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Project Dual

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Day Six: (The home air compressor is once again working properly. The replacement magnetic starter was different, and Scott told me how to connect all the wires properly.)

Due to the significant space limitations on the left side of the engine, the manifold required a number of modifications to achieve an acceptable result. We still aren’t done, but we’re pretty far along in the process. We needed to move the outlet flange forward quite a bit, and getting the rear cylinder’s exhaust gasses to flow in the desired direction required a bunch of work.

We had planned to move some things before working on the manifold, but decided to postpone the relocating and make some more headway on the manifold. (I'm not looking forward to the relocating phase.)

Earlier, we had added a wedge piece to align the rear cylinder’s runner with the rest of the manifold. Well, moving the outlet flange so far forward was going to have the rear cylinder’s gasses flowing in the wrong direction to join with the exhaust flow from the other three cylinders. To avoid that situation, we decided to cut off a big chunk of the rear cylinder’s runner and splice in a section from another manifold. But of course the respective parts did not align very well. So, Scott would clamp the various parts to the shop’s welding table, heat the part needing some persuasion red hot, and then put a large adjustable wrench on the part needing some encouragement. Generally the parts cooperated, though sometimes they needed a second heating and bending. By doing this he was able to get the individual pieces in reasonably good alignment before welding them. Here are a couple pics.

This is the outlet flange piece and the red section needed to be bent outward to make it wider. This is on the side of the manifold that faces the engine. (It had cooled a bit before I got my camera out and took the photo.)

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Here, Scott is making more adjustments to the outlet flange after tack welding it to the manifold. He’s about to bend the red hot section down for better alignment with the manifold.

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In true Gorilla fashion the parts fit together pretty well and the not-complete-but-pretty-far-along manifold is looking remarkably good.

After welding everything in the jig we let it cool and then bolted the manifold to the engine to check our progress. The current plan is to cut the outlet flange itself off, then shorten the runner where it attaches, and re-weld it in the shortened location. But we’ll also change the angle the flange is welded to the manifold to more optimally aim the exhaust outlet toward where it needs to go.

After it was initially welded, I wanted him to add some additional weld in places so I could make the parts blend more smoothly as part of my planned cosmetic enhancement. You should have heard the howls from the self-proclaimed “precision surgeon”. “It’s fine” as it is", “You can’t see it anyway”, you get the idea…. Now he is calling it his "Frankenstein manifold".

Here are some pics. You can see the runner to the outlet flange can be shortened substantially, and the angle of the flange itself can be repositioned as well. Yes, we need to add another threaded boss to attach the heat shield.

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Travler

Active member
GOLD Site Supporter
BFT i am kinda with scott on this it is starting to look pretty good to me , take it out and run it Steve said just put some black header paint on it and run it , at 7 MPH and the hood closed on one will see your remarkable job any way , I am sure it will be as good as it can be before you take it out
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
BFT i am kinda with scott on this it is starting to look pretty good to me , take it out and run it Steve said just put some black header paint on it and run it , at 7 MPH and the hood closed on one will see your remarkable job any way , I am sure it will be as good as it can be before you take it out
Travler,

My posts almost always lag where we actually are in terms of progress on a project. Typically, I’ll write the post in draft form and share it with Scott before posting. If he takes major exception to something, I’ll usually revise it (I pretty much expect some objection - it’s just his style). But that means there’s a delay between action and the forum post.

I’ll spill the beans and admit at this point the manifolds are essentially ready to be installed. The previous manifolds were installed with ARP 12-point stainless steel flange bolts. Those manifolds didn’t have heat shields, these do. GM used a stud and one nut to secure the exhaust manifold to the cylinder head, then the heat shield, and a second nut. I’ve ordered ARP stainless steel studs and 12-point nuts to attach the heat shields, and some short ARP 12-point stainless steel flange bolts to attach the heat shields to the manifolds. I‘ve found Allen's Fasteners in Needles, CA has an excellent selection, and while I hate to use the term “reasonable prices” on anything that comes from ARP, it's fair to say their prices are better than most.

We still need to re-route/re-plumb the transmission cooler lines, the engine oil cooler lines, the brake line and the hydraulic lines from the orbitrol to the steering cylinder. Thundercat is a 1980 model, and your 1544 is a 1986. During the interim period Tucker made a number of changes to the machines, one of them was relocating the orbitrol inside the cab. That would provide a lot more room for an exhaust system, but alas, we have the older setup with a steering column that goes through the floor to the orbitrol below. We’ve started the re-routing/re-plumbing process, and it’s slow and tedious. The brake line is just about finished and in theory the engine oil cooler flex lines have been done. I say “in theory”, because I’m not proud of how they look, and I think there’s some room for improvement. We’ve started on the orbitrol, but barely.

