Interesting discovery inside 318

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prorac1

prorac1

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Upon disassembling the 1984 318 for my son Jason's project car, we discovered something very interesting. Just wondering if anybody has ever run into this.

As you can see from the pictures, 7 of the pistons are flat tops and 1 is a 4 valve relief piston.

The engine has been together for years, and appears to be mostly factory.

I know Chrysler quality control in the 80's was lax, but was it this lax? Dealer replacement piston? after market hack job.

Thanks. Eric and Jason.


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The 4 eyebrow is a replacement piston.
 
usually the replacement pistons (ie. Badger) were the same weight and compression ratio so youd never know it was in there.
 
Thank you for the replies guys. I was a little concerned about the balance and when it was done. But it sounds fairly standard fare.

I'll have to check for a sleeve.

Thanks again guys. Eric and Jason
 
Just a little of the history of the engine. Who ever did the repair did it well. It lasted this long.
 
pishta said:
usually the replacement pistons (ie. Badger) were the same weight and compression ratio so youd never know it was in there.
Click to expand...
LOL, you beat me to it. I was just thinking that a different piston would through everything out of whack.
 
I have a 1970 340 That has two different style pistons in it. Supposedly it ran and was in a dirt track car!
 
So were 7 pistons stock or 1?
My 82 block appears to have flat pistons too. Really want to look at the innards....
 
I had a small block years ago that ran great. Even ran it at the track a few times. Tore it down and it had two completely different heads on it! Different valves sizes and combustion chambers. It idled so smooth your would never know.
 
My buddy tossed a rod on his 400 sbc dirt late model years ago...two weeks left in the season. Scored the cylinder. Fixed it by boring the hole time fit a Ford piston he picked from his junk pile... Bored the small end of the rod to fit the junk piston, picked the rings from a trash can then went out and won the feature two weeks later!

I've torn down Ford flatheads that had 3 steel pistons and 5 aluminum ones....
 
Krooser said:
My buddy tossed a rod on his 400 sbc dirt late model years ago...two weeks left in the season. Scored the cylinder. Fixed it by boring the hole time fit a Ford piston he picked from his junk pile... Bored the small end of the rod to fit the junk piston, picked the rings from a trash can then went out and won the feature two weeks later!

I've torn down Ford flatheads that had 3 steel pistons and 5 aluminum ones....
Click to expand...


I've built probably a hundred flatheads and seen many more and I've NEVER ever seen a steel piston.
 
A good friend of mine bought a good running 70 Nova, thrashed on it for a few years, then sold it to another friend.
When the motor finally needed an overhaul, it was tore down and had dished, flat and domed pistons, with both hydraulic and solid lifters on the cam.
So it was basically a parts motor, that someone threw together out of left overs, that actually ran good, and lasted many years of thrashing.
 
bought a 71 340 4 speed duster in 92 motor was built drove it till 2000 and traded it for a 55 chevy project. the boy i traded it to sold it the next week and thay tore motor down and had 2 flat tops 2 fore valve relief pistons 2 two relief pistons and 2 dished pistons and crank was turned .030 on one rod journal only! ol car run strong no body would race it, all were skeerd of it...
 
100 years ago the cast aluminum stuff was not as good as todays castings and forgings. so some engines had cast steel pistons. with the right clearance and a layer of oil = no problem
 
Some pictures of the 7 + 1 engine from the first post, cleaned up a bit. Lol

Thank you everybody for your help. I'm hoping once we clean it up a bit, and add a new oil pump and timing chain, it will run well for a good long time.

Thanks. Eric and Jason.


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also pull 1 lifter at a time and check that none have a concave face. do not be concerned about a slightly different piston
 
Marcohotrod said:
also pull 1 lifter at a time and check that none have a concave face. do not be concerned about a slightly different piston
Click to expand...

Yeah. I'm almost afraid to pull the cam and lifters for fear of project snowball. Lol. We're notorious for it. Lol. The struggle is real. Lol
 
We've given thought to throwing in a small summit cam and lifters with the limp factory valve springs just for the lope. Lol
 
I would spend the money on a hone, fresh rings and bearings, before a cam.
 
I just noticed the ridge line on top the cylinders, a quick hone job, and fresh rings will go along way to prevent an oil burner.
 
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