# Round port headers for 66 GTO



## Fredrick (Feb 13, 2011)

Hi!

I would need some help to find round port headers for my 66 GTO.
They should fit to 3" exhaust and the primary tubes should be thicker then 1 3/4". The car has pw steering and pw breakes. Anyone who knows where i can find it? 

Best regards

// Fredrick

:seeya:


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## pontiac (Mar 6, 2011)

since round port heads did not come from factory in 66, best to tell us which year engine, heads and trans you have.


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## BearGFR (Aug 25, 2008)

Fredrick said:


> Hi!
> 
> I would need some help to find round port headers for my 66 GTO.
> They should fit to 3" exhaust and the primary tubes should be thicker then 1 3/4". The car has pw steering and pw breakes. Anyone who knows where i can find it?
> ...


Doug Thorley D-567 - I bought a pair in raw steel and then sent them to Jet Hot in Arizona to be coated with their 'Extreme Sterling' coating. Here's what they looked like before I installed them, and  how they look on the car.  These headers have 1-7/8" primary tubes.

Word to the wise. If you do go with some sort of coating on a new engine, make sure you break the motor in _using something else_ other than the headers. During that first break in run, they'll get hot enough to mess up the coating.

Bear


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## Mr. P-Body (Jan 20, 2011)

I'm afraid the headers Bear has for his '69 won't "fit" the '66. The frame rails are a bit closer together. 

Doug's DOES have a part number, but I don't have it "at hand". Rick Holladay's '65 has them. Call Thermal Tech in Hopewell, VA. They are a Doug's dealer, and coat them MUCH better than the cheap ceraimc coating Doug's applies. 

Keep your exhaust system "size" at 2 1/2 until CID exceeds 500. Noticeable loss in low-end power with the 3" pipes. No loss of high-end power with the smaller pipes.

Jim


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## JustAl (Mar 20, 2010)

I've installed the Dougs D567 in a '65 GTO and they do indeed fit. The closest clearance issue was at the brake distribution block, left side frame. While overall tight, there really isn't a major problem elswhere. I did "adjust" the brake lines a bit on the right side, but as I bent them up myself that wasn't a problem, probably could be done with pre-bent or exsisting lines. I have them connected to a 2.5 Flowmaster system. All side references based on sitting in car.


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## BearGFR (Aug 25, 2008)

JustAl said:


> I've installed the Dougs D567 in a '65 GTO and they do indeed fit. The closest clearance issue was at the brake distribution block, left side frame. While overall tight, there really isn't a major problem elswhere. I did "adjust" the brake lines a bit on the right side, but as I bent them up myself that wasn't a problem, probably could be done with pre-bent or exsisting lines. I have them connected to a 2.5 Flowmaster system. All side references based on sitting in car.


I had to tweak my brake system as well. I wound up relocating the distribution block to the top of the frame rail and making one new brake line, the one that goes from the distribution block to the rear brakes, because it needed to be longer to allow moving the distribution block. I was able to use all the other lines. 

Headers are "fun"... :willy: if I ever have to remove the passengier side lower control arm, I'm going to have to move that header out of the way before the rear bolt will come out. If the bolt were turned "the other way" so that the threaded end of the bolt was next to the header, the end of the bolt would stick out far enough to rub a hole in that tube.


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## Instg8ter (Sep 28, 2010)

lookin good Bear, you gonna make them cut-outs electric so you can open them up at a light?...they won't mistake you for stock then.


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## Fredrick (Feb 13, 2011)

Thanks everyone for the answers! i will try to find a good set of Dougs D567 in bare steel so i can get them coated myself. 

The engine that is going in the car is a 1974 400" block stroked and bored to 461" with KRE highport heads and a hydr. roller. the 3" stainless steel exhaust is allready installed by the owner before me, they got no cross-flow and they sound wicked as hell, even though it only has the original 389 in it. i think there are flowtech or hooker headers on it now. Some cheap stuff anyhow.


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## BearGFR (Aug 25, 2008)

Instg8ter said:


> lookin good Bear, you gonna make them cut-outs electric so you can open them up at a light?...they won't mistake you for stock then.


It has enough "attitude" even with everything buttoned up that it's going to be hard to get away with it.... but yeah, I'm seriously considering a set of those electric doo-dads


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## BearGFR (Aug 25, 2008)

Fredrick said:


> Thanks everyone for the answers! i will try to find a good set of Dougs D567 in bare steel so i can get them coated myself.


That's what I did. I'm VERY happy with the results and the service I got from Jet Hot in Arizona. I bought them and had them direct shipped there, but when they arrived they'd been damaged - due to poor to non-existant packing. Jet Hot contacted me, let me know what had happened, and even sent me digital photos of the damage. They got returned to the vendor. The next set I had shipped directly to me so I could inspect them and the packing first, then I sent them to Jet Hot myself. Even though the time limit on the "limited time special" they'd had on the coating I wanted had long since expired, they honored it anyway even though none of what happened was their fault.



> The engine that is going in the car is a 1974 400" block stroked and bored to 461" with KRE highport heads and a hydr. roller.


Not too different from mine. I built my 461 using my original 69 block. It's running a moderate solid roller cam and #722 heads.

Bear


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## Fredrick (Feb 13, 2011)

BearGFR: Do you know if Jet Hot can get them shipped to me in Sweden? You guys over there get get your stuff way cheaper then here. Then also i would not have to pay so much taxes to get them in here aswell if they can send with lowered price. 

What kind of coating did you get from them? Sterling, extreme sterling, sparkle etc.?
How long has it been since you got them coated and how is the coating today? Been driving alot with those headers? 

Thanks!

Edit: ill chekc with them now about the shipping...


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## BearGFR (Aug 25, 2008)

My car isn't drivable yet, I'm still getting it put together. I got the extreme sterling on their recommendation, based on the motor and how I'm going to be using the car. While I was getting the total advance dialed in, running the motor at close to 3000 rpm for 5-10 minutes, I got the headers hot enough to start glowing red --- the coating still looks fine.

I'd recommend you contact Jet Hot and ask them about the shipping details, though.

Bear


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## Fredrick (Feb 13, 2011)

Where did you find the doug d567 headers in bare steel? I can only find them coated.


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## BearGFR (Aug 25, 2008)

The uncoated (raw) headers have a different part number: D567-R

I bought mine through a place called Performance Peddler. I went to their main site and was unable to find them, but using google's shopper search tool I found them at this link and at several others.

Bear


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## Fredrick (Feb 13, 2011)

Thanks papa Bear! I´ll order them now and send them to Jet Hot to get them coated!


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## 66tempestGT (Nov 28, 2009)

BearGFR said:


> It's running a moderate solid roller cam
> Bear


  

if the coating held up on the dyno why not buy them already coated?


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## BearGFR (Aug 25, 2008)

66tempestGT said:


> if the coating held up on the dyno why not buy them already coated?


Ah, because when I ran the motor on the dyno they were still raw steel. I didn't send them out to be coated until after the motor was broken in. 

Bear


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## 66tempestGT (Nov 28, 2009)

BearGFR said:


> While I was getting the total advance dialed in, running the motor at close to 3000 rpm for 5-10 minutes, I got the headers hot enough to start glowing red --- the coating still looks fine.Bear


:confused guess this isnt dyno time but whats the difference.


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## BearGFR (Aug 25, 2008)

66tempestGT said:


> :confused guess this isnt dyno time but whats the difference.


Ah, ok ---- those first few runs on the dyno got them a lot hotter than that. That indicent where I (unintentially) got them glowing was after break-in, when I got it home and in the car, after sending the headers out for coating and getting them back.

Bear


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## Fredrick (Feb 13, 2011)

Im thinking of ordering the Hedman Hustler, like the ones i got to my 1970 Firebird but for the GTO. But i need some advice...

Differences between the Doug´s and the Hedman headers:

Dougs:
Primary tube thinkness: 1 7/8"
Primary Tube Gauge: 16-gauge
Flange Thickness (in): 3/8 in.

Hedman:
Primary tube thickness; 2"
Primary tube gauge: 18-guage
Flange thickness (in) 5/16 in.

What would you guys choose? They are in the same pricerange

i got the hedmans for the firebird and i love them.
What i don´t love is that you guys in the states not use the metric system so i would know more exactly how they are.


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## BearGFR (Aug 25, 2008)

Fredrick said:


> Im thinking of ordering the Hedman Hustler, like the ones i got to my 1970 Firebird but for the GTO. But i need some advice...
> 
> Differences between the Doug´s and the Hedman headers:
> 
> ...


Well, 16 gauge is thicker steel than 18 gauge (counterintuitive I know, but that's the way it works), and 3/8 is thicker than 5/16. The big story though is the tube size. Unless you're making some significant power and have some really good heads, 2" is probably too big. Big enough that it's going to cost you in terms of low rpm torque. All the simulations I ran, and the sage advice I got from experienced folks like Mr. P Body, told me that 1 7/8 was the right size for my engine - 2 inches would have been too big. My motor displaces 461 cubic inches, has a moderate solid roller cam, and the heads flow 282 cfm at 28" water on the intake side at .600 lift, 212 cfm on the exhaust side.

Bear


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## Fredrick (Feb 13, 2011)

BearGFR said:


> Well, 16 gauge is thicker steel than 18 gauge (counterintuitive I know, but that's the way it works), and 3/8 is thicker than 5/16. The big story though is the tube size. Unless you're making some significant power and have some really good heads, 2" is probably too big. Big enough that it's going to cost you in terms of low rpm torque. All the simulations I ran, and the sage advice I got from experienced folks like Mr. P Body, told me that 1 7/8 was the right size for my engine - 2 inches would have been too big. My motor displaces 461 cubic inches, has a moderate solid roller cam, and the heads flow 282 cfm at 28" water on the intake side at .600 lift, 212 cfm on the exhaust side.
> 
> Bear


OK, so the Doug´s seems better since it got thicker steel. And i guess it wont be noticible if losing minimum toprange HP with 1 7/8" insteed of the 2".
The heads i got are Kauffman Highport heads and have initial flow of 330cfm on the intake. I don´t know the exact numbers on the hydr roller cam, the guy who is doing the job on the engine and balancing the rotating kit have ordered a special cut cam for me with some overlap that i requested (will lose some low rmp tourqe for that i know) but it hade a little bit over 600 in lift i think.


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## BearGFR (Aug 25, 2008)

Fredrick said:


> OK, so the Doug´s seems better since it got thicker steel. And i guess it wont be noticible if losing minimum toprange HP with 1 7/8" insteed of the 2".
> The heads i got are Kauffman Highport heads and have initial flow of 330cfm on the intake. I don´t know the exact numbers on the hydr roller cam, the guy who is doing the job on the engine and balancing the rotating kit have ordered a special cut cam for me with some overlap that i requested (will lose some low rmp tourqe for that i know) but it hade a little bit over 600 in lift i think.


Doug's may have some 2" headers also. Before you let me talk you out of the 2", it sounds like your motor is going to make more power than mine does and very possibly might be able to use the larger tubes. Ifn' it were me, I'd run the combo by Mr. P-Body and get his opinion on it. Do you have the specs on your cam? (lift, duration @ .050, LSA, etc.)

Bear


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## Fredrick (Feb 13, 2011)

BearGFR said:


> Doug's may have some 2" headers also. Before you let me talk you out of the 2", it sounds like your motor is going to make more power than mine does and very possibly might be able to use the larger tubes. Ifn' it were me, I'd run the combo by Mr. P-Body and get his opinion on it. Do you have the specs on your cam? (lift, duration @ .050, LSA, etc.)
> 
> Bear


sorry, i don´t have the numbers on the cam. And i don´t want to disturb the guy who is building the egnine for me since they are working 12-14 hours shift right know with some cummins diesel engines that cost like $2000 every day they stand still. But i know that he ordered the cam from Jeffrey Kauffman and i guess i can send a mail to him and ask.

But, i know people who have +1000hp engines and they dont need like 3" primary tubes to get to those numbers. So i think that 1 7/8" will be enough but cill check if i can find 2" doug´s and if i do i will go with them.


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## BearGFR (Aug 25, 2008)

Doug's D522/D522-R are round-port headers with 2" primaries for the GTO/Lemans. Still though, I strongly recommend you do some planning with detailed information before you just go buy some. Information needed would be things like:

cubic inch displacement (bore & stroke)
carb (brand and cfm)
intake (type - single plane or dual plane. If aftermarket, brand and model)
heads (type, static compression ratio, flow rates and port work if any, valve sizes)
cam & valve train (type - flat/roller, solid/hydraulic, intake/exhaust duration @.050', lobe lift, lobe separation angle, rocker arm ratio and type) 

I can plug that information into an engine simulator I have and then compare the effects of different primary tube sizes.

Bear


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