I want more power! I am debating if I should change out my cam or not. Running a .40 over 350 with Speed Pro Powerforged pistons advertised @ 9.7CR. I am using Dart IE Plat. 64, 200cc heads, 1.5 RR, victor Jr Intake, Holley 750 cfm 3310 with a 4 speed and 3.08 rear. Also headers and full dual exhuast. Car sounds and runs very nice up to 6200RPM but I feel like I am leaving lots on the power table with my current cam. Here are the specs.

CRANE 113841:
Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 3,000-6,500 RPM
Intake Duration at 050 inch Lift: 238
Exhaust Duration at 050 inch Lift: 248
Duration at 050 inch Lift: 238 int./248 exh.
Advertised Intake Duration: 278
Advertised Exhaust Duration: 288
Advertised Duration: 278 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.500 in.
Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.500 exh. lift
Lobe Separation (degrees): 114
Intake Valve Lash: 0.022 in.
Exhaust Valve Lash: 0.022 in.

Looking at the summit catlog I found this cam:

Lunati 40134
Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 3,000-6,500 RPM
Intake Duration at 050 inch Lift: 239
Exhaust Duration at 050 inch Lift: 249
Duration at 050 inch Lift: 239 int./249 exh.
Advertised Intake Duration: 278
Advertised Exhaust Duration: 288
Advertised Duration: 278 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.517 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.543 in.
Valve Lift with Factory Rocker Arm Ratio: 0.517 int./0.543 exh. lift
Lobe Separation (degrees): 106
Intake Valve Lash: 0.018 in.
Exhaust Valve Lash: 0.020 in.

I am wondering if I would see a fair amount of performance increase with the lunati as the two CAM durations are almost identicle but Lunati has much more lift to take advantage of the large port size of my DART heads.

Would this be a good move for better street performance as I still have brake booster and pop up headlites?

thanks for your help!

Not like it helps but here is a pick.

 

The crane will idle better 112 vs 106 lobe separation. I'm running a lunati in my BB , and like it. Ron B.

 

[QUOTE=ferndog4;1559578783]I want more power! I am debating if I should change out my cam or not. Running a .40 over 350 with Speed Pro Powerforged pistons advertised @ 9.7CR. I am using Dart IE Plat. 64, 200cc heads, 1.5 RR, victor Jr Intake, Holley 750 cfm 3310 with a 4 speed and 3.08 rear. Also headers and full dual exhuast. Car sounds and runs very nice up to 6200RPM but I feel like I am leaving lots on the power table with my current cam. Here are the specs.QUOTE]

Your only direction to take would be an under the hood supercharger with minimum boost.

You have a 356" SB, with 9.7:1 c.r., 200 cc heads, a Victor Jr., a 750 carb, a 4 speed, and some 3.08's out back. It's about as wrong a package that you could choose for something with power brakes yet.

A cam change in any direction is not going to help anywhere. A set of 3.73's or 3.90's out back will wake it all up! Without some major calculations car should be able to hit about a 160 mph flat-out now, if it has anywhere near a 27" tall tire!

Just my opinions here!

Harry P. Hunter

 

We have nearly identicle motors and cams.

I have .030 over with flat tops making @10.6 C/R

I have a port matched Lt1 aluminum intake with the cut down divider. So it is not a single plane

Did you understand that using 1.6 ratio roller rockers like I use gives you a couple of degrees more .050 duration and more lift? .512/.533.

My motor has been balanced and blue printed. I use a 7000 rev limiter and my motor is very happy doing it. I'm surprized that yours doesn't run above 6200.

George here on the forum used to run the same cam also out to 7800 rpm in his tunnel rammed street rod.

I'm just asking, is it possible that your springs are not strong enough and your into valve float or was the cam installed advanced?

 

308s with a 4 speed and cammed 350 don't make a good combo
you need at least a 3.73 to wake it up.

 

I had 3.08 rear, 4 speed ( 2.87 first gear ) , 355ci with 200cc Sportsman II heads, Victor Jr. intake, 10:1cr flat top pistons, 750 Holley DP, CC 282S solid cam and it ran great, lots of power ( 300 RWHP and 330 RWT ) Nice little motor everything worked together perfectly.

I would suggest 1.6 rockers if your springs will take it, changing to the Lunati cam is probably not a good idea with power brakes and headlights etc.

 

You can not change camshaft duration by using 1.6 rockers. Camshaft duration is set by the shape of the lobes. The only way to change it is to regrind the camshaft. The valve will only open when the camshaft lobe opens it, and not any sooner. Once the valve begins to move it opens faster because it has to open further in the same amount of duration. 1.6 rockers do not change camshaft geometry.

BigBlockk

Later.....

