273 to 340

[Vinny ‘65]

I’m replacing my 273 Commando engine in my ‘65 Barracuda with a ‘70 340. Will my exhaust manifolds from the 273 fit on the 340?

 

[toolmanmike]

I’m replacing my 273 Commando engine in my ‘65 Barracuda with a ‘70 340. Will my exhaust manifolds from the 273 fit on the 340?

They will work but they will choke the 340 down. There's a bit of difference in the ports and outlet sizes. They will work but not the best.

 

[Treblig]

Here the 340 exhaust gasket (silver) and the 273/318 gasket (blue). The exhaust ports on the 273 manifolds are much, much smaller than the ports on the 273 manifolds.:

 

[Vinny ‘65]

Thanks for the help guys.

 

[thesiren74]

Yeah choke city! We did this in my father's 64 valiant with a 360 and had to grind a little off the drivers side head, it really killed power.

 

[Treblig]

If you have manual steering the best solution is 60s 340 driver's manifold and 96/97/98 Jeep Grand Cherokee passenger's manifold. You might have to do a little grinding here and there but other FABO members have done it. GREAT FLOW!!!

 

[Vinny ‘65]

If you have manual steering the best solution is 60s 340 driver's manifold and 96/97/98 Jeep Grand Cherokee passenger's manifold. You might have to do a little grinding here and there but other FABO members have done it. GREAT FLOW!!!

It has power steering.

 

[Vinny ‘65]

What gets in the way with power steering?

 

[Treblig]

The power steering sector (box) and the power steering pump. Even with manual steering it's very close.

 

[Vinny ‘65]

So guess my only choice is to use my 273 manifolds.

 

[Treblig]

With power steering..yep. Unless someone else has a better idea??

 

[Vinny ‘65]

With power steering..yep. Unless someone else has a better idea??

Thanks

 

[AJ/FormS]

I ran a 340 with the 318 top end and factory 318 cam. Even the 2bbl on it. All stuffed into a 65 Valiant wagon. Funtastic combo. Wish I still has it.
Allbeit with fenderwell headers, for all the good they did lol.
That was 1975. I don't think today's gas would work in such a combo.

 

[thesiren74]

Im not saying the 360 with manifolds isn't quick and torque monster but from my duster wich is a couple hundred pounds heavier than the valiant it knocked a full second off 1/4 mile times 13s to 14s.

 

[belmateo]

One persons solution, not sure how you can discard muratic acid properly.

 

[belmateo]

This method has been around for years and works qutie well.

 

[belmateo]

Here are the results.

 

[krazykuda]

I’m replacing my 273 Commando engine in my ‘65 Barracuda with a ‘70 340. Will my exhaust manifolds from the 273 fit on the 340?

I would take the timing chain cover and water pump from the 273 and put it on the 340 so all of the original pulleys and radiator hoses line up...

I would use the original vibration damper from the 340 so the balance is correct... The mark for the vibration damper will be off, but that's easy to fix... Put the engine at TDC and then use the 273 timing tab and make a mark on the original 340 damper for TDC to line up at 0° on the 273 timing tab...

 

[toolmanmike]

Here are the results.View attachment 1715424527

A little off track here but........
I wish I had a big checkbook balance. It would be cool to extrude hone some 273 and then some 340 manifolds and flow them before and after. Here's a 273/318 exhaust manifold before and after. It has to help whether it's worth the money who knows.

 

[Vinny ‘65]

Thanks for all the tips guys. Really appreciate it.

 

[thesiren74]

The design of the early a manifolds is so restrictive i dont think it would help that much.

 

[toolmanmike]

The design of the early a manifolds is so restrictive i dont think it would help that much.

Yep especially the bottle neck on the drivers manifold.

 

[thesiren74]

Yep especially the bottle neck on the drivers manifold.

Isn't that nuts the way they made that! It's flat!

 

[toolmanmike]

Isn't that nuts the way they made that! It's flat!

It has to be that way to go around the steering shaft.

 

[thesiren74]

Yeah i know but damn!