I have been over committed for the last couple of months and I missed this go by back in November. Hopefully this will still be in time to help.
First, you made no mention of brakes. DO THE BRAKES FIRST… Go to the tech topics on my web site www.tgsi.com
and read, “Give Me a Brake”. Go with everything new or rebuilt… professionally rebuilt. (I don’t rebuild any of the brake stuff myself). Don’t try to save any bucks here… your bodywork will thank you for it.
If you have not already done it, get the SCCA rulebook and read it… no… study it. You should get to the point where you have dissected and analyzed every sentence applying to ITB. You should know the rules better than the “SCCA tech person” when you go racing. Then analyze every part of the car “bumper to bumper” and consider how you can improve it while staying within the rules. Creative thinking here can go a long way. Keep the rule book handy and every time a new idea comes up re-read the rules and see if the creative thinking will be within the rules.
For your first couple of years making your car reliable will be the most important thing you can do. Your weekend will be ruined and you will not improve as a driver if you spend your weekend trying to patch together the car. ITB cars in general are very reliable when properly prepped. But with our 30+ year old cars, the little things will keep you off of the track. Replace every bushing, bearing, ball joint and any other part that can wear in the car… again bumper to bumper. When you take to the track, your car should not be a used car… it should be remanufactured.
Cooling is indeed a problem.
First the easy and free stuff. No fan… stock or electric. At race speeds a fan is just in the way of air trying to pass through the radiator. Get rid of the thermostat and don’t use a blanking plate. (A lot of experts from places like FLUIDYNE and RON DAVIS RACING RADIATORS will tell you that you must have a blanking plate… NOT SO FOR OPELS… and several others).
Now the not so easy or free stuff. The ITB rules require you to retain the heater core so make good use of it. The heater core is just another small radiator so make sure it is really good and that the “rebuilt” heater fan works very well. Yea… this will put a lot of heat into the drivers compartment which you DON’ WANT, but it is taking that heat out of the engine. Here’s an area where being intimate with the rules pays off… ducting for driver comfort is allowed. So with the rules in mind take care of the heat.
I’ve left the most expensive cooling stuff until last. You MUST go with a new radiator and an under drive water pump pulley. Neither of these will be cheap if you do it right… neither is a “fried engine” if you don’t do it right. At the risk of blatant commercialism, we (TGSI Racing) have the stuff to do it right so contact me directly by email. And if you don’t get it from TGSI, then go to someone who does racing stuff professionally. This is not a place to save money on the cheap stuff.
Since the “money topic” keeps jumping up, I might as well say it now. You’re building a race car, not a junk yard “banger”. Don’t try to do anything the “cheap” way or it will end up costing more… the cost to do it the cheap way first and the second cost to do it the right way and throw away the cheap stuff.
Back to the car… Transmission and differential.
The rules require you to use a stock 4 speed and if you have a good one it is perfectly adequate from a reliability standpoint. But if it is “tired” it will let you down. You really won’t know until you put it on the track. So the best thing I can recommend here is get a spare from the Opel GT Source. They have tested used transmissions in stock.
The stock rear end is fine from a reliability standpoint as long as it hasn’t been abused. If it is starting to howl then you will need another one but other than that it should be fine. The rules allow you to go with a “locked” (welded) or limited slip differential. The only option here is go with a limited slip Quaife differential. (contact me for current pricing) DON”T go with a welded differential even though it seems the “cheap way out” (RE above). In this case the “cheap way out” is also slower. A locked differential costs about 5 HP while cornering… you have to scrub the rear wheels through a corner… so on corner exit or in the sweepers when you’re trying to accelerate you’re giving up the HP you can’t afford to give up. So until you’re ready to “pop” for the Quaife, stay with the stock differential.
Torque tube/Central Joint.
You should completely rebuild the central joint with the “good stuff” from the Opel GT Source including “heavy duty” donut. They (OGTS) are back ordered for a couple of the pieces but wait for them to come in and do it right. Plan on rebuilding the central joint after every season of racing.
The last piece of advice I’ll give for now is don’t think that ITB racing will be cheap or easy just because it is a supposedly “lower” class. In most areas of the country, “IT” racing may be the most intense and competitive class in SCCA. And while “IT” may offer the most “racing for the buck” of any class, it will cost a lot to run “up front”. Those that run “up front” will have their car prepped as well as if not better than a lot of “National” cars.