CNC Header Flanges

[opelbits]

I should clarify my thinking on the tubular sprint idea.

It works for FI and carb. It is a multifit item, one pattern for GT/Kadett/Model 50. It should (in theory) be a direct swap with the stock cast iron manifold.
Flows better (again, in theory) than the stock manifold with heat riser, hopefully as well as, or better than, the stock FI manifold.

However, I would not think it would perform as well as a decently designed header. But, not everyone is looking for a full header and the required exhaust work. I may be wrong on this point, but the well designed performance header sought by so many may have disadvantages on a stock or mild motor. Paul is correct about the cost probably being as near to equal as makes no difference. But to use the nice header may require upgrading other things. Bigger carb (at least rejetting), headpipe and exhaust work, intake manifold work, etc. I guess the question here is what sort of header is wanted? A nice header for a stock/mild motor, or one that gets the most out of a hi-comp (10.0 +), big cam, big valve, big carb motor? Can it be the same header for both?

The cast iron FI manifolds have been increasing in price over the past few years. I sold one about 5-6 years ago for a little over $100. Now I see them going for $150-$200. I doubt the prices will come down as they get more scarce, but they seem to sell pretty quickly. It would be interesting to know how much traffic there is in FI manifolds at OGTS and the other suppliers. The 2.2-2.4 manifolds can be pretty pricey. I figured a tubular sprint replacement would be popular, especially if there is the option of a larger headpipe flange.

Gumby- I didn't mean for the thread to drift of topic. Plese keep my name on the list for two flanges!

[Gumby]

It's no big deal. This has lead to some interesting conversation about what people want. If there really is that much interest in a tubular sprint manifold then maybe I need to make more than just a couple of them. Ultimately it will be up to someone like OGTS to make them readily available.

Just remember the flanges come before the turbo headers which come before the tubular sprint manifolds so we are still a little ways off on that project.

Are there anymore takers on the flanges? I plan on putting in the order for the steel tomorrow.

[jeff denton]

Originally Posted by opelbits I guess the question here is what sort of header is wanted? A nice header for a stock/mild motor, or one that gets the most out of a hi-comp (10.0 +), big cam, big valve, big carb motor? Can it be the same header for both?

No way.
Any header that claimed to be such would only be a "combination of compromise".
There might be a certain RPM that it would work well on either engine, but it wouldn't be the same RPM on both.
Chances are that it might be better at most RPMs than a stock manifold, though.
Header design is an exhaustive science, no pun.
Smokey Yunick said in his autobiography that no man could live long enough, working at it every day, to understand and perfect the science. So far the best anyone has done is get the perfect header for a specific RPM that stays extremely effective within 400 RPMs of that specific, tuned RPM. See them at NASCAR. Step headers, suddenly now the rage in our Mini/Compact (Mustang, Pinto, etc.) class.
And he played with it a lot. For many years. Had some pretty interesting innovations in that field!

[Paul]

Originally Posted by jeff denton No way. Any header that claimed to be such would only be a "combination of compromise". There might be a certain RPM that it would work well on either engine, but it wouldn't be the same RPM on both. Chances are that it might be better at most RPMs than a stock manifold, though.

My take on what Jeff said...
All headers are a compromise, even specifically designed race headers...

The headers available today, the Pacesetter type, with very unequal length primarys, are not even remotely a decent header, but people such as myself have installed them and the car will continue to function. I do happen to believe a header could be designed that would be much better that what's currently available and cover about 70% of thouse out there with mild motors, read as a better compromise. I believe the mild HP upgrades out number everyone except pure stock. So from a sales standpoint there is some potiential volume in this bracket. The people who have made major modifications or are in it to race, will have the need and resouces to fabricate a better header that is more specific to their needs.

I didn't think oabut rejetting... while it may not be a necessity for the car to be driven, rejetting would bring out little extra power the header provides... not a bad thing in my book. This is similar to porting the intake in that reguard...

Great discussion.... for the record, I can't wait to see/hear a few turbo Opels running around!!!

