Introducing..Summit Pro LS Forged Pistons!!!!!
#61
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Yup... It seems like the high dollar pistons always list an average weight, but cheaper ($400-500) ones do not. I'd really like to see the weights for a 6.0 based motor, as I'm building one currently.
I'd rather not have to add 100 grams of heavy metal to balance. I'd rather spend more on pistons and have to remove weight from the crank, then add a bunch.
I'd be a buyer if they are what I'm looking for.
I'd rather not have to add 100 grams of heavy metal to balance. I'd rather spend more on pistons and have to remove weight from the crank, then add a bunch.
I'd be a buyer if they are what I'm looking for.
#64
6.0 ls compression on e85
Hey summit I’m lookin at the pro LS pistons for my turbo 6.0.. u say the turbo pistons are targeted around 9.5 compression.. is that for gas or E85..? Would u recommend a higher CR for an E85 turbo motor..? Which piston in my lq4 with the 317 71cc heads would u recommend..? Thanks..!
Folks, we are proud to introduce you to our new Pro LS Forged Pistons lineup. This project has been in the works for almost a year and it's been hard not to let the cat out of the bag. First and most importantly, THEY ARE MADE IN THE USA. American Forgings, Designed, Machined, - the whole ball of wax. Heck even the rings they were designed around are 100% Made in the USA.
We've been monitoring these threads for a while and we wanted to have THE answer for every one of the questions you folks have had over the first year. We Listened and the lineup is awesome. 4.8L/5.3L/5.7L and 6.0L at this time and we'll be expanding the lineup too.
This is the best lineup of pistons ever offered. EVERY last detail was considered. Every exact CC of Dome or Dish volume was designed to give you exactly what you need without milling heads just out of necessity. Not just some lazy-cheap-to-make Flat-Tops. For this reason, there aren't a lot of flat tops....in fact the only place they made sense was the 6.0L pistons. Putting valve reliefs on a 4.8L/5.3L/5.7L flat top and you'll be leaving about 20hp worth of compression on the table. Not with Pro LS pistons. You'll find 2 and 3cc domes on the 4.8L/5.3L/5.7L pistons that gets you into the 10.5:1 range without head milling and right in the sweet spot 11 to 11.5:1 range with milling. Choose your octane folks! This is quite a gamble because people just search for "flat tops" even though they're almost always the wrong answer. We upped the compression a bit on the 5.7L LS1/LS6 and the strokers because we know you're not playing around at that point. The boost pistons target 9.5:1 for the most part.
No one...not one single piston company has every combination for Press-fit Gen. 3, Full-Floating Gen. 4, 6.125in. Aftermarket, and then 4" Stroker versions with 6.125 in. rods. Summit has done that for you. All the popular bore sizes including std. and .005" over so it's just a hone job. Anywhere we could save you money on machine work $ - we have. In fact, we even included cir-clip grooves in the press-fit pistons in case you have a set of Gen. 4 rods laying around with small-ends that need cleaned up.
What about strength? These pistons are 2618 Alloy Strutted designs with the best strength-to-weight ratio available. We maxxed-out Ring-Land thickness for you. A minimum of .275 tops on the 5.3's an .300 in. on the 5.7L and 6.0L pistons. All the domes and dishes and valve relieves and even the edge around the top have the smoothest radii possible for best combustion performance and detonation resistance. Pressure-fed pin-oiling of course. The pins that come with them are good for about 1000whp. If you are beyond that or are running a 300+ horsepower shot of nitrous...we have thick-wall 9310 Tool Steel pins available that will drop right in.
