Author Topic: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM  (Read 3816 times)

olds403

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THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« on: August 09, 2015, 04:05:37 PM »
Well, I decided to give the Thornton 350Jr's a try on my Olds403.  I am redoing the entire suspension and really did not like how low the existing exhaust was going to sit.  So, over the July4th Holiday saw these 350Jrs on sale for $300 shipped so pulled the trigger.  I was actually pretty impressed with them as they solve a lot of short comings and make the passenger side exhaust much more accessible under the car.  I do not think I will see that big of a HP improvement, but least I will have clean look.  I have had every exhaust system on this car you can imagine over the last 30yrs.  From stock to Hooker Super Comps to modified custom exhaust.  Including Flowmaster. 

In my search for a complete kit I kept coming up short like many of us do working on the Old403 so I made my own kit.  I got really discouraged now that Torque Tech no longer makes downpipes.  I thought for sure I would find some...nope.  I started with the rear section of the Pypes header back kit and put some ball and sockets to the Pypes street Pro mufflers on it so I can drop it out when I need to do any tranny work or any other work.  I bought a set of Pypes Olds downpipes and tried them.  Don't waste your time on any of current Olds downpipes from Pypes.  While these would likely fit they have this funny JOG just under the driver side starter which I imagine is to clear the Gbody control Arm.  It would have been a huge hasssle to cut out the jog and reweld them....that was a PlanA.  I was really bummed so off to plan B. 

Just got back from testing and the system fits - PLANB .  Don't know how many bolt on kits we have seen on the Olds403, but this one works and found some nice stepped stainless clamps.  Hard part was getting a set of downpipes and finding a company that would listen to me and was sent a set of PLANB which means I ate the PYPES - PLANA plus PLANB just to make this kit.  My car has been a guinea pig for many of the parts repoe'd now - no names, but just trying to keep the dream alive.  It will be a few more weeks before I can get this all back under the car as its 105F here today and my old body just will not allow me to this except for a few hours a day.  PLANB is not a kit you can buy and frankly I don't have the time to make them myself, but perhaps with interest I can get more downpipes. Just two cuts to size the main Pypes Xpipe and was done.  I just took out "PlanB" to take pictures.  Sorry about the shadows, but I have a big oak tree in my back yard and only shade here right now. 

Stay tuned..........

http://thorntonmusclecars.com/products/manifolds/350-jr-exhaust-manifolds









« Last Edit: August 09, 2015, 04:13:08 PM by olds403 »

PARTSMAN76

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #1 on: August 10, 2015, 11:53:40 AM »
Looks good so far.
I ran a very similar set up on my 79 TATA
Thornton manifolds, Pypes down pipes, (customized by V8 TV & Restoration) & Pypes header back kit with transverse muffler.
Fits great and sounds really good.
Good luck.
Look forward to seeing it on your car.
79 ANNIVERSARY T/A

seac79ta

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #2 on: October 25, 2015, 07:18:28 PM »
I'm interested in the downpipe kit. I'd like to run thorntons on my rebuilt 403 opposed to headers

Aus78Formula

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #3 on: October 25, 2015, 09:21:46 PM »
Custom downpipes are basic for exhaust places to bend up, and off the shelf would have to cater for every car body type and exhaust system option to be able to work with many. Even then they'd often have to be trimmed, shortened from either end, and by then could have just made them.

olds403

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #4 on: October 25, 2015, 10:49:08 PM »
PlanB was the american thunder kit for a 65-67 Olds Cutlass. 
Call Flowmaster and tell them you want down pipes from the kit

They normally sell them in their American Thunder kit, bit they sold me just the downpipes and guess WHAT ? They fit ! Who would have known ? Me..... Took a huge risk, but they work

I guess I was the guinea pig as I tried the Pypes Olds downpipes as well.  I ate those in the quest to figure this out. If some one feel like sending me $150 for this tech tip as it would make me feel better :)

 The center sections is the Pypes X pipe.  The ball and sockets I got from Ram Air Restoration. 

