243 vs 317 head question
Thread Starter
Staging Lane
Joined: Aug 2020
Posts: 94
Likes: 10
243 vs 317 head question Sorry to bring up another post asking questions about what head is better. But I couldn't find an answer to my specific question. So yesterday I pulled an LQ9 out of a 2004 Escalade from my local U Pull n Pay. Got it on sale for only $175 out the door. Anyway I plan on replacing the pistons with forged ones for a street nitrous motor. This motor will replace the LS6 I have in my Corvette now. Anyway I have two sets of heads. 243's and now a set of 317's. It seems (from internet searching) that they both flow about the same. But the 243's being a 64cc chamber give higher compression.
Being that I'm buying new pistons anyway I can have whatever compression ratio I want with either head. With the 317 heads I could get -4.00cc pistons and net around 10.5:1 compression ratio. If I use the 243's I could use +3.00cc pistons and net around 10.6:1 compression ratio.
So my question is, is there any advantage to one set of heads over the other? I need around 10.5:1 compression. I can get that with either head depending on what piston I buy. They both have similar flow numbers. Any thoughts? Are there any factors I'm not thinking of? If it makes any difference I'm planing on spraying a 200 progressive shot of nitrous.
Being that I'm buying new pistons anyway I can have whatever compression ratio I want with either head. With the 317 heads I could get -4.00cc pistons and net around 10.5:1 compression ratio. If I use the 243's I could use +3.00cc pistons and net around 10.6:1 compression ratio.
So my question is, is there any advantage to one set of heads over the other? I need around 10.5:1 compression. I can get that with either head depending on what piston I buy. They both have similar flow numbers. Any thoughts? Are there any factors I'm not thinking of? If it makes any difference I'm planing on spraying a 200 progressive shot of nitrous.
Sorry to bring up another post asking questions about what head is better. But I couldn't find an answer to my specific question. So yesterday I pulled an LQ9 out of a 2004 Escalade from my local U Pull n Pay. Got it on sale for only $175 out the door. Anyway I plan on replacing the pistons with forged ones for a street nitrous motor. This motor will replace the LS6 I have in my Corvette now. Anyway I have two sets of heads. 243's and now a set of 317's. It seems (from internet searching) that they both flow about the same. But the 243's being a 64cc chamber give higher compression.
Being that I'm buying new pistons anyway I can have whatever compression ratio I want with either head. With the 317 heads I could get -4.00cc pistons and net around 10.5:1 compression ratio. If I use the 243's I could use +3.00cc pistons and net around 10.6:1 compression ratio.
So my question is, is there any advantage to one set of heads over the other? I need around 10.5:1 compression. I can get that with either head depending on what piston I buy. They both have similar flow numbers. Any thoughts? Are there any factors I'm not thinking of? If it makes any difference I'm planing on spraying a 200 progressive shot of nitrous.
Being that I'm buying new pistons anyway I can have whatever compression ratio I want with either head. With the 317 heads I could get -4.00cc pistons and net around 10.5:1 compression ratio. If I use the 243's I could use +3.00cc pistons and net around 10.6:1 compression ratio.
So my question is, is there any advantage to one set of heads over the other? I need around 10.5:1 compression. I can get that with either head depending on what piston I buy. They both have similar flow numbers. Any thoughts? Are there any factors I'm not thinking of? If it makes any difference I'm planing on spraying a 200 progressive shot of nitrous.
Thread Starter
Staging Lane
Joined: Aug 2020
Posts: 94
Likes: 10
Thanks for the reply. The 243's I have only have 200 miles since they had a valve job and the guides checked. So they aren't just pulled by any means. If I were to use the 317's they would get the same treatment. I can't justify the cost of having them ported. My power goals are 500 hp at the crank all motor. Lots of people have reached that without port work. So I figured I would give it a shot.
Hot Rod had an interesting article on these heads this month. They compared the 317, to the 243, and the 862 LS3 head. To shorten the story, the 243s were the favorite including when compared to the LS3 head. All heads were stock,and the 317 came in last. Its a good read, check it out.
243s was the performance head for a reason imo. Stock ports can make 500whp.
