I need a cam reconmendation for my 496 bbc. The engine consist of the following parts.
4.25 4340 steel crank
.60 over 10.5 to 1 pistons
990 heads 2.19 intake 1.88 exhaust exhaust ports have been ported and polished
weiland stealth or performer rpm manifold (have both)
basset headers
holley 800dp carb
The engine is being built for my 21.5 daycruiser jet. If you need more info let me know
RICH
My advise would be to consult a few cam grinders, such as Clay Smith, Crane or Erson. That's a big boat and a jet so I would say you need low end more than anything. See how close the cam guys agree with each other. Then I would report back here and maybe see what Info would have to say as I think he works on big boats.
I'm no expert, but here's a guess: hydraulic roller, 250-260ish duration @50, .600ish lift, 114 l/c (to minimize reversion). Is that close?
How many RPM's do you intend to run? Low RPM's would need short duration.
Let the cylinder heads tell you what lift they like.
That is a bit too much compression for pump gas. You would need a late closing intake valve to compensate for that.
110 LSA for normally aspirated deals. I normally reserve the 114 for blown deals.
See what the cam experts have to say.
[ October 16, 2003, 05:13 AM: Message edited by: Infomaniac ]
Hey info what would happen if you ran a 110 on a blower deal??
Those 320 cc rectangle intake ports are to big for a 496 running at 5500 rpm or lower. You need to compensate by running a little smaller camshaft than you would if you had the correct size intake ports.
Most carbed 502 engines run better with oval intake port heads (example; GM 502/502 crate uses 290 cc oval port heads).
I suggest a roller camshaft with 224/230 intake/exhaust duration on a 112 degree LSA. As long as you run only a moderate amount of exhaust duration (only 230 degrees)the valve overlap will not be excessive with a 112 degree LSA.
A camshaft with .510 to .530 valve lift and installed at 112 degrees intake lobe centerline will help keep water ingestion at idle low
(higher lift and a 106 intake lobe centerline will create more water ingestion, especially with the Bassets). If you still have problems with water ingestion you can kill some intake manifold vacuum with a two inch tall open spacer between the carb and manifold.
You should make 500 horsepower at 5500 rpm if you can keep it from detonating with the 10.5:1 compression ratio (you may need racing gasoline).
Good luck
Dennis Moore
www.mooreperformance.org
110 works great on my deal, Clay Smith cam.
I believe Dennis has probably done more of them than I have.
Not that mine run bad.
110 on a blown deal has a bit more overlap. relieves boost out the exhaust.
Thanks info, I was wondering bout that, I have a 110 in my boat right now, but I am pulling the blower off so it should be ok.
Any advantage to say a 115 or 116 cl??
[ October 16, 2003, 12:58 PM: Message edited by: Blown 472 ]
Smooth idle but at a big sacrifice in performance.
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