What about Power? We mentioned careful attention to the domes and dishes. We've given you valve reliefs that are adequate for almost any cam up to large Solid Rollers. We designed these pistons in conjunction with a 1.5 x 1.5 x 3.mm ring pack on the 5.3's and 1.2 x 1.2 x 3mm on the 5.7L and 6.0L. These are Steel (Plasma or Nitride depending on bore) top rings with Martensitic Ductile Napier seconds and 13lb standard-tension oils. We were very careful with the cross-sections we used through the crown...more than enough...but not too much...so the pistons are light for the power they will support. We are VERY big on getting the skirt profiles correct. The skirt taper is minimal and the break point where we start to introduce it is .120 above the bottom of a 5.430 length iron block with 4" stroke. This will support the pistons well and their skirt life will be long. We added skirt coatings too, but gave you a gauge point dot in the skirt coating to set these up with .004 in. piston-to-wall. The skirt coating is top notch and tightens clearance to .0028" net, so these forged pistons will be as quiet as they come. Don't let your machinist add .0005 or .001 to the bores...these ride absolutely fine at this clearance even with big boost or nitrous. Of course the pistons are machined extremely nicely including the positive-angle super-flat and shiny ring-grooves.
There are 73 new part numbers including oversizes and we've photo'd every one on our website so you'll know exactly what you're getting. Our instruction sheet is a full 8 1/2 x 11 of details that will keep builders out of trouble. We also put each of the 4.8L, 5.3L, 5.7L, and 6.0L sections into a catalog format. This makes it easy for engine builders to quickly determine what stroke, rod, bore and the compression ratios with 4 common chamber volumes. We've prepared a full tech article that gets into the all the tiny details that gone into giving you THE BEST piston lineup on the market.
We're attaching the master catalog here along with smaller 4.8L, 5.3L, 5.7L, and 6.0L sections separated out to make it easier to print. We hope you'll enjoy the tiny details.
Oh, you want to know the price? $499!!! It doesn't matter if it's a dome, dish, or even the lonely 6.0L flat-tops...they're all $499. What's the catch? Where does Summit price the rings? Rings with so much tech we could sell them for $200 on their own. Well we skinnied the heck out of the margins and and priced them at $99. How can we do this? Volume. We're not big on cutting corners when we have our name on the line. We're proud to present you with the only pistons that can earn the Pro LS distinction. Thank you folks for your consideration.
[/QUOTE] We've been monitoring these threads for a while and we wanted to have THE answer for every one of the questions you folks have had over the first year. We Listened and the lineup is awesome. 4.8L/5.3L/5.7L and 6.0L at this time and we'll be expanding the lineup too.
This is the best lineup of pistons ever offered. EVERY last detail was considered. Every exact CC of Dome or Dish volume was designed to give you exactly what you need without milling heads just out of necessity. Not just some lazy-cheap-to-make Flat-Tops. For this reason, there aren't a lot of flat tops....in fact the only place they made sense was the 6.0L pistons. Putting valve reliefs on a 4.8L/5.3L/5.7L flat top and you'll be leaving about 20hp worth of compression on the table. Not with Pro LS pistons. You'll find 2 and 3cc domes on the 4.8L/5.3L/5.7L pistons that gets you into the 10.5:1 range without head milling and right in the sweet spot 11 to 11.5:1 range with milling. Choose your octane folks! This is quite a gamble because people just search for "flat tops" even though they're almost always the wrong answer. We upped the compression a bit on the 5.7L LS1/LS6 and the strokers because we know you're not playing around at that point. The boost pistons target 9.5:1 for the most part.
No one...not one single piston company has every combination for Press-fit Gen. 3, Full-Floating Gen. 4, 6.125in. Aftermarket, and then 4" Stroker versions with 6.125 in. rods. Summit has done that for you. All the popular bore sizes including std. and .005" over so it's just a hone job. Anywhere we could save you money on machine work $ - we have. In fact, we even included cir-clip grooves in the press-fit pistons in case you have a set of Gen. 4 rods laying around with small-ends that need cleaned up.
What about strength? These pistons are 2618 Alloy Strutted designs with the best strength-to-weight ratio available. We maxxed-out Ring-Land thickness for you. A minimum of .275 tops on the 5.3's an .300 in. on the 5.7L and 6.0L pistons. All the domes and dishes and valve relieves and even the edge around the top have the smoothest radii possible for best combustion performance and detonation resistance. Pressure-fed pin-oiling of course. The pins that come with them are good for about 1000whp. If you are beyond that or are running a 300+ horsepower shot of nitrous...we have thick-wall 9310 Tool Steel pins available that will drop right in.
