Have a look at this youtube vid of Martins, it may help you.

 

Beat me to it....Seems like the last time I looked, those headers were no longer available...

 

There are a LOT of better ways to spend $1,000. :surprise:

 

Yo, I'm curious what you would spend the grand on instead of or before buying headers. Serious question, I'm here to learn (and also building an 02 HO...)

Thanks man

 

What kind of power increase do they provide on an HO with full 3" exhaust?

 

hmm.... does that mean theres interest for a group buy?

 

Not sure about anyone else, but count me in on a group buy if it happens

 

not available anymore...

 

I understand Thorley is finishing up a batch shortly. Unfortunately no one there told me and now the batch is sold out. So they're all going somewhere - maybe Summit Racing will get some? I'd suggest calling Thorley and speaking with either Shelby or Jennifer. They might know if any of them have been sold to vendors for stock.

Mike Johnson was my sales rep over there for over 15 years and kept me in the loop on production. He left the company a couple years ago and I guess I lost my place in line

 

Thanks man

 

They only make the one set for the 4.7. It deletes the precats so it's not going to be emissions legal in areas that require emissions tests and/or underbody inspections.

 

It says that they're in stock here, and this is the best price I saw by a couple hundred dollars.

https://www.speedshopstore.com/doug-thorley-headers-thy-637y-c-long-tube-w-y-pipe-jeep-1999-04.html

I found this by searching for the part number THY-637Y-C

 

It says that they're in stock here, and this is the best price I saw by a couple hundred dollars.

http://www.speedshopstore.com/doug-thorley-headers-thy-637y-c-long-tube-w-y-pipe-jeep-1999-04.html

I found this by searching for the part number THY-637Y-C

I've came across this website selling it as well, I've been reluctant since I'm not sure how legit it is, but I haven't had much luck anywhere else.

 

Got it. Not looking for the wagon to be a faster ride, other heads are actually made, not for more power or speed but to solve the dropped seat problems.

Mines the H.O. So I've got decent cams already.

Headers, exhaust, and few other minor things , for drivability and updating the power plant is my intent.

Thank you for your input. [emoji109]

Sent from my Pixel 5 using Tapatalk

 

Got it. Not looking for the wagon to be a faster ride, other heads are actually made, not for more power or speed but to solve the dropped seat problems.

I'm not aware of anyone that makes new aftermarket heads for the 4.7, especially performance heads. All of the ones I've seen are just cleaned up junkyard heads with new valve seats. Take a look at the aftermarket heads available for other V8's (even other Mopar stuff) and you'll find heads that will turn an engine into a fire breathing, tire shredding beast. There are tons of options. Intake port size, exhaust port size, spark plug location, max valve lift, chamber size, camber shape, etc.

Have a look at https://www.summitracing.com/search/part-type/cylinder-heads?kr=heads to see a bit more about what's out there.

If you want to learn more about which parts do and don't make power, check out the Engine Masters channel on YouTube.

Also, don't be fooled by articles that show a 50+ HP increase just by adding headers. That can happen if you're running stock exhaust manifolds on an engine with a huge cam and high-flowing heads, because in that situation the manifolds really are a restriction. But putting that same set of headers on a stock engine isn't going to give you the same gains.

 

I've been modifying the WJ 4.7 since it came out in 1999. Exhaust alone is worth nearly 20hp if done correctly. It's a very restrictive stock setup. And there's solid gains with programmers, air intakes (for the standard 4.7) and ported throttle bodies. Mike Leach of Mopar Performance fame and Ron Zimmer of Z industries did some great work with the fuel and spark maps back in the days before Superchips, Diablo and SCT. Those guys loved the 4.7 because it responded so well to tuning. Mike Leach, Tom Fox and Ron Zimmer had the contract with Mopar Performance to do the Mopar Performance tunes but as many of you may remember, the plug got pulled by Daimler back then. I was involved in a final year sendoff for the 2004 WJ that Milous/Resumespeed was working on for Jeep. It was going to be the equivalent of the 5.9 ZJ - a "pre SRT" model with a bunch of handling and power-adding goodies for the 2004 model year, but that all got canceled too. Would have been a blast since we had a pile of good upgrades ready to go.

The HO cams were also a great power adder as was the HO intake manifold. There's no need to spend thousands for good power and efficiency gains.

I'm not going to argue for or against expensive mods such as the Thorleys or ported heads but to say there's not good gains to be had with the basics is incorrect.

 

Well Thorley convinced me to order some headers for the 4.7 and they arrived the other day! If anyone in interested in a set, please PM me here on the forum or email me at kolak@aol.com - I have 3 sets remaining

 

I would think headers will give the 4.7 a nice boost in power as the stock manifolds look horrid.

Sadly for me the Thorley ones would cost way too much in freight.

 

I would rather go to the dentist for 4 root canals than to do that header mod.

 

Cant see it being any harder then any other car.

 

Martinbuilt to the rescue, as usual, with a detailed video of the procedure.

 

BUMP! I got a set of headers from Kolak this summer. Unfortunately my SO 4.7 decided to drop a valve seat 3 days before they arrived, HAHA! So I never got to install them /: (disappointing) got an ‘02 4.7 HO now, that I’m deciding to bolt on 08-13 4.7 heads, manifold/TB, custom tune. Currently I have K&N CAI, Thorley Headers, flowmaster super 10, all stock HO internals/components. Will update as the money trees decide to fruit for me.

 

Any updates? I have an 04 4.7 HO that's toast. I haven't pulled the heads to see if they're salvageable, but you've got me curious about the 08-13 heads. I know the HO cams and intake would be a nice upgrade for any non-HO 4.7, but this is the first I'm hearing of using the newer heads. I know the HO intake isn't as hot as it used to be, since the newer 4.7s broke 300hp and have an even more performance-oriented manifold. I've been out of the WJ scene for a while. This is the first I'm hearing of headers as well. What's the best combo for someone looking to resurrect an old Jeep?