Making a LS7 head rev?
Thread Starter
Staging Lane
Joined: Mar 2006
Posts: 62
Likes: 1
Making a LS7 head rev? I'm looking at building up a short stroke motor with LS7 heads so I can get a nice high rev range. Here is my basic plan:
Darton Sleeved LS2 block with 4.125 final bore
CP Pistons
Manley Billet Rods
Callies 3.625" Crank
What kind of valvetrain is needed to reliably rev to 8k? I'm not going to be running a crazy cam since this is for a forced induction application. My first thought would be to go to a Jesel Roller rocker setup.
What are my best options for valves, push rods and roller rocker setup?
Regards,
Justin
Darton Sleeved LS2 block with 4.125 final bore
CP Pistons
Manley Billet Rods
Callies 3.625" Crank
What kind of valvetrain is needed to reliably rev to 8k? I'm not going to be running a crazy cam since this is for a forced induction application. My first thought would be to go to a Jesel Roller rocker setup.
What are my best options for valves, push rods and roller rocker setup?
Regards,
Justin
solid roller for sure....
Is this a road race or drag race combo?
A 427 can go to about 7200-7400 with a hydraulic roller cam and you don't have to mess with setting the lash every few thousand miles.
Why give up the cubes? Are you limited by the class you are racing in?
Is this a road race or drag race combo?
A 427 can go to about 7200-7400 with a hydraulic roller cam and you don't have to mess with setting the lash every few thousand miles.
Why give up the cubes? Are you limited by the class you are racing in?
TECH Addict
Joined: Aug 2004
Posts: 2,866
Likes: 4
this might sound stupis but why go our to 427?????
you can make 1000bhp with a stock desplacement motor!
if i where you i would use the Darton sleved block and run a stock throw crank! this should let you rave the thing! are you going turbos or supercharger???
thanks Chris.
you can make 1000bhp with a stock desplacement motor!
if i where you i would use the Darton sleved block and run a stock throw crank! this should let you rave the thing! are you going turbos or supercharger???
thanks Chris.
Thread Starter
Staging Lane
Joined: Mar 2006
Posts: 62
Likes: 1
I'm going to be running Twin G40R's 1.06 a/r. My goal is 1000whp on pump at around 15psi.
I'm looking at making the topend flow the best I can, and thats why I'm interested in the LS7 heads. Just trying to make a nice free reving monster with a nice flat torque curve. I would like to use a shorter stroke to keep a better rod/stroke ratio and larger compression height to get a nice reliable ring package in the motor.
The car will be used for some road racing track days, but mostly drag racing.
Regards,
Justin
I'm looking at making the topend flow the best I can, and thats why I'm interested in the LS7 heads. Just trying to make a nice free reving monster with a nice flat torque curve. I would like to use a shorter stroke to keep a better rod/stroke ratio and larger compression height to get a nice reliable ring package in the motor.
The car will be used for some road racing track days, but mostly drag racing.
Regards,
Justin
IMHO, for that kind of power you should just be looking at a stroker iron block, but that's just my preference. Post up in the forced induction section and see what they say. I don't think you need to spend so much money with the 427 setup, when you can get 402s or 382s for less money and still meet your goal. (although I'm not sure if I have ever heard anyone going 1000 with pump gas )
Remember that revs put more strain on the rotation assembly (bottom end) than torque does. Every mechanical engineer here will atest to the fact that its more reliable to have a ~6500rpm motor making 800rwhp than a 8000rpm motor making only 550rwhp.
Thread Starter
Staging Lane
Joined: Mar 2006
Posts: 62
Likes: 1
I agree that reving the motor puts more stress on the rotating assembly. That is one of the main reasons I'm looking at going with a short stroke. It allows lower average piston speed per rpm, which lowers load. It also give me a longer rod with better geometry in the bottom end, so the bearings will last longer. I really dont like the tiny compression height and 1.5:1 rod stroke ratio of the ls7 for longevity.
Regards,
Justin
Regards,
Justin
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TECH Veteran
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From: Ft. Lauderdale, FL, USA
Originally Posted by Grimes
IMHO, for that kind of power you should just be looking at a stroker iron block, but that's just my preference. Post up in the forced induction section and see what they say. I don't think you need to spend so much money with the 427 setup, when you can get 402s or 382s for less money and still meet your goal. (although I'm not sure if I have ever heard anyone going 1000 with pump gas )
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Verdad Gallardo TECH Veteran
Joined: Dec 2001
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From: Ft. Lauderdale, FL, USA
Originally Posted by Darkness
Remember that revs put more strain on the rotation assembly (bottom end) than torque does. Every mechanical engineer here will atest to the fact that its more reliable to have a ~6500rpm motor making 800rwhp than a 8000rpm motor making only 550rwhp.
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Staging Lane
Joined: Jun 2006
Posts: 68
Likes: 0
Originally Posted by JustinOlson
I agree that reving the motor puts more stress on the rotating assembly. That is one of the main reasons I'm looking at going with a short stroke. It allows lower average piston speed per rpm, which lowers load. It also give me a longer rod with better geometry in the bottom end, so the bearings will last longer. I really dont like the tiny compression height and 1.5:1 rod stroke ratio of the ls7 for longevity.
