Low and Mid Range Torque
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Junior Member
Joined: Nov 2001
Posts: 12
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From: Mesa, AZ, United States
Car: 1991 Z28
Engine: 350
Transmission: TH700R4
Low and Mid Range Torque
I plan on changing my cam, but I want to keep my Camaro a daily driver (but still as much of a street monster as possible). I might go to the track a few times, but that's no much of a concern for me. Anyway, I was planning to change my cam and rockers in December when I'm off school. I want to get the GM Performance Parts ZZ4 Cam and Pro Magnum Roller Rockers with 1.6:1 ratio. I wrote to Summit just to get another opinion on how it would react, and they told me all they could guarantee is a loss of low-end torque. Anyway, what I really want is to increase my low and midrange torque (or at least keep it about the same) while increasing my horsepower. I've got the specs of my stock cam and the ZZ4 cam below. I'll be using stock heads, and I'll be changing valve springs to accept the lift. I've also got 1 3/4" SLP headers. Any suggestions or comments or questions would be greatly appreciated; feel free to e-mail me.
Stock '91 L98
.05" Duration: 202/207
1.5:1 Lift: .413/.428
1.6:1 Lift: .441/.457
Lobe Seperation: 114.5 deg
ZZ4 Cam
.05" Duration: 208/221
1.5:1 Lift: .474/.510
1.6:1 Lift: .510/.544 <-- Intended Combo
Lobe Seperation: 112 deg
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1991 Camaro Z28 350 Hardtop
Stock '91 L98
.05" Duration: 202/207
1.5:1 Lift: .413/.428
1.6:1 Lift: .441/.457
Lobe Seperation: 114.5 deg
ZZ4 Cam
.05" Duration: 208/221
1.5:1 Lift: .474/.510
1.6:1 Lift: .510/.544 <-- Intended Combo
Lobe Seperation: 112 deg
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1991 Camaro Z28 350 Hardtop
TGO Supporter
Joined: Jul 1999
Posts: 402
Likes: 0
From: Madison, AL, USA
Take Summit's advice with a grain of salt. The ZZ4 cam is a great choice on a TPI to retain decent low end while adding top end. You might lose a little low end but that will just make it easier to hook up on the street.
The bigger issue is trying to run that cam with stock heads. In addition to valve springs, you'll also need to worry about spring retainer to valve guide clearance. Most Chevy heads will only handle up to .470-.480" valve lift without problems. Most common fix is to pull the heads and mill down the top of the valve guides. You'll also want to convert from pressed-in to screw-in studs with that much lift and beefier valve springs. I'm sure someone out there will disagree but I don't think it's worth the cost or work.
My advice would be to look at the Crane 2032, Comp 264HR, and Accel 74216 if you want to run stock heads. All these cams are designed for TPI and valve lift is less than or equal .480" with 1.5 rockers.
The bigger issue is trying to run that cam with stock heads. In addition to valve springs, you'll also need to worry about spring retainer to valve guide clearance. Most Chevy heads will only handle up to .470-.480" valve lift without problems. Most common fix is to pull the heads and mill down the top of the valve guides. You'll also want to convert from pressed-in to screw-in studs with that much lift and beefier valve springs. I'm sure someone out there will disagree but I don't think it's worth the cost or work.
My advice would be to look at the Crane 2032, Comp 264HR, and Accel 74216 if you want to run stock heads. All these cams are designed for TPI and valve lift is less than or equal .480" with 1.5 rockers.
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