It would not be hard to put a complete bolt on kit now for the 77-79 Olds 350/403 in F body.  The Thorton manifolds work great.  My father in law commented this weekend and could not believe how professional the system looks and he knows I did it with hand tools

I am using a g force crossmember which allows the down pipes run straight back.  Highly recommend as this way you can run the system high and tight

Hope that helps. 
« Last Edit: October 25, 2015, 11:00:43 PM by olds403 »

Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #4 on: October 25, 2015, 10:49:08 PM »

droptopron

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #5 on: October 28, 2015, 12:16:50 PM »
I have the manifolds and had head pipes bent by an exhaust shop.  I don't think it ended up costing me any more & I didn't have to lie under the car doing it. 
Former 1979 TATA
Current 1970 442

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seac79ta

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #6 on: October 31, 2015, 04:56:19 PM »
Olds403, do you feel like you are sacrificing alot of power with the thorntons? Reason i ask is, i just picked up my rebuilt 403 from J&S!! It has a bit of a lopey cam. Running on his engine stand, it's has amazing throttle response and revs QUICK. Wondering if I should just bite the PIA bullet and go headers. There's a short video of it running on YouTube,  search Jim Lapikas, Chris 403 if you want to see
« Last Edit: October 31, 2015, 04:58:38 PM by seac79ta »

Grand73Am

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #7 on: May 24, 2017, 09:01:46 AM »
Olds403...you said the down pipes you got from Pypes didn't fit. I did some research on the 65-67 cutlass down pipes, and found that they are the same as 68-72. And Pypes has these for 68-72, which I was hoping would fit. Are these the ones that didn't fit for you, or did you buy something different? Here's the link:  http://pypesexhaust.com/i-12200762-68-72-olds-442-2-5-downpipes-2-bolt-dof10s.html
Steve F.

olds403

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #8 on: May 24, 2017, 07:59:40 PM »
Those pypes have an odd jog in them on the drivers side.  They will fit, but getiing the starter out will be difficult.  Too bad flowmaster stopped making the ones that fit

Grand73Am

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #9 on: May 24, 2017, 08:15:55 PM »
Okay thanks for the warning. Summit has them on sale for $100 with free shipping, so I'll go ahead and give them a try. I have cutting and welding tools, so I'll modify it if I have to. Or take that pipe loose if I have to pull the starter :) .
« Last Edit: May 25, 2017, 04:29:09 PM by Grand73Am »
Steve F.

via3d

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #10 on: July 26, 2018, 12:35:51 AM »
Grand73am... did the downpipes work for ya'?
~ J

Grand73Am

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #11 on: July 26, 2018, 06:49:17 AM »
Yes, they worked good for me. They are 2.25 at the manifold end, and come with the flange on it for connection to the manifold. The rest of the pipe is 2.5". Bolted right up to my Thornton manifolds. I put them on, and bought a couple of lengths of 2.5" straight pipe(from a local exhaust shop for $50) to connect to the them and ran that back to the mufflers under the rear seat area, which I connected to Walker 2.25 intermediate and tail pipes with chrome splitters. So, I was able to have a usable system doing it at home, without having to take the car to an exhaust shop. The straight pipes really should be positioned further inboard so they fit higher. That would take a couple of curved pipes connected to the downpipes to move the straight pipes inboard, up inside the driveshaft tunnel on each side. I might take it to an exhaust shop later to have that done. But I can use it now as it is. My car is stock height so clearance isn't really a problem. And I have good starter clearance.
Steve F.

lugnuts

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #12 on: August 28, 2018, 12:29:09 PM »
Those pypes have an odd jog in them on the drivers side.  They will fit, but getiing the starter out will be difficult.  Too bad flowmaster stopped making the ones that fit

well that sucks. I have the pypes x-pipe back system on my car with the old manifolds and down pipes that an exhaust shop made years ago. I'm planning on getting the Thorntons manifolds and need to replace the downpipes.

any other options that might work as a bolt in without having the jogg in the pipe?
Check out the progress of my restoration on my YouTube Channel. Click here: TheOriginalLugnuts (Updated Weekly)
  
" daddy my hat blew off, I hope your darn head was in it"

Grand73Am

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #13 on: August 28, 2018, 12:35:19 PM »
Those pypes have an odd jog in them on the drivers side.  They will fit, but getiing the starter out will be difficult.  Too bad flowmaster stopped making the ones that fit

well that sucks. I have the pypes x-pipe back system on my car with the old manifolds and down pipes that an exhaust shop made years ago. I'm planning on getting the Thorntons manifolds and need to replace the downpipes.

any other options that might work as a bolt in without having the jogg in the pipe?