What about Power? We mentioned careful attention to the domes and dishes. We've given you valve reliefs that are adequate for almost any cam up to large Solid Rollers. We designed these pistons in conjunction with a 1.5 x 1.5 x 3.mm ring pack on the 5.3's and 1.2 x 1.2 x 3mm on the 5.7L and 6.0L. These are Steel (Plasma or Nitride depending on bore) top rings with Martensitic Ductile Napier seconds and 13lb standard-tension oils. We were very careful with the cross-sections we used through the crown...more than enough...but not too much...so the pistons are light for the power they will support. We are VERY big on getting the skirt profiles correct. The skirt taper is minimal and the break point where we start to introduce it is .120 above the bottom of a 5.430 length iron block with 4" stroke. This will support the pistons well and their skirt life will be long. We added skirt coatings too, but gave you a gauge point dot in the skirt coating to set these up with .004 in. piston-to-wall. The skirt coating is top notch and tightens clearance to .0028" net, so these forged pistons will be as quiet as they come. Don't let your machinist add .0005 or .001 to the bores...these ride absolutely fine at this clearance even with big boost or nitrous. Of course the pistons are machined extremely nicely including the positive-angle super-flat and shiny ring-grooves.
There are 73 new part numbers including oversizes and we've photo'd every one on our website so you'll know exactly what you're getting. Our instruction sheet is a full 8 1/2 x 11 of details that will keep builders out of trouble. We also put each of the 4.8L, 5.3L, 5.7L, and 6.0L sections into a catalog format. This makes it easy for engine builders to quickly determine what stroke, rod, bore and the compression ratios with 4 common chamber volumes. We've prepared a full tech article that gets into the all the tiny details that gone into giving you THE BEST piston lineup on the market.
We're attaching the master catalog here along with smaller 4.8L, 5.3L, 5.7L, and 6.0L sections separated out to make it easier to print. We hope you'll enjoy the tiny details.
Oh, you want to know the price? $499!!! It doesn't matter if it's a dome, dish, or even the lonely 6.0L flat-tops...they're all $499. What's the catch? Where does Summit price the rings? Rings with so much tech we could sell them for $200 on their own. Well we skinnied the heck out of the margins and and priced them at $99. How can we do this? Volume. We're not big on cutting corners when we have our name on the line. We're proud to present you with the only pistons that can earn the Pro LS distinction. Thank you folks for your consideration.
#65
Hi summit racing, if you read this I have a question about your 4.00" bore pistons, i want to know if the valve notches will clear 12 degree valve angles. If you can ask whoever is manufacturing them if they can find out. If you offered all your 4.00" + bore size pistons to suit both 15deg and 12deg valve angles (as the JE assymetrical line does) would be great because small bore ls7 heads are becoming more common. Thanks
#66
Compression ratio
Sure, SUM-326943400012 would be standard bore -12 cc. How we made the part numbers is this: SUM-(compression height)(pin)(bore)(volume) So in this case it's a 1.326 standard compression height, .943 pin, 4.000 bore and -12cc. The 4.005 bore versions are SUM-326943400512. The .030's and .040's are the same way.
.945 pins would be SUM-326945xxxxxx
Slightly shorter pistons for 6.125 aftermarket rods are SUM-299927xxxxxx
4" stroker with aftermarket rods become SUM-110927xxxxxx
With a standard 5364 casting 70cc head, the compression on those is 9.2:1 with .045 piston to head and standard bore. If you punch it out .030 over, it goes to 9.3:1. Milling to 68cc would put it at 9.5:1.
.945 pins would be SUM-326945xxxxxx
Slightly shorter pistons for 6.125 aftermarket rods are SUM-299927xxxxxx
4" stroker with aftermarket rods become SUM-110927xxxxxx
With a standard 5364 casting 70cc head, the compression on those is 9.2:1 with .045 piston to head and standard bore. If you punch it out .030 over, it goes to 9.3:1. Milling to 68cc would put it at 9.5:1.
