75 FI Head Pipe

[jordan]

Would anyone happen to have a 75' efi headpipe that they are willing to part with, or have pictures of aftermarket ones so I can try and design from?

[GTJIM]

They are the same as ordinary ones since the "Sprint" exhaust manifold has its flange positioned in exactly the same place as the ordinary one.

[BQS4]

Originally Posted by jordan Would anyone happen to have a 75' efi headpipe that they are willing to part with, or have pictures of aftermarket ones so I can try and design from?

Jordan;
You can use the stock GT headpipe on this. The headpipe for the actual cars that had F.I., i.e., the Manta/Ascona won't work on a GT, as the bends are not correct. But, as Jim states, the flange where the GT headpipe bolts up to, is the same and is in the same location as for a GT with the stock intake/exhaust set up.

[jordan]

I have the 2.0l sprint which has the larger flange.

[GT Tim]

I had the same problem.I have a 2.2 exhaust.I had to order a gasket from OGTS.Then I had the flange cut from the gasket.Then ran the pipe using the stock as an example.I don't have pics now but I should on Monday.Thanks Tim

[RallyBob]

Originally Posted by jordan I have the 2.0l sprint which has the larger flange.

European-spec headpipe then! None of the US cars used that flange.

PM me, I think I still have a few custom-made flanges for those manifolds however. They are sized for larger 1.75" primary tubes in lieu of the original 1.625" tubes. I can check my barn tonight or tomorrow for them.

Bob

[GTJIM]

Have a look here on eBay:

eBay Motors: OPEL HI-PERFORMANCE CIH SPRINT MANIFOLD SET-UP (item 290097749115 end time Mar-30-07 17:25:56 PDT)

[jerseydave]

I now realize that I have the same problem. I thought the manifold would fit the stock headpipe, duh

Now I'll have to put the pacesetter back on the car for now.

[tekenaar]

Originally Posted by GTJIM Have a look here on eBay

Very nice job but, as I've said before, while both flange and matching gasket are indeed larger (wider) and the gasket has larger exhaust holes, the "as-cast" exhaust ports for the later "Sprint" manifolds are the same size as those of the '75 Sprints . . . at least the three that I had sent from Germany, and subsequently sold, were.

[jake]

Most people buying the sprint manifolds from Europe don't know that the downpipe flange is a totally different size and will not bolt up to your stock downpipe. One way you can tell the USA Sprint is that it has a OPEL BLITZ emblem before the cast part number on the manifold. The European sprint has the GM emblem on it. They are also being sold here in the USA by people that are reselling their European ones that they bought because it costs too much to custom make the downpipe. They look alike if you don't look at them carefully.

[Mike Preble]

If Jordan is going to need custom pipes produced would it be advantagous to him to increase or decrease the length of the head pipes? I don't know the specs of his engine but depending on those and if he wants more low end torque or high end horsepower is shorter better or longer?

Just a little fore thought.

Mike

[hrcollinsjr]

Originally Posted by Mike Preble ...advantagous to him to increase or decrease the length of the head pipes? ...if he wants more low end torque or high end horsepower is shorter better or longer? Mike

Longer pipes for torque.

Harold

[jordan]

From my understanding longer head pipes with a sprint manifold will only be advantageous to a certain extent. I don't know what that certain length is, maybe bob will chime in with some numbers, I put the exhaust system on the back burner until I have the suspension back on so I can get the car on the lift to put the engine back in, Then it is EFI and exhaust time!

[GTJIM]

The 'Sprint' (and stock) Opel exhaust manifolds work under different principles than a four-tube header. They are designed to damp exhaust pulses and give a smoother power curve over a larger rev range.
It is possibly even advantageous to leave the cast manifold at its original internal diameter and bolt up 2" secondary pipes so there is a distinct 'step' where they meet to provide reversion damping in the exhaust flow.
Definitely some dyno time needed with varying secondary pipe diameter!

