HELP please
Thread Starter
Junior Member
Joined: Nov 2001
Posts: 12
Likes: 0
From: Mesa, AZ, United States
Car: 1991 Z28
Engine: 350
Transmission: TH700R4
HELP please
I originally submitted the following letter question to Chevrolet's technical help center. They informed me they were not able to answer my question, and directed me to a local dealer or a Camaro club. I decided to come to you guys for help. Here's the original message:
To whom it may concern,
I bought a 1991 Camaro Z28 last year, and I've decided to increase its performance a little with some GM Performance Parts. The Camaro has the L98 350 with stock centerbolt cast iron heads. Immediately below are some of the part numbers and specifications of the modifications I would like to install. Below that are my questions.
Stock '91 L98 Cam
..05" Duration: 202/207
1.5:1 Lift: .413/.428 <-- Stock
1.6:1 Lift: .441/.457
Lobe Separation: 114.5 deg
ZZ4 Cam (Part # 10185071)
..05" Duration: 208/221
1.5:1 Lift: .474/.510
1.6:1 Lift: .510/.544 <-- Intended Combo
Lobe Separation: 112 deg
Aluminum Roller Rocker (1.6:1 Ratio) Part #: 12370839
According to the GM Performance Parts catalog, I should use retainer # 14003974, spring # 10134358, and valve seal # 10132714.
I would like to install the ZZ4 cam and the 1.6:1 ratio rocker arms. This car is not intended to be an all out racing machine; I want to make it a daily driver with the possibility of light strip use. I want to keep most, if not all, of the L98's bone-twisting low and midrange torque. A loss of 100 lb-ft would be unacceptable in the low RPM range. I do not intend to rev the Camaro above 5500. Now for my questions.
1. What would be absolutely MANDATORY on the car for the ZZ4/1.6 combo to work? I.e. valve to piston clearance, valve guides, spring pockets, rocker studs, etc.
2. Besides mandatory modifications, what would you recommend to make this setup run well?
3. Are the springs listed with the ZZ4 cam on its catalog adequate for the .544 lift associated with this camshaft?
4. I understand it is impossible to accurately predict the reactions of engine modifications, but what kind of performance gains may I be able to predict with this setup?
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1991 Camaro Z28 350 Hardtop
To whom it may concern,
I bought a 1991 Camaro Z28 last year, and I've decided to increase its performance a little with some GM Performance Parts. The Camaro has the L98 350 with stock centerbolt cast iron heads. Immediately below are some of the part numbers and specifications of the modifications I would like to install. Below that are my questions.
Stock '91 L98 Cam
..05" Duration: 202/207
1.5:1 Lift: .413/.428 <-- Stock
1.6:1 Lift: .441/.457
Lobe Separation: 114.5 deg
ZZ4 Cam (Part # 10185071)
..05" Duration: 208/221
1.5:1 Lift: .474/.510
1.6:1 Lift: .510/.544 <-- Intended Combo
Lobe Separation: 112 deg
Aluminum Roller Rocker (1.6:1 Ratio) Part #: 12370839
According to the GM Performance Parts catalog, I should use retainer # 14003974, spring # 10134358, and valve seal # 10132714.
I would like to install the ZZ4 cam and the 1.6:1 ratio rocker arms. This car is not intended to be an all out racing machine; I want to make it a daily driver with the possibility of light strip use. I want to keep most, if not all, of the L98's bone-twisting low and midrange torque. A loss of 100 lb-ft would be unacceptable in the low RPM range. I do not intend to rev the Camaro above 5500. Now for my questions.
1. What would be absolutely MANDATORY on the car for the ZZ4/1.6 combo to work? I.e. valve to piston clearance, valve guides, spring pockets, rocker studs, etc.
2. Besides mandatory modifications, what would you recommend to make this setup run well?
3. Are the springs listed with the ZZ4 cam on its catalog adequate for the .544 lift associated with this camshaft?
4. I understand it is impossible to accurately predict the reactions of engine modifications, but what kind of performance gains may I be able to predict with this setup?
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1991 Camaro Z28 350 Hardtop
Supreme Member
Joined: Nov 2001
Posts: 4,456
Likes: 3
From: Ocean, NJ
Car: Check The Sig
im bringing this back up top cause i have the same questions.. someone help us out... ive been flyin around the board, lookin for answers.. and have yet to find them... thanks guys