Neat/pro looking way to clearance headers?

[vlad01]

Has anyone successfully clearanced headers or exhaust pipes in general in a way that looks neat and professional?

Like something that would look like it was done when manufactured.


I googled this a fair bit yesterday and was horrified on the big auto mag articles I saw on how to "professionally clearance headers"

I couldn't find any good examples, but if it's possible to press or beat a neat flat spot or rectangular depression would be preferred than cutting and welding in a notch.


When I restored and modded the red car a few years back, the headers fitted well, as long as the engine didn't move, but with stock mounts on the driver side the engine moved some 30mm in the vertical direction and there were lets say some scary moments with the steering

The areas of clearance in question were controlled with the use of solid-ish engine mounts from Mace, originally I used tuff mounts but they were non conforming and were a poor fit either way, the Mace ones were heaps better and have slight conforming which helped the NVH a little but still not ideal.

But for future projects, it will be handy to be able to clearance the tubes in some key areas by some 5-7mm for example to gain extra safety margin even with use of solid mounts, clearance for stock mounts still would not be enough, they just move way too much on cornering. But the main point would be to do this before coating and avoid damage in the first place rather than finding out after they've been fitted and taken the car for it's first hooning.


I am actually looking at retaining a Mace solid mount on the driver side and then modding a OEM good quality hydraulic mount like Kelpro for example to limit stretch under acceleration but retain full normal operation during cruise and more normal driving. The passenger side can get away with movement a lot more than the driver side, so having a OEM type mount at least there will help NVH a lot!, even though this order of mounts isn't conventional. I originally had a solid mount pass side and OEM on driver, the NVH was the same as factory, but as mentioned the movement on the driver side OEM mount was so much my steering jammed on cornering.


Even with the current solid mounts, the clearance on one of the pipes to the rack input housing Allen bolts is like 6mm, it doesn't hit currently under WOT, but I imagine it would be damn close. There are marks there from when I had the OEM mount.


If anyone has pics of clearance mods and how they were done, please share, coz the "how to's" on the net are disgraceful

[Tre-Cool]

im guessing they were just heating up the pipe, then whacking it with a flat steel bar or wood?

I'll probably have to do something similar with my corvette headers that i got since they are made for lhd. I've not got around to even test fitting them yet because i suspect i'll need belt them into shape to clearance the steering shaft.

I guess if u just need to squash a pipe down to make some clearance u could heat up with an oxy then use a bench vice.

[VK_3800]

The only way to really do it right is to make the headers actually fit. I find that most need ground clearance mods anyway (customers expect things to bolt in so suppliers play it a little too safe with floor clearance at the expense of hanging down too low) so just start chopping

Sometimes you can do things like re-route primaries for specific installations. Modifying headers costs either in cash, or in your own time - I prefer the latter.




Having said that there's nothing functionally wrong with a suitably sized dent at all, it's just hard knowing it's there!

[vlad01]

That would be too easy, but being a 2nd gen commodore chassis which was never designed for V engines in general, Pacemaker have done a pretty damn good job routing their headers to fit well enough in the very constrained space of the driver side.

The headers in question are the Buick competition headers which are a much larger 1 5/8" and when they designed them, they re-routed the primaries a bit over the street 1 1/2" headers which also struggled with space. They managed to keep clear of everything except the bell housing which is what it is and I never had an issue with the 2 primaries hugging the cut out, even the factory barely fit through and they are close to the rack input housing allen screw as mentioned.


The unexpected result of this slight re-routing on the comp headers is they fit better to the chassis than the street headers, but an unforeseen issue is the OEM mounts move so much, probably more of a problem with the ones available today than when they designed the headers, (current OEM V6 mounts are way more stretchy than the genuine Aussie made ones of yesteryear). So the entire primary moves up 30mm on hard right turns until the input shaft clamping bolt smacks straight into the primary jamming the steering momentary.


This is a non issue with decently solid mount on the driver side, but I would consider extra clearance to add safety margin just in case. I shortened the bolt as well as the solid mount to get some 12-15mm, but if I could do this without chopping the bolt the 5-6mm iirc, that would make me feel better about it.


With the floor clearance, Pacemaker, at least for the V6 are more tight on the floor and have tons to the ground.


It was so hard to find examples of what would consider neat and ample clearance without looking like a exhaust shop junky hacked it up.

There was one more example I found the other day that was even better, but for the life of me I couldn't find it again, google image search is terrible at the best of times.


Also, the stock V6 logs and down pipes, the down pipes are heavily squished to fit as well on the driver side. So it looks as far as I can figure out a necessity to get the safe clearance needed.


