317s on a 5.3?
On The Tree
Joined: Nov 2005
Posts: 184
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I wouldnt do it because chamber is around 4.0" and 70+cc size, it will fit but that is not a good idea. The valves wont hit the bore but the block deck surface will be exposed to the chamber. I run these heads on my 5.7 but i milled them to get 62cc chamber size, which also decreased chamber slightly smaller than 4.0" to match the 3.90" bore.
317s spec as 71 cc stock, while your 706s spec as 61 cc, so you'd drop from 9.5:1 to around 8.5:1. That's not helpful, even with 15 psi of boost. If you insist on swapping heads, either do milled 243s / 799s, or buy some cnc ported 5.3 heads.
I wouldnt do it because chamber is around 4.0" and 70+cc size, it will fit but that is not a good idea. The valves wont hit the bore but the block deck surface will be exposed to the chamber. I run these heads on my 5.7 but i milled them to get 62cc chamber size, which also decreased chamber slightly smaller than 4.0" to match the 3.90" bore.
I dont know alot about it, but how is lowering compression not helpful when running high boost? I thought lower compression the more boost you can run?
Not at the limit of stock pistons.
Tirefryins10 already showed us that 15 psi through a cam-only LM7 is possible, but he was pushing his luck, and said so.
If you want to buy forged pistons, then go ahead and up the boost. But if you're gonna do that, then you should pick some heads with better exhaust port flow. Like maybe the AFR 205 heads with 72 cc chambers.
The 317s aren't best for ANY 5.3 build. They can be made to work in some applications, but are never the best choice.
Also, milled 317s don't equal un-milled 243s / 799s, despite comparable flow, because the 243s had more efficient combustion chambers. Why put inefficient chambers on a boost build?
My first choice would be coated AFRs, but my budget would limit me to 243s, with self-ported and polished exhaust ports and polished combustion chambers.
Tirefryins10 already showed us that 15 psi through a cam-only LM7 is possible, but he was pushing his luck, and said so.
If you want to buy forged pistons, then go ahead and up the boost. But if you're gonna do that, then you should pick some heads with better exhaust port flow. Like maybe the AFR 205 heads with 72 cc chambers.
The 317s aren't best for ANY 5.3 build. They can be made to work in some applications, but are never the best choice.
Also, milled 317s don't equal un-milled 243s / 799s, despite comparable flow, because the 243s had more efficient combustion chambers. Why put inefficient chambers on a boost build?
My first choice would be coated AFRs, but my budget would limit me to 243s, with self-ported and polished exhaust ports and polished combustion chambers.
Last edited by Isolde; Jan 9, 2011 at 07:01 PM.
Not at the limit of stock pistons.
Tirefryins10 already showed us that 15 psi through a cam-only LM7 is possible, but he was pushing his luck, and said so.
If you want to buy forged pistons, then go ahead and up the boost. But if you're gonna do that, then you should pick some heads with better exhaust port flow. Like maybe the AFR 205 heads with 72 cc chambers.
The 317s aren't best for ANY 5.3 build. They can be made to work in some applications, but are never the best choice.
Also, milled 317s don't equal un-milled 243s / 799s, despite comparable flow, because the 243s had more efficient combustion chambers. Why put inefficient chambers on a boost build?
My first choice would be coated AFRs, but my budget would limit me to 243s, with self-ported and polished exhaust ports and polished combustion chambers.
Tirefryins10 already showed us that 15 psi through a cam-only LM7 is possible, but he was pushing his luck, and said so.
If you want to buy forged pistons, then go ahead and up the boost. But if you're gonna do that, then you should pick some heads with better exhaust port flow. Like maybe the AFR 205 heads with 72 cc chambers.
The 317s aren't best for ANY 5.3 build. They can be made to work in some applications, but are never the best choice.
Also, milled 317s don't equal un-milled 243s / 799s, despite comparable flow, because the 243s had more efficient combustion chambers. Why put inefficient chambers on a boost build?
My first choice would be coated AFRs, but my budget would limit me to 243s, with self-ported and polished exhaust ports and polished combustion chambers.
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ALL the LS4 FWD 5.3s had the 243 heads, and some 58x truck versions. The LS4 versions got flat top pistons from the 4.8L to fix the compression issue.
You shouldn't have any trouble finding a buyer for the 317s, they're still in demand. Especially guys who have a '99 or '00 LQ4, when those had iron heads.
I traded my 317s for a pair of 241s, all it cost me was shipping.
You shouldn't have any trouble finding a buyer for the 317s, they're still in demand. Especially guys who have a '99 or '00 LQ4, when those had iron heads.
I traded my 317s for a pair of 241s, all it cost me was shipping.
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Verdad Gallardo ALL the LS4 FWD 5.3s had the 243 heads, and some 58x truck versions. The LS4 versions got flat top pistons from the 4.8L to fix the compression issue.
You shouldn't have any trouble finding a buyer for the 317s, they're still in demand. Especially guys who have a '99 or '00 LQ4, when those had iron heads.
I traded my 317s for a pair of 241s, all it cost me was shipping.
You shouldn't have any trouble finding a buyer for the 317s, they're still in demand. Especially guys who have a '99 or '00 LQ4, when those had iron heads.
I traded my 317s for a pair of 241s, all it cost me was shipping.
