4.8 and 5.3 piston
10-12-2012, 06:29 PM
#52
Hey everyone. I finish paid a LS2 STYLE Rods with dmiple dot on the rod. Its floating. From guy name SS99z51 Hes machine shop IN TEXAS. I am consider about my lm7 block send to him and do all the works. Will get good piston new one. Get all arp bolts, everything will be new in my block. Im going run a stock crank, but will do port job and milled my 862 heads to make 10.5 cr for that. 5.3 bore to 3.898 5.7 now im figure out which I should get intake Ls6? TBSS? Eldbrock high ram intake? Give me some idea.
10-20-2012, 06:40 PM
#55
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Bill- yeah I just want to open idea. So I can decide what to do. More likely want to take it machine shop do some work. Like as rebuilt and going to be new one.my engine is LM7 as well. Which people like go to do 4.8 piston into 5.3 block or 5.3 bore to 5.7 Give me a poll 
Im start process do my project. Take me a while.
Im start process do my project. Take me a while.Before you buy a single part for a 5.7 build you have to get the block over to the machine shop and figure out what you have in regards to the deck height of the block and the thickness of the bores. I found on my motor the deck was closer to 9.230" than it was to the standard LS1 deck of 9.240". You might need to adjust your gameplan if you have a shorter deck (GM gives .010" tolerance for factory motors so it can be from 9.235" - 9.245"), or you find out you need to deck the block. The pistons are supposed to be anywhere from .004 - .010 out of the hole stock on the aluminum motors I believe, so I definately would want to keep it around .006 at the most on an iron motor. Your piston is going to expand in all directions due to heat just like it would in any motor, the problem is that the iron block will only expand at 1/2 the rate of the aluminum. So cold the piston might be .006" out the hole, but once everything is warmed up it could be closer to .008" or more on an iron block.
Well, if your block is 9.235 and you buy a set of pistons with a 1.335 or 1.340 compression height (they are out there for the 5.7s BTW look at Summit) you could put the piston .009 - .014 out of the hole on an iron block which IMO I wouldn't even think about doing on a street motor. So figure out what you have for a deck height.
Also, your bores may not be suitable for boring to 3.898". They are out there. I was going to bore the 5.3 block I have over to a 5.7 and found out in short order that the bores were not thick enough to comfortably do so. Some of these blocks have some shift in them that makes them perfectly AOK as 5.3 blocks but makes them unusable as a 5.7 candiate. Mine was one of those such blocks. Different machinists will tell you different things but the guy that looked at mine wasn't comfortable going any thinner than .125" on the thrust side of the bore. Remember you're taking .060 out of each side or going .120" bigger total. That's alot of material, so it will cost you alittle to bore that far. Here is the sonic scan sheet.
10-24-2012, 04:56 PM
#56
Going with 5.7 pistons is definately the way to go if you're rebuilding it IMO. Opens your head options up alittle more and you can run a slightly larger cam and have the motor run better off WOT if you chose to. Problem is that you don't know if your block can be bored to 5.7 or not.
Before you buy a single part for a 5.7 build you have to get the block over to the machine shop and figure out what you have in regards to the deck height of the block and the thickness of the bores. I found on my motor the deck was closer to 9.230" than it was to the standard LS1 deck of 9.240". You might need to adjust your gameplan if you have a shorter deck (GM gives .010" tolerance for factory motors so it can be from 9.235" - 9.245"), or you find out you need to deck the block. The pistons are supposed to be anywhere from .004 - .010 out of the hole stock on the aluminum motors I believe, so I definately would want to keep it around .006 at the most on an iron motor. Your piston is going to expand in all directions due to heat just like it would in any motor, the problem is that the iron block will only expand at 1/2 the rate of the aluminum. So cold the piston might be .006" out the hole, but once everything is warmed up it could be closer to .008" or more on an iron block.
Well, if your block is 9.235 and you buy a set of pistons with a 1.335 or 1.340 compression height (they are out there for the 5.7s BTW look at Summit) you could put the piston .009 - .014 out of the hole on an iron block which IMO I wouldn't even think about doing on a street motor. So figure out what you have for a deck height.
Also, your bores may not be suitable for boring to 3.898". They are out there. I was going to bore the 5.3 block I have over to a 5.7 and found out in short order that the bores were not thick enough to comfortably do so. Some of these blocks have some shift in them that makes them perfectly AOK as 5.3 blocks but makes them unusable as a 5.7 candiate. Mine was one of those such blocks. Different machinists will tell you different things but the guy that looked at mine wasn't comfortable going any thinner than .125" on the thrust side of the bore. Remember you're taking .060 out of each side or going .120" bigger total. That's alot of material, so it will cost you alittle to bore that far. Here is the sonic scan sheet.
Before you buy a single part for a 5.7 build you have to get the block over to the machine shop and figure out what you have in regards to the deck height of the block and the thickness of the bores. I found on my motor the deck was closer to 9.230" than it was to the standard LS1 deck of 9.240". You might need to adjust your gameplan if you have a shorter deck (GM gives .010" tolerance for factory motors so it can be from 9.235" - 9.245"), or you find out you need to deck the block. The pistons are supposed to be anywhere from .004 - .010 out of the hole stock on the aluminum motors I believe, so I definately would want to keep it around .006 at the most on an iron motor. Your piston is going to expand in all directions due to heat just like it would in any motor, the problem is that the iron block will only expand at 1/2 the rate of the aluminum. So cold the piston might be .006" out the hole, but once everything is warmed up it could be closer to .008" or more on an iron block.
Well, if your block is 9.235 and you buy a set of pistons with a 1.335 or 1.340 compression height (they are out there for the 5.7s BTW look at Summit) you could put the piston .009 - .014 out of the hole on an iron block which IMO I wouldn't even think about doing on a street motor. So figure out what you have for a deck height.
Also, your bores may not be suitable for boring to 3.898". They are out there. I was going to bore the 5.3 block I have over to a 5.7 and found out in short order that the bores were not thick enough to comfortably do so. Some of these blocks have some shift in them that makes them perfectly AOK as 5.3 blocks but makes them unusable as a 5.7 candiate. Mine was one of those such blocks. Different machinists will tell you different things but the guy that looked at mine wasn't comfortable going any thinner than .125" on the thrust side of the bore. Remember you're taking .060 out of each side or going .120" bigger total. That's alot of material, so it will cost you alittle to bore that far. Here is the sonic scan sheet.
10-24-2012, 05:35 PM
#57
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If you are dead set on boosting that motor then forged 5.3 Wiesco slugs are just about all you can really do. If you were just running a healthy cam on a NA motor I would just run hypereutetic pistons.
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