flat top pistons

peddeler · 01-29-2008, 07:42 PM

HI guys, I bought a remanufactured 360 to replace my 318. All the machine work has been done, and it came with new pistons (.030 over) already installed on the rods, it just needs to be assembled. Every aftermarket piston I"ve seen for the 360 has reliefs cut in the top for the valves, but these don't Why is that? Do I need to be concerned that they might hit the valves. Will these lower or increase compression? Can someone enlighten me why some pistons have valve reliefs and some don"t

thanks, Scott

CAT-TECH · 01-29-2008, 07:58 PM

Your reman 360 is running stock compression ratio and you have no worrys as to the valve kissing the piston. When you see pistons with valve reliefs cut in them it is cause the piston crown is higher than stock and raises the compression ratio. you have no need to worry.

440roadrunner · 01-30-2008, 10:45 AM

Bear in mind that while the 360 is "almost" a bolt in, there are two important differences:

ONE: Your 318 pan won't fit, so I hope you have a new pan

TWO This is most important!! 360 engines are externally balanced, and need the proper front balancer as well as a special flywheel--in the case of a stick. for auto's I'm not sure whether the drive plate is weighted or the converter, be SURE to check this out. Any good transmission shop will know this.

DO NOT run a 360 without taking care of this. Not only will the engine shake badly at some RPM's, but you might just break a crank!!

peddeler · 01-30-2008, 05:34 PM

Thanks for the info guys,

I do know about the 360 being externally balance and the 318 being internally balanced, Ive already ordered a weighted flex plate and I"m looking for a balancer, I also know about the oil pan. The one thing that I"M still unsure of is the difference with the engine mounts. I know the mount is different on one side ( I forget which side). What exactly do I need to make the engine mounts fit.....is it an adaptor or do I just need to use the 360 motor mounts from lets say a '74 Challenger. By the way I"m doing the engine swap on a 1973 Challenger. The 1974 is basically the same but the 360 replaced the 340 for that year.

Thanks in advance, Scott

440roadrunner · 01-30-2008, 07:35 PM

I don't remember about the mounts. I do remember vaguely that when I put the 340 in my old '70, and used mostly 318 hardware---then, there WAS NO factory 340 in a B body---

seems to me I reversed the 318 motor brackets from pass. to drivers side, but I don't remember for sure. I also remember vaguely that I shimmed one bolt (drivers?) on the engine mount bracket.

Generally, you want small block brackets and mounts that go with the BODY that you are using.

I would think that the '74 brackets and mounts would fit.

01-29-2008, 07:42 PM	#1 (permalink)
peddeler Junior Member Join Date: Jan 2008 Posts: 2	flat top pistons HI guys, I bought a remanufactured 360 to replace my 318. All the machine work has been done, and it came with new pistons (.030 over) already installed on the rods, it just needs to be assembled. Every aftermarket piston I"ve seen for the 360 has reliefs cut in the top for the valves, but these don't Why is that? Do I need to be concerned that they might hit the valves. Will these lower or increase compression? Can someone enlighten me why some pistons have valve reliefs and some don"t thanks, Scott

01-30-2008, 05:34 PM	#4 (permalink)
peddeler Junior Member Join Date: Jan 2008 Posts: 2	thanks Thanks for the info guys, I do know about the 360 being externally balance and the 318 being internally balanced, Ive already ordered a weighted flex plate and I"m looking for a balancer, I also know about the oil pan. The one thing that I"M still unsure of is the difference with the engine mounts. I know the mount is different on one side ( I forget which side). What exactly do I need to make the engine mounts fit.....is it an adaptor or do I just need to use the 360 motor mounts from lets say a '74 Challenger. By the way I"m doing the engine swap on a 1973 Challenger. The 1974 is basically the same but the 360 replaced the 340 for that year. Thanks in advance, Scott

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

01-29-2008, 07:58 PM	#2 (permalink)
CAT-TECH Member Join Date: Jan 2008 Location: Cali Posts: 42	Your reman 360 is running stock compression ratio and you have no worrys as to the valve kissing the piston. When you see pistons with valve reliefs cut in them it is cause the piston crown is higher than stock and raises the compression ratio. you have no need to worry.

01-30-2008, 10:45 AM	#3 (permalink)
440roadrunner Senior Member Join Date: Nov 2007 Posts: 272	Bear in mind that while the 360 is "almost" a bolt in, there are two important differences: ONE: Your 318 pan won't fit, so I hope you have a new pan TWO This is most important!! 360 engines are externally balanced, and need the proper front balancer as well as a special flywheel--in the case of a stick. for auto's I'm not sure whether the drive plate is weighted or the converter, be SURE to check this out. Any good transmission shop will know this. DO NOT run a 360 without taking care of this. Not only will the engine shake badly at some RPM's, but you might just break a crank!!

01-30-2008, 07:35 PM	#5 (permalink)
440roadrunner Senior Member Join Date: Nov 2007 Posts: 272	I don't remember about the mounts. I do remember vaguely that when I put the 340 in my old '70, and used mostly 318 hardware---then, there WAS NO factory 340 in a B body--- seems to me I reversed the 318 motor brackets from pass. to drivers side, but I don't remember for sure. I also remember vaguely that I shimmed one bolt (drivers?) on the engine mount bracket. Generally, you want small block brackets and mounts that go with the BODY that you are using. I would think that the '74 brackets and mounts would fit.