lq9 build
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Teching In
Joined: Jan 2021
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lq9 build My first LS build, so go easy on me fellas.
Picked up an LQ9 that needs a little work. Had some decent pits and rust in the cylinders so decided to go .030 over but keeping the crank and rods stock. It's going to be a street-driven truck that will stay N/A and live mostly under 4k rpm. I've got the stock 317s but may end up getting some 706s in the future.
I've got two questions: I've been looking mostly at Summit and haven't had any luck finding piston sets(pins, rings, etc) that aren't forged, should I just go with those even though I won't be making that kind of power? And second, they're milling the deck as well for straightness, does that put flat top pistons off the table as far as clearances go?
Picked up an LQ9 that needs a little work. Had some decent pits and rust in the cylinders so decided to go .030 over but keeping the crank and rods stock. It's going to be a street-driven truck that will stay N/A and live mostly under 4k rpm. I've got the stock 317s but may end up getting some 706s in the future.
I've got two questions: I've been looking mostly at Summit and haven't had any luck finding piston sets(pins, rings, etc) that aren't forged, should I just go with those even though I won't be making that kind of power? And second, they're milling the deck as well for straightness, does that put flat top pistons off the table as far as clearances go?
Summit Racing sells replacement oversized hypereutectic replacement flat top pistons In both Speed Pro and Silv-O-Lite brands.
Speed Pro H1129 .75MM https://www.summitracing.com/parts/slp-h1129cpa75mm
Silv-O-Lite 3517HC .75MM https://www.summitracing.com/parts/uem-3517hc-75mm
Hastings Rings for that size piston https://www.summitracing.com/parts/hsn-2m4862030
Speed Pro H1129 .75MM https://www.summitracing.com/parts/slp-h1129cpa75mm
Silv-O-Lite 3517HC .75MM https://www.summitracing.com/parts/uem-3517hc-75mm
Hastings Rings for that size piston https://www.summitracing.com/parts/hsn-2m4862030
Just remember to get it re-balanced. I'd stay with the 317's and if I you can swing it then get some better rods too. I have an LQ9 with over 340,000 miles and I'm not sure just how many heat cycles those things can take.
Thread Starter
Teching In
Joined: Jan 2021
Posts: 4
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Summit Racing sells replacement oversized hypereutectic replacement flat top pistons In both Speed Pro and Silv-O-Lite brands.
Speed Pro H1129 .75MM https://www.summitracing.com/parts/slp-h1129cpa75mm
Silv-O-Lite 3517HC .75MM https://www.summitracing.com/parts/uem-3517hc-75mm
Hastings Rings for that size piston https://www.summitracing.com/parts/hsn-2m4862030
Speed Pro H1129 .75MM https://www.summitracing.com/parts/slp-h1129cpa75mm
Silv-O-Lite 3517HC .75MM https://www.summitracing.com/parts/uem-3517hc-75mm
Hastings Rings for that size piston https://www.summitracing.com/parts/hsn-2m4862030
Thread Starter
Teching In
Joined: Jan 2021
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Interesting. I thought 317s were more for boosted applications with the larger chamber?
My truck has them and that motor is quite responsive in stock form. Boost don't care and the 317's are sought after due to the larger combustion chambers to aid in lowering the compression but they do have the larger intake valve which will be better for the bore over the small bore heads.
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TECH Resident
Joined: Jun 2011
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Well first, as you mentioned, you'll be milling the deck. So that will increase compression ratio. Second, increasing the bore will also effectively increase the compression ratio as well. And you have to consider where your rod/stroke/piston put you above deck height. The pistons listed have zero dish like the LQ9 pistons had (which was 10:1 from the factory). Plus, whatever heads you choose, you'll want to clean up those surfaces as well, which bump compression even more. Your best bet is to assemble your short block first, calculate your compression ratio with 317s and then decide.
Stock for stock, the 706 are at a flow disadvantage, they just help in increasing static compression ratio. And once you get your short block together and mill the 317 heads, you'll probably find it's plenty of SCR for a mostly street truck. Even the factory LQ9s with 10:1 were intended to run best on premium.
Stock for stock, the 706 are at a flow disadvantage, they just help in increasing static compression ratio. And once you get your short block together and mill the 317 heads, you'll probably find it's plenty of SCR for a mostly street truck. Even the factory LQ9s with 10:1 were intended to run best on premium.
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