Summit racing.. could u please tell me how u came up with the 9.2 Cr with that 6.0 standard piston.. according to the calculator using all the factory lq4 specs.. with the -12 cc piston like u say puts it at roughly 10.5 to 1..now goin the other way if u meant +12 cc then puts it at roughly 8.3 to 1.. what am I missing..??
Last edited by chinaoreo; 06-30-2019 at 12:41 AM. Reason: Adding pics
#67
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Hi summit racing, if you read this I have a question about your 4.00" bore pistons, i want to know if the valve notches will clear 12 degree valve angles. If you can ask whoever is manufacturing them if they can find out. If you offered all your 4.00" + bore size pistons to suit both 15deg and 12deg valve angles (as the JE assymetrical line does) would be great because small bore ls7 heads are becoming more common. Thanks
As for not laying the reliefs to 12, there is a reason behind that. It's surprising how quickly laying a pocket down reduces volume. The loss of volume from the angle would require a dome on the 6.0L and a taller dome on the 6.2L pistons to hit the target volumes. This would compromise the majority of the people that use these pistons, so it would be better to run the JE's in this with the small bore LS7's. We've got them on the shelf in most cases!
#68
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Summit racing.. could u please tell me how u came up with the 9.2 Cr with that 6.0 standard piston.. according to the calculator using all the factory lq4 specs.. with the -12 cc piston like u say puts it at roughly 10.5 to 1..now goin the other way if u meant +12 cc then puts it at roughly 8.3 to 1.. what am I missing..??
All Pro LS piston's compression heights are set to be zero deck at 9.235 in. This is .005 below the factory deck height spec rather than +.006 positive deck. The reasoning behind this we've seen some 6.0 iron blocks come in as shorter than 9.240 spec or in other cases allows a machinist to mill and clean up the decks a bit and adjust with gasket thickness.
If you had a block with a true 9.240 deck and a .051 gasket, the compression ratio for the -12 cc piston starts at 8.9:1 at 4 in. bore and rises to 9.04:1 at a 4.040 in. bore. If that's a little low for your taste, we have a pretty wide selection of gasket thicknesses or you cut mill the heads to set the number on kill.
Thanks for your consideration and let us know how we can help.
#69
Hello, the Summit Pro LS pistons compression ratios are all figured with .045 in. Net piston to head clearance. In your calculation, you've added .045 deck to .051 gasket and that's why the numbers are coming in low.
All Pro LS piston's compression heights are set to be zero deck at 9.235 in. This is .005 below the factory deck height spec rather than +.006 positive deck. The reasoning behind this we've seen some 6.0 iron blocks come in as shorter than 9.240 spec or in other cases allows a machinist to mill and clean up the decks a bit and adjust with gasket thickness.
If you had a block with a true 9.240 deck and a .051 gasket, the compression ratio for the -12 cc piston starts at 8.9:1 at 4 in. bore and rises to 9.04:1 at a 4.040 in. bore. If that's a little low for your taste, we have a pretty wide selection of gasket thicknesses or you cut mill the heads to set the number on kill.
Thanks for your consideration and let us know how we can help.
All Pro LS piston's compression heights are set to be zero deck at 9.235 in. This is .005 below the factory deck height spec rather than +.006 positive deck. The reasoning behind this we've seen some 6.0 iron blocks come in as shorter than 9.240 spec or in other cases allows a machinist to mill and clean up the decks a bit and adjust with gasket thickness.
If you had a block with a true 9.240 deck and a .051 gasket, the compression ratio for the -12 cc piston starts at 8.9:1 at 4 in. bore and rises to 9.04:1 at a 4.040 in. bore. If that's a little low for your taste, we have a pretty wide selection of gasket thicknesses or you cut mill the heads to set the number on kill.
Thanks for your consideration and let us know how we can help.
