273 into a 70 Challenger?

[BriceRoad]

My 70 Challenger (340 4-speed) has a seized 340 and I have this 273 from a A body stick car lying around so I was wondering if it would bolt right in without any modifications? Will the 340 exhaust manifolds bolt on to the 273? This car is pretty ratty and I was thinking I would like to drive this car the way it is and possibly someday down the road restore it.

 

[moparleo]

The 273 was the smallest LA engine and has the smallest ports. The exhaust manifolds may not seal. People with old A-bodies are looking for the old 273 engine in their restorations. I would place adds for your engine asking for a possible trade for a later 318/360.

 

[basketcase70]

Even the earliest of 273s should be a drop in, and a good plan to get the car back up and running on the cheap.

If the 273 lower radiator hose outlet is opposite from your 340 (earlier models), use the later parts off the front of the 340 on the 273 to get the outlet to match the radiator, or alternatively, cobble a combination of lower radiator hose connections that could be considered temporary at best.

Early model 273s also have intake manifolds (and matching heads) that do not interchange with later model 273, 318, 340, or 360 due to a different intake mounting bolt arrangement. If your motor is complete and running, this would be a non issue to making the motor swap on the cheap.

The 340 exhaust manifolds may have a port mismatch, they should bolt on and work fine.

A 70 340 should have a steel crank with neutral balance and would be the same as the 273, so no mods will be needed to bolt the 273 to the drivetrain.

I’m in the same boat as you and intend to do a temporary roadkill version of my Challenger with the plan to someday restore it.

Freiburger and company would be proud.

 

[rklein71]

You could always sleeve the 340.

 

[moparleo]

If the 273 has a 2 bbl carb the throttle linkage and brackets will not just bolt up. Need to be modified or replaced as well.
Easy to say it will just drop in with no mods, but that is seldom the case.

 

[BriceRoad]

Thank you very much for the replys. I definitely did not consider some of the points made but I did know about the timing cover/hoses. I don't know what year my 273 is but it does turn and should run.

Maybe I will try one more time to free up the 340. It sure would be cooler to have a 340. The car has been sitting mostly outside since 1984. If you ever watched Rust Bucket Resto on YT the guy who does those videos found a 2nd gen Charger in the woods. One video showed him trying to free up the engine and man it was really bad inside. I think I will do a little more tare down on my engine and see how bad it is. Maybe if I take the heads off I can get enough transmission fluid or Marvel Mystery oil in it to free it up. The one thing that gives me hope is the oil looks brand new on this engine. If that doesn't work maybe I will look for a running 340 to put in it's place. I just hope that someday I can free up the 340 because it is the matching numbers engine.

 

[rklein71]

Thank you very much for the replys. I definitely did not consider some of the points made but I did know about the timing cover/hoses. I don't know what year my 273 is but it does turn and should run.

Maybe I will try one more time to free up the 340. It sure would be cooler to have a 340. The car has been sitting mostly outside since 1984. If you ever watched Rust Bucket Resto on YT the guy who does those videos found a 2nd gen Charger in the woods. One video showed him trying to free up the engine and man it was really bad inside. I think I will do a little more tare down on my engine and see how bad it is. Maybe if I take the heads off I can get enough transmission fluid or Marvel Mystery oil in it to free it up. The one thing that gives me hope is the oil looks brand new on this engine. If that doesn't work maybe I will look for a running 340 to put in it's place. I just hope that someday I can free up the 340 because it is the matching numbers engine.

I think you are right in disassembling the 340 and trying. A lot can be done to save it and like I said earlier, sleeving is an option to save it.

 

[Richard Rach]

If you want to try free up the 340, pull plugs & mix acetone & ATF together 50/50 mix or whatever you desire down cylinders and leave it sit. The Acetone sucks the ATF into the rusted parts. Have used this method many times over and have had good results, hope this helps.

 

[Cuda Hunter]

If you want to try free up the 340, pull plugs & mix acetone & ATF together 50/50 mix or whatever you desire down cylinders and leave it sit. The Acetone sucks the ATF into the rusted parts. Have used this method many times over and have had good results, hope this helps.

Interesting...

 

[Bobby Sixkiller]

My buddy bought a polara few months ago for 600 bucks with a stuck 360. I told home to try marvel in the cylinders. He’s been driving it for a couple weeks now. But each situation is different.

 

[BriceRoad]

rklein71, yes I want to do whatever I can to try to save it. It will definitely make the car more valuable and cooler too.

Richard Rach, that is a very interesting idea. I will give it a try. If it doesn't work I don't see how it could hurt anything.

Bobby, your buddy is lucky. I tried Marvel and it didn't work for me but I wonder if I put enough in the cylinders. Do you fill up the cylinder totally?

 

[Cuda Hunter]

I have a warranty 69 440 block that was seized.
I put every product known to man in those cylinders, both top and bottom.
Wouldn't free up. After several weeks of trying, a 2x4 knocked em loose.

 

[DetMatt1]

If you want to try free up the 340, pull plugs & mix acetone & ATF together 50/50 mix or whatever you desire down cylinders and leave it sit. The Acetone sucks the ATF into the rusted parts. Have used this method many times over and have had good results, hope this helps.

X2. I have used this mix with good results. I wonder how Kroil would free up a stuck engine? It’s hands down the best penetrant for stuck fasteners but could be expensive for the amount needed to free up pistons in a bore.

 

[340challconvert]

When I started working on my A66 340 engine after the car sat in inside/garaged storage for sitting 34 years; I could not get the engine to turn over manually. I used Kroil and PB Buster initially through the spark plug holes for a number of weeks. Still would not turn. I finally pulled the heads and used these materials directly on the pistons. Slow but sure and putting pressure on the crank bolt, the engine freed up. The process also loosened up the small amount of carbon that was on top of the pistons.
Cylinder walls were in good condition with minimal ridge. I found one cylinder with pieces of oak nuts? How the heck did a rodent get into one cylinder? A small amount of light corrosion was evident on the cylinder wall in that cylinder.
Long, short story, I am picking up a 360 rebuild to use while I put the 340 on the stand for a rebuild.

 

[Challenger RTA]

First off your not going to go to the corner salvage yard and pick up a 340.Is it numbers matching? Second the a 273 runs.Drop it in and find the issues and resolve them. You have a 273 and A body parts that solves a lot of problems,just make it work for now. 3rd you don't know the internal issues ( rings pistons or crank might do more damage)of the 340,try all of the above or just tear it down and get a plan to rebuild while running the 273. rebuilding the 340 will take longer than dropping the 273 in.Not to mention getting the 340 parts and time in the machine shop and $$$$. Then sell the 273! Make the best of what you have.

 

[Rons340]

I agree with Moparleo. I would consider trying to work out a trade. Those 273ci engines are getting very hard to find.
Don't get rid of the 340 though, especially if it's numbers matching to your car! It can definitely be fixed, but the trade would get you on the road sooner where you could take your time and repair it. Good luck to you!