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Old 11-07-2008, 07:11 AM
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sbc 350 choosing cam mild build

i have posted this once but, i did so before reading the post about not including (please help).So, ill try it again.Im new to this, i hope you guys can help me. I have a 350 bore .060 over with hyp. flat top pistons and vortec heads and will be running a performer rpm air gar intake. i want a rough idle and as much power as i can get.(motor will be in a truck.)carb-650 vac 2nd.The tranny is a 5 speed.i was thinking of the performer rpm cam.I was told by my local performance shop that with flat top pistons and vortec heads i am looking at 9.75:1 to 10:1.Heads can handle .550 max and .520 safe.

Thank you for the help

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Last edited by quickchevy95; 11-07-2008 at 07:19 AM.
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Old 11-07-2008, 07:24 AM
How fast is fast enough?
 
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262 cam. And you do not want a lot fo power in a truck- you want a lot of torque- BIG DIFFERENCE! And a rough idle ina truck will just lower your towing capacity, lower your milage, lower your usable power, and increase your running temps.... I'm not sayin gits a bad idea, I'll let the next guy do that.
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Old 11-07-2008, 07:32 AM
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How heavy is the truck and what is the rear-end ratio? What size rear tires? Are you gonna use this truck for any truck-like duties? I also agree you probably want a xe262 or equivalent. I have that cam in my camaro and it sounds stock, and makes good power off idle up to about 5000rpm.

If you want to use a rough idle cam you are probably going to need to re-gear your differential(s), taking into account your tire size too.
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Old 11-07-2008, 07:45 AM
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truck weighs 4800 and i will be using 31x11.5r22. the gear ratio can be changed to what it needs to be. the truck will be used as a street truck no hauling.also i really would like a rough idle. thanks for the info
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Old 11-07-2008, 07:57 AM
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If you use too small of a cam with that much cr, you will have detonation problems.

look for a cam with 270 degrees advertised (for 9.75:1 cr) to 280 degrees (10:1 cr) on the intake and another 6 to 8 on the exhaust. A 107 or 108 lsa will help low speed torque and give you the idle you want.

31 in tires will need a 3.90 to 4.11 gear for that cam, cr, and trans.
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Old 11-07-2008, 08:02 AM
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Quote:
Originally Posted by 454C10
If you use too small of a cam with that much cr, you will have detonation problems.

look for a cam with 270 degrees advertised (for 9.75:1 cr) to 280 degrees (10:1 cr) on the intake and another 6 to 8 on the exhaust. A 107 or 108 lsa will help low speed torque and give you the idle you want.

31 in tires will need a 3.90 to 4.11 gear for that cam, cr, and trans.
thanks for the help

Last edited by quickchevy95; 11-07-2008 at 08:07 AM.
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Old 11-07-2008, 10:04 AM
How fast is fast enough?
 
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I would still go with something like a XE268 on a 108 LSA- rough idle and yet good torque.
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Old 11-07-2008, 11:22 AM
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Quote:
Originally Posted by ap72
I would still go with something like a XE268 on a 108 LSA- rough idle and yet good torque.

A good cam but I feel he will have too much cr, especially if he builds a 10:1 engine. xe 268 cam with 9.75 would most likely require 93 octane fuel. Maybe 89 if the vortecs do their job, but the load is high pulling that truck

9.25:1 to 9.5:1 cr would be a good match for the xe268 since these cam were designed to make cylinder pressure.
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Old 11-07-2008, 11:58 AM
How fast is fast enough?
 
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well, you can always retard it 4 degrees... And it probably will require 93 octane, though if he goes with 4.56 gears it may not.
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Old 11-07-2008, 12:52 PM
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With around 10.0:1, you'll need more cam ground on a tighter lobe separation angle for rump-rump. 106 degree LSA should do it, something like these....

http://www.cranecams.com/?show=brows...tType=camshaft

http://www.cranecams.com/?show=brows...tType=camshaft

If you build the motor with squish of 0.035" to 0.045", you should have no trouble running pump gas. A 750 carb and 1 3/4" headers will maximize the combo for power.
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Old 11-07-2008, 01:21 PM
How fast is fast enough?
 
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I'm all in favor of big cams, you can look at the cars I drive to shwo that- but in a full size truck with a 350 that is driven on the street I cannot justify going with such a big cam. It will be slower than if he used a 268. He can go to a narrower LSA to get more midrange and a rougher idle. putting it on a 108, or even a 106 at 4 degrees retarded is more cam than that thing will ever need.

another thing you have to look at is his cruise RPM. When he hits the throtle on the highway with my cam, it will glide right by the truck using the other ones that are being recomended.
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Old 11-07-2008, 01:47 PM
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Everybody needs to screw this up at least once in their motor building experience and this young man is no exception. His statement is "i want a rough idle and as much power as i can get". Either of the cams I listed will do that. He has his mind set on what he wants and no amount of logic will change it in my opinion, so I'm simply providing recommendations based on his wishes.
Right now, he's thinking of a Performer RPM and I think that would be a REALLY BIG mistake in a 350 at 9.75-10.0 static c.r.
7102* 308° 318° 234° 244° .325 .340 .488 .510 10° BTDC 44° ABDC 59° BBDC 5° ATDC 112° 107°.
The 109.5 LSA won't give him what he wants in rump-rump, so I'm just trying to fill the bill with 106 on the Crane cams.
Gears will take care of moving the cruising point up past the dead zone.

All of us have done it. It's just that now it's this young man's turn to experience it.
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Old 11-07-2008, 06:28 PM
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Here's a novel idea, call the cam company and get their recommendations on compression ratio. Most mild performance cams now a days are designed for that 9.25:1 thur 10.25:1 (because that is what most of today's gasolines can support with decent heads). Read just about any mild (400 hp) engine build up story in the mags and they are using xe262 to xe274 cams with that CR spread. Get into race motors and radical cams, it might mean something.
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