218 heads fit 230??

[Jarv69]

Both bolts on my 230 head snapped at the thermostat housing, so I drilled them out and prepared to use helicoil's, But I do have a head off my 218 that the holes are good and was wondering if the heads interchange. I'm new to site so if it's been posted somewhere please guide me to it as I've tried to search, no luck, but may be doing it wrong. Thanks

[Niel Hoback]

Swap away, it'll work perfectly.

[Jarv69]

Thanks probably a better idea than the helicoil's I was going to do. I'll shave it down 1st and clean it up you have a recommendation on how much to shave while I'm doing it?

[Plymouthy Adams]

shaving a head to true it only is minimal removal of metal to bring the surface back to an even flat....to pick a number greater than that not knowing the history of the head, if been shaved in the past to true, or shaved for performance at any other period of time could be just guessing.  You may need to CC the head or as a minimum do a valve to head check with modeling clay.  Odds are you may be good to go with just a minimal removal for trueing the head..but again...you still just guessing.

[_shel_ny]

,,,

Edited December 17, 2015 by shel_ny

[Frank Elder]

Can it be drilled and tapped to the next size?...... that would be my choice over a helicoil.

[Dave72dt]

Properly installed helicoils will hold just fine.  They'll hold head bolts in an aluminum block if need be.  Cast iron should be no problem.

[austinsailor]

Next time find someone with a tig welder. Have them build up the broken bolt till you have a big mass above the surface. Put a vice grip on it, turn it out. If your new "head" breaks off, just weld it up again. You get unlimited tries.

The welded on knob gives you something to turn, the heat in doing it loosens it so it comes out. I've done as much as an entire manifold set before, it's always worked

[dpollo]

Putting a 218 head on a 230 is a cheap and effective way to increase compression. 

You lose none of the breathing space so vitally needed.  If you calculate the cylinder volume of a 230  and a 218

38.33  and 36.33 cubic inched per cylinder,   then given that both engines started life with say  7:1 compression (1951) then the difference has to be made up in the volume of the chamber.  Therefore, the 218 chamber must be smaller than the 230.

 

Any overbore also has to be figured in.   If you put a 230 head on a 218, you lower the compression ratio.  My 50 Ply. with a 230 equipped with a 218 head and .040 overbore pumps up 150 lbs per cylinder.   Stock was about 115.

[Jarv69]

Thank you all! I'm going to machine shop now to have the 218 head shaved so I can put it on the 230. Piece of mind knowing the water inlet is secure and not rigged! If I only had 1 head then no brainier but with the extra I'm confident! Thanks again! Jarv

[Frank Elder]

I thought that the rods and crank were the only difference between the 218 and 230....I've never heard a thing about the heads being different,,,,,?

[greg g]

heads are either internal or external bypass for thermostat controlled coolant flow.  A lot of people have suggested there is some cut of date for internal vs external bypass.  My 46 218 engine and my 56 230 engine are both internal bypass.  I have seen 36 engines that have either or, so I do not think is related to manufacturing date.  What I might suggest is that deluxes being entry level like savoys in later years had internal,and up market models had the external by pass.  So if your parts retain the same type among original and donor the heads will exchange.

[Frank Elder]

Sorry....knew about internal external.....I'm talking about a 218 head having a different compression then a 230 head of the same year.

[greg g]

Compression ratio between Dodge and Plymouth was the same depending on year from 6.7 to 7.6 to 1 across the board.  Later heads having the bigger squeeze.