273 heads on 318

[RogerK]

I'm looking to try to port a set of heads over the winter and have a pair of 1966 273 heads that will need a valve job anyway. Would these heads be a decent choice for a port job?

I'm not looking for huge performance gains, I just want to improve the performance over the stock 318 heads I am currently running.

 

[JBurch]

I've done that; works good. My advice would be to put 1.88, 1.6 valves in, and cut the heads .030. Starting with a small chamber, and then cutting the head down you'll end up with a reasonable compression ratio. Put a set of headers on the car, be they Doug's, TTi's, or shorties and it's a nice wake up.

 

[65Val]

Roger...what are the casting numbers of the 2 sets of heads you're referring to? Locating a set of "302" heads might be advantagious...they already have hardened seats for unleaded gas.

 

[RogerK]

Roger...what are the casting numbers of the 2 sets of heads you're referring to? Locating a set of "302" heads might be advantagious...they already have hardened seats for unleaded gas.

The heads I currently have on my 318 are casting number 2843675. This number is from the bottom of the head,same side as the valve face, not under the valve cover, where the valve stems are.

I say it like that because the 273 heads I have don't have any numbers except in the valve stem area under the valve covers. I have a set from a 1967 273 and and a 1966 273, both not commando engines, and I checked a head from each.

EDIT....

OK! FABO ROCKS! I found a post that lists some casting numbers. The 273 heads are 2656920.

http://www.forabodiesonly.com/mopar/showthread.php?t=249026&highlight=273+casting

 

[C130 Chief]

You'll want to do hardened insert exhaust valve seats. If you were to put the bigger valves in "302" heads you'd need to do this as well.

 

[toolmanmike]

The heads I currently have on my 318 are casting number 2843675. This number is from the bottom of the head,same side as the valve face, not under the valve cover, where the valve stems are.

I say it like that because the 273 heads I have don't have any numbers except in the valve stem area under the valve covers. I have a set from a 1967 273 and and a 1966 273, both not commando engines, and I checked a head from each.

EDIT....

OK! FABO ROCKS! I found a post that lists some casting numbers. The 273 heads are 2656920.

http://www.forabodiesonly.com/mopar/showthread.php?t=249026&highlight=273+casting

The 675 heads are 318 heads. Probably very similar to the 273 heads. tmm

 

[SGBARRACUDA]

The 920 heads are closed chamber and will up your compression over the 675 318 heads. Have the harden seats put in them. I think your on the right track here.

 

[RogerK]

Thanks for all the replies and info. I can assemble an engine but it doesn't mean I'm an engine builder.

New valves, guides, springs and seats will be in order of course. I think I'll get the heads cleaned up and checked for cracks before I spend any time porting them.

I wouldn't want to waste my time porting to find out there's a crack. ](*,)

 

[66fs]

Early heads rarely crack, but checking will give you peace of mind.

 

[RogerK]

I've done that; works good. My advice would be to put 1.88, 1.6 valves in, and cut the heads .030. Starting with a small chamber, and then cutting the head down you'll end up with a reasonable compression ratio. Put a set of headers on the car, be they Doug's, TTi's, or shorties and it's a nice wake up.

Ok, A follow up. I plan on the valve upgrade as well as the machine work to lower the CC for more compression. My bottom end is all stock with flat top pistons. What is a safe lift to use on the cam with out risking valve to piston damage? Below is the cam I want to use.

Summit Cam & Lifter kit PN: SUM-K6901 Duration 276/288, Lift .441/.441

 

[toolmanmike]

Here's a little porting.

 

[RogerK]

@ToolManMike

Thanks for the pictures, they will help. I'm just concerned that if I cut the heads .030" I may get valve to piston issues. Am I safe with a stock bottom end and flat top pistons?