You must not have read my post that was just before yours. I used those down-pipes on my 79 TA with 403, and they fit fine. The "jog" didn't cause me a problem at all. Starter clearance is good. I just don't see a problem with it. I was able to install my own pipes with them in my driveway. I recommend them.
Steve F.

lugnuts

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #14 on: August 28, 2018, 01:06:37 PM »
Those pypes have an odd jog in them on the drivers side.  They will fit, but getiing the starter out will be difficult.  Too bad flowmaster stopped making the ones that fit

well that sucks. I have the pypes x-pipe back system on my car with the old manifolds and down pipes that an exhaust shop made years ago. I'm planning on getting the Thorntons manifolds and need to replace the downpipes.

any other options that might work as a bolt in without having the jogg in the pipe?

You must not have read my post that was just before yours. I used those down-pipes on my 79 TA with 403, and they fit fine. The "jog" didn't cause me a problem at all. Starter clearance is good. I just don't see a problem with it. I was able to install my own pipes with them in my driveway. I recommend them.

I did see it but wasn't sure if the jog would effect mating to the pypes x-pipe width as it is a fixed dimension and it doesn't sound like you used one. I'll just get them and see how they fit mine.
Check out the progress of my restoration on my YouTube Channel. Click here: TheOriginalLugnuts (Updated Weekly)
  
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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #14 on: August 28, 2018, 01:06:37 PM »



olds403

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #15 on: August 29, 2018, 06:11:57 PM »
The pypes pipes suck.  I have a source now. 

lugnuts

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #16 on: September 13, 2018, 06:19:34 PM »
The pypes pipes suck.  I have a source now. 
How can I get a set of down pipes?
Check out the progress of my restoration on my YouTube Channel. Click here: TheOriginalLugnuts (Updated Weekly)
  
" daddy my hat blew off, I hope your darn head was in it"

Aus78Formula

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #17 on: September 13, 2018, 08:14:33 PM »
Go to exhaust shop, ask for downpipes to be made to suit.

olds403

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #18 on: September 14, 2018, 07:44:53 PM »
Will post them when I get them. I had two sets made - were not cheap like the Flowmasters.  No one will like the price so won't be selling them. 

olds403

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #19 on: September 19, 2018, 08:17:56 PM »
Had two sets -  Mocked up - perfect.



lugnuts

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #20 on: September 20, 2018, 09:21:35 AM »
they look nice
Check out the progress of my restoration on my YouTube Channel. Click here: TheOriginalLugnuts (Updated Weekly)
  
" daddy my hat blew off, I hope your darn head was in it"

olds403

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #21 on: September 21, 2018, 04:06:31 PM »
My brother and Dad both have these on their cars now too.  Boom.
Back in business making the Olds403 guys happy again

via3d

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #22 on: October 24, 2018, 11:25:00 AM »
Lugnuts,  did you get the hedman or Thornton shorties?

install yet?
~ J

lugnuts

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Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #23 on: November 07, 2018, 02:04:47 PM »
Lugnuts,  did you get the hedman or Thornton shorties?

install yet?
I got the Thornton shorties. Not installed yet, these will be going on my new motor once its built. Also need to pull the old motor and clean up the engine bay. I hope to have them installed in January. I will make a video of the install and give feedback on how easy/hard it is.
Check out the progress of my restoration on my YouTube Channel. Click here: TheOriginalLugnuts (Updated Weekly)
  
" daddy my hat blew off, I hope your darn head was in it"

Re: THORNTON 350JR BOLT ON W/DOWNPIPES COMPLETE SYSTEM
« Reply #23 on: November 07, 2018, 02:04:47 PM »
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