3785 Gets a 400 swap, fabbed 180's and fabbed mufflers

Here are the pieces tacked together and the ends being shaped for the 2 ½ tube on the end.
I made the jaws out of some ¼ inch steel and welded them to some vise grips.



Here is the 2 ½ end tube tacked in place.



While that is still tacked I start on the slip rings. It is important to sand the ridge from the seam weld flat or it can cause a leak at the slip connection.



Here are the rings installed in the alignment tool and tacked together. They will stay in this tool throughout the rest of the process.The rings are 1 7/8 dia and 1 1/2inches long.

Now I start building the Merge bullet assembly. These are the individual parts.

These are super cheap and are available also from http://www.coneeng.com/tech_assist.html
The website also has a great tutorial on the welding of one of their collectors.

Here are the pieces in the aligning tool.



Here is the part all welded and the edges sanded smooth sitting on top of the collector rings waiting to be tacked.



Here is the bullet welded to the collector rings.



Here it is with the finish sanded smooth.

I check the fit of the taper assy and the collector rings for alignment then finish weld the taper assy.



Here is the taper tacked to the rings ready for final welding.



If you end up with two pieces that look like lunar landing craft you did it correctly.

Here is a view from the end.I used a 220 grit sanding roll and polished the entire inside of the collector.

Header Flange Modification
The header flanges I purchased from Speedway Motors pn# 418-1142. They are 5/16 thick.
http://www.speedwaymotors.com/

I will be running MPG port plates in my 4V heads. The purpose of these plates is to raise the port floor to increase velocity. The problem with the port as cast is the drastic drop off after the short side radius.
It didn’t make sense to me to spend money to correct a problem only to re-introduce it again at the header flange with a drastic drop off into the tube.
Here is the difference between the plates and the flanges.



I went to the Hardware store and bought some square key stock. I then cut it to the shape of the lower opening in the flange.



I then fit them individually into the openings. I made them a little lower than the port plates to that I didn’t have to flatten the bottom of the tube to fit the opening and it allowed for a good transition. At the time the Hardware store only had 3/8 square stock so I had to grind them to fit the 5/16 thick flange.



Here they are all welded up. I will be running a 4V sized header gasket. The opening is below the weld so there won’t be any problems with leaks.

Ready to run some tubes yet?

The tubes I purchased from Speedway Motors, it is their 1 ¾ combo mandrel bend pn# 91013872. I purchased 15 pipes.
The only thickness they come in is 16ga. At about $14 ea they are a good deal for the amount of tube you get and that it includes both a U bend and a 90 degree bend.
Most companies want $15 for just a U bend. I also like how these tubes do not come full of grease like some companies tubes do. This saves having to clean all the pieces with solvent.
They are bare steel that is covered in a light oil that wipes off with Brake cleaner. I also prefer bare tubes to aluminized ones. This saves having to sand the coating off of all the ends to get a good weld at the joint.
16ga tubing has a .062 wall where as the more common 18ga has a .049 wall. This makes the 16ga tubing heavier. I am not concerned about the added weight on my car.



As part of my design, I use the most direct route for the cyl’s that are the farthest away from the collectors. As the cyls move closer to the collector I run the pipes in increasing longer routes to offset the diminishing distance. This will help keep the pipes to a more similar length.

I made a simple tool out of a piece of 2X4, a deck screw and 1/16 TIG rod. This enabled me to mark the tubes for cutting at different degree angles referencing from the center of the radius.



It is difficult to run tubes if you don’t know where to run them to. I made this Erector set looking fixture to mount the collectors so I would have a target to run to. Because I am going to exit at a angle to clear the A/C condenser I positioned the collectors close to the engine. This makes the bends tighter around the block. If I were to exit out the rear of the car I would have moved the collectors much closer to the rear of the car to get a more sweeping motion with the primaries



Here are the collectors mounted in the fixture.

*Edit* I wanted to make note at the beginning of this segment that I am not building these tubes to any certain design length.I realize that might sound crazy given the amount of work I am about to do.
I am running them port to collector freehand using the routing I designed and will see where they end up for length. I have not built a set of 180's before or measured a existing set so Im not sure where the dimensions will fall.
I know the currently available undercar headers for a Pantera feature unequal and very short primaries. I am hoping to be able to gain some length with this design.
When my car is done I will chassis dyno it and then have a real number to reference if I need to make a header change. I am not trying to make these equal length because I do not know what length the engine needs. This will be accomplished by the chassis dyno testing.I also do not know how a 180 is affected by a unequal primary. My goal is to keep the discrepancy minimal (less than 8 inches)given the design and the room I am working in. *End of Edit*

I start by mounting a header flange to another 400 I have in the shop. I am not using starter stubs because of the lack of room between the header and the car. I run the number 1 pipe back to the general direction it needs to go. I am using a metal strap to locate the end of the tube so that I don’t run it too low. The Right hand bank cyl’s 1-4 will be the bottom tube set. The LH bank cyl’s 5-8 will be the upper tube set. In order to keep the primary pipes and flanges one piece from side to side I am going to construct them in this overlapping fashion.



I do the same for cyl #2



And #3



I then mount the flange and pipes into the car. I remove the #3 tube to have better access to run the #1 and #2 tubes.
I run the #1 tube first. Where cyl #1 is the furthest away from the collector I run it to the closest collector opening.



I run cyl#2 to the closest opening in the other collector. Since this side of the engine will be the lower bank of tubes I angle the pipe downward as it exits the collector. I need to give myself plenty of room for the pipes that will go on top.

Now is when it gets complicated.
I run the #4 tube from the collector to back alongside the #2 tube. I do not connect it to the flange at this time. The reason for running the #4 tube back to there is so that I know where to locate the upper bend in the #3 tube to go over it.