[RallyBob]

Originally Posted by Gumby Previously they were 3/8" with welded on washers to bring the bolt locations to the correct height but since I'll be making these out of 1/2" it allows more flexability in the thickness of the flange. My preference would be to make them a touch thicker (.4 - .45") to help prevent warping while welding.

What's really important is that the flange thickness under the bolt heads is 12 mm (.472") thick to match the intake manifold thickness and ensure good sealing of both manifolds.

[RallyBob]

Originally Posted by BQS4 Bob; I understand your point, but, you even stated that with a header, there's going to be a bazillion ways that people want it to fit their motor/driving yadd a yadda, but, if there was just the one design, which most want to get i.e. the cast iron sprint,, why not copy it? Just thinking out loud here

I have been asked to prototype a GT header, that's all. And we have someone who wants to buy them, and someone who wants the work building them (not me BTW). I'm not involved with the actual contract work building the headers, only building a prototype.

As far as a Sprint manifold copy, all someone has to do is supply a manufacturer with an original Sprint and pay for them to get copied!

[RallyBob]

Originally Posted by neuropel Bob, Since these manifolds are designed for a GT, would they also fit a Manta?

As mentioned before, probably not.

Also, would the swain coating be needed on a stainless header (assuming they can coat stainless)?

Coating stainless is possible and has some advantages. But it's not necessary. Stainless retains heat about 3 times better than mild steel, and won't rot out under high temps either.

[RallyBob]

Originally Posted by Gumby Rallybob can you send me general dimensions of the turbo you have? I can only find dimensions for the flange on their website and I'd like to get started on layout next week.

Does this help at all?

http://www.atpturbo.com/root/turbopi...s/gt25rdim.gif

If not I have my turbo still mocked up on my engine stand. I could measure it in the next day or two.

[RallyBob]

Originally Posted by opelbits I guess the question here is what sort of header is wanted? A nice header for a stock/mild motor, or one that gets the most out of a hi-comp (10.0 +), big cam, big valve, big carb motor? Can it be the same header for both?

It won't be 'ideal' for both. But it will be better than the Pacesetter was for either. I ran some simulations, and came up with a pretty fair compromise. For anywhere from 85-120 flywheel hp, the header design variation was actually pretty minimal on a 1.9-2.0 litre engine, assuming peak power was made between 5200-5500 rpms. If you have a 'big' cam and your peak power occurs a lot higher than that, all bets are off! OGTS wants to sell headers. A lot of people here want headers.

By far the majority of the Opel owners here have:
*Opel GT's
*manual transmissions
*1.9 or 2.0 litre engines
*less than 120 hp

So if I design for this core market, then we have a saleable item. If I design for 2% of the market, we have very little potential for sales. If the sales numbers are higher, more are made, the jigging costs are spread out, and the product becomes more affordable.

If you have a high compression 2.2 with twin DCOE Webers and a very hot cam...you must either build your own header or have a custom one built. Simple enough. That's why the flanges were made available previously by me and now by Gumby, because it was the single hardest item to procure to make a custom header.

I hope this explains the thought process going on here.

Bob

[Gumby]

Originally Posted by RallyBob Does this help at all? http://www.atpturbo.com/root/turbopi...s/gt25rdim.gif If not I have my turbo still mocked up on my engine stand. I could measure it in the next day or two.

That looks like it will work. More information is always better but this is enough I think to get us started.

If I don't have drill this weekend I should have the flange modeled so I can start proofing the design and code.

[neuropel]

OK.
Count me in for one steel turbo manifold and one flange.

Todd K.

[Gumby]

Originally Posted by neuropel OK. Count me in for one steel turbo manifold and one flange. Todd K.

Mild steel or Stainless Steel Flange? Same question applies to the manifold.

[neuropel]

I'll contact you offline by PM.
Todd K.

[Gumby]

For those interested to know what material costs are running mild steel is $1.3-1.5/lb and 304 is almost $5/lb in small quantity orders so instead I'll be ordering the flat bar in 20' sheets to get the price down within reason. That puts the 304 down to $3.76/lb but the downside is that it means I have to buy about 12 flanges worth of material. So feel free to spread the word that they are available! I know there are at least two other message boards on the net that relate to Opels and I am not opposed to shipping to Europe.

