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My New Doug Thorley Headers (Clamp Size)


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#1 OFFLINE   William

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Posted 24 November 2012 - 01:45 PM

Hi. Well .... my Doug Thorley headers recently arrived (Thanks to Steevo).
Everything looks Ok and ready for the install.

However, I was puzzled by a small "round cylinder-shape" part that came in the same bag
along with the Bolts and Nuts.

Does anyone know what is it for?

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William

#2 OFFLINE   William

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Posted 24 November 2012 - 01:50 PM

Another question about the same headers.

Should I just slide the 2 pipes that connect the EXTENSION PIPE with the Y COLLECTOR, Weld them or put a CLAMP around them to make sure they do not separate?

I am slightly inclined towards the CLAMP. Do you happen to know the diameter of these 2 pipes?

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#3 OFFLINE   William

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Posted 24 November 2012 - 01:58 PM

Last question about those headers :blush02:

I am aware that the DT THY-464-2-C headers for the VG30E need the standard 8mm Studs.
(which I already got from Alkorahil as follows:


Part # Description Qty
14065-V5004 STUD-MANIFOLD 12
14037-V5005 WASHER-LOCK 12
14039-W1500 NUT 12

However, upon measuring the diameter of the holes on my new headers, they came to
be 10mm (which I believe is the size recommended for the VG33E and not the VG30E).

Does that make sense to you or am I wrong somehow?

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#4 OFFLINE   Precise1

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Posted 24 November 2012 - 02:04 PM

Yes, they are larger than necessary; that is not an error, nor is it a problem. If anything, it makes mounting and aligning them easier as you have some wiggle room. Speaking of which, when you put them on, just barely snug everything until you have the crossover pipe and EGR tube connected, then snug everything. I had good luck with a lap joint band clamp (Walker brand IIRC) to seal the slip joint of the cross over pipe.
Yep, I dug in the garage and found my spare, it is Walker Mega-clamp #33230
http://www.summitrac...parts/wlk-33230

Lookin' good Bud! :aok:

B

Oh, I merged the three threads just to keep the info together. Since it was a group buy, I'm sure a lot of others will have the same or additional questions. ;)

Edited by Precise1, 24 November 2012 - 02:15 PM.


#5 OFFLINE   William

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Posted 24 November 2012 - 10:59 PM

Thanks B.

Does that mean that if I swap my engine for a VG33E, I won't need to "widen" the header stud holes from 8mm to 10mm anymore since they are already 10mm?

William

#6 OFFLINE   silverton

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Posted 25 November 2012 - 12:33 AM

If you swap to vg33, you'll need to drill the holes out on your vg30 exhaust manifold to accept the 10mm studs.

#7 OFFLINE   William

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Posted 25 November 2012 - 02:14 AM

If you swap to vg33, you'll need to drill the holes out on your vg30 exhaust manifold to accept the 10mm studs.


Dennis,

I am confused. If I swap my engine to a VG33E which uses 10mm studs and use these DT headers. Why do I even need the old VG30E Exhaust Manifolds?

William

#8 OFFLINE   Kyle94

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Posted 25 November 2012 - 02:24 AM

You dont, lol, i think Dennis was confused as well. The vg33 has the 10MM and so do the DT's. So now problem there. but if you were to keep your stock manifolds from the vg30 youd have to drill them out.

#9 OFFLINE   William

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Posted 25 November 2012 - 05:08 AM

Does anyone know what is it for?

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#10 OFFLINE   Precise1

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Posted 25 November 2012 - 08:41 AM

Nope. I think mine came with one also but I'm sure I had no use for it. By the cut out on top it appears to designed to be welded to a pipe OD at 90 degrees, but why I have no idea.

Thanks B.

Does that mean that if I swap my engine for a VG33E, I won't need to "widen" the header stud holes from 8mm to 10mm anymore since they are already 10mm?

William

You are welcome, and yes, that is exactly right. 1 size fits engine upgrades. :aok:

B

#11 OFFLINE   dmag23

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Posted 27 November 2012 - 12:17 PM

The short tube you are asking about is used on a throttle body pathfinder (87-89). Not sure if it would be used on the 90-95. It is the heated air pick up tube. It is secured to one of the driver side header tubes in a vertical orientation using a hose clamp to secure the tube to the header. Foil duct runs from the underside of the air cleaner to the pick up tube so you get heated air into the engine during warmup on a cold day. Mine came welded onto the header. Your arrangement just allows the pick up tube to be put wherever allows for the best placement.

