making some changes...need cam advice

[Frankenstang65]

Ok, so here's the story. I just got a sweet deal on a set of heads for my '65, so I've decided to make some other upgrades in the "GO" department as well. I've got pretty much everything picked out at this point except for the cam, which always seems to give me the biggest headache.

Here's what the combo will look like:

'70 351W - . 030 over..otherwise stock shortblock
Holley Aluminum Heads- 2.02/1.60, competition 3 angle valve job
Crane Roller Rockers - 1.7, pedestal mount
Edelbrock Performer Intake
Holley 650 double pumper
Hedman Shorties
2 1/2 custom exhaust system with h-pipe, 2 chamber flowmasters
C4 Auto- manual valvebody, shift kit, stock converter (for a while)
8"- 3.55 gears (will install 9" w/3.25s, trac-lock, this summer)

My dilema is this: I want to pick a cam that is a agressive enough to make a sizeable increase in power and take advantage of the heads, but I want to make sure that with my stock converter and somewhat tall gears I'll be able to make use of that power on the
street.

After looking at cam after cam it seems that the more radical they get, the higher up they make up their power too. And even though the final HP numbers are significantly higher over milder cam choices, I think they would make my car a dog leaving the stoplight, not helping me all that much (though at least I could get traction...maybe.. ).

I was looking at the Crane Powermax... 216/228 duration (@.050) , .484/5.12 lift, & a 112 LSA.(2000-5500 rpm) Desktop Dyno says 375 hp (a little optimistic probably)...but the power curve seems to fit my application.

Somehow, I still think I could get away with something a little more wild...lol..they have another cam that is 226/236(@.050) .502/.520 lift and also has the milder 112 LSA. (3000-6000 rpm) Desktop Dyno on that one gets me close to 400 hp, in theory. Do you think I could get away with this one using the stock converter? What cams are you running in your cars? Any other cams come to mind? I'd be interested to hear your combos.

I'd like to get somewhere close to 300hp at the wheels, and hopefully be able to make a sub 13 sec pass or two with street tires.

Sorry for the novel... but any insight would be great.

Thanks!

[hobgoblin351]

Sounds to me like you're doing your homework. Thats always a good thing. What compression ratio are you planning on running?
The first cam sounds like a good compromise. The second might be a little too much. ie; requiring a high stall convertor and higher compression. If I remember correctly the Performer"s max RPM is around 5500. So you would not be able to take advange of the 2nd cam's high end power anyway.

[Rev]

I use a Comp Cams 268 HE. That is 268/268 advertised duration and 218/218 @ .050. It's about right for a stock torque convertorand 3.00-3.50 rear end. CC also makes an Extreme Energy cam with about that same duration but it's a dual pattern cam with a little more duration on the exhaust side. I can't remember the specifics, check their web site. BTW, my combo (see link to User's rides) will make power to 6000 with the Performer intake and a 625 Road Demon.

Rev

[Frankenstang65]

Thanks for the replies...

hobgoblin351: I think the stock heads had 64cc combustion chambers....the new ones have 60cc...with a normal gasket I'm thinking compression should be somewhere close to 10:1

Rev: I was a little worried about the permomer intake, I'm glad to know it will still make power above 5500 (thought I probably wont shift it any higher than 5800 with the stock short block). I'll definitely look into the XE cam too. Did you run that 13.3 with street tires? That's impressive, but I guess I forget how light these cars are.

Eventually, I plan on changing to an RPM air gap, beefed up AOD w/ 2600-2800 stall, and 3.73's. Then, when my rings fianally go, I plan on stroking to 408 and strengthening the bottom end a bit. Looks like the smaller cam is probably a better choice for now...then I'll have to step it up a bit when I make the other changes down the road.

Any other suggestions would be great though...thanks!

[Rev]

My engine power peaks at 5500 and I shift at 6000. Bottom end is stock except for Pioneer after market rod bolts and TRW forged flat top pistons. The 13.3 was on BFG Radial TA's 235/60/15. There was lots of VHT on the track and it was 40 F and 37% relative humidity. HRP is also near sea level.

Rev

[hobgoblin351]

If the advertised comp ratio of the pistons you are running with the 60cc chamber is 10-1, in reality it will probably be lower. The larger the cam the more compression you'll need. Hey Rev those are good number with that setup. If he's running that you can to and still be streetable.
To calculate comp ratio:
Swept volume+ chamber volume
Comp ratio= ----------------------------------------
Chamber volume

Swept vol- is the capacity of the piston. The stroke x the volume of the bore

chamber volume-the vol of the combustion chamber+ the volume of the compressed gasket+ any valve reliefs+ The volume lost from deck clearence+ the are between the piston and bore down to the top piston ring

Now the swept vol is easy, the vol of the chamber,compressed gasket, and valve reliefs are all given too. (if you're running a dished piston subtract the volume of the dish) You can guesstimate the volume lost from deck clearence and around the piston. Take the deck height x the volume of the bore, that should get you close enough. Add 1 or 2 cc's for the area around the piston above the rings if you want. The thing is most advertised comp ratios on pistons dont use the gasket volume or the deck clearence in their calculations. Surprisingly your comp ratio could be lower than you think.

[hobgoblin351]

ok so when i put it in the formula looks confusing. it should be CR=(SWEPT VOL+CHAMBERVOL)/CHAMBERVOL