Regards,
Justin
Regards,
Justin
Increasing your bore, youre decreasing your knock tolerance, larger bore=more nock.
2 big turbos 346 motor 8000 rpm is more like 1500+ hp and very ichy.
DoC
Last edited by duke of cruel; Jul 3, 2006 at 10:39 AM.
7400 is as high as we have spun some of our LS7 stuff with out issue. That is a stock head, stock rockers, stock pushrods, Comp 921s, new Ti valve with out the lash cap and a inconel exhaust valve. I wouldn't hesitate spinning it to 7600, but beyond that, I would have to do more testing. The cam is going to play a major role as well as your choice of valvetrain. The bottom end should be no problem, even if it was a 4" stroke.
Louis
Louis
TECH Enthusiast
Joined: May 2006
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From: south jersey
are there even aftermarket rockers for the ls7 yet, they arent the same as the ls1 style. as i came to find out, looking to buy rockers that i could buy now, use on my ls1 and, also use on ls7 style heads.but the ls7 are offset rockers.
Originally Posted by Louis
7400 is as high as we have spun some of our LS7 stuff with out issue. That is a stock head, stock rockers, stock pushrods, Comp 921s, new Ti valve with out the lash cap and a inconel exhaust valve. I wouldn't hesitate spinning it to 7600, but beyond that, I would have to do more testing. The cam is going to play a major role as well as your choice of valvetrain. The bottom end should be no problem, even if it was a 4" stroke.
Louis
Louis
Originally Posted by 00454sscamaro
are there even aftermarket rockers for the ls7 yet, they arent the same as the ls1 style. as i came to find out, looking to buy rockers that i could buy now, use on my ls1 and, also use on ls7 style heads.but the ls7 are offset rockers.
I'm wondering if there are any solid roller springs available that will work on ls7 heads
Why not build a 4.125 inch bore/ 3.00 inch stroke motor? That would make a 321 inch motor. At that bore to stroke ratio 8k rpm shouldnt be a problem at all. Hell 8k+ shouldnt be a problem. If your going to go turbo just compensate by adding more boost, tune for 2 things street and track. On the street turn your boost down and when you go to the track, put in race gas and crank up the boost. This setup will spin up faster and on the street get better mileage.
Originally Posted by ram09
Why not build a 4.125 inch bore/ 3.00 inch stroke motor? That would make a 321 inch motor. At that bore to stroke ratio 8k rpm shouldnt be a problem at all. Hell 8k+ shouldnt be a problem. If your going to go turbo just compensate by adding more boost, tune for 2 things street and track. On the street turn your boost down and when you go to the track, put in race gas and crank up the boost. This setup will spin up faster and on the street get better mileage.
On The Tree
Joined: May 2006
Posts: 148
Likes: 0
I've asked this question before with little response. So from what i have been able to gather from some SBC circle track guys i know....
The valvetrain is the issue. The heavier the parts the heavier the springs you need to control it. Although some of the trends i have been seeing has been to stiffen the pushrods even though that adds weight...the idea is to not have the valve train go into resonance. Stiffer = higher natural frequency = better valve train stability and that lets you rev it higher. If you still try to keep lightweight parts in there that does help...valves are a big one, along with retainers and locks(ie beehive springs). Push rods don't have to be super light as they are in compression so stiffness rules there. We could go on all day about valvetrain dynamics.
I would suggest the Jesel or T&D(if they have LS parts yet) rockers. Valves as light as you can stand, Big diameter pushrods, then call someone on the correct springs and cam for the application.
Keep the stroke down if you can, otherwise, you'll need really good stuff down there.
From the LS7 flow numbers(stock or ported)....you should get 600-700hp on good pump gas with a 427" engine. And with that, if it's for the street, you may need to watch your stall speed if you run an automatic.
I still wouldn't run this combination daily....it will probably suck driving it on the street and it would probably be a bit expensive.
The valvetrain is the issue. The heavier the parts the heavier the springs you need to control it. Although some of the trends i have been seeing has been to stiffen the pushrods even though that adds weight...the idea is to not have the valve train go into resonance. Stiffer = higher natural frequency = better valve train stability and that lets you rev it higher. If you still try to keep lightweight parts in there that does help...valves are a big one, along with retainers and locks(ie beehive springs). Push rods don't have to be super light as they are in compression so stiffness rules there. We could go on all day about valvetrain dynamics.
I would suggest the Jesel or T&D(if they have LS parts yet) rockers. Valves as light as you can stand, Big diameter pushrods, then call someone on the correct springs and cam for the application.
Keep the stroke down if you can, otherwise, you'll need really good stuff down there.
From the LS7 flow numbers(stock or ported)....you should get 600-700hp on good pump gas with a 427" engine. And with that, if it's for the street, you may need to watch your stall speed if you run an automatic.
I still wouldn't run this combination daily....it will probably suck driving it on the street and it would probably be a bit expensive.