 

The Crane does idle very nicely with good power and street manners. No problems with any power accesories. So does the 106 lobe seperation on th Lunati kill it for street manners?

thanks

 

[QUOTE=HP Hunter;1559579670]Thanks for the opinion youd be suprised how well the current cam idles and pulls great vacume for the booster and lights. I understand the need for bigger rear gears but I can still light up the 3.08s pretty good? Yes I am running a 27.1' tire so vipers watch out

 

No it won't kill it but it will surely shake a little more at idle. The 106 lobe separation is used primarily on circle track applications since they need a lot of mid range torque (6000-8000). The 106 ls tends to put it there and we find that these cams do well in street strip cars. The duration @50 number is low enough that I would probably say you could get away with it without a problem if you wanted to. As for a cam with 239 deg duration@50; it will never hit 7000 RPM hard like you want it to; look into the 250's at least for that.

 

I hear the benefits of the 1.6 rockers but I also hear alot about them benefiting the intake side only. I hate to purchase another set of Harland Sharps for only 8 Rockers. Anyone want to go halves?

Actually this cam was a recomendation from George but based on smaller camel hump heads. Not sure right combo for the DART heads.

Well, I am now running an Eagle Cast crank. I am a little scared running my engine up that high since i lost my last forged crank at 6700 RPM when a rod broke loose. Only 1000 mi since rebuild and still not really putting my foot into it yet. I feel like it can pull more RPM but not sure what it would really get me besides broken parts.


Thanks for the insight.

 

Your cam starts pulling at 3000 RPM. It takes a while to get there with 3.08 gears. It's probably not a good around town driver. With the 308 you are also dropping out of your working RPM range at each shift. Seems sluggish. A TKO 500 with a .83 OD or a 3.73 or even better a 4.11 will make it a different car. That is what you have the motor built for. Go to the cam website and look. With that cam in a 350 I will bet they request low gear differential. The 106 LSA cam will make this problem worse JMHO

 

Technically, using 1.6:1 ratio rockers arms will increase the duration @ .050" length, but only slightly:
using 1.5:1 rockers and a dial-indicator, you'd begin when the lobe raises the indicator .0333", while .050"-lift with 1.6s is achieved at .0312" lobe-lift.

Just goofing-around in a friend's shop one evening, he wanted to know if going to 1.6s would change the .050"-lift duration figures, so we mocked-up this test, using his 468" BBC and his big roller-cam:
I believe the .050"-lift duration-dimension 'only' changed 1*-2*, and I don't think that (alone ) would change the characteristics once in the motor.

 

Technically, using 1.6:1 ratio rockers arms will increase the duration @ .050" length, but only slightly:
using 1.5:1 rockers and a dial-indicator, you'd begin when the lobe raises the indicator .0333", while .050"-lift with 1.6s is achieved at .0312" lobe-lift.

Just goofing-around in a friend's shop one evening, he wanted to know if going to 1.6s would change the .050"-lift duration figures, so we mocked-up this test, using his 468" BBC and his big roller-cam:
I believe the .050"-lift duration-dimension 'only' changed 1*-2*, and I don't think that (alone ) would change the characteristics once in the motor.

Obviously, the Forum thinks this information is SO-important, it wants it posted twice!

 

Quote:
Originally Posted by Lt1er
Did you understand that using 1.6 ratio roller rockers like I use gives you a couple of degrees more .050 duration and more lift? .512/.533.


It really is simple math. I said @.050 If your rocker ratio is lifting your valve to .050 in a shorter number of degrees of rotation. Does it increase the total of number of degrees that the valve is actually off the seat?

Or isn't the valve going to be flowing more cfm during every degree of rotation that it is open?

Lets build two identicle motors. One with 1.5 rockers and one with 1.8's How do you think that they will each act?

I can tell the difference in how my motor runs just by changing my lash .008

 

I disagree ... true absolute zero" seat-to-seat duration does not change ... but 0.050" duration does increase 1-3 degrees as RAR increases.

 

[B][/ferndog4B] The only real bad part in the puzzle of your motor build would be the intake manifold. First off it is an over rated **** poor 20 year old design 4000 - 8000 rpm racing single plane. You have a motor that you keep the rpm down just to make it last longer.

I like my motor also. That is why I never run it over 6500 as a general rule. It is 12 or so years old and I hope that it last much longer.

I would investigate the larger dual planes like I have and get the TQ back up.

As to gearing. I have 3.55 and a 4 speed. I wish i had 3.08 for freeway cruising. We have 4 gears compared to the poor suckers with power robbing 3 speed auto trannys.

I truelly believe that dual plane is the answer and I use 1.6 on both intake and exhaust. Lift is the key to higher flow. I have not ever understood the logic behind higher lifting the intake valve. I think alot of motor builds are done by bench racers who go with something they heard a rumor of. You don't hear stuff like that from people that work in dyno rooms or enter motors in the nation motor challenges.

 

Isn't this this a mute point with a cast crank? IMHO I think you are limited to 6,500 with that crank anyway. Your current cam is slightly similar to the GM LT-1 cam but with a bit more lift and slightly less duration. A LT-1 has NOOO problem hitting 7K and it runs a high rise dual plane intake. For a street car, I'd ditch the victor Jr. and go to a RPM or Air Gap or Holley clone of the LT-1/Z-28 intake manifold.