Will a 1966 273 take later unleaded 318 heads?

[thomas93254]

1966 273 2 BBL. I want to make sure this engine goes the distance but know that it is not set for unleaded fuel. I could get the factory heads machined and hardened seats put in but would swapping them out to a 74-76 318 unleaded head be more cost effective? I know the 273 has a solid lifter cam in it will the valve train hardware need to be changed as well?

BTW the engine is all stock if this helps to know

I know this is a newbie question :icon_redface:

Thomas

 

[YY1]

You will probably lower the compression.

 

[thomas93254]

You will probably lower the compression.

What would you recommend?

Thomas

 

[67Dart]

Try to find the mid 80's 318 hi-swirl heads...casting number ends in "302"... Chambers are the same size as the older , standard "920" heads, and they will bolt to your '66 and later intake. All your current valve gear will work...these heads are a bolt-on upgrade.

 

[thomas93254]

That was the info I needed. Thank you

Thomas

 

[YY1]

Agree.

 

[thomas93254]

Any one have a picture of where to find the casting numbers that end in 302 or 308?

 

[Cranky]

How long has this engine been running with the leaded heads? Are you having a problem sinking valves? So far, I haven't had any problems running the leaded heads on my stock factory engines....

 

[thomas93254]

All its life. The factory 273 has about 68000 but I believe that it may have burnt valve(s). Rough running and vacuum fluctuations indicate that might be the issue. I'm going to do a valve adjustment on it as soon as the weather cools off enough, but I like to be prepared for the worst, just in case. Plus I have been told that the 273/318 heads can suffer from seat sink age, which the valve adjusting would tell me if that is happening.

Thomas

 

[Cranky]

Do a compression check and also check to see of none of the valves are too tight. Being over adjusted can cause burnt valves and pretty fast with leaded or unleaded gas. I never installed hardened seats unless I absolutely have to but then I'll try to get a bit larger valve first.

 

[thomas93254]

This car is to be a cruiser only, so bigger valves, cam etc don't really apply to me, but I understand what your saying

Thomas