Could I get some one to please desk top dyno this combo to see what cam is going to work the best. I am building a 496 BB with 781 cast oval port heads. Heads have mild port and bowl work with 2.19/1.88 valves. 9.5 to 1 forged pistions. Engine is going into '69 chevelle, about 3800 lbs, 3:31 gears, 26" tires, turbo 400, and 2500 stall. Car will be used for cruise-ins and test and tune at the local drags. I am planning on using a hydrolic roller cam. I have talked to comp cams tech people about 2 different cams. The first one is there xr276hr with 224/230 duration at .050 and .510 lift. The other cam is there xr282hr with 230/236 duration at.050 and .510 lift, both with 110 lobe seperation. The first cam seems a little on the conservative side to me (I want the car to sound like it has a healthy cam in it). But the comp cam people think the xr276hr would make the best all around power. How much would I give up in response and tork if I use the xr282 hr? I would sure appreciate anyones help on this choice.

whats your actual compression ratio?? 9.5:1 pistons can be all over the place, especially if your chamber size is different. ALso look at quench, gasket thickness..etc.

Actual compression is go to be close to 9.5:1. The heads are a open chamber at 119cc's.

IMHO, both of those are too small for a 496 motor. Not so much in duration (at least the 282) but in lift. Personally, for a 496 motor, I would look at a wider lobe sep (about 112), also would be nice to get the lift in the mid to upper .500's. Staying with Comp, take a look at the XM284HR Marine roller. But you may also want to consider a .600 lift flat tappet. Isky makes some .585 - .600 lift hydraulics that will work great in a 496 motor.

I would go with the 282 cam. IMO low end power with a 496 and oval ports should be no problem, roasting the tires should be real easy. The cam in my signature has similiar specs and acts very mild. My guess is that the smaller of the two cams you are looking at, would have little to no lope. It will probably peak pretty low also. I am thinking around 5000 for the power peak and with the 282 cam it should carry power another 500rpm or so (if you get the heads/exhaust/intake/carb right).

D2K say's my about 9.8 to 1 CR., 496 should make right at 550hp at 5500 rpm and 580t at 4500 rpm with just a good old CC 282S solid cam, a Strip Dom. and Holley 3310-2 750 cfm carb. and cheap, 1.75" four tube, long headers..

First Gen. car with an M-20, 3.31's and 26" tall tires.

Drag say's if it will hook without breaking anything and driven aggressively, it should go like 130 pmh at 10.5 seconds in the quarter.

I KNOW these are just SIM. PROGRAMS but I inputted a lot of different combinations and watched the trends so that hopefully I would be in the ball-park as to making my motor the way I wanted it the first time..

And I will be happy if it hit's low 11's ans somewhere around 120 mph!!

I guess what I am trying to say that a 496 or sdo BB doesn't really need much fancy to run very well!!!

pdq67

PS., and D2K did b/c I went from a small high lift Erson torque hy-cam and a Weiand 8005 dual plane to the CC solid and Strip Dom. plus used shims vs composite headgaskets to up my CR., .3 a point from 9.5 to 9.8 and gained about 30 sim. hp... Which to me was worth the price of D2K alone since I wasted that much money changing cams and intakes..

NAw. why build a 496 and put such a wimpy cam in. Look more along these lines.. ( btw, I dont think Comp has a good HR lineup for bbc - their 290HR cam is the only decent one for your app imho).

http://www.iskycams.com/productdisplay.php?productnumber=396570&sku=1978&hdwt=31101&loc=101&dealer=no

Check pg. 47 in the Crower catalog. The 404 looks about right. .600 lift. Now, that's what I'm talking about. 403 fits your gearing and compression better.

http://www.crower.com/misc/m_cat.shtml

If you are not going to go street solid roller like a CC 288AH then think solid lifter cam....... Save some bucks is all...

(And I'm only talking about a good street solid lifter cam is all here)..

As alway's, jmho..

pdq67

Just want to add this up date. I talked to comp cams techs again yesterday, and now they are recomending there XR288hr (I guess it depends on which tech you get on the line)which has 336/242 duration at .050. and .521/.540 lift. It is similar to the crower 404 but has a little less lift. I appreciate all of your input.

How about Comp's XR300HR-10?

I haven't paid much attention to Comp's hydraulic roller cams, but looking in my Comp catalog, the xtreme energy cams have very low lift for the duration. I don't understand that at all. The benefit of HR is higher ramp rates than a flat lifter. You can get the same lift rate in flat hydraulic and save big bucks.

I also see that Comp's Magnum (single pattern) HR's have lots more lift per duration than their Xtreme Energy dual pattern. What's with that? I'd ask their tech guys what the deal is.

Bottom line: If you only want .510-.520 lift, go with flat hydraulic and save money. If you want to take advantage of the roller hydraulic lifter capabilities, I'd look at Crane, maybe their part number 139721.

Ken