Ok summit thanks for that ..The Pistons I am needing for 6.0 will be for turbo.. u say the turbo pistons are targeted around 9.5 compression.. is that for gas or E85..? Would u recommend a higher CR for an E85 turbo motor..? So with that Which piston in my lq4 with the 317 71cc heads would u recommend..? Thanks..!
#70
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Ok summit thanks for that ..The Pistons I am needing for 6.0 will be for turbo.. u say the turbo pistons are targeted around 9.5 compression.. is that for gas or E85..? Would u recommend a higher CR for an E85 turbo motor..? So with that Which piston in my lq4 with the 317 71cc heads would u recommend..? Thanks..!
For other's reading, some of the 6.0L's (LS2, LFA or LZ1 for instance) came with Cathedral Port heads with as little as 65cc out of the box. When we targeted volumes for the Pro LS pistons, we took the two common chamber volumes for each displacement (4.8/5.3/5.7/6.0) and split the difference volume wise to give the builder flexibility.
#71
9.5:1 is pretty aggressive for pump gas, but very good with a race gas mix or E85. There's a couple ways to hit 9.5:1, but you should check your deck height to know for certain what you're in for. The Cometic MLX (stopper) gasket part number is CGT-C5505-040 gets you to 9.1:1 at a 4.000 in. bore if your block were a true 9.240. Milling those heads .030 should land you 66cc chambers and 9.55:1 compression.
For other's reading, some of the 6.0L's (LS2, LFA or LZ1 for instance) came with Cathedral Port heads with as little as 65cc out of the box. When we targeted volumes for the Pro LS pistons, we took the two common chamber volumes for each displacement (4.8/5.3/5.7/6.0) and split the difference volume wise to give the builder flexibility.
For other's reading, some of the 6.0L's (LS2, LFA or LZ1 for instance) came with Cathedral Port heads with as little as 65cc out of the box. When we targeted volumes for the Pro LS pistons, we took the two common chamber volumes for each displacement (4.8/5.3/5.7/6.0) and split the difference volume wise to give the builder flexibility.
I really have no way of measuring my deck height as there are no longer pistons in the block.. but it is factory specs as it’s never been apart or machined.. so I believe I will prob just go with that gasket and piston like u say.. should get me close enough anyways
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#73
A machine shop is an option, but yes you should be plenty safe with that combination. Of of our favorite tools is a bridge indicator like these. You'll know what you have for certain and can adjust from there. Thank you for your patronage.
Thanks.. you seem to be way more knowledgeable about this than the summit tech line… Do you have a direct number or email that I can chat with you… I was thinking about maybe going to 6.125 Rod’s and so forth
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Sorry, I don't have a direct line as I don't work in the Sales or Tech department directly. Feel free to PM me though. Happy to help where I can with a recipe and part numbers and get you over to Sales/Tech. to get your order placed.
#75
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I've never used a set of forged STD bore pistons, what exactly is the procedure or requirements for using them with any random given engine? Or the requirements for the engine in question (mileage / wear concerns?) I'm assuming the diameter of the piston is less than a factory cast unit. I'm concerned some engines would lose more material than others (say a .003 vs .001) vs the "STD" size piston available, especially when doing it 'themselves' (no machine shop) amd what sort of impact that would have (under what circumstances would you be looking for 0.005 piston instead of "STD")
in other words, is there some procedure outline or recommended prep/service for factory bore engines using "STD" size forged pistons as offered here, or as a designation for using 0.005" (specific hone/ring) size pistons instead
in other words, is there some procedure outline or recommended prep/service for factory bore engines using "STD" size forged pistons as offered here, or as a designation for using 0.005" (specific hone/ring) size pistons instead
#76
Super excited to start my build. LC9 - stock rods, crank, and these pistons. Backordered for two weeks! I'm looking forward to some reviews from happy customers while I assemble my first boosted LS. I have a bonehead question for you all however - The stock pistons have asymmetrical valve reliefs, mirrored across piston centerline. These and all aftermarket pistons have more traditional reliefs. Was there some logic to the relief placement by gm? VVT clearance Im guessing?
