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Discussion Starter #1 (Edited by Moderator)
engine mods

I have recently found your site & believe it is just what I need for my '72 GT restoration. First question is about cylinder bore & cam grind. Is there an optimal combo? I would like to go .030 or .040 oversize bore. What would be a good lift/duration cam to compliment this? I am looking for street performance only. I already have the Weber carb & will run stock exhaust, as you say that they flow pretty well.

Thanks
Ken
 
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Discussion Starter #2 (Edited by Moderator)
It's hard to put a label on what is *optimal*, as this is often subjective. My optimal and another person's optimal can be two drastically different things.

Regarding cylinder bore size, basically I'd go as large as possible to reap the benefits of increased displacement. The Opel 1.9 has fairly beefy cylinder walls, and can handle a .090"; overbore just fine. This will give you a 2.0 litre. As far as the cam goes, you're restricted by the stock valvetrain to about .430 valve lift. Duration and lobe separation will establish your powerband, but you didn't mention what you were looking for in this regard.

The comments about the Opel exhaust were pertaining to the exhaust port flow of the cylinder head, not the exhaust system itself. You would get an appreciable increase in power AND torque by enlarging the exhaust to 2 inches (stock is only 1 5/8, and is quite restrictive). I'd also recommend a 38DGAS Weber instead of the 32/36, and an electronic ignition. You may also need to recurve the distributor, depending on your camshaft choice. Duration figures above 220 @ .050 will pretty much require a recurved distributor for the engine to run smoothly. Hope this helps out somewhat.

Bob
 
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Discussion Starter #3
piston choice

Hey RallyBob, much appreciated info. I was told that a stock 350 Chevy piston will work fine. Is that accurate? Are there any particluar years that work with valve clarance? Is this a good choice? They seem to be a LOT more avaliable.

Powerband?? I figure to gain SOME bottom end power with the overbore, so I´m probably looking for mid-range improvement. I don´t need to go too fast @ top end..... Ga. police are tough.

2" exhaust is no problem for my fabricator or is there aftermarket avaliable? Parts seem to be rather expensive or I´m looking in the wrong places. I´ve seen prices from OpelGT source. Are there alternatives?
Thanks, again
Ken
 
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Discussion Starter #4 (Edited by Moderator)
Whoa! Don't go out and order those 350 Chevy pistons just yet! The 350 Chevy has a 4.00 inch bore, the Opel is only 3.66 inches. I think the pistons you are thinking of are the Chevy 265 pistons. This engine was produced from 1955-1957. The bore is 3.75 inches, or .090 more than a 1.9 Opel. They are flat-top piston, and they have a piston pin that is .927 instead of .906 (stock Opel), so the Opel rods have to be opened up to fit. You also need to bore the block .090, and get yourself a 2.0 litre head gasket. That's about it.

For a camshaft, I think you would be looking for something with about 225 - 230 degree duration @ .050. This will be strongest from 2000-6000. I prefer to use 108 degree lobe separation for better torque, but it will idle a little rougher. Most people use 110 degree lobe separation, it idles smoother but has less mid-range *oomph*.

Opels are not cheap cars to modify, at least not anymore (the '70's were another story). We tend to forget they ARE German cars ($$$$), and they are sort of bastard cars in this country, so parts are not readily available everywhere. Opel GT Source does a great job of not only stocking these hard to find parts, but also reproduces a great deal of parts. Some other guy that sells parts for multiple makes but carries a few Opel parts may save you five bucks here and there, but really doesn't give a damn about you or your car in the long run. I try to support the guys who are supporting US.
As far as other parts sources, there's Opel GT Source, as has been mentioned, Opels Unlimited, Goin Manta, TGSI for performance parts, Orphan Imports, and a few others I can't recall offhand. In the past 10 years, at least 10-15 other business' specializing in Opels have gone out of business. Not using the existing companies may contribute to their demise, and the day you need a specialized part the local store can't get, you'll be out of luck!

Well, enough of my lecturing, I didn't mean to turn this into a documentary on "Saving the Opel";.
 
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