Rebuilding a 318
02-03-2014, 09:23 AM
#1
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Rebuilding a 318
I am currently rebuilding a 318 for my 86 Dodge W150. I have already had the block, intake manny, and heads hot bathed and cleaned up as well as the heads magnifluxed and a valve job done. The pistons got cleaned too and the cylinders got honed as well. After getting it back I realized that my pistons are no longer marked for what cylinder they came out of. I know that the half moon cut out on the top of the piston has to face forward for a Mopar engine, but my concern is will it matter what piston goes in what hole now that they all have new rings and seals and the cylinders were honed. I looked at the top of the piston and they all have a 2, 3, or a 7 on them. Not sure what this means and if they have to go in a certain position. As for the rods, they were never taken off the piston heads, but they have no distinct markings either for what is front or back or what cylinder they were in. Does anyone know what a good place to find out what I need to do or if it even matters what piston goes where at this point? I dont want to get this thing back together just to blow it up. Especially after cleaning it and painting it.
02-03-2014, 09:50 AM
#2
In one sentence you say "bored," another you say "honed". If the engine has been bored, you must have NEW pistons to fit the new overbore, and it does not matter which piston to which bore.
If you did not bore the engine, but rather had it honed, it still might not be that important, but would be desirable. You can get some idea by inserting all 8 into the same bore, and using feeler gauges (I assume you have no micrometers) to get an idea of variation in size.
If that results in one or more being larger than the rest, then insert that "largest" piston into all 7 other bores and see how the fit compares.
Weren't the rods marked? I dearly hope you have the rod caps installed onto the original rods. That is probably the very most important one thing, as they do not interchange.
Main caps have the markings cast in, so if you pay attention, you'll get them correct.
If you did not bore the engine, but rather had it honed, it still might not be that important, but would be desirable. You can get some idea by inserting all 8 into the same bore, and using feeler gauges (I assume you have no micrometers) to get an idea of variation in size.
If that results in one or more being larger than the rest, then insert that "largest" piston into all 7 other bores and see how the fit compares.
Weren't the rods marked? I dearly hope you have the rod caps installed onto the original rods. That is probably the very most important one thing, as they do not interchange.
Main caps have the markings cast in, so if you pay attention, you'll get them correct.
02-03-2014, 12:33 PM
#3
Generally the pistons have a notch-- goes towards the front, The rods large chamfer towards rear on right bank. large chamfer to the front on left bank. SHould be able to at least figure out which bank the piston goes on.. THE ring placement on the piston needs to be verified not just slapped in.. check the book !!
02-03-2014, 02:49 PM
#4
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Tough one. I think the first thing I would do is weigh each piston rod assembly with an accurate scale. If they happen to be all the same then you could size them for best clearance. If they are different weights, I have no idea what to do.
02-05-2014, 09:34 AM
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In one sentence you say "bored," another you say "honed". If the engine has been bored, you must have NEW pistons to fit the new overbore, and it does not matter which piston to which bore.
If you did not bore the engine, but rather had it honed, it still might not be that important, but would be desirable. You can get some idea by inserting all 8 into the same bore, and using feeler gauges (I assume you have no micrometers) to get an idea of variation in size.
If that results in one or more being larger than the rest, then insert that "largest" piston into all 7 other bores and see how the fit compares.
Weren't the rods marked? I dearly hope you have the rod caps installed onto the original rods. That is probably the very most important one thing, as they do not interchange.
Main caps have the markings cast in, so if you pay attention, you'll get them correct.
If you did not bore the engine, but rather had it honed, it still might not be that important, but would be desirable. You can get some idea by inserting all 8 into the same bore, and using feeler gauges (I assume you have no micrometers) to get an idea of variation in size.
If that results in one or more being larger than the rest, then insert that "largest" piston into all 7 other bores and see how the fit compares.
Weren't the rods marked? I dearly hope you have the rod caps installed onto the original rods. That is probably the very most important one thing, as they do not interchange.
Main caps have the markings cast in, so if you pay attention, you'll get them correct.
02-05-2014, 09:37 AM
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Generally the pistons have a notch-- goes towards the front, The rods large chamfer towards rear on right bank. large chamfer to the front on left bank. SHould be able to at least figure out which bank the piston goes on.. THE ring placement on the piston needs to be verified not just slapped in.. check the book !!
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