I make the collector ends to the #6 and #7 tubes so that I can see where the #3 tube has to be routed to clear them. Remember the LH cyl bank will be the upper set of tubes.



I then finish the #3 tube



Lastly for this side I run the #4 tube the rest of the way to the flange.

I start the RH bank the same way as the LH side by running the starter tubes while the flange is mounted to another 400.Here is cylinder #5



And #6



I mount the flange with the starter tubes into the car and finish running #5 to the collector.



I then do the same with cyl #6. This side differs from the other side in that cyl#2 went to the opposite collector at the bottom and #6 runs to the opposite collector at the top. Because of these differences one side is not a copy of the other.



I then run cyl#8 from the collector to the front of the engine. I do this so I know where cyl#7 can come up and cross over. I do not take cyl #8 all the way to the flange at this time.

I take cyl #7 from the collector to where is starts angling down towards the flange. I have to be aware of how close it is to the fuel tank shield and the gas strut mounting tabs.



#7 gets ran to the flange. Then I route #8 to the flange



Now the headers are ready to be removed from the car and the joints solid welded. After that they will get fit to the car again and the tubes hard tacked to the flanges.
I'm not done yet, lots of work still to do and more collector tricks. Stay tuned for more pics and info to come..

I wanted to take this time to give a BIG thank you to George/Cowboy From Hell.
If it weren't for his help with using Photobucket to post these pics this would have been MUCH harder than it was.

This has got to be one of the coolest posts I have seen in a while. Awesome job on everything. I cant wait till I get my shop.

Blaine

Brooke,

I thank you for taking the time to photo and document this project, a truly awesome job on your part, I envy your skills.

One question; Is it important to keep each tube from the flange to the collector of equal length?

Wow ! amazing post. needs to go in a tech manual or something !
I hate to think of the man hours in this !

I think that if you ask what brand of car has the most knowledgable, techsavvy, eager to experiment, no-fear owners, the answer has to be the Pantera. Some of the things I read about here...

Brooke Awesome photos and awesome work. I can't tell you how many things I have picked up from your photos. I really like the collector construction.

I think you should consider writing an article for Car Craft. It would be a great non standard exhaust construction article!

Sorry I have not been writing more. I have been flying my ass off; which is good! We have a couple pilots out and our crews are a little thin. It should ease up late fall.

Gary

By the way I stopped by on a flight to visit my engine builder in Fairmont MN. I was able to show him up front the issues with the bellhousing and where to drill the embosments for the engine mounts should some one else go through him.

Amazing! Great job...

Thanks for the Comments!

I went back in this morning and added some more pics that I had forgot to post last night. I also did some tweaking to the text.Never ends..

I realized that the way I presented this segment made it appear like these "built a car in a week" reality shows where everything just goes together smoothly.
I want to say that at the point of the last pics you are seeing a months worth of construction time.
Some of the pipes I redid 3 and 4 times to get them right.
It is very tough to build in the middle where you have the beginning and end tube established because the transition has to match perfect.

The cluster at the collector where Cyls #3,6and 7 come together took me 4 hours.

Joules: Getting the primary lengths the same is a debate that has raged on for years in the header community. Sides For and Against are very passionate about their views.

*Edit* Joules, As I reread my above answer I realize that I didn't answer your question at all.Here is my view.

As I understand it,the side for equal length believes that equal length primairies are important to achieve the best scavenging characteristics.They believe this to be from the pressure wave timing being the same from cyl to cyl. They also believe that equal length achieves better cylinder to cylinder balance as the individual cylinders don't go in and out of tune at different RPM's. They believe this also has a positive effect on the intake side of the motor.

As I understand it, the side against equal length believes that the discrepancy broadens the torque band which is benificial to a street car. They also believe that two tubes both 34 inches but one having more bends than the other will not time equally anyway. They also believe that no one knows the correct length to build their headers to so everyone builds them equal to the wrong length.

You can decide who you think is wrong or right for your application. *End of Edit*

My thinking was simply to get them to a similar length to reduce the cylinder to cylinder imbalance and to aid scavenging.

From a construction stand point building a equal length header is very very difficult.
I have done it but I didn't do it here.

Gary, I wondered where you had gone.
1905 is feeling neglected....

quote:

Originally posted by Pittcrew:
Thanks for the Comments!

Gary, I wondered where you had gone.
1905 is feeling neglected....

YES IT IS!

Here are the pipes out of the car and mounted to a 400 block and heads on a dolly. I can’t bolt them to a engine on a engine stand because they hit the arms on the stand.

This is the RH side header I am very happy with how this one turned out. I want to point out some design considerations on this side of the engine. The header flange bolts are diagonally staggered with the upper bolt to the front. This makes it easy to lay the pipes back towards the rear of the car and still have good bolt access. Because I moved my water tanks this also gives this side more room to run pipe and is easier to build with spark plug clearance. You can also see that the pipes take a longer route the closer to the rear of the engine they get.



Here is the LH header. I don’t like this at all. The space is so cramped to work in because of the fuel tank shield that you can’t see how it looks very well.



I cut all the pipes off so I could take and tweak that side. It’s better to take some time to fix something that is bugging you now than to have it bother you forever.



Here is Ver2.0 for the LH header. I like this much better. This side the upper header bolts are staggered to the rear of the engine so the pipes exiting the port can’t lay back as far and still have good bolt access. With the fuel tank shield you always have to be aware of how wide the header is during construction. You need to leave room to slide the header out away from the cylinder head for removal from the car.



The other problem the fuel tank shield makes is that the plug access is worse because you can’t run the #5 cyl pipe as wide as you can run the #1 pipe on the other side. The #8 plug will have to be reached from the bottom.Remember I am building these on a 400 which has a taller deck, a 351 will have more room here. Note that I have full access to all my valve cover bolts.