I don't think building a motor for a hp goal is the right route. Look at the entire car as a package and build to a acceleration goal.
If it were me i would slam those 243s on the 6.0 with some thinner head gasket and mill them atleast .020. If you're doing this yourself throw some ring gap in it and spray away.
I don't think building a motor for a hp goal is the right route. Look at the entire car as a package and build to a acceleration goal.
If it were me i would slam those 243s on the 6.0 with some thinner head gasket and mill them atleast .020. If you're doing this yourself throw some ring gap in it and spray away.
Thread Starter
Staging Lane
Joined: Aug 2020
Posts: 94
Likes: 10
243s was the performance head for a reason imo. Stock ports can make 500whp.
I don't think building a motor for a hp goal is the right route. Look at the entire car as a package and build to a acceleration goal.
If it were me i would slam those 243s on the 6.0 with some thinner head gasket and mill them atleast .020. If you're doing this yourself throw some ring gap in it and spray away.
I don't think building a motor for a hp goal is the right route. Look at the entire car as a package and build to a acceleration goal.
If it were me i would slam those 243s on the 6.0 with some thinner head gasket and mill them atleast .020. If you're doing this yourself throw some ring gap in it and spray away.
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The 243 and 317 have the same runners on the intake, not 100% but I think they are the same on the exhaust as well. The 243 has the smaller chamber for more compression.
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From: Central Cal.
Thread Starter
Staging Lane
Joined: Aug 2020
Posts: 94
Likes: 10
Thanks for all the advice guys. I wish I could get E85 here. I think I've only ever seen one gas station that sold it. Being that I drive the car to work from time to time I need to stick with regular pump gas.
The only reason I wanted to stick with a lower lift cam was because the 243 heads I have already have PAC 1218 springs that are only good for .600 lift. I was just trying to save some money.
The only reason I wanted to stick with a lower lift cam was because the 243 heads I have already have PAC 1218 springs that are only good for .600 lift. I was just trying to save some money.
Thread Starter
Staging Lane
Joined: Aug 2020
Posts: 94
Likes: 10
After looking at cams some today I keep looking at the new Summit Racing cams. The stage 2 Pro LS seems interesting. 226/238 113+3, .600/.600 Lift. The PAC 1218 springs say they are good up to .600 lift. You guys think I could get away with this cam with 1218 springs? Anyone have any input on how this thing would run with 11:1 compression in a 6.0L and this cam? Also I'm fairly convinced I'm going to sell my LS6 intake and buy a FAST 102.
After looking at cams some today I keep looking at the new Summit Racing cams. The stage 2 Pro LS seems interesting. 226/238 113+3, .600/.600 Lift. The PAC 1218 springs say they are good up to .600 lift. You guys think I could get away with this cam with 1218 springs? Anyone have any input on how this thing would run with 11:1 compression in a 6.0L and this cam? Also I'm fairly convinced I'm going to sell my LS6 intake and buy a FAST 102.
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Joined: Jan 2008
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Phobos84,
Our Pro LS stage 2 SUM-8707 would be a great fit for your combo. It will have a nice steady lope but it tunes well and is easy to live with. The planned 11+:1 compression, FAST 102, 3,600 rpm converter, and 3.73 gears will really help this cam shine. In a lightweight Corvette, this would be an absolute joy.
PTV clearance shouldn't be an issue with our stage 2 even with the .020" milling of the 243's. You could likely mill .030" to bump compression even more. 11.5:1 is common and still good for use with 93. We do recommend checking PTV before final assembly. We designed this cam with the use of .600 lift beehives like the PAC 1218's in mind. They'd be good for near 7,000 rpm operation. If you wanted to turn 7,000 + rpm we'd recommend .660 lift duals such as the TFS-2500286.
SLP IROC-Z mentioned 11/32 pushrods. We really like that recommendation to help keep the valvetrain stable. We have our 11/32 .120" wall HDR pushrods.Typically a 7.425" pushrod will work with an unmilled stock head and LS7 lifters with .060-.080" pre-load. Things vary especially with milled heads and the travel of aftermarket lifters. This is why we always recommend measuring for pushrod length before purchasing pushrods. If you don't already have a pushrod length checker we offer the TFS-9501.