[RallyBob]

Originally Posted by jordan I don't know what that certain length is, maybe bob will chime in with some numbers,

Jordan, I don't have any hard numbers because it depends on the car specs of course.

I do know that when the do-it-yourself Swedish header kits (Rohret and Rohret 2) are welded together, the rally guys typically shorten the secondaries by a decent amount compared to the baseline that the kit comes with.

I have run a restricted-class 1.9 litre circle track racer with the Sprint manifold, and what I ended up doing was porting the manifold, making larger secondary pipes (1.75"), and shortening them to about 15" long, merging into a 2.25" main pipe which ran back to just in front of the right rear tire (on a Manta). We tried making the main pipe shorter, and we lost too much torque off the turns. The specs of this engine were mild however, .030" flat-tops with a decked block, a milled head, 2.0 intake valves, hydraulic cam with .410" lift and 240* duration @ .050", mildly ported intake, reworked 32/36 Weber with a 31.5 mm secondary venturi, and a Pertronix ignition with an MSD red coil painted black and fitted with a Bosch sticker...

Bob

[opelnut10]

Originally Posted by RallyBob Jordan, I don't have any hard numbers because it depends on the car specs of course. I do know that when the do-it-yourself Swedish header kits (Rohret and Rohret 2) are welded together, the rally guys typically shorten the secondaries by a decent amount compared to the baseline that the kit comes with. I have run a restricted-class 1.9 litre circle track racer with the Sprint manifold, and what I ended up doing was porting the manifold, making larger secondary pipes (1.75"), and shortening them to about 15" long, merging into a 2.25" main pipe which ran back to just in front of the right rear tire (on a Manta). We tried making the main pipe shorter, and we lost too much torque off the turns. The specs of this engine were mild however, .030" flat-tops with a decked block, a milled head, 2.0 intake valves, hydraulic cam with .410" lift and 240* duration @ .050", mildly ported intake, reworked 32/36 Weber with a 31.5 mm secondary venturi, and a Pertronix ignition with an MSD red coil painted black and fitted with a Bosch sticker... Bob

Would porting the two flange outlets slightly and blending a taper at the flange with a slightly larger bore flange be of any benifit along with the larger diameter flange pipes. I bet you were the only ones "fudging" at that track also

[booeman]

Originally Posted by jerseydave I now realize that I have the same problem. I thought the manifold would fit the stock headpipe, duh Now I'll have to put the pacesetter back on the car for now.

I have the same problem, the sprint manifold I got from germany measures center to center on the bolt holes;(outlet) length 3.400 inches; width 2.750 inches. the gasket that came with the rebuild kit measures, bolt hole center ot center; length 3.700 inches; width 1.700. looks like I'm needing a gasket and a new header pipe.

[lewdawg]

I as well have bought the European sprint manifold and have the same problem. Bob, if you do have some of those downpipe flanges laying around still I would be very appreciative if I could purchase one from you. I believe from there, I can get the down pipe fabricated. I do have a stock downpipe that is in outstanding shape but it's not doing me any good right now. My 72 has a header on it but I'm not too crazy about how the collector hangs down below the car. Yea, call me picky but its one of my pet peeves.

[Gordy]

As far as the header hanging down below the car, I had bought a new Hedman Header in 1979 and it's been in use on my GT ever since but did create some clearance issues on bumps etc. I did buy a header off E Bay which will be taking it's place where the collector is actually much further forward and more on the downward part of the header. The old one went clear back beyond the trans mount!
I was lucky on the sprint manifold I picked up off of E Bay -the seller actually pointed out the problem with European manifolds and the different sized headpipe requirement. His was the US version and should bolt right up on my Manta when I get to that point. Check the emblem and #s and that should be the one to look for for straight forward installation. http://www.opelgt.com/photos//data/5..._exhaust_2.jpghttp://www.opelgt.com/photos//data/5..._exhaust_1.jpg