One of the examples is a factory group a shorty header that has a reasonably neat clearance, I couldn't find any pics of the actual group a long headers, I know the entire sides of both headers have a row of dents like this to clear the chassis rail.

Screenshot 2024-01-01 at 12-11-28 HSV VL COMMODORE GENUINE WALKINSHAW GROUP A EXTRACTORS N.O.S. eBay.png (446.31 KiB) Viewed 8717 times

Screenshot 2024-01-01 at 12-13-14 ehaust header clearance - Google Search.png (489.21 KiB) Viewed 8717 times

[MudDuck514]

I know it's not quite what you are asking, but back in the 90's I put headers on a 1977 Pontiac Trans AM.
After driving over a "Speed Bump" a bit too fast, I had nicely flattened collectors!

Mike

[vlad01]

I know it's not quite what you are asking, but back in the 90's I put headers on a 1977 Pontiac Trans AM.
After driving over a "Speed Bump" a bit too fast, I had nicely flattened collectors!

Mike

[VK_3800]

30mm seems a bit excessive for engine movement, 10-12mm is usually the standard for exhaust clearance so that really narrows your options. Also weird that it's the driver side coming up with the direction of engine rotation?

You're right it is difficult to find any pics but the VN/VP Group A/HSV setup (the one with the two-pipe flange much closer to the heads because exhaust mods were free from the first joint) is much neater than that and doesn't have any weird crimps. They also have the correct 1/5 and 3/7 joins on the driver side to suit the firing order, hard to tell but I think the pic above is just a cheap set that is (was?) multi-piece for easier installation. Fitting everything really should only get difficult if you want equal/tuned length primaries.

1 5/8" is entry level these days for V8s at least, used to be able to find the odd set of 1 1/2" but haven't seen any in some time. Should be easier with the V6, one less primary to worry about! Commodores are fairly spacious compared to Torana as you have room above the chassis rail and doesn't squeeze in at the back, although different configuration with the rear mounted steering.

edit: actually thinking about V6, I had Pacemaker 1 5/8" in the VK and they were fine. The primaries go forward from the head a little before curving down into the collector so there's heaps of clearance for the steering. I initially built the main pipe too high and had to fix that as it knocked on the floor occasionally but it was way too close, didn't have to do anything unusual and no mods to the headers for once.

[vlad01]

I looked back at my old pics for that built, and those comp V6 pacemakers do have good room in the usual spots and contact in the areas that literally don't have a choice, like the bell housing. But since those can take the heat fine and are snug, there is no issues with noise or vibration.


The 30mm movement is from lateral G forces when cornering, not from the engine torque as the driver side compresses under acceleration but I was seeing the opposite movement and only on right hand cornering, didn't happen on decel.

The way that primary is routed, slightly on an angle and curves around at the bottom at the rack housing below the input shaft, when the header would lift with the engine, this curved part would reach the plane where the intermediate shaft bolt would hit as it rotated around, it normally had sufficient clearance in resting state and under compression it had even more clearance (accel).

But when looking at the pics, I had not much floor clearance for the pass side, it was touching the floor shielding until I first modded the Tuff mounts to be lower, then eventually installed the Mace ones which are slightly lower again. (The need to be removed and the welding redone, awful welding!) So I was thinking going modded OEM on the pass side but the small clearance probably won't be enough and might need to stick Mace mounts all round.

On the future project, if I ever get enough money to start that with any confidence in completing I will be chopping the flanges off and redirecting and going for a transition cone to 3" to v band most likely for more floor clearance and dual cats and even Y pipe if possible, but it depends on the collector to Y pipe specs and sizes, transitions etc that I'll get Burns stainless to do a sim/report for me or get something like pipemax to work that all out.

If you are cutting and modding, might as well have it all calculated for your engine prior so you are at least ball park optimal and not a complete detriment.

[immortality]

But when looking at the pics, I had not much floor clearance for the pass side, it was touching the floor shielding until I first modded the Tuff mounts to be lower, then eventually installed the Mace ones which are slightly lower again. (The need to be removed and the welding redone, awful welding!) So I was thinking going modded OEM on the pass side but the small clearance probably won't be enough and might need to stick Mace mounts all round.

That's a shame, I've got a set here and the welding looks good. Maybe they are using a different manufacturer now? Those mounts originally came from TTT Engineering and sold via MACE but then they stopped manufacturing them and MACE took it over.

[vlad01]

Yeah, when I got my set I complained about the welding. Looks nothing like the quality of the original TTT ones. But otherwise they are an excellently designed and engineered mount, nothing on the market comes close.