[RallyBob]

Okay, this gets confusing. I don't give out particular part numbers because the parts I use these days tend to be a bit pricier than some people are willing to pay. I don't believe in scraping the bottom of the barrel, even for Chevy parts. Here's a general guideline however.

But to try to answer your questions, I use standard length small block Chevy valves. Retainers are critical to establish spring height. A flat retainer will require a shorter spring than a high-step retainer. I tend to go for a +.080" or +.100" height retainer. When the spring seats are machined for the larger spring diameter, the exhaust spring seat is usually the correct height as it is, but the intake must be milled about .055" (don't take this as gospel, the machinist must establish this...there are variances from year to year and it also depends on valve seat depth). At this point, the spring installed height should be about 1.625" - 1.675".

Depending on camshaft choice, spring pressure should be around 100 - 115 lbs on the seat. Do not exceed 125 lbs, stock rockers will break like china at this point! Open pressure will vary as well with spring choice and valve lift, but stay below 250 for a street engine. I used to run 240 lbs with a .430" lift, 242 @ .050" duration camshaft, and valve float occurred at 8400 with this combo. Should be more than adequate for the street.

Opels have screw-in studs already. You can't use Chevy studs for two reasons. One, the flange from the Chevy stud may interfere with the Opel rocker arm. Two, the Opel stud is drilled for oil flow to feed the rocker arm. If you use a Chevy stud, you stop the flow of oil to the rockers. The rocker will burn up in about 3 to 5 miles. I've had the oil galleys plug up before, it will destroy the entire head. Not pretty.

Bob