I've got about 3500 miles on my rebuild of my 1975 350. Turbo 400 trans with a mild shift kit. At end of build engine dyno'd at 309 with 360 torque at 4650 RPM at flywheel. Since the dyno I installed shorty headers, true duel exhaust with crossover, Performer intake, 650 cfm edelbrock carb. I was happy with the power but just wanted a little bit more so I put a set of Brodix IK180 alum. heads on. The heads are 70cc with 180 cc intake. I noticed no improvement in power, and was told to expect about 50 more ponies. The cam that is in is a Crower 241
Intake: Duration 270 deg Lift 456
Exhaust: Duration 276 deg Lift 458

I talked to a few people that think I am undercammed and that the heads will work better with the correct cam. So I talked to Comp cams and they suggested a Xtreme energy Hyd cam #12-246-3.
Specs:Intake duration 274
Exhaust duration 286
I'm not a cam guy but the spec sheet doesn't give any other lift.
Will this cam produce more low end power? Will it give my motor a nice sounding lope, and will I have to change stall. I just don't feel the combination I have isn't to the limit it should be and as far as sound, there is no lope to the engine. This car is driven several days a week. Thanks in advance guys, you've always been right on the money in the past.

 

C'mon engine guys, tell me what you think!

 

The real duration numbers for this cam are 230/236 @ .050 and the lift is .490 with a 1.5 rocker arm. Definitly a step up from what you have and it should produce more power. MAke sure the rest of the motor is setup correctly. Timing and AF ratio need to be set correctly for best power.

 

With these heads will this cam be a good match. Will it have a nice lope. And what about stall? I'm at 9.5 to 1 on compresion before the heads were installed. Thanks

 

Is that the advertised duration or at .050 lift? The high lift and long duration cams produce power at the mid to high revs. (2200-6800 and so on) If this is the case you will need a higher stall convertor. That is not a bad cam (the comp cam) If your budget allows it get a roller cam. If not maybe a flat tappet/dual pattern cam but you must strictly adhere to break in procedures, ensure the springs are compatible with the cam and use plenty of break in lube with a high level of zdddp and use a high zdddp motor oil due to the steep ramps of the flat tappet cam designs.

 

Duration at .050" is intake: 230 and exhaust 236

 

C'mon guys give more info!

 

Whats your compression ratio with the 70 cc chambers

 

I don't know, but before the alum. heads were installed it was 9.5 to 1

 

What is the power range with either cam? Is the manifold the base performer manifold? If so that will be a weak link. Edelbroks rpm air gap is a good manifold and so is a weiand stealth manifold. Your manifold, heads, should be as close to the power band of your cam. Your carb should also feed enough fuel to the engine. You probably can go with a larger cam (.500+ lift and a little more duration) These are some of the things Gordonm was saying about having your a/f ratios close as possible to make power. You could pm Mako 63, Billa, or Scott Marzhal as they are knowledgeabe and Mako 63 will fudge numbers for you. (Guys don't kill me for pointing him in your direction)

 

How many cc s where your old heads and what head gasket came on your old engine?
Your also using Edl performer and shorty headers it would be better to use edl performer rpm and long tubes.

I like the spects of the zz 383 cam from GM pp you might check it out if you are going to go roller.

 

No
Yes
No, but you should

Your current cam is tiny. The Comp your looking at is fairly large for a 350.
I would recommend that you drop down a bit smaller on the cam if you dont plan to change the converter.

 

I am assuming you had 75 CC heads and went to 70 CC to bump compression. This cam is what I would use if that is the case. Same advertised duration as what you have to maintain same DCR but bigger duration @.050, more lift for better cylinder filling and good LSA (wide powerband) to allow you to not do a convertor upgrade.
http://www.compcams.com/Company/CC/c...x?csid=97&sb=2

 

The rule of thumb I use is at what lift is the highest CFM for the heads and get a cam that lifts the valve a tiny bit or at least the same amount. If your heads flow say 240cfm @ .4" lift and 254cfm @ .500" lift I get a cam that lifts the valve at least to the max flow of heads, meaning .500" lift or more.

This is where you find the real need for 1.6 ratio rockers you get a higher lift and the cam other cam specs remain relatively the same.

No point in putting on heads that flow~280cfm @ .500" and~320cfm at 7000RPM and then put in a cam that reaches it's highest lift with the valve opening at .550" lift, you just wasted a good set of heads.

It all comes down to doing the homework and matched every part correctly.
First things first, the Performer isn't a very good manifold but what we really need is exact static compression ratio and the flow numbers for your heads or you are just guessing at components and not matching them for optimal performance

*I put this on all my posts: Please post back to those who helped you, the final outcome of your initial post

 

Why not try a set of 1.6 RRs 1st? A lot easier than a cam swap.

 

Yep you be needing a new cam no wonder the heads did nothing that Crower 241 cam is for a 302, 327 with 214 / 218 duration at .050"

 

IK 180 flow numbers
Lift 0.200 0.300 0.400 0.500 0.600
Intake 138 188 234 243 245
Exhaust 112 149 167 175 178
The head flow numbers are about flatlined somewhere below @ .500 lift.
The cam lift on the Comp cam is .480 .498. Advertised Duration is 270 which matches your Crower. If you have no detonation issues now try and keep your advertised duration where it is. A bigger advertised duration cam will close the intake valve later reducing dynamic compression. this costs you power and is what is referenced to as "overcammed". Duration @ .050 is 226 intake and 234 exhaust. This is a huge difference from the Crower 214/218 and wher you will see a noticable increase in power due to better cylinder filling and compensation for a reletively weak exhaust flow on those heads. With a flat tappet cam at a certain lift you will see no more gain as motorhead said and more lift is harder on valvetrain components. A roller cam would be your best option but it seems no one wants to spend the extra $. This cam will work with a stock convertor.

 

This is perfect example of where "I" would use 1.6 ratio rockers, the heads are flowing more at .600 lift than at .500 lift and considerably more than .400" , your cam lift is maxed out below well below .500".

1.6 rockers gets you .512" intake and .532" exhaust. I have used 1.6 rockers to get me over .500" lift on 355's and use them on my 427ci to put my lift in the .640" range while still maintaining the original specs of the cam which was designed to be easy to drive on the street.

So if anyone has read this far you now know the reason for 1.6 or 1.7 and so on ratio rockers. If you put them on your stock L48 they ain't doing nothing except lighten your wallet

 

so it sounds like this cam will be a good match for my heads and carb and intake. Thats good , no convertor change. What about vacuum? Any problem forseen? Also will this cam give me any added bottom end power and will it have a street driveable atitude and still lope nice? What all will I need with a roller cam? Differeent lifters and what else? Thanks again

 

I don't understand what adding a set of 1.6 rr will do?