OK ENGINE GURU'S I HAVE A QUESTION FOR YOU

[65+PLEASE]

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

[Fiat48]

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.

[DogHouse]

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?

[Infomaniac]

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 ]

[Blown 472]

Hey info what would happen if you ran a 110 on a blower deal??

[Dennis Moore]

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 (http://www.mooreperformance.org)

[Schiada76]

110 works great on my deal, Clay Smith cam.

[Infomaniac]

I believe Dennis has probably done more of them than I have.
Not that mine run bad. :D
110 on a blown deal has a bit more overlap. relieves boost out the exhaust.

[Blown 472]

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 ]

[Dennis Moore]

Smooth idle but at a big sacrifice in performance.

[1FastHallett]

im running a 256/266 at 50 solid cam with 108 and a vicotr jr. runs great for my but i have a 19 hallett not hat big of a boat.

[1FastHallett]

i meant me not my

[Blown 472]

Dennis Moore:
Smooth idle but at a big sacrifice in performance. ON a blower dealio??

[65+PLEASE]

How much of a difference will the oval port heads make. I have a set of 820's I could use. I would have to get the valves done . 10.5 TO 1 is not the exact compression it is a little lower. 500 hp is all can get out of this set up.IM not looking to break speed records. I do however want to run 65 mph or as close as possible to that.
Thanks for your advice
Rich

[Dennis Moore]

Good oval port heads (pocket porting with 2.19 intakes), roller camshaft, Basset headers, Edelbrock Performer RPM intake manifold and a two inch spacer should get you to 520 horsepower at 5000 rpm with lots of torque and very little water ingestion. Use a good flame arrestor (K+N), total ignition timing should be 34 degrees at 3600 rpm , use Champion RV15YC4 spark plugs gapped at .045 with a 12 volt breakerless induction style ignition system (not Mallory Unilite).
Dennis Moore

[Dennis Moore]

Blown 472
On a blower dealio? Yep, on any dealio! A tight LSA of 110 will always make more power than a wider 112 or 114 LSA. Many experts believe that 109 is best for most high performance engines while 112 is best for most standard performance (non smog) engines. Marine engines use a little wider LSA (on bigger camshafts) to cut down on water ingestion and smooth out the idle (sacrificing some performance). The stock GM marine camshaft for the small block Chevy has a 109 LSA.
With a blower dealio a tighter LSA will blow more fresh air/fuel mixture out of the exhaust at overlap, the fuel economy will be terrible, it will run dirty, idle rough, but still make more power.
Top fuel cars blow a lot of raw fuel out of the exhaust but they don't care! They makes tons of horsepower.
Who ever said a maximum performance engine isn't radical? Bad fuel economy and a rough idle goes with big performance, and valve overlap (tight lobe sep. angles) contributes to this.
Dennis Moore

[DEL51]

Dennis, from what I read a wide Lobe separation angle allows cylinder pressure to hang a little longer providing more work against the piston.Nitrous cams out of the books usually have a 112 LSA and event timing is compensated with a higher lift on the exhaust side. This may be compared to blower cams of similar design. However, i believe my cam is a 110 overlap and I think the cams in the BDS catalog are 110.Please comment

[Dennis Moore]

Many of the older camshaft companys such as Clay Smith Cams or Iskenderian Cams (for instance) grind camshafts with a 106 or 108 LSA. It is traditional for short track/circle track engine builders to use camshafts with 102 or 104 Lobe Separation Angles. To these guys, a wide LSA is 110 degrees.
Most of the major camshaft companys, like Crane and Crower, grind camshafts with a 112 or 114 LSA. By their standards a tight lobe separation angle is 110. Comp Cams fits in the middle of the extremes and grinds most camshafts with a 110 LSA.
The difference whether a LSA angle is tight or wide is in the philosophy of the engine builder/camshaft manufacturer.
It could be that a camshaft expert that recomends a 110 believes that it is a wide Lobe Separation Angle. In the marine industry, 110 is generally regarded as a tight LSA.
Dennis Moore