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Quasi-Traction
"I have petals"
Joined: 24 Oct 2005
Posts: 3873
Location: stumptown
1986 Chevrolet Camaro Berlinetta
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 Posted: Sun Feb 05, 2006 8:51 pm Post subject: Camshaft Question. |
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A friend of mine is thinking about a new cam for his 72 C-10. Block has a casting number of 3956618. According to my SBC guide that should be a 4 bolt. The heads are Center Bolt heads, obviously off a post 86 motor, most likely a caprice or impala. He says they are vortec heads and supposed to have 1.94/1.5 valves in them.
(disclaimer)--the reason why I'm so intrested in this is because I may get this truck from him, for my 64 Fairlane and a couple hundred bucks if I help with the cam swap....
The car has Power Disc Brakes up front with what looks like the orginal booster and master cylinder
The cam he has picked out is a Comp Cam Magnum 270H with lifters.
The truck has a TH350 with a shift kit, and some aftermarket converter of unknown orgin.
I've never done a cam swap before but know the basics about it. He's done it twice both on Windsor block fords, so hes the experienced one. I was concerned if there'd be enough vaccum generated at idle to operate his transmission and or brake booster or if we're gonna need a vaccum cannister also. He sounded pretty confident it'd be fine, I'm more doubtful.
I don't know what's on there now, but assuming its stock..Will we need aftermarket rockers arms? perhaps a 1.6 or 1.7 ratio for the increased lift?
I really don't want him(us) to screw this motor up, because I do want it for my 84 camaro.
What should I be aware of going into this?
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Twilightoptics
Hardcore (12sec Club)
Joined: 13 Jan 2004
Posts: 9191
Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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| Posted: Mon Feb 06, 2006 1:13 pm Post subject: |
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Do a little research.
What are the specs on the cam?
Only big blocks can run 1.7 rockers. I don't think 1.6 rockers are worth it IMHO. More likely to fail valve train.
With the new cam reguardless, you need to check pushrod geometry (Pushrod length will probably change with the new cam) or could be off already.
Vortec heads? Are there 4 intake bolt holes on each head... or 6? If there are 4, they are vortec.
I run a really big cam, and I can use my brakes and it operates my TH350 just fine. IMHO I'd pick an XE line from COMP if going comp... otherwise one of Lunati's Voodoo cams in the 220/228 @.050 duration on a 110 would suit you perfectly. |
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rice B-4
Member
Joined: 24 Jan 2004
Posts: 55
Location: Portland, OR
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| Posted: Mon Feb 06, 2006 7:34 pm Post subject: |
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Cam specs, 270 adv 224 @.050 470 lift 110 lsa
Aftermarket rockers are highly recomended. 
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"Horse power is how fast you hit the wall, Torque is how far you take the wall with you."
99 Camaro Z28 LS1 |
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Quasi-Traction
"I have petals"
Joined: 24 Oct 2005
Posts: 3873
Location: stumptown
1986 Chevrolet Camaro Berlinetta
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| Posted: Mon Feb 06, 2006 8:37 pm Post subject: |
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cool. Paul you'd also recomend different pushrods? Do you also think we should go to a roller tip rocker? I don't know what's in there, but I'll definately get back to you when I do. With the roller rockers should we possibly have the heads machined for screw in studs? If I end up with this motor, it'll probably get pushed to 4500-5000 rpm often.
We'll take the motor and transmission are coming out of the truck next week sometime. I'll count the intake bolts then.
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Twilightoptics
Hardcore (12sec Club)
Joined: 13 Jan 2004
Posts: 9191
Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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| Posted: Mon Feb 06, 2006 10:50 pm Post subject: |
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| Quasi-Traction wrote: | cool. Paul you'd also recomend different pushrods? Do you also think we should go to a roller tip rocker? I don't know what's in there, but I'll definately get back to you when I do. With the roller rockers should we possibly have the heads machined for screw in studs? If I end up with this motor, it'll probably get pushed to 4500-5000 rpm often.
We'll take the motor and transmission are coming out of the truck next week sometime. I'll count the intake bolts then. |
I wouldn't worry about pushrod type unless you spin above 5500 regularly, and or have guideplates. Screw in studs RULE but if you don't have them, don't worry about it for now. You need to check the geometry of the pushrods. Take a sharpie and coat the valve stem with it. Then bolt your rocker arm down as normal.. then crank the engine around to make that rocker go full lift and back... then unscrew the rocker. The wear should be in the very center of the stem. If not.. you need longer or shorter pushrods. Longer pushrods will I believe bring the wear line toward the pushrod, and shorter will push it towards the header. Comp makes adjustable length pushrods to be used to find the actual size you need. If you get roller rockers it's even more important, because just the tip of the roller rides on the stem. You don't want that sliding off.
If you run too big a cam, the valve guides need to be cut down to accomodate the lift. Not sure what the limits are. Same go for springs. Whatever cam you get, get the proper spring recommended for it.
Roller tip rockers are a waste of money. They don't add any power, or free up power or anything. I had BAD luck with Comp Magnum tip rockers. If you go with stock type... get summit's long slot stamped steel ones. They work great. If you really wanna go roller, get harland sharpe full rollers or the Comp Pro Magnum full roller. Spendy, but I love em. |
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