header interchange for ON centre gn1r heads

[karolko]

Hey guys,

quick question, I have a set of 4 bolt TA headers that are currently bolted onto my 109 block, and just for fun I tried to slide them onto my Stage II On center motor and they slipped right on the studs.

I am a little confused as I remember reading a sticky on this Sub-Forum saying that off center headers will not bolt onto on center heads.

Am I missing something here? are the exhaust ports infact in the same location as off center heads, and just shifted forward accordingly?

OR are these things boltsing on but the ports themselves are offset.

I have not done much digging just yet, but would like to hear from the more knowledable guys on the forum about this as I am sure they have encountered it already.

Thanks a lot,

Adrian Karolko

 

[forcefed3.8's]

The heads are the same. The heads are shifted on the block.

 

[rag231]

You will see your issue once you try to connect the crossover pipe. You can make those work with some fabrication skills.

 

[forcefed3.8's]

I had ATR's on my 109, and used them on my on center with no problems. The TA's I have now came off an offcenter S2. No problems, no fabbing.

 

[coach]

I had ATR's on my 109, and used them on my on center with no problems. The TA's I have now came off an offcenter S2. No problems, no fabbing.

You are correct Rob. The shift between the 2 engines is less the an 1/8". 0.120 to be exact. With either the TA or ATR crossover pipes being 2 pieces, it should be easily adjustable and mount without any issues. A 1 piece crossover would require a slight "massaging" to get it to fit and seal.


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[karolko]

Thanks a lot guys,

I guess my next question will be which is a better option to have:

ATR or TA headers?

I have both sets and they are both 4 bolt and both are stainless. Is there going to be much of a power difference, or spool time difference between the two. I am going to be running a 7675 turbo.

Adrian

 

[coach]

What size downpipe? Depending on which ATR's you have, the crossover can interfere with a 3.5 pipe or bigger. The TA's work with just bout any downpipe. There have been a few threads on crossover pipe clearances that have popped up in the past few months.

 

[karolko]

Coach, I had cross over pipe clearance with my flywheel, The pipe is very close, we're talking 3/16" to the front face of the flywheel. but it fits. I plan on making a 5" downpipe, which will likely blend into a 4" inside the engine bay. I just don't think I can get away with a 5" all the way. I think I have one of the last generation of ATR headers. How would I be able to tell? The 4 bolt flange is tapped. I know that much. Adrian

 

[coach]

Coach, I had cross over pipe clearance with my flywheel, The pipe is very close, we're talking 3/16" to the front face of the flywheel. but it fits. I plan on making a 5" downpipe, which will likely blend into a 4" inside the engine bay. I just don't think I can get away with a 5" all the way. I think I have one of the last generation of ATR headers. How would I be able to tell? The 4 bolt flange is tapped. I know that much. Adrian

You got me. I have never used ATR headers. I just remember reading in the thread. I have only ever had Kenny Bell and TA headers.

 

[karolko]

anyone else? TA or ATR? I'll do some searching as well.

Adrian

 

[rag231]

My ATR headers were switched with the heads to a different block and it was off by a little more than 1/8 inch. But it wasnt anything major. The primaries were big, the only problems were spark plugs of 4 and 6. You almost had to take the header loose to get to 6. If they were came out from the flange about 3/4 of another inch, they would have been perfect. I forgot that there is a wastegate welded on my crossover, hmmm. I have 2 Delta gates, they were on the car when I bought it.