Aug 2003 fastrack.

Wow...awesome news. I had not read the new Fasttrack. It's about time we can use the flat-tops, the dished pistons are f*****g pathetic for a racecar.

The valves have been legal for the GT for a couple of years, a bunch of us had written to the BOD to get them legalized. For comparison, a stock 1.9 head flows about 88 cfm on the intake ports. With legal ITB prep work, I get them to about 92-94 cfm. With the 2.0 intake valves, it improves again to about 100-101 cfm.

All in all it adds substantial power to an otherwise restricted engine. The trick is to add the legal replacement valve seats (I use L-Joy intake and exhaust seats). The throat area is far larger, and with a 3-angle carbide seat cutter, the bowl area opens substantially and improves the airflow. Opels have fairly large ports compared to the valve area, so larger valves DO help the airflow here.

As you may know, Opel used gross hp ratings in the late '60's. So those 102 hp ratings on the early engines are overated. They are rated at 90 ps in Europe (about 88 hp). But I have found them to be closer to 82-85 hp in reality (at the flywheel).

With correct mods, 110-115 'real' hp is achievable. Mill head for 9.5:1 compression, use Total Seal rings, proper valve job with the bigger intake valves, 'Euro' camshaft, properly selected intake manifold, 32/26 Weber, and a good header....this will get the car competitive.

Bob

Yes, the FI will flow better than a stock carbureted intake and 32/36 Weber. Not to mention the longer runners are better for torque, which the Opel sorely needs.

In terms of a header, you simply need to get a proper header to reap the results the header can offer. There is no off-the-shelf header that works worth a damn, they're all far too short (usually under 28" primaries)v and only help high rpm power.

I agree the cast iron Sprint manifold offers a better torque curve than a shorty header. But a custom 4-into-1 header with 1.5 "primary tubes that are 36-38" long will run much better than a Sprint manifold. Not to mention, that's a lot of weight (the manifold) to be removed from the front of the car, and quite high up as well.

I'd try a 2.25" exhaust pipe too, 2.5" is too big for a 1.9 litre. It's 24.5% larger in area than a 2.25" pipe...which is a lot. You lose a lot of scavenging effect with that big a pipe. You might gain a touch on the very top end, but a smaller pipe will do much better in the mid range.

In fact, I use a 2.5" pipe on my friend's 185 hp 2.5 litre Opel engine! And that head flows almost 60% more than a 1.9's!

Bob

First, you should double check the fast track. I petitioned the SCCA comp board and provided them with the information needed to get both the 42mm valves and 9.0:1 compression. (July Fastrack). However, I have not received confirmation of the change. (I also have not gotten an August issue of "Sports Car".

Now, I'm going to get into your wallet. I have been building race and championship winning IT heads for years. They have been protested and torn down and they are LEGAL. So, if you want to run up front you have two choices. First, convince Rally Bob to come out of retirement and send it to him... he's built a lot of winning heads too.... or second send it to me. You're local machine shop just wants to make money... and they probably didn't (or still don't) know how to spell OPAL until you showed up. Rally Bob and I want OPELs to win. Yea... we have to make money... and it will cost a lot more than your local machine shop... but running at the back of the pack sucks.

Or, you can pay them now and then pay me (or Rally Bob) after you get your doors blown off.

A bunch of stuff to address, so this will be kind of long.

As promised, here is the GCR rule from the SCCA 2003 rule book.

Paragraph 17.1.4.C (pg ITCS-6) says in part:

To maintain the stock basis of Improved Touring, updating and/or backdating of components is only permitted within cars of the same make, model, body type (eg., sedan, station wagon, convertible, etc.) and engine size as listed on a single Improved Touring Specification Line. Any updated/backdated components shall be substituted as a complete assembly 0engine long block, transmission/transaxle, , differential/axle housing.) No interchange of parts between assemblies is permitted.

...(TGSI NOTE: that takes care of the FI system. It goes on.) ...

No interchange of parts between assemblies is permitted, and all parts of an assembly shall be as originally produced for that assembly (such parts may, however, be painted or plated). Additionally, it is not permitted to "create" a model or type of car by updating or backdating assemblies.

... (TGSI NOTE: it goes on to say a bunch more about the manufacturer "superseeding" parts are OK...

So, we are not creating a new model. The Manta 1.9L was/is the model. We are not creating a new type of car... we are not creating a Yugo nor an electric/steam/flux-capacitor powered car.


Would any year Manta work just as well? Yea... considering all the stuff it takes to turn it into a front running ITB it really doesn't make a lot of difference. It's just easier to get everything all at once and know it's working to start with... then replace it all. The FI rules require a stock harness too so that would be a lot easier than creating a new "stock" harness. In reality, very little of the stock stuff will get used without being replaced or having significant changes... I don't even care about the computer except for the housing. The rules allow anything inside the stock housing.

The '75 does also have the "big brakes"... but I would go with only new rotors and calipers. I could just as easily "update" an earlier model, so earlier brakes don't really matter. I did just think of one thing. The early Mantas didn't have the big 5 MPH bumpers and they're ugly. So, I guess any Manta would be fine.

Rally Bob... Come over to the dark side? I guess that I've always been on that side since I've always liked the Mantas a lot. It's just that they could never legally be made to run anywhere near the front. As far as handling goes, I think a properly done GT and Manta will be about equal. So the real difference will come down to the FI. With a real engine management system (electromotive) stuffed into the stock housing, the FI will probably make enough more HP to bring me completely over to "the dark side".