TA rocker question.

[spoolinhard]

I'm looking at a TA longblock. One of the rocker arms is missing. The owner suggested that this is not one of the offset rockers and could be sourced from a regular 340. Is this true?
Pic:

 

[floyd]

No, regular 340 rockers are not adjustable and are completely different. You’ll need to find a correct 340-6 replacement.

Here’s a good reference pic

 

[moparleo]

 

[gzig5]

I think the exhaust rockers were just regular straight ones, same as used on the 273 motors with solid lifters. 340's used stamped rockers, which would theoretically work if one would fit on the shaft. The distance from the shaft to the ex valve was the same. I have some straight adjustable ones if you need to buy a single.

 

[spoolinhard]

I think the exhaust rockers were just regular straight ones, same as used on the 273 motors with solid lifters. 340's used stamped rockers, which would theoretically work if one would fit on the shaft. The distance from the shaft to the ex valve was the same. I have some straight adjustable ones if you need to buy a single.

Should the deal go through, I will take you up on that.

 

[moparleo]

Wrong. The 273 rockers are different. The 340 T/A rockers are stronger made to deal with high rpm, heavier springs.

 

[gzig5]

Wrong. The 273 rockers are different. The 340 T/A rockers are stronger made to deal with high rpm, heavier springs.

Maybe, I dont' know. But I know that 273 rockers have been used on plenty of 340/360 builds making 400+hp with no ill effects. I'd bet many of those cams had more spring than the original TA motors.

 

[moparleo]

Mopar says different. But if you are trying to build a higher horse/torque motor, why use stock iron rockers anyway. The after market has NEW not 50 year old parts that are without question better quality and stronger. If this as a stock, resto build I can see using stock parts. But it is his money. The stock rockers for a 273 and a T/A 340 are definitely not the same. Someone will always say that they know someone who did something or other and didn't have a problem. Not everybody gets the Covid-19 flu either but that doesn't mean not to be careful just in case.

 

[budascuda]

Are the new rocker arms made in the US ?

 

[spoolinhard]

The deal went through, and I own the complete long block minus one rocker. I can tell you with 100% certainty that the 273/ 340 TA rockers are different

 

[Chryco Psycho]

Congrats !

 

[spoolinhard]

Congrats !

Thanks!!!

 

[fk5aar]

The offset rocket heads for TA are worth double to triple the money also

 

[fastmark]

You are correct that 273 and TA rockers are not the same, however, I had a bud who bought an AAR years ago. It had the TA heads and six pack but a regular 340 block when he got the car. For some reason, it only had the offset TA rockers and all the straight one were stock 273. It worked fine for many years with no problems, so it can be done.

 

[Cuda Hunter]

Spoolinhard, Would you be willing to share the vin stamp on the block you have purchased?
Congrats on finding an aar motor! Hard one to find. Good price?

 

[moparleo]

Another " I had a friend and it worked for him" story. Why don't you just agree that it is not the ideal set-up or the factory would not have spent the $$ on R & D to develop the T/A rockers. You can use all kinds and brands and countries of different origins parts that will " work". If it wasn't your money, and it isn't, wouldn't you prefer to use the "correct" parts that were designed for the engine rather than parts that will just "work" ? When you shop for things do you look just for stuff that "works" or what does the best job for your budget or needs?
As the owner verified after he acquired the motor, the T/A parts are definitely not the same as 273 parts. That should settle it.
Always use items that were designed for a specific item and not just what will "work". Congrats again on the T/A motor. A real piece of automotive history, and something that many of us would love to possess .

 

[fastmark]

Some people just have to complain about everything. I said it worked just fine. I did not say it was the exact correct piece. I worked on the car and even owned it for awhile so you could say it even worked for ME. I’ve got set of of 273 rockers on my AAR right now because I have regular 915’s on it and the original TA heads are off. I regularly shift at 6500 rpm with no ill effects. You need to remember that this rockers were designed for the RACE trans am cars. They would have been overkill for the street. SO, in a pinch, you can use a straight 273 rocker. Is it 100% correct? No. Chances of finding just one rocker will be slim. Somewhere I’ve got a set of unmachined W2 rockers. Both straight and offset. I’ll look to see if I can find them and compare them to the straight oem TA rockers I have. If you can find some one to machine it, I’ll give it to the OP.

 

[mowerman36]

The deal went through, and I own the complete long block minus one rocker. I can tell you with 100% certainty that the 273/ 340 TA rockers are different

I'm in the same boat Need a #8 intake rocker

 

[DTCMMLF]

Adding what I had in my archives, about the TA rockers issues. (And agreed, unless someone is building a period correct motor, the newer Aluminum Arms w/rollers do so much better. Not to mention the weight reduction....)
The below is from: Interesting Dodge Muscle Car Facts

Fact 51: The 340 Six-Pack stands as the only Chrysler engine produced with adjustable rocker arms and a hydraulic camshaft. These features rarely converge, but in the case of the 1970 340 Six-Pack, the relocated intake pushrods prevented the use of existing 340 stamped-steel rocker arms because the balls and cups were no longer aligned.


While it probably would have been cheaper to whip up some specific stamped-steel offset rocker arms to solve the problem, Chrysler invested in high-strength, cast-steel rocker arms incorporating the proper offset to do the job. Doing it this way spared racers the expense of trying to find suitable aftermarket rocker arms when swapping a solid racing cam in place of the stock hydraulic unit.

 

[MoparCarGuy]

The bottom line answer to the OP's question is, yes, you can use any of the straight, cast-iron mechanical rocker arms. All LA engines used straight rocker arms (not offset) for the exhaust valves, even the T/A's exhaust rocker arm is straight but it is cast-iron and adjustable.

The 273's straight, mechanical rocker arm will work but is not a heavy-duty piece so it should not be your first choice to replace your missing exhaust rocker arm. Crane and Isky used to make aftermarket versions that duplicated the factory look but were stronger than the factory 273 pieces. You may be able to find one of these aftermarket, cast-iron adjustable straight rocker arms to replace your T/A exhaust rocker arm. Your best choice is to find one of the pricey and rare T/A or W2 cast-iron, adjustable exhaust rocker arms.

Note: Both 273 intake and exhaust rocker arms are straight with no offset. T/A intake rocker arms are uniquely offset and W2 intake rocker arms are uniquely offset and these intake rocker arms are not interchangeable.

Look at the straight rocker arms on the far-right of each of these pictures and tell me if you can see a difference. The T/A straight rocker arm is stronger than the 273 but look almost exactly the same.

Mopar Engine Performance Guide: Valvetrain - Mopar DiY

At what horsepower and torque level do you need aftermarket roller rockers, pushrods, and valves? When building a 500-hp (or greater) engine, I recommend upgrading from the stock stamped steel to heavy-duty aluminum roller rockers. The roller rockers provide much more strength, they tend to...

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