Head issue

[Frank Dinatally]

Hi guys
Question is. Is there a difference between 273 heads at exhaust ports. Just replaced my 273 with a rebuilt 318 and the driver side exhaust has an exhaust leak. Any reason you could think of? Any help is greatly appreciated. Thank Frank

 

[RustyRatRod]

Very possibly. Also depending on the year 318 head, it may well have the air injection holes under the exhaust ports that would not be covered up with stock 273 manifolds or headers. So I would look for those holes directly under the exhaust ports. I bet they are there.

 

[junkyardhero]

in the same vein, post 72 the 318 exhaust port is larger, so it may not be totally sealed by the manifold as well.

 

[RustyRatRod]

in the same vein, post 72 the 318 exhaust port is larger, so it may not be totally sealed by the manifold as well.

Yup. What he said too^^^ Could be multiple issues. You really need a correct 273 head.

 

[Frank Dinatally]

Very possibly. Also depending on the year 318 head, it may well have the air injection holes under the exhaust ports that would not be covered up with stock 273 manifolds or headers. So I would look for those holes directly under the exhaust ports. I bet they are there.

Engine is from 1979

 

[Frank Dinatally]

Engine is from 1979

Any pics of the extra hole that would not be covered by exhaust

 

[RustyRatRod]

Engine is from 1979

Oh ok. My no readin azz just reread it. My bad. I would certainly suspect the air injection ports under the exhaust ports then.

 

[RustyRatRod]

Any pics of the extra hole that would not be covered by exhaust

All you gotta do is LOOK under the exhaust port. See the red arrows.

 

[junkyardhero]

derp. RIF.

yeah man, if you're using the OG manny-folds then the exhaust ain't gonna match.

remflex gasket might be able to cover the sins, however if it's that late, you got smog ports like RRR said.

 

[Dana67Dart]

ALSO... early A 273 exhaust manifolds sit at a different angle than 67 up and my understanding is the early A manifolds can / do hit the air port bosses and fail to allow the manifold to seat propperly

 

[dano]

What's the car? Someone might know what manifolds will work.

 

[66fs]

If an early A, your exhaust manifold is hitting the drivers side exhaust port. You are lucky you did not crack the exhaust manifold. Those heads will not work with those manifolds.

 

[RustyRatRod]

ALSO... early A 273 exhaust manifolds sit at a different angle than 67 up and my understanding is the early A manifolds can / do hit the air port bosses and fail to allow the manifold to seat propperly

Now how bout THAT? That's somethin I didn't know.

 

[66fs]

ALSO... early A 273 exhaust manifolds sit at a different angle than 67 up...

This is not true, but the rest is. The drivers side exhaust manifold hits the last boss and will not lay flat. If you grind the head you may hit the coolant passage or grind the exhaust manifold you will weaken it. If he is real careful, maybe a little of both or thicker exhaust manifold gasket might work.

 

[Frank Dinatally]

What's the car? Someone might know what manifolds will work.

65 barracuda

 

[Frank Dinatally]

This is not true, but the rest is. The drivers side exhaust manifold hits the last boss and will not lay flat. If you grind the head you may hit the coolant passage or grind the exhaust manifold you will weaken it. If he is real careful, maybe a little of both or thicker exhaust manifold gasket might work.

On M9nday we are going to try double aluminum gaskets. If not he is going g to rebuild my 273 heads and put back on. Question do you have to replace both heads or can we just replace driver side. Passenger side works great on 318 manifold and block

 

[Dana67Dart]

This is not true, but the rest is. The drivers side exhaust manifold hits the last boss and will not lay flat.

The shape of the exhost manifold is different than 67 and it comes in closer to the block , correct? And that close ness won't let it sit flush to the head with those exhost bosses.

I guess saying it sits at a different angle was to simplistic so thanks for correcting my error.

And yes I said manifolds when i should have said manifold

 

[Frank Dinatally]

This is not true, but the rest is. The drivers side exhaust manifold hits the last boss and will not lay flat. If you grind the head you may hit the coolant passage or grind the exhaust manifold you will weaken it. If he is real careful, maybe a little of both or thicker exhaust manifold gasket might work.

Is it possible to rebuild just the driver side 273 head and install it or would there be a conflict of any kind to hav8ng the 273 head on driver side and 318 on passengers side. Performance or otherwise.

 

[junkyardhero]

The shape of the exhost manifold is different than 67 and it comes in closer to the block , correct? And that close ness won't let it sit flush to the head with those exhost bosses.

that's correct. the driver's side early A is especially unique from all the rest. the swoop down is very pronounced.

 

[RustyRatRod]

I would not mix and match heads. Either run 2 matching 273 heads or 2 matching 318 heads.

 

[Frank Dinatally]

I would not mix and match heads. Either run 2 matching 273 heads or 2 matching 318 heads.

Gotcha

 

[Frank Dinatally]

Gotcha

Since the 273 heads came off a 273 with the wider intake manifold would they work with the 318 edelbrock intake or would that be the next fitment issue. I would like to keep the original exhaust manifolds and the custom exhaust on the car. I don't know alot about this stuff but I would like to get all this crap to turn out good. Sorry to be a PITA but you guys are the best source I have

 

[mvh]

On M9nday we are going to try double aluminum gaskets. If not he is going g to rebuild my 273 heads and put back on. Question do you have to replace both heads or can we just replace driver side. Passenger side works great on 318 manifold and block

I would think you would have a problem mixing one 273 head and one 318 head — the combustion chambers would have different volumes as well as shapes. Compression would be different on each bank.

Remember, if you are using the 273 intake, make sure it's not for the early heads — it may not seal with the 318 heads. I would check the 273 heads for cracks, if you use those — it seems almost all of them wind up cracked. I went through 7 to find 2 good ones.

I know JYH has run a 318 in a narrow body (64 Dart), but I think he had Spitfire headers.

 

[Dana67Dart]

My 2cents.

The 65 273 heads have a smaller combustion chamber than a typical 318
They also have a different configuration for the intake manifold bolts then 67 and up.
The manifold will fit on either heads correctly but the bolts might not line up


If you are using a 67 up intake it might not have the holes aligned for the early 66 maybe 65 and older (I just don't remember) heads. Some after market manifolds have holes and bosses for both.

So before you switch back to the 65 heads be sure your intake will bolt on properly.

 

[66fs]

My 2cents.

The 65 273 heads have a smaller combustion chamber than a typical 318
They also have a different configuration for the intake manifold bolts then 67 and up...

Only 64 and 65 intake bolts are 5/16 with a 1/2 head and a different angle.