Wanted I need a part made...

[Steamchick]

I have seen the bright orange glow from exhaust manifolds during engine dyno testing (Full throttle, poor cooling draught!) - and yes, I agree. that would melt aluminium. But I don't know that the joint area for this tapered spacer would get red hot... or even melt solder...
Just re-checked and found this...
" This wedge isn't going against the head, it's going between the header and the factory exhaust."
SO, it needs to be steel, as who knows how hot it is there?
K2

 

[HMEL]

Bill is absolutely correct. I have never seen in any engines diesel or gas any exhaust system which had aluminum parts. And I have fitted thermocouples in manifolds to ensure the gas temperatures stayed below certain values like 1100 degrees F. The correct fix is to pull the headers and realign the flanges given the engine does not have a problem with its mounts. I spent a good bit of my time working in a shop with my father on everything from diesels to stock cars. Now as a retired professional engineer I would never specify aluminum for that service. But as Bill said not my car and not going to argue about it.

 

[Joe]

Well to end speculation the parts are indeed steel. Made from a chunk of 8x8x 3/8 structural tube salvaged from a construction site. I offered to make these parts for Bill as I thought they were an opportunity for me to learn something. Work holding could be and was a challenge.
The way I approached this was to first of all make a jig to hold the flange blanks. It was just a square block of steel that I accurately located two undersized holes at the location of the bolt holes. I then shimmed the plate on the mag chuck of my surface grinder to get the right angle to produce the taper. After the first grind I had to regrind with a cigarette paper doubled up under the one edge to get the angle just right. I then set it on parallels in the mill vice and cut two grooves on opposite edges so I still had a way to hold the jig without the taper.
Two square blanks were cut on the bandsaw. On the lathe I drilled and bored the center holes and then drilled two undersized holes where the bolts would eventually go. The blanks were then mounted to the jig using roll pins in the undersized holes. The outside shape was then milled with the jig sitting on the parallel edges in the vise and then mounted on the other side of the jig and ground on the surface grinder.
The flanges were a total fail, but it is now after my bedtime and I type too slowly to continue tonight. I'll finish up tomorrow.
John

 

[Steamchick]

Well done John. A good explanation.
I hadn't figured how properly to make these plates... though I had considered making them as shown in the crude sketch attached. (hope this has enough information?).
First, make a mounting block with correct taper on it : to be secured to the Milling machine.
Second, mount the blank - looking skew, but actually with the axis of the part across the taper. The taper is milled on the blank for the space where the finished part would be, Not where the temporary mounting holes/corners exist.
Third: view of the part - pre-drilled on a blank of steel... the mounting corners would be cut-off after the blank had been machined with the taper.
Final profiling would simply be a case of bolting the part to the machine using its own holes.
But really, I think your explanation is basically the same?

I didn't have any 1/8" steel 3" wide to volunteer making the parts (Only Aluminium sheet), and shipping from the UK isn't reliable for this sort of stuff... it evaporates at Customs!
K2

 

[Joe]

K2,
Yes, a very similar approach indeed and by your location and the fact that your taper is not aligned parallel or perpendicular to the bolt hole axis I presume you are the other individual in contact with Bill off group. I had considered bolts but as I was planning on grinding the finished surfaces I would have lost the holding once I ground through the heads although in hindsight there would still have been some head left. In edge milling the outside profile I found I needed to add a couple of clamps as the mill flutes introduced a lifting effect stronger than the roll pins could effectively counter.

I missed describing one step yesterday. Part of the attraction of this little project to me was that the part needed to be made to a plan. Virtually all of the work I do is out of my head, make to fit sort of stuff, so here was an opportunity to hit numbers for a change, and so I wanted to hit those numbers as good as I am capable of. Measuring the thicknesses accurately would be a challenge without a taper micrometer so I made sure the taper on the jig was spot on, easy enough to do on the surface plate. I then ground the blanks flat and parallel to exactly the thicker dimension. Then simply grinding on the jig till the taper met the thick edge assured the hard to measure thin edge would be correct too.

