273 to 318 swap in 67 Cuda

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cybrtygr32

cybrtygr32

1967 Ratfish Fastback
Joined
Jun 23, 2008
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Alabama
Hey guys, help this old guy out.
I have a nice rebuilt, 30 over, 318. It is just a long block. My 67 Cuda has a 273 2 barrel engine. Will all my brackets for power steering and alternator, starter, etc. fit the 1971 318 engine and are the engine mounts the same? Since I'm asking questions, what about the 273's exhaust manifolds, will they bolt onto the 318 as well? I would like to maintain the 2 barrel for now, will the 273 cast iron intake fit or will the ports be smaller and cause problems. I know I need to just get a Weiand or Edelbrock with 4v carb, but not in the budget for now. Any help on mating these 2 engines will be appreciated.

Mike in Alabama
 
The biggest obstacle that you will run into is the timing chain cover/water pump.

In 70 they switched from the cast iron to the aluminum water pump. The outlets for the radiator and timing marks changed (90° different) to the other side of the engine. To make the aluminum water pump set up work, you will have to change the radiator to the newer 71 style (if it will fit).

Or, you could put the old timing chain cover on with the old cast iron water pump, but keep the original vibration damper (the timing marks will be 90° off). Before swapping the timing chain cover and water pump, put the engine at tdc. Then pull the damper and install the old timing chain cover (with timing mark bracket if timing marks are not cast into the cover) and old water pump. Then remark the tdc mark where the old bracket/timing marks are lined (i like to use white paint or white out as it makes the marks easier to see with a light also). Now you can use the existing radiator without changing it and all the old p/s and alt brackets will work.


Everything will bolt on like motor mounts ets. The 273 and 318 hae the same size intake and exhaust ports so the intake and exhaust manifolds are completely interchangeable/compatible.
 
Thanks for info. The 318 engine already has a new water pump and fuel pump bolted on. I was planning on getting a new aluminum radiator as mine is toast. So I can just bolt on my 273 exhaust manifolds and cast iron 2 barrel intake? That is good news! Are you saying I need to use the cast iron water pump to utilize my PS and Alt brackets? Sorry about all the questions, but it has been a while since I worked on older Mopars.

Mike In Alabama
 
Previous reply is correct. The later model timing cover and water pump will change pulley depths mounting brackets, belt length required, fan spacer length, etc...

I would suggest getting a later model dual plane intake rather than use the single plane that is stock on the 273. Get yourself a thick base gasket for that 2 brl also. Have the parts guy look up 75 model e-body or similar.
A recent thread showed where some later model heads ( 302s for example) are just different enough to break the left side exhaust manifold from a 273.
Which way you want to route the fuel line or should I say which OEM fuel pump to carb line you plan to use will dictate which Carter fuel pump you use. The 2 pumps listed have their line out fitting in different positions.
I prefer the later model line routing with the fuel filter mounted low and vertical.
All of these little differences will help the 318 perform better than the same ol' 273.
 
stock cast iron 4v manifold and used 600 edelbrock would be a good fit and usually don't cost much.
 
Thanks for all the help guys. I got the engine home and on the stand. It is rebuilt, 30 over, valve job, new water pump and fuel pump 318 (talked to the engine builder),,,BUT I discovered something else. It is not a 1971 318, but a 1978 318 after checking numbers and pulling the vavle covers. The heads have the small holes below the exhaust ports where the pollution tubes once were. I guess I need to plug these and how? Thanks again for the replies. I'm just tryig to put together a Saturday night cruise in driver for my daugher (no sons).

Mike
 
Don't quote me on this, but I believe the air injection ports are pipe thread fittings...should be able to just plug them off without much ado.

Are you all squared away on the accessory mounting choices and induction?
 
The 273 torque converter has a smaller snout. You will have to use a 318 or 340 torque converter. How do i know? That is what I had to do because the previous owner put a 273 crank in a 318 and my later higher stall converter would not fit.
 
Thanks txstang84 and Ted. Didn't know about the converter size. I will inform my 904 builder to get me a 318 torque converter. As far as the induction choice, I really would like to use my 273, remaned 2 barrel and my exhuast manifolds if possible, for now. I also think I will use the 273 water pump to maintain my brackets for power steering and alternator. After getting my radiator checked out, it is not that bad. Thanks again guys from me and my daughter as we do this thing. This forum is one of the best I have seen!

Mike and Autumn in Alabama
 
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