Our Pro LS stage 2 SUM-8707 would be a great fit for your combo. It will have a nice steady lope but it tunes well and is easy to live with. The planned 11+:1 compression, FAST 102, 3,600 rpm converter, and 3.73 gears will really help this cam shine. In a lightweight Corvette, this would be an absolute joy.
PTV clearance shouldn't be an issue with our stage 2 even with the .020" milling of the 243's. You could likely mill .030" to bump compression even more. 11.5:1 is common and still good for use with 93. We do recommend checking PTV before final assembly. We designed this cam with the use of .600 lift beehives like the PAC 1218's in mind. They'd be good for near 7,000 rpm operation. If you wanted to turn 7,000 + rpm we'd recommend .660 lift duals such as the TFS-2500286.
SLP IROC-Z mentioned 11/32 pushrods. We really like that recommendation to help keep the valvetrain stable. We have our 11/32 .120" wall HDR pushrods.Typically a 7.425" pushrod will work with an unmilled stock head and LS7 lifters with .060-.080" pre-load. Things vary especially with milled heads and the travel of aftermarket lifters. This is why we always recommend measuring for pushrod length before purchasing pushrods. If you don't already have a pushrod length checker we offer the TFS-9501.
Thread Starter
Staging Lane
Joined: Aug 2020
Posts: 94
Likes: 10
Phobos84,
Our Pro LS stage 2 SUM-8707 would be a great fit for your combo. It will have a nice steady lope but it tunes well and is easy to live with. The planned 11+:1 compression, FAST 102, 3,600 rpm converter, and 3.73 gears will really help this cam shine. In a lightweight Corvette, this would be an absolute joy.
PTV clearance shouldn't be an issue with our stage 2 even with the .020" milling of the 243's. You could likely mill .030" to bump compression even more. 11.5:1 is common and still good for use with 93. We do recommend checking PTV before final assembly. We designed this cam with the use of .600 lift beehives like the PAC 1218's in mind. They'd be good for near 7,000 rpm operation. If you wanted to turn 7,000 + rpm we'd recommend .660 lift duals such as the TFS-2500286.
SLP IROC-Z mentioned 11/32 pushrods. We really like that recommendation to help keep the valvetrain stable. We have our 11/32 .120" wall HDR pushrods.Typically a 7.425" pushrod will work with an unmilled stock head and LS7 lifters with .060-.080" pre-load. Things vary especially with milled heads and the travel of aftermarket lifters. This is why we always recommend measuring for pushrod length before purchasing pushrods. If you don't already have a pushrod length checker we offer the TFS-9501.
Our Pro LS stage 2 SUM-8707 would be a great fit for your combo. It will have a nice steady lope but it tunes well and is easy to live with. The planned 11+:1 compression, FAST 102, 3,600 rpm converter, and 3.73 gears will really help this cam shine. In a lightweight Corvette, this would be an absolute joy.
PTV clearance shouldn't be an issue with our stage 2 even with the .020" milling of the 243's. You could likely mill .030" to bump compression even more. 11.5:1 is common and still good for use with 93. We do recommend checking PTV before final assembly. We designed this cam with the use of .600 lift beehives like the PAC 1218's in mind. They'd be good for near 7,000 rpm operation. If you wanted to turn 7,000 + rpm we'd recommend .660 lift duals such as the TFS-2500286.
SLP IROC-Z mentioned 11/32 pushrods. We really like that recommendation to help keep the valvetrain stable. We have our 11/32 .120" wall HDR pushrods.Typically a 7.425" pushrod will work with an unmilled stock head and LS7 lifters with .060-.080" pre-load. Things vary especially with milled heads and the travel of aftermarket lifters. This is why we always recommend measuring for pushrod length before purchasing pushrods. If you don't already have a pushrod length checker we offer the TFS-9501.
Thank you for the advice. I think this is the route I'm going to go. I'll be stopping by the Ohio store later this winter.
Thanks again everyone!
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