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Discussion Starter · #1 ·
This is an idea that's been bouncing around my brain for a while. Seeing the lack of available for sprint manifolds and some of the negative coments about alot of the headers I wondered if a middle ground could be reached.

What I'm thinking is a RallyBob flange with 1 1/4 all the way to where the collector combines then 2 inch from there on out to keep some of the low end torque for a semi stock motor but still make it breath better.

This would be all stock gaskets and hangers with a modified resonator for 2 inch but still stock.

Any comments?
 

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Hmmm...

I am not sure if you described your idea very well, but I am guessing that you are substituting the head pipe for a single 2 inch? Are you talking about an engine-back exhaust kit? Where on the car does your idea start and end?
 

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Discussion Starter · #3 ·
Ok a sprint knock off all done in 1 1/4, a modified collector going from 1 1/4 to a 2 inch main but keeping the same dimensions to a turbo muffler at 2 in and out then over the axle to a modified stock resonator to take 2 inch.

It starts at the exhaust gasket and ends behind the car.
 

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If I am understanding this correctly you basically want to replace a sprint manifold with one of the exact same size except the exits from the head would all be 1 1/4" pipe and then combine into one flange that is identicle to the one at the end of a sprint manifold. If this is the idea, the distance to make all the bends is very short and it would probably have to be done out of formed elbows all welded together. It is something that I will try to mock up when I get the time, but no promises. My shop is extremely busy right now.

Bob,
Do you still have flanges available?
 

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Discussion Starter · #5 ·
I picked up the box of elbows and 45s yesterday.I also made sure the trimix bottle for the welder was full and picked up the modified collector from the exhaust shop. I already formed 2 of the square to round adapters as well as removed a stock intake from an exhaust to make sure it will fit right.

The biggest issue is the short turn for the center 2 ports but it looks doable.

Another issue is the availability of exhaust flanges as this seems to be a wanted item. I got all I could afford when they were available. I should have brought this up at the time and they would have sold like hotcakes instead of slow sales that makes me wonder if Bob would even consider making any more.

I still need to make the mating flange but have the steel for it. I also need a bit more tubing, but those are small issues.

Basicly I was wondering if anybody saw a flaw in the idea.
 

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Dave;
What about those of us who did by one of Bob's flanges and don't know what to do with it, other than hang it on the wall as pure artwork (which it is actually :D )
Gene
 

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Dave, again you are attempting to provide a product that is badly needed within the community. With the scarcity of Sprint manifolds and the hasle of getting a header to fit and tuck properly, your exhaust system would be welcome and obviously, so far, in great demand. I, for one, run a header (not a shorty) and I am not happy with the way it hangs under the car. We talked about this at the last meet. I'm sure others are experiencing the same cosmetic problems when running this type of header and would welcome an exhaust that tucks under the car and doesn't hang down detracting from the looks of the GT. The shorty header offered by OGTS is on the pricey side, so if you can produce this sprint knock off exhaust manifold then I'm sure you will be busy...Good Luck and keep us posted.
 

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Discussion Starter · #8 ·
I've been planning this for a while, just the timing or a test car wasn't at hand. Now I have all the pieces to do it and enough to get it right. Designing the turbo exhaust was alot harder than copying a known design you can look at for dimensions.

I got 5 of the flanges but won't use them all on this project.

Gene that's an interesting point. I started to keep this quiet but wanted some feedback if it was too wild or had flaws I missed. I decided to put it out there to be critiqued so it went well. Along the way I'll give dimensions and parts used so it can be redone.

This one is being done for Marks GT (Lewdawg) and will be easily ready for the Utah show and tell next month.

On a design note, I went with a little heavier tubing to make it a bit more robust but still match the weldable fittings in ID.
 

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Sounds like a good idea Dave. I was considering a very similar manifold to sell some time ago. But I honestly just don't have enough hours in the day or enough motivation to consider manufacturing anything like this.

I was initially hoping to make a replica Sprint manifold from the weldable cast steel fittings, which would fit the stock headpipe (direct fit for those W/O a Sprint manifold available to them), and then a long-tube version for more 'tuned' engines with a custom downpipe to match.

As far as the flanges, I don't have any more, and don't have the funding to be able to produce another batch (52 pieces to get the price down to something 'reasonable').

No drawing is available either, I made my prototype from sheetmetal then had it redone in CAD by the water jet company. Although I guess I could just trace the prototype onto paper.

Bob
 

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Discussion Starter · #10 ·
A couple minor issues

A couple of minor glitches to start with. Seems the guy that modified the collector was dislexic. Bend in the 2 inch is backwards.

Ok the Mig is the companies but free for me to use, however it cam back a bit hosed up from the last job.

For the spacing to come out right a square to round adapter can't be used and fit under a stock intake manifold.

