Originally Posted by opelwasp
sorry i was not clear bob. i am currently porting a 1.9 head with 2.0 int/exh valves in it. i would like to effectivly grind off the the whole shebang. but i dont want to remove too much of the guide if it will adversly affect reliability or increase posable component failure. and if done, what is the worst that could happen on a street engine?
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Okay, on a 1.9 head I wouldn't grind the intake guide completely away. It seems to do better with a small bump 'in the way'. For the intake port, try to make the guide area look like a GT hood bubble, with the round side facing the port opening, and the tapered side facing the valve opening. In fact, basically 180 degrees off from what I've done to the 2.4 exhaust port in the pics I posted.
The exhaust of a 1.9 is VERY efficient, it can outflow the 2.4 head with ease, so my suggestion is to basically knock 1/8" off the top of the guide and just blend it in. Don't get crazy. If you improve the exhaust flow too much, the EGT's get higher, and the ports/guides/valves will run hot. So in this case you
need as much guide as possible for heat transfer.
You didn't mention your cam profile or spring rates, but aggressive cams and/or high tension springs will put a ton of side-loading on the valves, and will wear the guides accordingly. So a shorter guide will wear even faster if you have these modifications. Based on this, yes, racing Opel heads wear guides pretty fast. Shortened guides, big cams, stiff springs....probably need guides replaced every 2-3 years (about every 500-750 miles!). But if you don't go crazy and leave the guides basically there (streamlined), with a street cam and modest springs you should get 50-60k out of a set of guides in a performance engine with hard use.
Synthetic oil helps a lot BTW, high heat really kills mineral based oils, and self-metering viton seals really kick ass too.
Bob