high compression egge pistons for 273

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housecat

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i am rebuilding a 1967 high performance plymouth 273. everything checks out that it is the hp version. when i took the old pistons out they were the flat top standard non hp pistons. the engine had been rebuilt at some point and bored .030 over, it does not look like any of the decks were shaved or any other machining. i ordered egge high compression pistons they are called an irregular dome. the possible issue is that at tdc without gasket on just the domed part of the piston ( horizontal above the wrist pin) sticks out of the block about .060. i called egge and a machine shop and they did not think that sounded right. either the pistons are ground wrong or that is how it was supposed to be from the factory. i know i could put flat top low compression pistons back in it, but i want it to be original as intended. any thoughts besides just to put a different motor in it, the whole car is original and i want to keep it that way.
 
I have those pistons in my 273 and I don't remember them sticking above the deck. I will have to look at my build thread photos to check it out. I know I went with .040 over and checked my valve to piston clearance and I had a lot of clearance with a commando/spec cam.
 
They're fine. Yes the domes are above the deck surface. I wish I would have taken some different pictures.

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DesertRat said:
I have those pistons in my 273 and I don't remember them sticking above the deck. I will have to look at my build thread photos to check it out. I know I went with .040 over and checked my valve to piston clearance and I had a lot of clearance with a commando/spec cam.
Click to expand...
thank you for the info, i will check clearance when i get the heads back
 
Left is always driver side. Mopar part numbers play the same game. Odd numbers on the left, iirc
 
housecat said:
i am rebuilding a 1967 high performance plymouth 273. everything checks out that it is the hp version. when i took the old pistons out they were the flat top standard non hp pistons. the engine had been rebuilt at some point and bored .030 over, it does not look like any of the decks were shaved or any other machining. i ordered egge high compression pistons they are called an irregular dome. the possible issue is that at tdc without gasket on just the domed part of the piston ( horizontal above the wrist pin) sticks out of the block about .060. i called egge and a machine shop and they did not think that sounded right. either the pistons are ground wrong or that is how it was supposed to be from the factory. i know i could put flat top low compression pistons back in it, but i want it to be original as intended. any thoughts besides just to put a different motor in it, the whole car is original and i want to keep it that way.
Click to expand...

Check the rods. Could be 6.125 rods or other aftermarket rods
 
information, the original deck hgts are, min .095 to .129 above the deck. this dome hgts, the flat is .011 down below deck. this from factory specs.
 
I would use those hi-tops in a NY minute, and machine them to fit as may be required. It's really hard to get decent cylinder pressure in those small bores, for anything but a small solid-lifter cam, any other way.
Part of the problem, you're gonna find out real quick, is getting a decent headgasket.
Nobody makes the special 273 gaskets anymore, and what you can get instantly drops the compression ratio quite a bit.
IMO, those hi-tops are Gold, just fit them very carefully.
Another problem that you might encounter, is keeping a composition headgasket in them. The cure is very flat decks and heads, with a slightly rougher than usual surfacing.. and retorquing after break-in................... This ain't your grampa's lo-compression 318.
If you will be running an automatic and hi-way gears, I highly recommend a solid-lifter factory type cam, and a tight squish, just to keep the cylinder pressure up. There is a pretty good debate on how little squish you can run; which is gonna depend a lil on which rods you are planning to use. I'll leave that to other smarter-than-me-guys to talk about. But I can tell you that my 367 has the heavier 318 bushed rods in it, and those I have run to 7200 under alloy heads for years (decades actually) without contact, with as little as .028 clearance.
Before you bolt the heads on, be sure you measure everything, calculate your exact compression ratio. Then, when you have retorqued your heads, and checked your valve lash, do a compression test. The results of the test will point to what fuel you may have to run when at WOT, to avoid detonation.
Happy hot-rodding
 
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