Tri Y headers

[neilswheels]

Hi Fellas, I'm building (having built at the moment) a 40 ford with a 348 motor. I was going to run fenderwell headers, but for various reasons have now decided to run tri y's. Can anyone give me any tube lengths and diameters to work with? Its going to have to be a custom made set, but i'd like to get them right! Its a stock early 348 with tripower, so about 250hp.
Any help appreciated.

 

[models916]

Watch out for that 4/7 cam swap thing with the cylinder merging. I would run no bigger than 1.75" tube. Maybe 36" long? Post pic when you get 'em.

 

[neilswheels]

' Watch out for that 4/7 cam swap thing with the cylinder merging'

What's that then??

 

[jim_ss409]

You can do a Google search and find a better description but basically you have to pair certain cylinders together.
This picture shows a set of Tri Y headers with a regular Chevy firing order.
These days it's getting popular to use a cam that has the #4 and #7 cylinders switched in the firing order. IF you happen to have one of those cams, you'd have to pair different cylinders to get the best effect out of the Tri Y headers. It's not likely your engine has a 4-7 swap cam unless it's been recently rebuilt because these cams have only really become popular in the last five years or so.
You can check by following the wires from your distributor to see if it follows the standard Chevy firing order... 18436572




I ran your specs through the Pipemax program and here's what it says...

First Y segment... outside dia. 1.572" length 18.1" to 19.7" long
Second Y segment... outside dia. 1.697" length 18.1" to 19.7" long

Collector outside diameter... 2.443" to 2.693"

Best collector length... 22.7"

The collector length won't matter if you're just reducing it down to a smaller exhaust size but if you're going to put in a cut out or a crossover pipe it would be best at 22.7" from where the secondary tubes end.
Your engine is pretty mild so you shouldn't expect a huge bump in power with the headers, but they will help a little,,, and look cool.

 

[neilswheels]

Thanks Jim, thats very helpfull. looking at the header pic, it would appear that the tube length isn't a 'must have', as the drivers side header, pipes 5 and 7 appear shorter than 1 and 3, and the pass side header, pipe 8 is shorter than all of them, and the secondary tubes seem to be a few inches out. I assume its best practice to go for equal lengths, but due to little things like steering box's and suspension, maybe not essential, unless its all about the hp. The collector on those seems to narrow and then flare out, any thing special happening there?
Regardless of all that, it 's time to go and buy some plastic tube, and work out where to squeeze 37 odd inches of pipe in!

Thanks again Jim.

 

[jim_ss409]

They say primary length isn't all that critical. You just try to get them as close as you can.
The collector is a bit like a merge collector. They say the pinched down area should improve the bottom end power a bit without hurting the top end power. There's not a whole lot of difference though. I see many of the Engine Masters entries use merge collectors but many don't.
On a mild engine, I'm guessing there's probably not more than 5 horsepower difference between a pretty good set of headers and a really good set.

 

[neilswheels]

Thought I’d update this thread a bit. So I’ve started on my tri y’s. The first pic shows a quick bit of tooling I made for a fly press to make the tube fit the flange. Going on the measurements provided, the primary’s are about 19, now moving into the secondaries, so made the final collector so I can work out where I’m ‘aiming’ for. This is the drivers side, unfortunately I can’t get the 2nd primary as long as I’d like, just not enough room with break pipes, steering box and oil filter. I may come back to it once I get the other side done.

 

[Ishiftem]

Looks great!

 

[Don Jacks]

Yes it does.What size tubing is that?

 

[61BUBBLE348]

Hey Neil,

first thing, what happened with the Poms down here.

Looks like you are making some progress on the Tudor. I like the drift you made keep up the good work

Grub

 

[models916]

I want to buy that flange tool from you. Just getting started on my new headers. I hate to have to make my own.

 

[neilswheels]

Thanks fellas.
Not sure Grub, for a game we invented, we’re doing particularly bad at it. It’s good to be working on the 40 again.
So this is where it’s at, tacked up. Had to remove the inner fender for a little clearance modification, so good time to take a pic.

Yes it does.What size tubing is that?

Tube sizes, primaries 44mm, secondaries 50, collector 63, so about 1 3/4, 2 and 2 1/2 inch. I went with 1 3/4 primaries because most aftermarket headers for W’s seem to be this size. I’m running a 22 inch long collector which will have a 'T' off in 2 1/2" that runs to the muffler, also 2.5 internal diameter, then drops down to 2 to the back of the car. Apparently this is what Chevy ran from 59 till end of production on the 348’s. I’ve got a lot of tig welding ahead of me...

 

[Phil Reed]

Umbelieveable!!!!!! I can not imagine how you come up with the final design!!!!!!

 

[El Rat]

Out of sight!

 

[neilswheels]

Umbelieveable!!!!!! I can not imagine how you come up with the final design!!!!!!

Necessity Phil, its the only way it would all fit in there with the bend diameters I have access to.

 

[neilswheels]

Little update, finally got the other side tacked together today, despite it being -1 in my garage. I may revisit the drivers side in an attempt to get the ‘short’ pipe closer to the rest, but I’m glad I’ve finally got two headers mocked up.

 

[Jeff Olson]

Looks like that took a lot of hours and measuring.

 

[MRHP]

And about 4 bottles of asprin.

 

[63 dream'n]

Nice........