joe73vette

Just as I pulled into my driveway this evening I heard the "death rattle" of a spun rod bearing. The rebuild tht I was going to do next winter will come early, hopefully before the good weather gets here. I am planning on using vortec heads, Performer manifold, flat top hyperutectic pistons (9.3:1?), 3.08 gears, daily driver, automatic trans, q-jet. I'm going to put in headers and an OD tranny, too, sometime in the future.

These are the cams I am thinking about, and the manufacturer's web page info:
Crane PowerMax H-266-2 Good idle, daily usage, off road, towing, economy, good low and mid range torque and HP, 2400-2800 cruise RPM, 8.5 to 10.0 compression ratio advised. Basic RPM 2000-5000; 210/216@.050; .440/.454 lift; 114*lobe sep.
Crane PowerMax H-272-2Good idle, daily usage and off road, towing, performance and fuel efficiency, 2600-3000 cruise RPM, 8.75 to 10.75 compression ratio advised. Basic RPM 2000-5000 216/228@.050; .454/.480 lift; 112*lobe sep.
Comp Cams XE262 Xtreme Energy has excellent response, good mid range with a noticeable idle. 1300-5600RPM; 218/224@.050; .462/.469 lift; 110* lobe sep. 415 ft-lbs @ 3700 RPM, 348 HP @ 5300 RPM
GMPP 350HO with Vortec heads: 212/222@.050; .435/.460 lift; 112* lobe sep. 9.1:1 compression, 330HP 380TQ

Any advice or experience? I like the XE262, but not the narrow lobe sep, as I don't want a lopey idle. The Crane cams seem to stradle the XE in numbers; is the 266 too mild?, 272 too much? GM put a lot of thought into their cam, but it will be more expensive, I'm sure.

What do you think? Joe

joe73vette

Is anyone using vortec heads yet? What cam are you using? Joe

stalker

Joe I've built 3 engines with vortec heads ...don't be afraid of going with a close lobe sep. The tight lobe duration goes a long way to boost low end torque. If you get the duration right; the idle will be fine. The Vortec exhaust port is really good. My experience has been these heads don't need the extra duration and lift on the exhast lobe. Isky's 264 MEGA can be used with the stock springs and no work on the valveguide. This cam has a 108 degree lobe sep with 214 degrees @ .050". and .450" lift with 1.5 rockers. Just built a 350 with 9.0 comp. and this cam installed at an intake center of 104 degrees. The engine idles with just a little rumble in the idle and 16" of vacuum. The low end and trottle response is great, really important with your 3.08 gears.

joeveto

Man, sorry about your car.

I have the Comp Cams 268H. Take a look at my sig.

There is a mild lope to the idle. The car is quick around town, it will spin the rears, and on hard acceleration, the rear end will try to step out. But on the freeway, the car really takes off. When I put my foot in it, the thing jumps from 60 to 120 before I know it. Very dangerous.

Anyway, the above cam is a suggestion.

Good luck with it.

cardo0

Without a smog check required Iskenderian (Isky) 264 Mega cam gets my vote. Only company selling 108 lobe separation cams off the shelf. Why 108? Best for 350 is all I'll say here as I need some sleep.
If smog check is required then I'd choose the Crane H-266 first then Comps XE262 just to stay legal. Good Luck. :seeya

mountainmotor

Compression = Torque so I would shoot for 9.8-1 or there abouts if possible because the combustion chamber design will allow for it.
With the 3.08 gear I think it would be tough to beat the single pattern Comp 260H with or without headers especially with future plans of a 700R4. The Crane Energizer 210 -210 comes in a close second.

BB wowbagger

Why not a Roller setup?Sure its a little more money,but its worth it :cheers: :cheers:

Eddie 70

I have the XE 262 in my 70 and so far so good. Pulls alot harder than what was in there before the rebuild. I am tickled with it. Sometimes I wish I would have gone bigger though.

joe73vette

Thanks guys, I was able to find dyno curves for the XE262, 266H and GMPP cams, and the XE peaks highest, but it falls fastest, too. Can anyone do a desktop dyno of the 272H and the Comp 268H mentioned above? Thanks, Joe

joe73vette

cardo, now that you've gotten some sleep, would you explain why you think the narrow lobe sep angle is better? I was under the impression that wider was better for low end torque, and with 3:08 gears and an automatic, that's what I need. Joe

