not even had to re adjust them I had a 406 with a .630 roller that after 3 years all the valve lash 's were within .003. If you don't want to run a solid then go with a hydraulic roller. This is one VERY important part of the combination a cam lobe can not be aggressive when you have a flat tappet cam, when you go to a roller the lobe can be much more aggressive in return increasing all your port velocities and improving (lowering) your torque curve! The last time I used a flat tappet cam in an airboat was about 5 years ago!
Thanks for the reassurance! I didn't think I was going crazy :twisted: when I thought to myself it would be the best way to go! 8) Valves open sooner and longer with more lift. Just looking at the roller lobes I would think the valves would be open within 80% of max lift for somewhere around 70% of the event. 8)
Thanks Waterthunder! I got around to calling your cam guy and I think he knew right off what You wanted! :lol: