piston identification on 273

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EmersonC

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I just removed my 920 heads off the 66 273 dart. I'm trying to thread to help id the pistons. They have 4 valve reliefs and say 040 on the dome. I'm really mostly curious what the 040 means and it there is any way to tell if they are stock
 
Generally if a part has a number like 010, 020, 030, 040 this is the oversize label. I would bet that your engine has already been bored out .040 over factory bore. I don't recall how much oversize a 273 can take but I think that is around the max.
 
4 valve reliefs means its a 2 barrel engine....040 means its been bored 40 thousandths over factory bore.

Below are 2 barrel pistons...std. size.....
 

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65Val is on it, +.040 and 2bbl: no 4bbl pistons have 4 reliefs. They have 2 and a 3 sided dome. Great pic here from FABO member ???
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Sweet! So my 273 has the good 920 heads, is overbored 40, this is nice... I'm guessing it doesn't have a stock cam, can I ID the cam with it still in the engine?
 
EmersonC said:
Sweet! So my 273 has the good 920 heads, is overbored 40, this is nice... I'm guessing it doesn't have a stock cam, can I ID the cam with it still in the engine?
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The '920 heads aren't necessarily the "good" heads...they are the standard heads. The "good" heads, if you're rebuilding your engine, are the "'302" heads...'85-'92 318 hi-swirl, heart-shaped chamber heads, with hardened seats already installed!
 
Way to bring me back down to earth 65val.

Does this mean stock head gaskets won't work?
 
EmersonC said:
Way to bring me back down to earth 65val.

Does this mean stock head gaskets won't work?
Click to expand...

Nope...they'll work fine, but, you can't get 273-specific head gaskets any more(unless you want to pay Cometic ~$150 for a pair). The standard head gaskets available these days are 4.00+" bore and .028"+ compressed, which is bigger and fatter than the 273's 3.625 bore and ~.020" original steel shim head gasket.
 
I have cometic gaskets holding my 340 together, best damn gaskets money can buy!
 
I wouldn't be thrilled about a 40 mil over-bore. Usually blocks are bored to re-use them, not for more displacement. Yours is probably at the limit and can't be bored again, unless there are 0.060 pistons for a 273. Anyway, re-boring a 273 is usually out of love because the price of a new piston set is much higher that later small blocks, so it is usually more cost-effective to switch to one of those, plus better parts availability.
 
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