Short intake manifold interfering with exhaust header

[P.J. Romano]

I am struggling with the issue that I am not sure if it is caused by the aftermarket manifold or by the exhaust header, also aftermarket.
The short intake manifold was obtained via eBay from Greece. It appears to be true copy of Irmscher short manifold (he might have made molding out of Irmscher manifold).
The exhaust header is of unknown origin but looks solid.
The problem is that the outside header pipes (cylinders #1 and #4) are interfering with the intake manifold. Have a look at the attached photos.
Did anybody else experience similar issue? Should I look for a different exhaust header or for a different intake manifold? I am suspecting that the culprit is an exhaust header but I could be wrong.

[jordan]

I would say that you are correct in your assumption that it is the after market header that is causing the problem. The stock exhaust manifold 'hugs' the block a little more and eliminates the contact. Also the pacesetter (which is what your header looks like) had many varying (mostly unintentional) differences.

[soybean]

Jordan and you are correct on the header.
Your other option might be to cut, or trim the bar that connects the header.
Jarrell

[P.J. Romano]

The header bar is OK. Intake manifold is interfering with the #1 and #4 pipes. One of the possibilities would be to heat-up those pipes and try to pry them away from the manifold. This is the reason that I made that sturdy jig shown on the picture. It would secure that the header flange remains flat.
Still, this would be too risky and I might wind-up with bad header. As you know, they are expensive like gold.
So, I am hoping to receive some advice from somebody who resolved similar issue.

[soybean]

The last posts picture makes it clearer. A good question, and heating and bending it might be the idea. I'm sure others will chime in.
Jarrell

[davegt27]

I have a TWM side draft manifold and the one that goes toward the front of the motor is a two piece manifold

That is they cut the mounting flange (the part that bolts to the head) in half

This makes the manifold a little easier to install

I don't know what they used to cut it (band saw maybe) but it's a very precise cut

So that is an option you might consider

The other thing you could do is take a hammer and punch and try to deform the header at just one spot

Then send the header to the machine shop to check for flatness of the mounting surface
and they can machine it flat again if need be

Almost all my header I get I send to the machine shop to be shaved for flatness

HTH
Davegt27

[nobody]

Oh my yes, I've been down this road. There isn't enough material to rebend it but it can be fixed to fit if your brave and can weld. Roughly 25 bucks in parts and about 2 hours should do it. Have you tackled the thermostat housing issue yet? I can give you a step by step on making it all fit if you'd like. Pictures and part numbers and sources of course, it was on my to do list anyway.

[P.J. Romano]

Didn't tackle thermostat, yet. I know that it has to be modified but not sure how. For the beginning, I bought an extra thermostat housing which I can play with. Your advice would be greatly apprecciated, for sure!

[opelwasp]

You could always get a 2.4L exhaust manifold from OGTS which likely flows at least as well, and has an O2 sensor bung built in. Could run a wide band O2 sensor for tuning. The 2.0, 2.2, and 2.4L exhaust manifolds fit very nicely in the GT. The tubes are mounted front to back not side to side like stock.

I was never happy with my header, lost my bottom end torque. With the 2.0L manifold It flows great and I have tons of torque. Manifolds are cheaper than the headers, and quieter too.

How much did you pay for the intakes? And does he have any more?

[P.J. Romano]

Thanks for the advice on the exhaust manifold. I will definitely take this into a consideration.
Regarding intake manifold you may contact Motorman directly. I found them very responsive. My contact was John Palmos: motorman253@yahoo.com, phone number in Athens, Greece: (30) 210 5763535

[GTJIM]

Most USA GT headers were built to fit with the standard 2bbl intake manifold - and not too well in some cases.
The header you have there is simply incompatible with the DSD intakes you have ... that is why the "Sprint" type Opel exhaust manifold is so popular - they fit with minimum modifications when DSD intakes are used. The header is designed for peak horsepower whereas the Opel setup is designed for improved torque over a much wider rev. range.

Neither of the designers knew you were going to try to use them together .....

You have not much alternative than to cut, hack and reweld that header if you want to use it with those intakes - they were never designed to fit together.

Motorman253 lists on eBay and also has the correct thermostat housing that goes with the DSD intakes - though you can modify the standard housing by several methods.

Have a look through this Thread: http://www.opelgt.com/forums/afterma...de-drafts.html

[nobody]

To fit a header to the short Irmsher type you can't exceed 90 mm to the outside of bends on all 4. 1 and 4 have to go straight down first then swing back to clear the intake. You can redo the header with a standard weldable 90 and a 45 on 1 and 4 to get them to clear. 1 1/4 size from Mcmaster or whoever you choose will make it fit. About 20 bucks and 2 hours of work would be about right to fix it. That simple design tip will allow your header to clear every intake on the market. While your at it you'll need at least 5 inches of 8mm all thread for your next project to make it all fit. If you cant weld find somebody that does mig and tig both, I'll explain why in a bit.

[P.J. Romano]

Just ordered modified thermostat housing from Greece. At US$ 80 (including postage) it is not cheap but at the end of the day, it will probably be worth that money.

Didn't make my mind yet on the header - to go for the Sprint one or to modify the existing one. In any case, the advices you guys gave me are excellent.

I have quite an extensive experience with DCOEs on other cars. I was expecting some fiddling with venturi tubes and jets but not interference with the header and thermostat (not to forget the heater box)!

Anyway, playing with my Opel GT is re-living the young age dream (my wife calls it mid-year crisis!)

[nobody]

Dean posted a list of jets and such for his OEs that work well. I did one for the OMs at altitude. Dean also did an enrichener cable that is too cool. I don't know if he did a write up on it but I'm sure he could tell you how to make one.