For the first 2 I managed to get a new regulator from Airgas for free and fix the welder, I can then cut and turn the 2 inch to be rewelded for the collector.

last one means forming weldable fittings into a square, this seems like a tricky maneuver as they are on a pitch and thick little buggers.
 

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Bash Them .....

nobody said:
last one means forming weldable fittings into a square, this seems like a tricky maneuver as they are on a pitch and thick little buggers.
Dave, It may be easier to get slightly larger diameter bends and just flatten the centre bends on the side that they touch together. Weld them together along the centre and then place them ON the flange and butt weld them to it. As long as the internal bore of the fitting is bigger or as big as the diagonal size of the square hole in the flange a wee bit of a step will not hurt gas flow - and may even add to the anti-reversion characterisitcs of the system.
A bit like this:
 

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Jim, in theory this will work just fine (shouldn't hurt flow), but remember those damn intake/exhaust hold-down bolts need to be accessible! Running a large diameter round tube usually entails some sort of beating of the tubes to allow fitment of a suitable tool to loosen and tighten the attaching bolts. Major PITA otherwise!

I've built some large-tube racing headers before that were a nightmare to bolt up due to this fact, so for those applications I started installing 3/8" Helicoils into the head and using external 12-pt stainless ARP intake fasteners from a Chevy small block (they use a 7/16" wrench/socket to tighten). With this at least the large tubes don't render a 15 mm wrench or socket as useless!

Bob
 

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Bob, I'm not sure what the thread is is on the standard manifold bolts for the 1.9, but ARP does have an 8mm X 1.25 12 point bolt that has a 10 mm head on it about an inch long. I got some for Willit? and its 3.4 GM engine.

Dave, I gotta tell you, when we build the manifolds for Willit?, one thing we should have done was to weld the tubes on the inside of the flange rather than the outside, for the reason Bob stated. I had to grind a fair amount of weld to clear the bolt holes for the bolts and washers to sit flat against the flange. Even though I did use small ARP exhaust bolts as stated above, there was a lot of grinding to make it work. HTH.
 

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9mm!

Yes, Bob - my biro got a bit carried away with the outer circumference of those tubes! I think just "squashing" the two bends may be a better idea, since the exhaust ports are higher than they are wide.
Ron, "Those damn intake/exhaust hold down bolts" are 9mm X 1.25 !!!
Yes, Opel have done it again with non-standard bolts, this time ......... Looks like the 3/8" NC helicoils is the way to go. And allen-head cap screws.
I went to all the trouble of starting to make a set of stainless steel allen heads - made from 10mm bolts turned down to 9mm - which I am still cutting the threads on ( *!!* non-standard threads - well "standard" but non-preferred which means that the button die was just a bit hard to find ....)
Allen heads will give lots more room though ...... 3/8" ones sound real good.
 

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Discussion Starter · #15 ·
Posting a pic took a bit. Download software and reboot, find pcmcia to flash adapter and change rem from config. sys, learn new software and save after finding the file. Main computer is on wipe out so laptop for now.

Left side is tacked in and the rest is getting cut and made so all is good. It would be so much easier if 1 and 4 were outside not inside. Pic of todays progress......I hope

Oh and note the bolts and socket on the manifold bolts.
 

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Discussion Starter · #17 ·
Actually there is a reason 1 and 4 is toward the motor. The collector is of two different length pipes to compensate for the unequal lengths of the exhaust manifold.

And an early thanks to Bob, Jim and Ron for keeping me on track and not screwing up so you couldn't bolt it on, plus an idea to simplify adapters for 1 and 4. What if they were oval not round to allow the bolts to fit and give room to weld?
 

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It looks like you are going to use a stock style flange from header to pipe. Is this to ease header only installs? Ever think about running the header pipes into a ball style at the collector end? It seems to me that it would give a little bit of adjustability to the fitment of the pipe to the rear of the car and a little leeway in the fabrication vs. a flat flange. I think it would also be easier to work on down the road.
Danny
 

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Jim, my personal opinion on "Allen head" bolts, garnered from years of using them on my model racing boats, is, they are prone to stripping out inside the head. It would take an allen socket to get the correct torque on the bolts, and of course anti-sieze compound on the threads, or they may never get removed normally. I would think the 12 point ARP exhaust bolts would be a better bolt in this application, and they are available in SAE and Metric threads. I wonder if you could use an 8mm heli-coil in a 9mm thread. An interesting thought.

Dave, I noted you are using the McMaster-Carr type fittings, here's a bit of info for you, they do have shorter 90 degree fittings by about 3/4" in their on-line catalog. I had to use the shorter ones on the driver's side exhaust manifold on Willit? to get a bit more clearance down the steering shaft. HTH.
 

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Discussion Starter · #20 ·
I chose this idea because of the availability of sprint manifolds that have been know to work and fit better than headers. It flows good and doesn't leave something hanging funny under the car.

Ron these are standard radious and doing it with them gives me the same dimensions as a sprint and clears the intake just enough to work.
 
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