We’ll wait until the re-routing/re-plumbing phase is complete before installing the manifolds. Then it will be off to the exhaust shop….
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
BFT we buy a lot of fastners from specialty in chino ca
Thanks Travler.

I looked at their website and they have a great selection. I like AN washers, and Scott hates them with a passion, or at least he pretends to. Specialty carries AN washer kits with an assortment of different sizes. That gives me an idea for a Christmas gift for The Gorilla!

As The Infamous WBJ1 would say, “MUAHAHAHA”.
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Day Seven involved modifying the outlet flange and runner to get them into a more optimal configuration.

We had a section of 3” exhaust tubing with some bends in it laying around, and one bend was close to what we were going to need. We cut that from the rest of the tubing so we could use it for mock-up purposes. Then we bolted the manifold to the cylinder head and used the bent tube to visualize what changes we needed to make to the manifold.

Back to the shop and Scott cut the manifold runner, removing about 1 1/4” in front and 1" in back. This would both shorten the runner and change the angle of the outlet flange. Then he tack welded it in position and we took the modified manifold back to check our progress. We had removed the expanded metal side shields for better access, but in our fitting and mock-up attempts we wanted to ensure there was adequate clearance between the side shields and the exhaust tubing when the exhaust system is installed.

Here’s a pic of the runner section Scott removed.

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We thought shortening the runner further would be beneficial, and it would also help to adjust the angle of the outlet flange some more. In addition, we wanted to slightly rotate the outlet flange to reposition the studs more optimally for the exhaust tubing to fit, as well as where the studs were in relation to the orbitrol.

Back to the shop for more refinement. Scott then fully welded the outlet flange in it’s new position on the shortened runner.

We also modified the heat shield which required a lot of cutting, and some bending, to account for all the changes we had made to the manifold itself. Finally, Scott welded on a threaded boss salvaged from a scrap piece of manifold for heat shield attachment purposes.

I took the manifolds home for their cosmetic enhancement to try and make all these modifications look better… so we can cover most of them up when we install the heat shields. Here are some pics of the manifolds. Right side.

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Left side.

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A "before" photo of both manifolds.

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And an after.

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In my last post I mentioned Scott had started referring to the manifold as his Frankenstein manifold (it’s comprised of six pieces from four different manifolds). My recollection is Frankenstein was not the monster, but rather the name of the doctor who created the monster. That would make Scott “Dr. Frankenstein”. However, in deference to the Mel Brooks movie "Young Frankenstein", I’ll change the spelling to the phonetically correct pronunciation “Fronkensteen”. Scott was of course quick to point out that would make me Igor (pronounced Eye-Gore in the movie).

Honestly, these manifolds exceeded my expectations as far as the way they fit and should allow a true dual exhaust system to be fitted to Thundercat. Of course they’re not perfect, but they’re a more than acceptable work product from a couple of knuckleheads.

But now the less fun aspects of rerouting the various lines begins….
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
BFT is there a Tacom screw close to you we buy a lot of stuff there they even stock BIG hammers that Gorilla could use LOL
The Gorilla and hammers. Hmmm, that’s a bad combination. If a little force doesn’t work - hit it harder. If that doesn't work - get a bigger hammer. You get the idea….

And it’s easy to damage the surface, so you use a wood block... or something. The concept of using soft face or dead blow hammers rarely occurs to The Gorilla. I think it was in 2022, Trusty-Cook, a US dead blow hammer manufacturer, had a sale at Christmas and their blems were ridiculously reasonable and shipping was a bargain, too. I bought The Gorilla their biggest dead blow sledge hammer. Twelve pounds worth. I was hoping that would have a positive impact on his methods of persuasion.

Almost 18 months later... I’m not sure it’s been used.

These days my preferred SLC bolt supplier is Fastener Engineering. I get great customer service from James and their selection and pricing are pretty darn good. “The guy behind the counter” is crucially important, and many companies don’t seem to grasp that concept. To management, it’s "all about the cheap”, yet customers build relationships with the guy they work with, and that relationship breeds loyalty. Maybe they don’t understand my loyalty is to James, not the company.

Stainless steel fastener selection tends to be more limited, and that where Allen’s Fasteners comes in. I don’t know of any company in SLC that stocks stainless steel AN washers. Allen’s Fasteners has them in both various sizes, and thicknesses, and they’re inexpensive. That's a win all the way around.
 
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