Camshaft opinion

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Nov 16, 2002 | 06:10 PM

bigxd

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Joined: Nov 2002

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From: --

Camshaft opinion

Hi Guys,

Im starting to prepare for a rebuild of my 71 460 and have a question regarding the camshaft. The profile I'm currently looking at has the following specs:
Intake Open 33
Intake Close 69
Intake Adv. Duration 282 - or 234 @.050"

Exhaust Open 74
Exhaust Close 38
Exhaust Adv. Duration 292 - or 240 @.050"

108 Lobe Center
Lift at Lobe .085"
Lift at Valve .547
Suggested comp 10:1

I like this cam because it is longer on the exhaust, but im a little worried about the lobe centre angle. With 108 it might be a little tight for a truck? (F150 SWB)

Anyone know what the characteristics of this cam will be like?
Am I gonna need some serious porting on the heads or will I be able to get away with just some smog bump removal?

Im currently running a C6 and 3.00 at the diff. Would I need to consider a stall converter or maybe dropping the ratio to say 3.55 or even higher?

Any clues on what vacuum will be like? (poor/good?)

Any help would be greatly appreciated.

Thanks,
Steve

Nov 17, 2002 | 08:25 AM

DeenHylton

Elder User

Joined: Jan 2000

Posts: 966

Likes: 2

From: Crooked River Ranch, OR

Camshaft opinion

That cam will be way too big for your truck unless you intend to use it for racing. Looking at Summits generic cam guide they state your power band would be 3000-6500 rpm. They also recommend a stall converter 2000 RPM above stock which would put you around 3000-3200 stall. I'd go further than that and say you'd also need a 3:73 to 4:11 gear depending how tall your tires would be, headers, dual exhaust, aftermarket ignition, 800 CFM and up carb.
If your truck is used mainly for street use and off road 4-wheeling get something similar to the Comp Cams 268 series or the CompXtreme series. Other cam MFGs. have similar grinds

Nov 17, 2002 | 01:52 PM

gray79f250

Senior User

Joined: Apr 2002

Posts: 482

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From: lake ariel usa

Camshaft opinion

That cam would need more gear and convertor for sure. You should try to get a cam with split duration and lift to help with the small exhaust. I would say porting for sure. Be sure to change the springs also if you go over 500 lift with stock springs you will get coil bind and bend the pushrods. I bought a rebuilt 429 for $300 because someone used stock springs and a big cam. They couldnt get it started lol my lucky day.

Nov 18, 2002 | 10:42 AM

georgedavila

Postmaster

Joined: Aug 2001

Posts: 2,882

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From: Nevada

Camshaft opinion

As others have said, that cam is way too big for stock heads. Even removing the smog bumps won't be enough for them to flow that lift. .520 is about max lift with the smog bumps removed.

Nov 18, 2002 | 09:47 PM

LxMan1

Moderator

Joined: Dec 2001

Posts: 22,436

Likes: 17

From: Louisville,Ky.

Camshaft opinion

Use the CompCams 268h. I love it. Use a good double roller timing set and put on matching valve springs any time you install a larger camshaft!!
Jimmy

Nov 19, 2002 | 01:24 AM

merc460

More Turbo

Joined: Sep 2001

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From: Kelowna

Camshaft opinion

Nov 19, 2002 | 03:57 AM

bigxd

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Joined: Nov 2002

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From: --

Camshaft opinion

What kind of horsepower / torque can I expect from the CompCams 268h? (after I port the smog bumps etc) Ive seen a lot mentioned about this and the 272h.

Has anyone had experience with oversizing the exhaust valve? I was reading somewhere that a 1.8 - 1.9" valve works great as it ups the valve/port ratio and the inlet/exhaust ratio. They say you still need to port it, but really only to remove the bumps and help with the bowl shaping. No need to go wild with the die grinder. Using the smaller valve requires a lot more port work because of the valve/port ratio.

Does any of this make sense?

I want my old beast to COME ALIVE!

Thanks in advance,
Steve

71' 460
Holley 850 Dbl Pumper
Stock Heads D3VE-A2A's
Stock Manifold
Stock everything!
2.5" Stainless X-pipe and dual 2.5" high flow mufflers
31x10.5x15 Dunlops
3.00:1 rear
C6 with shift kit
62mph in 1st and still pullin!