#12 OFFLINE   Precise1

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Posted 27 November 2012 - 02:59 PM

Ok, that makes sense now! It's a TBI only part, the 90-95 MPFI don't have any heated air tube. Thanks for clearing that up. :aok:

B

#13 OFFLINE   MY1PATH

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Posted 01 February 2013 - 05:01 PM

Yes, they are larger than necessary; that is not an error, nor is it a problem. If anything, it makes mounting and aligning them easier as you have some wiggle room. Speaking of which, when you put them on, just barely snug everything until you have the crossover pipe and EGR tube connected, then snug everything. I had good luck with a lap joint band clamp (Walker brand IIRC) to seal the slip joint of the cross over pipe.
Yep, I dug in the garage and found my spare, it is Walker Mega-clamp #33230
http://www.summitrac...parts/wlk-33230

Lookin' good Bud! :aok:

B

Oh, I merged the three threads just to keep the info together. Since it was a group buy, I'm sure a lot of others will have the same or additional questions. ;)

That part that comes up is a 2" Lap Joint Clamp... So the crossover pipe is 2"? that's kind of a step down considering the collectors are listed as 2.5"



#14 OFFLINE   Tungsten

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Posted 01 February 2013 - 07:48 PM

Use the 2" band clamp. Just don't forget to add some sealant on the clamp before you put it on.

 

The collector is made for a 2.5" exhaust pipe but the cross over is 2". I don't see anything wrong with that.


Edited by Tungsten, 01 February 2013 - 07:51 PM.


#15 OFFLINE   MY1PATH

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Posted 01 February 2013 - 10:15 PM

my longtubes are 2.25" crosover from 2.25" collector.
the short tubes are 2.0" crosover from 2.5" collector.

Its ruducing a whole 0.5"



#16 OFFLINE   Tungsten

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Posted 02 February 2013 - 09:26 PM

Both down pipes are 2 inches so by them meeting at a Y-pipe and going into a 2.5 inch pipe actually does nothing. The 2 inch down pipes are still larger than what the factory cross over is. You can reduce the 2.5 outlet back down to 2.25 or even 2 with no problems if you use a special reducer. The reason why they went with a 2.5 outlet is that generally some of the best mufflers are actually 2.5 inches in and out. So you can run a 2.5 inch pipe from the collector back or smaller if you do a reducer so it doesn't just shoulder down.



#17 OFFLINE   sewebster

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Posted 03 February 2013 - 10:57 AM

Cross sectional area is what matters.  If the outlet into the exhaust system is 2.5" then that is an area of 2.5^2*3.14/4= 4.91 square inches.  A 2" pipe has 2^2*3.14/4= 3.14 square inches.

 

So since the 2" area is more than half the 2.5" area, there is no problem, it is not a restriction.



#18 OFFLINE   MY1PATH

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Posted 03 February 2013 - 01:48 PM

Both down pipes are 2 inches so by them meeting at a Y-pipe and going into a 2.5 inch pipe actually does nothing. The 2 inch down pipes are still larger than what the factory cross over is. You can reduce the 2.5 outlet back down to 2.25 or even 2 with no problems if you use a special reducer. The reason why they went with a 2.5 outlet is that generally some of the best mufflers are actually 2.5 inches in and out. So you can run a 2.5 inch pipe from the collector back or smaller if you do a reducer so it doesn't just shoulder down.

The collector is where all the primaries meet not where it meets the rest of the exhaust. so its going
1.5" primaries (x3) ---> 2.5" collector---> 2" down/crossover pipes ---> 2.5" Y pipe.

David pointed this out to me He REALLY doesn't like it lol. On the other hand, I can see how a reduction in diameter (usually .25" not .50") keeps velocity up until the merge with the other bank.



#19 OFFLINE   Precise1

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Posted 03 February 2013 - 05:35 PM

Well, if David said... :lol: Nope, the Thorleys aren't perfect, they are just the best out there that is generally available, life time warrantied and CARB legal. Hell, in Cali the biggest cat I can legally mount has 2" input and output, so the Thorleys aren't the choke point. It is still a significant improvement over the restrictive stock set up; the differences you talk about are minor unless you are at high RPM. The Pathy isn't a race track vehicle and who wheels @ 5000RPM? Is 5 HP going to make the difference? :unsure:

 

That part that comes up is a 2" Lap Joint Clamp... So the crossover pipe is 2"? that's kind of a step down considering the collectors are listed as 2.5"

I'll measure/confirm tomorrow.

 

B



#20 OFFLINE   Tungsten

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Posted 03 February 2013 - 07:41 PM

The inlet and outlet size of the catalytic converter does not affect its emissions. I verified this myself. The cat has to be CARB certified for it to be legal in California. All a bolt in cat does is include the flanges.

 

The primary collectors (after the smaller primary tubes) on the short tubes seem to be 2" and not 2.5" just like the down pipes and cross overs. The cross overs are also 2" so the lap joint band clamp should be 2" in diameter.

 

The only size change I see is after the Y-pipe where it exits into a 2.5" pipe.

 

FYI the short tubes were actually proven to perform better than the long tube variant on the VG30E. I have to dig that bit of information up again where I found it.






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