I've already got the jig made up in my head on how I plan to do this. All that's left to do is get Rallybob's example and compare it to the model I'm making. Figure another two weeks before I start collecting money for the flanges and shipping them out. PayPal will be the preferred method of payment however I'll also accept check or postal money order. Shipping costs will be actual, so that will be determined at the time of payment. I don't want to quote shipping costs now with the way they have been fluctuating lately.

[Tru-Craft]

So you will be using 1/2 steel bar stock and then mill counterbores for the bolt & washer to .472 (12mm).
CNC milling the port openings will be the most accurate way to do it.
The end mill will be pretty small in diameter to match the head port internal radius.
1/4 diameter?
Should be a very strong and flat flange!
Nice.
Lyle

[Gumby]

Yes 1/2" bar stock. I haven't measured it yet but eyeballing it makes me think it is closer to a 1/2" radius. I'll be facing both sides to get the correct height. That also removes the scale left over from the hot rolling process and it makes sure both sides are flat. That's probably overkill but we'll see.

[Gumby]

Here is a copy of the original manifold's flange.

Rallybob does your design have any advantage over the original shape?

[Paul]

Originally Posted by Gumby Here is a copy of the original manifold's flange. Rallybob does your design have any advantage over the original shape?

You need to have the center port divider in your model.... You haev to in order to weld the 2 tubes in place....

[Gumby]

Originally Posted by Paul You need to have the center port divider in your model.... You haev to in order to weld the 2 tubes in place....

Oh I know. This is just a model of the original exhaust manifold flange. Sorry I didn't clarify. I was referring more to the way the bolt locations are shaped than anything else.

[jeff denton]

That reminds me, let's not forget to make up lots of gaskets to fit the header flange! WITH the center divider, also. I think they should be separate from the intake gasket.

[Gumby]

Originally Posted by jeff denton That reminds me, let's not forget to make up lots of gaskets to fit the header flange! WITH the center divider, also. I think they should be separate from the intake gasket.

Other than say heat transfer to the intake why would you want a separate intake and exhaust gasket?

I'm sure a thin piece of copper could be cut out into the shape of the gasket if that is an issue.

[Gumby]

Originally Posted by Tru-Craft So you will be using 1/2 steel bar stock and then mill counterbores for the bolt & washer to .472 (12mm). CNC milling the port openings will be the most accurate way to do it. The end mill will be pretty small in diameter to match the head port internal radius. 1/4 diameter? Should be a very strong and flat flange! Nice. Lyle

I looked at the manifold and the head last night a little closer. The head is somewhere around 7/16 by the look of it and the manifold is in excessive of 1/2"

[RallyBob]

Originally Posted by Gumby Here is a copy of the original manifold's flange. Rallybob does your design have any advantage over the original shape?

Other than the center divider, I basically just cleaned up the stock design and made sure it fits aftermarket intake manifolds. I tried all the ones I had in my possession to make sure.

I did enlarge the ports a bit compared to stock (2.4's have bigger exhaust ports for example), which allows for almost any header tube size.

Bob

[RallyBob]

Originally Posted by Gumby Other than say heat transfer to the intake why would you want a separate intake and exhaust gasket? I'm sure a thin piece of copper could be cut out into the shape of the gasket if that is an issue.

The problem with copper is the lack of 'crush'. So the head's surface, the header, and the intake must be perfectly flat (no corrosion or warpage), and the intake and exhaust flange must be the perfect matching thickness. The intake/exhaust bolts also need to be perfectly torqued to spec, and checked frequently. There's no 'sprung' gasket to take up the slack here! It's been done before on race cars, but conditions must be perfect. The alternative is a car burned to the ground. Especially with a turbo!!!!!

Still, the thought of fuel leaking past the intake flange gasket onto a hot exhaust does not thrill me!

Bob

[Geek]

Somewhat related: What are you going to use to get the mill scale off? A (very) little experience has proven to be miserable.