cam shafts
Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,880
Likes: 4
From: Montgomery Texas
cam shafts
I am going to change out my factory TPI intake for one that I have ported out in a couple of weeks. While I have it off I thought about changing Camshafts. Will I gain much with a cam change? I do not have the factory motor in my 1990 c4 it has been changed to a ZZ4. If I do change cams what would be the best cam for my car? I have a 2800rpm stall, 307 rear end, etc.
Last edited by Crowhater; Feb 14, 2011 at 09:15 AM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Because the ZZ4 engine is such a good buy, cost wise ;
many buy one and then swap in a cam of their own choice
Also given that a ZZ4 looks identical to a '90 engine ; how do you know you actually have a ZZ4 installed
What numbers on block?
Last edited by rodj; Feb 14, 2011 at 07:05 PM.
Melting Slicks
Joined: Sep 2010
Posts: 2,422
Likes: 202
it's a close call to use 1.6 rockers on ZZ4 springs
your final lift will be .504 .540 you may have coil bind
they claim a max .550 lift that's pushing them especially if there older
your final lift will be .504 .540 you may have coil bind
they claim a max .550 lift that's pushing them especially if there older
Last edited by THE 383 admiral; Feb 14, 2011 at 09:09 PM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
ZZ4 /LT4 springs are only factory rated to .525
http://www.superchevyperformance.com...p/12495494.htm
http://www.gmpartsdirect.com/performance_part
s/store/catalog/Product.jhtmlPRODID=742&CATID=734.html
http://www.jegs.com/i/GM-Performance...oductId=761647
Some say they are safe to .530
http://www.superchevyperformance.com...p/12495494.htm
http://www.gmpartsdirect.com/performance_part
s/store/catalog/Product.jhtmlPRODID=742&CATID=734.html
http://www.jegs.com/i/GM-Performance...oductId=761647
Some say they are safe to .530
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Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,880
Likes: 4
From: Montgomery Texas
Guy please explain? Do I need to change my springs to run the 1.6 rockers? If so what springs do I need and what seat pressure do I set them up at? My ZZ4 engine has about 30k miles on it.
Melting Slicks
Joined: Sep 2010
Posts: 2,422
Likes: 202
yes upgrade your springs if you want to install 1.6 rocker ratio
I would use something close to compcams 986 springs
132 seat@ 1.75<> 293 open @1.25
I would use something close to compcams 986 springs
132 seat@ 1.75<> 293 open @1.25
Last edited by THE 383 admiral; Feb 14, 2011 at 09:30 PM.
Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,880
Likes: 4
From: Montgomery Texas
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Drifting
Joined: Feb 2003
Posts: 1,978
Likes: 2
From: San Antonio Texas
Like rodj says, you need to find out what Cam you actually have and go from there. As for 1.6 Rockers with the ZZ4 Cam... Kevin McClelland; who helped develop the ZZ4, " The reason I don't like 1.6 Rockers on the ZZ4 Camshaft profile is because when GM designed that Camshaft, the acceleration rates and the opening and closing velocities were pushed to the max. With the additional acceleration of the 1.6 Rockers, the valve actions become unstable. The Valve will bounce on the seat on closing at high engine speed. There is also a lot of inherent noise with adding these rockers to the lobe, which was designed for 1.5 ratio Rocker." (Chevy High Performance May 2009)
Aside from that, you want to keep the Cam pretty small if you're running a TPI on the street. It just isn't going to pull much over 5K even ported, because of the Runner length.
Aside from that, you want to keep the Cam pretty small if you're running a TPI on the street. It just isn't going to pull much over 5K even ported, because of the Runner length.
Last edited by Curveit; Feb 15, 2011 at 02:15 AM.
Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,880
Likes: 4
From: Montgomery Texas
Like rodj says, you need to find out what Cam you actually have and go from there. As for 1.6 Rockers with the ZZ4 Cam... Kevin McClelland; who helped develop the ZZ4, " The reason I don't like 1.6 Rockers on the ZZ4 Camshaft profile is because when GM designed that Camshaft, the acceleration rates and the opening and closing velocities were pushed to the max. With the additional acceleration of the 1.6 Rockers, the valve actions become unstable. The Valve will bounce on the seat on closing at high engine speed. There is also a lot of inherent noise with adding these rockers to the lobe, which was designed for 1.5 ratio Rocker." (Chevy High Performance May 2009)
Aside from that, you want to keep the Cam pretty small if you're running a TPI on the street. It just isn't going to pull much over 5K even ported, because of the Runner length.
Aside from that, you want to keep the Cam pretty small if you're running a TPI on the street. It just isn't going to pull much over 5K even ported, because of the Runner length.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Might want to reconsider that ;
3.07 is recommended best all round ratio for a TPI car.TPI cars have gone slower with lower gears because engine passes through the torque range too fast
Comments from someone who actually knows what he is talking about
http://forums.corvetteforum.com/1568185079-post21.html
As Curveit notes above
" It just isn't going to pull much over 5K even ported, because of the Runner length."
Do the rpm vs mph maths and see what the optional gear sets give you
3.07 is recommended best all round ratio for a TPI car.TPI cars have gone slower with lower gears because engine passes through the torque range too fast
Comments from someone who actually knows what he is talking about
http://forums.corvetteforum.com/1568185079-post21.html
As Curveit notes above
" It just isn't going to pull much over 5K even ported, because of the Runner length."
Do the rpm vs mph maths and see what the optional gear sets give you
Thread Starter
Drifting
Joined: Aug 2010
Posts: 1,880
Likes: 4
From: Montgomery Texas
Might want to reconsider that ;
3.07 is recommended best all round ratio for a TPI car.TPI cars have gone slower with lower gears because engine passes through the torque range too fast
Comments from someone who actually knows what he is talking about
http://forums.corvetteforum.com/1568185079-post21.html
As Curveit notes above
" It just isn't going to pull much over 5K even ported, because of the Runner length."
Do the rpm vs mph maths and see what the optional gear sets give you
3.07 is recommended best all round ratio for a TPI car.TPI cars have gone slower with lower gears because engine passes through the torque range too fast
Comments from someone who actually knows what he is talking about
http://forums.corvetteforum.com/1568185079-post21.html
As Curveit notes above
" It just isn't going to pull much over 5K even ported, because of the Runner length."
Do the rpm vs mph maths and see what the optional gear sets give you