cardo0

Hello Joe :flag .
The 108 lobe separation angle (LSA) works best for the 350 inch chevy because the largest valves (2.02 & 1.6") limit filling the cylinders fast enough at high RPM - valve limited . Tighter LSA has more overlap to create better breathing at high RPM - I suspect from better exhaust scavenging or at least opening the exhaust valve later with the piston futher down the bore on power stroke. And maybe shutting the intake valve sooner while piston is lower on compression stroke.
This is from David Vizard (the wizard) in his book How to build Max Performance CHEVY Small Blocks on a budget . Optimum LSA is related to cubic inches - cylinder volume to fill. Now for a 327 LSA 110 is optimum and for a 383 its 106. A 400 is optimized by 104 LSA. I've seen his dyno graphs in some of his books verifying this for the 350. Unless he's publishing lies I'll pay for his information/dyno experience.
Now the wider LSA cam has smoother idle and more vacuum with broader (whatever that means but thats how I read it) power band. But peak power will be less. How much? Vizard writes about 20 ft-lbs/20 hp on a mild 350.
I'm running a Crane Energizer H-266 which uses 110 LSA because it comes with C.A.R.B. document to be legal here in California.
Low end torque would be better with the wider LSA for your drive train but the vette is a light car. Yes if you plan to run the drivetrain as is the wide LSA would be the conservative decision. :yesnod: But for the same investment what would that extra 20 ponies feel like? :rolleyes:


[Modified by cardo0, 7:39 PM 5/18/2003]

stalker

Joe, Cardo's answer is pretty good...Once an engine's rpm comes up, overlap helps a valve limited engine by increasing the engines ability to fill the cylinder. This happens when both valves are open at the same time. When the intake tract is exposed to the scavenging effect of the exhaust it helps "suck" in the intake charge. A narrower lobe seperation gives a boost in torque due to the earlier closing of the intake valve. This increases the cylinder pressure. If two engines with the same cam specs except for the lobe seperation are given a compession test, the engine with the narrower lobe seperation will have higher readings. The rougher idle is caused by the longer overlap of the narrow seperation. If you watch your duration and pick a lobe sep that is good for your combo you'll be rewarded with an engine that seems to run a little better than others. BTW...I practice what I preach, the cam in my car is a crane 274H, .450 lift, 218 degrees at .050" lift and 106 degrees lobe sep. I'm runnin 3.08s too.

joe73vette

I can see how narrow LSA would maximize HP and torque, but don't you really want the most "area under the curve"? i.e., I'd be willing to give up a few peak numbers to gain a lot throughout the rpm range. While Mr. Vizard is a knowledgeable guy, those books are at least 20 years old now, and I think the cam grinders have made great advances since then. Still, if anyone has compared the different cams, I'd like to hear from you. Thanks, Joe

Ryan77

I'm trying to run this on desktop dyno, but can't find the vortec head flow numbers :confused:

joe73vette

I got these from Chevy High Performance:
Lift Intake Exhaust Exhaust w/pipe
.050 40 25 25
.100 70 48 49
.200 139 101 105
.300 190 121 137
.400 227 140 151
.500 239 147 160
.600 229 151 162
Thanks for taking the time.
Joe


[Modified by joe73vette, 9:07 PM 5/21/2003]

joe73vette

Anybody have any ideas about this cam:
* Advertised duration: 262 intake/270 exhaust
* Duration at .050 in. cam lift: 218 intake/226 exhaust
* Gross valve lift: .462 in. intake/.480 in. exhaust
* Lobe separation: 111 degrees
It's a Comp Cams XE262 4x4 cam, CCA-CL12-239-3, and it looks like a combination of the regular XE262 and the Crane 272 to me.

Ryan77

I used all you specs, but guessed that the vortec heads had 2.02/1.60 valves, not the 1.94/1.50 valves, and headers. Theses cams seemed to prefer to be 2 degrees advanced also.
The XE262 gets you 373hp@5500 and 390ft/lbs from 4000-4500rpm.
The XE262 4x4 gets you 374hp@5500 and 391ft/lbs@4500.
The Powermax 272 gets you 377hp@5500rpm and 393ft/lbs@4500.
The Powermax 262 gets you 349hp@5000rpm and 395ft/lbs@4000rpm.

I'd personally go with the Powermax 272 in this case. Good Luck
:cheers:

joe73vette

Thanks, Ryan. Did you happen to save the files? Which cam had the best torque at 2500RPM? Would you e-mail them to me? jsavino@myeastern.com Thanks, Joe

Ryan77

No, I didn't save each individual one, only the basics of the motor. I'm 99% sure though that the Powermax 262 whould have the most torque @2500rpm. It's the last cam I ran so that's the one I saved, and it showed 372ft/lbs@2500rpm :cheers:


[Modified by Ryan77, 7:42 PM 5/23/2003]

joe73vette

That's cool, thanks. BTW, where can I get a copy of that program? Is it sold online or at stores? How much is it? Thanks again. Joe