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Discussion Starter · #1 ·
So I have been working for the past several days to install a dual 40 DCOE set up on my 1.9L GT. I'm using the Dbilas shorty intakes with an OGTS shorty header. Currently I'm using the stock M9 x 1.25 x 30mm hex header bolts standard on US GTs, and have run into the problem of extreme difficulty torquing these to the proper specs. This has lead to an exhaust leak in cylinder #4. Honestly I'm pretty split on how to fix this problem. On one hand I would like to save money and try to make the stock bolts work. I could modify my custom linkage mechanism slightly and probably achieve proper torque. On the other hand, I'm seeing the benefit of socket head bolts and the ease of instillation/removal. Additionally, there have been several posts on this forum regarding changing the threads for the header/intake to a more common and forgiving size. This leaves me with a few questions.

1. With the Dbilas intakes, is it possible to get a ball ended Allen wrench on socket head Allen bolts with out removing the carbs from the intakes?

2. Is there any benefit to keeping the original hex header/intake bolts with this setup?

3. Can re-threading of the intake/exhaust bolt holes be accomplished accurately with the engine in the car?

4. Is there an easy solution to re-threading these holes, such as a simple insert?

5. What would be the best way forward with the least amount of money and time spent (while keeping the dsd setup)?

I probably missed something. Thank you for your input.
 

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On my dsd setup i grinded an Allen key to fit.
It has to be grinded and cut half way to fit.
I bought some special bolts with better clearance but ended up using the original ones :) will see if I can find a pic of the Allen key.
For the fit, I regrinded the holes a bit to have a perfect fit - this is though really time consuming with engine in the car. But use a smartphone and take some videoes down the intake with flash on to see the alignment and then check that the carb bolts for the dcoe’s are 100% aligned. Installation is not easy if you want a 100% fit but it is possible. On mine I considered some steering pins but it was too difficult to make as the engine was in the car allready.


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What did you do for isolating the heat?
I found that I had to use bottom shield and rubber o-ring gaskets for the dcoes not to boil. And I still have a bit of heat problem so I’m considering wrapping the header with power wrap.


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Opel Rallier since 1977
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I would suggest leaving any re-thread of the bolt holes to a last act of desperation in the car. Yes, it can be done, but this is in cast iron and so will be a bit trickier to drill and tap. Accuracy ought not be an issue but the drill bit working well may be, and tapping has to be done carefully in cast iron. If you break a drill or tap, then you'll have some real headaches. Certainly, you can use Helicoil inserts, but realize that threads in cast iron are quite strong (stronger than the hardened, medium carbon bolts that you have now), and it is nice to keep that strength in that critical area.

I would be surprised if you could not find these bolt in the same size with an Allen head. Try McMaster-Carr.
 

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Opeler
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Finding the Allen head bolts are a must in my opinion. You can definitely access them with the manifolds and carbs together. I got mine from OGTS years ago, see if they happen to have some. If not, McMaster Carr has pretty much everything under the sun.
 

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Can Opeler
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I have a huge hatred of socket head bolts and refuse to use them on any part of my car.

I just modified a 15mm wrench and shaved down a 15mm socket to fit.
 

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Just Some Dude in Jersey
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Gordo's Murphy's Law:
Every job on your Opel, no matter how simple, always requires every tool you own, two that you have to go out and buy, and one they haven't invented yet.

In my GT's, I have had all the different fuel management set ups: Downdrafts, dual side drafts, single side drafts, Opel fuel injection, plus all the different manifold set ups. I have found that each one requires different hoops for you to jump through to tighten the manifold and carb bolts. In many cases, EACH bolt requires a different tool. In many cases, I had to make those tools. In most cases, those bolts could only be accessed from under the various manifolds. It's one of the big reasons I gave up on DSD's and went with an SSD. I prefer to use the allen head bolts at the 4 middle bolt locations and hex head bolts at the 2 outside, exhaust only, bolt locations.

I posted on your Facebook comment about the 15mm wrench that I ground down that is much like the one Jacobhojrup posted, I'll repost those below. I also use long 8mm ball end allen wrenches, normal 8mm allen ones chopped off just after the bend, 8mm sockets on ratchet wrench extenders with u-joints, a flip-flop head speed box wrench, and I have used an 8mm Gear Wrench slipped over the shaft of a long ball end allen wrench to tighten certain bolts.

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Opeler
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I have a similar set-up with DSD 45s and Irmscher short intakes. Honestly, I liked the idea of socket head bolts but couldn't see how you can possibly get an allen wrench on the two in P.J.'s pic, so I never bought them. I too used a shaved down 15mm 12-pt box wrench.

Hard to tell for sure from your pic, but it looks like the intake flange might be slightly thicker than the header flange. That might explain part of the reason for the exhaust leak.
 

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You’re not going to find that the intake bolt thread is commonly available. It’s 9mm x 1.25 pitch. Very odd.

Easy options are to use the 15 mm headed bolts and some custom ground down tools, or the later factory 3.0 and 2.4 style socket cap screws that OGTS sells.

Another option that my friend Duane utilized was to machine down a set of stock bolts to a 13 mm hex head.

And lastly you could drill and tap for Helicoil inserts and use a 3/8” bolt with a small 7/16” 12-point head, such as an ARP bolt. I’ve done this on a few heads. Accuracy is important, since an angled bolt will not clamp properly. I’ve only done it on heads that were removed from the car.

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