Now I'm not sure why the flanges were a fail but what was happening was that as the part got close to it's final 0.0625" dimension, the portion by the large hole was lifting so that the two faces were no longer flat, parallel or to dimension. When looking down the taper the thin half around the large hole had very little material whilst the area around the bolt hole was considerably more substantial. I believe that the stress in the material was stronger than the the thin section was able to resist. I thought of making a tapered transfer block jig which possibly would have had enough holding power to overcome the stress but I didn't have any non ferrous material large enough nor a grinding wheel appropriate for that material.

I contacted Bill, describing what the issues were and suggesting that he might want to try the other person he had been in touch with. After some thought Bill responded that he thought the parts in fact could be made thicker and asked if i would mind giving it one more try. Indeed an extra 60 thou was sufficient to hold its shape and I was unable to detect any lifting at the thicker overall dimension.

Now the first ones I made would have probably worked fine, the error was only a few thou and the gaskets would likely have been able to make up for the error. But for me, two issues, one I was after the numbers and two, like several you I also have some experience with high performance engines. Over a period of years I conducted flight test programs on experimental aircraft. The most challenging part of the first one I did was the exhaust system, by the time we had it all sorted out I think we had redone it 9 times. My experiences with that one was invaluable in subsequent tests. Although a car is perhaps a little safer, unnecessary fires or CO issues need serious consideration.

So in the end I learned a bit and when I do get an appropriate wheel for the grinder I will try a transfer block jig and try to get the original design dimensions.

Cheers
John

 

[tim9lives]

A picture is worth a thousand words. Just my opinion. Also, what make/ model car is it ?

 

[animal12]

I stumbled on this pic of a hot exhaust last week
animal

 

[Steamchick]

Hi Animal, looks like it is on a dyno - where often there is inadequate exhaust cooling. This hot inside a car would almost definitely cause a thermal incident as there are a lot of kW of radiant heat that would certainly cook any car panels in the vicinity! But on a racer, maybe this is in open space with lots of air "racing" past?
There is an anomaly, in that the back pressure "in a car" - or other final application - is often quite different to the dyno under these test conditions. And that seriously affects the dyno readings, so the actual max gas pressure and temperature at the exhaust ports needs to be correctly simulated by the dyno. I suspect "not in this case"? It is "obvious" (to me at least?) that this is a racing engine (from the "Indy" badge!) at max fuelling, as no-one would want to waste so much exhaust gas "energy" in a regular vehicle application. In fact most racers cannot afford to waste the tens of kW being radiated by this array of exhaust piping. I have only seen this sort of thing on "domestic car" dyno tests when the cooling system (Air blower) for the exhaust is turned "Off".
But I have photographed ceramic burners that I have developed for my model boilers, and the camera "never lies" - yet I can get a very cool burner to look hot by altering the exposure.... - and do so as the camera records the infra-red that often we cannot see. So, as in this photo, you can clearly see the cooler and hotter zones in the pipework, that may not be visible to the naked eye. (Most human faculties are not accurate and repeatable recording devices, as the settings alter "automatically" depending on the "total" information being received).
Here are photos of a burner, at different fuelling conditions, where there are major changes in the surface temperature, yet to the naked eye this looks nearly uniform (I though it looked perfect until I saw the camera's views!):

Yours is an interesting picture though. It shows the hot-spots and cool spots! (as do mine).

K2

 

[Steamchick]

Hi John,
I understand "why" you made the parts, as well as "how". My curiosity was only the mental exercise (of "how"), not to try the real thing! Of course, you have proven how the machining stresses (not considered when you made the first parts) have to be managed properly, which you have done by increasing the thickness of the parts. I have learned an important lesson here - "Make it, to prove the real truth" - as "reality" is so often more complex than "simple imagination"!
Thanks for your explanations!
K2

 

[JLaning427]

Bill is absolutely correct. I have never seen in any engines diesel or gas any exhaust system which had aluminum parts.

I've seen aluminum exhaust manifolds for boats, but they are water cooled / jacketed. Not quite the same as is being discussed here. I believe Pleasurecraft and Crusader both use aluminum manifolds on their 6.0l boat engines.

James