#77
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Super excited to start my build. LC9 - stock rods, crank, and these pistons. Backordered for two weeks! I'm looking forward to some reviews from happy customers while I assemble my first boosted LS. I have a bonehead question for you all however - The stock pistons have asymmetrical valve reliefs, mirrored across piston centerline. These and all aftermarket pistons have more traditional reliefs. Was there some logic to the relief placement by gm? VVT clearance Im guessing?
#78
I've never used a set of forged STD bore pistons, what exactly is the procedure or requirements for using them with any random given engine? Or the requirements for the engine in question (mileage / wear concerns?) I'm assuming the diameter of the piston is less than a factory cast unit. I'm concerned some engines would lose more material than others (say a .003 vs .001) vs the "STD" size piston available, especially when doing it 'themselves' (no machine shop) amd what sort of impact that would have (under what circumstances would you be looking for 0.005 piston instead of "STD")
in other words, is there some procedure outline or recommended prep/service for factory bore engines using "STD" size forged pistons as offered here, or as a designation for using 0.005" (specific hone/ring) size pistons instead
in other words, is there some procedure outline or recommended prep/service for factory bore engines using "STD" size forged pistons as offered here, or as a designation for using 0.005" (specific hone/ring) size pistons instead
Summit racing..I would like to know the answer to this as well..
#80
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I've never used a set of forged STD bore pistons, what exactly is the procedure or requirements for using them with any random given engine? Or the requirements for the engine in question (mileage / wear concerns?) I'm assuming the diameter of the piston is less than a factory cast unit. I'm concerned some engines would lose more material than others (say a .003 vs .001) vs the "STD" size piston available, especially when doing it 'themselves' (no machine shop) amd what sort of impact that would have (under what circumstances would you be looking for 0.005 piston instead of "STD")
in other words, is there some procedure outline or recommended prep/service for factory bore engines using "STD" size forged pistons as offered here, or as a designation for using 0.005" (specific hone/ring) size pistons instead
in other words, is there some procedure outline or recommended prep/service for factory bore engines using "STD" size forged pistons as offered here, or as a designation for using 0.005" (specific hone/ring) size pistons instead
What is the reality though? We all know someone that built an engine on a dirt floor and was successful.
Let's start off with the first comment we hear... "The cylinder is like new, you can still see the cross hatch". The problem is a cylinder will still have cross-hatch at 200k miles and still be completely worn out because the crosshatch may be up to .008" deep to begin with. The result is excessive piston to wall. Smoke, Oil Consumption. Piston Slap etc. Remember even .001 over our .004 "metal to metal" spec is 25% more than we recommended to begin with.
So how do you measure it? Unfortunately, this is beyond feeler gauges and snap gauges. Dial bore gauges only accurate to .001 in. are better, but if you've ever used a quality dial bore gauge accurate to .0001, you will feel naked if you are forced to use anything lesser. Not many hobbyists have those tools though.
Option 2: Ok, so 90% of folks don't own a good dial bore gauge and/or 4-5" Transfer Micrometer. What's the next criteria to having success with a standard bore piston? Well, best case scenario is you are running a low mileage engine and it hasn't been opened up and sitting. Metal sweats in changes in heat/cold and it rusts.
So what hone to use? Never use a three stone hone for this type of work. We're all familiar with bottle or "dingle ball" hones and the Brush Research Flex Hone are the best of the bunch. This is the part number most commonly used with LS 5.3 through 7.0L engines. Here are the instructions. Another option we like is the Wiseco W6079 Soft Hone Brush...it cleans the bores without removing the material...meaning less chance for error by the operator.
Lastly, Clean the bores with acetone and white paper towels until they absolutely come up clean. This might take 30-45 minutes or more. A lot of stones and dingle ball brushes use aluminum oxide abrasives. ANY left in the bore will come loose and quickly wear out EVERYTHING.
This is really just the tip of the iceberg, but you really need to consider this before making your decision to stay standard or hone or bore/hone. We haven't hit on the importance of torque plate honing and often "sending the boring bar" down a perfectly good looking bore at .030 over won't clean up all surfaces.