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Discussion Starter #1
Here is THE 3.4L Doug Thorley headers thread. This will be thread for all questions and answers regarding these headers. They are full stainless steel construction, mandrel bent, laser cut flanges, and will be offered in chrome or ceramic coating. The following are the dyno charts from my truck, 240hp being baseline, and 256hp after headers. You will see the modifications in my profile. The headers are 1.5" primaries, 2.5" crossover with a one piece crossover. I will have pictures up shortly. And all other details will be coming soon!! Enjoy!!
 

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Thank you for your hard work on this Chris. I've been rating your other threads a 5 out of 5, and this one is the mother of all. :clapping:

Looks to me like you increased the area under the entire curve. Awesome results!

You mentioned the 1.5" primaries and 2.5" crossover. Does anyone know the difference between these and the TRD headers? The JBA headers?

Will these come with the same spring loaded flanges as the TRD headers? Will they be offered for 4runners as well as Tacomas?

Any pictures?

Please keep us updated! Great work!
 

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Very nice comparison graphs. I like seeing the addition in torque starting right at 1600 RPMs.

What's with the dip at 4800 on both graphs?

So what are the details on these? Any pictures? Does the crossover go OVER or UNDER the motor? Sorry if this was answered elsewhere.

Are there measures in place to prevent leaks like the ones that plague the TRD headers? If so what are they?
 

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Discussion Starter #10
Thank you for your hard work on this Chris. I've been rating your other threads a 5 out of 5, and this one is the mother of all. :clapping: Thank you.

Looks to me like you increased the area under the entire curve. Awesome results!

You mentioned the 1.5" primaries and 2.5" crossover. Does anyone know the difference between these and the TRD headers? The JBA headers? TRD Headers had 1 3/8" primaries, 2 1/4" crossover. TRD has the number 1 cylinder floating and not even on the same flange. And JBA requires extensive cutting and multiple flanges and pieces. Whereas ours only has 1 left, 1 right and a crossover.

Will these come with the same spring loaded flanges as the TRD headers? Will they be offered for 4runners as well as Tacomas? The will be ball flanges. And yes, we will fit as many applications as possible. We are also going to try doing an egr bung for the earlier guys.

Any pictures? I will see what I can do. I can tell you they look similar to JBA in that the number 1 cylinder loops around.

Please keep us updated! Great work!
I will for sure.

Very nice comparison graphs. I like seeing the addition in torque starting right at 1600 RPMs.

What's with the dip at 4800 on both graphs? We have noticed that on all the runs I have done on my truck. We couldn't seem to figure out what it was. It did it before the headers too. We think it might be the knock sensor bumping timing. I am unsure though.

So what are the details on these? Any pictures? Does the crossover go OVER or UNDER the motor? Sorry if this was answered elsewhere. The crossover goes over the motor and has the flange placed so it can be torqued easily. No pictures yet, soon though.

Are there measures in place to prevent leaks like the ones that plague the TRD headers? If so what are they?
Yes, less flanges, and using ball flanges. TRD pushed the collectors right in the middle arc of the crossover where it bends, thus attempting to solve leak issues. More like a band aid. We put the flange right near the first cat. Thus after the arc and not having as much of a load.

......and are they for every 3.4L
We are going to do as many applications as possible.

......and are they for every 3.4L. ......and does it matter if it's 2wd or 4wd?:shrug:
Not that we have determined yet.

Those are some nice to the wheel numbers. :headbang: Let us know when we can start placing orders. :waytogo:
Will do, they are still in early development, once I get some real parts and they are fixtured I will take some pictures very soon. I will see what I can do.


 

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Make some for my 2000 4runner okay? TRD discontinued theirs; sounds like these are better though. :headbang:
 

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TRD has the number 1 cylinder floating and not even on the same flange.
I can tell you they look similar to JBA in that the number 1 cylinder loops around.
Can you tell me what these two statements mean? I noticed TRD headers look "conventional" and the JBAs do some some pipe that loops. I've always wondered what the deal was there?
 

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Discussion Starter #13
Can you tell me what these two statements mean? I noticed TRD headers look "conventional" and the JBAs do some some pipe that loops. I've always wondered what the deal was there?
The difference between the "conventional" and JBA, is that the number 1 cylinder floated all the way to the collector, thus having another flange to the collector and and the head. This is good in the sense it is now longer tubes, but prone to leaking. TRD brought the collector all the way to back and cast it as well. Nice concept, but just had too many flanges. The JBA "loop" that I describe, keeps the length of the that tube similar to the others, thus helping the scavenging. This loop also functions for installation ease. In the S-Runner, the hardest one to fit, the steering column is right in the way and you need to get by that in order to install it. I attached the picture from Gadget's site that has the perfect angle for showing what I mean.
 

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Thank you for answering my questions. So basically these have some fatty tubes! With the hood open, do you hear pulsations through the headers?

Looks like these are going to be a hybrid between the TRD and JBA headers. Taking the best of both worlds so to speak. Nice explanation on the design differences. With more flanges, it would seem logical that the TRD ones are prone to leaks.

Can't wait to see the pics!
 

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Discussion Starter #15
Thank you for answering my questions. So basically these have some fatty tubes! With the hood open, do you hear pulsations through the headers?

Looks like these are going to be a hybrid between the TRD and JBA headers. Taking the best of both worlds so to speak. Nice explanation on the design differences. With more flanges, it would seem logical that the TRD ones are prone to leaks.

Can't wait to see the pics!
Exactly!! Because the TRD was a good kit, good idea, but just leaked, plain and simple. You could see in that last picture, how the entire tube was floating, not good. And if you look in the directions of the JBA it says you have to cut out the stock crossover, just to get it out!! And they have multiple flanges as well.
 

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Discussion Starter #17

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I found two old threads on YT that have some suggestions on these headers. I'm wondering if Thorley already considered these in the last three or four years:

This guy had the flanges cut, basically making all of the cylinder connections, "floating." Don't know how accurate this information is, but might explain why Thorley made the first cylinder floating in the first place for the TRD headers.

http://www.yotatech.com/showthread.php?t=15973&highlight=trd+headers+flanges

"The cylinder head expands and contracts varyingly when the engine is running, right? Well, the stock manifolds are made to expand and contract along with it. Headers are not. That is why most people have leaks. He said by cutting the flange, each pipe would be able to expand/contract with the head and at the same time, keep a good seal. It's also insurance against the pipes vibrating loose"

Gadget's comments on the type of gaskets that should be used, and a suggestion to improve the TRD headers:

http://www.yotatech.com/showthread.php?t=24652&highlight=trd+headers+flanges

"The stock setup works really well. It uses a crushing type gasket that will seal any oddity in the flange surface and the flanges are cut back in a way that you tighten the bolts down until the two flanges touch each other while putting the perfect amount of pressure on the gasket. TRD ignored this approach. To bad it worked really well.

I really wish TRD would have taken the time to make their flanges just like the OEM ones with a properly recessed gasket surface so it will properly load the gasket when the flange come flat against each other and not have any of these problem.

They have made a big improvement in the header to down pipe connection to solve that never ending prpblem. Maybe they will take my spacer idea and make it their own so that others won't have this problem.

Gadget"
 

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im also able to be a guinea pig if u need one for a 04 pre-runner 2wd just putting it out there...when are we gonna know the price on these and when we're gonna be able to order?
 

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Hey, ls customs

Would you suggest to Doug Thorley to product a downpipe to defeat the 1st cat on the cali spec 4runners for even better free flowing performance! Its the J pipe right after the outlet of the headers.
 
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