Valve sizes
 

Experienced fellow Pelicans,

Recommended valve sizes for a 1.9, running Web 86 cam, 0.035" deck height, 54cc combustion chambers, Weber 40's, SoCal climate? BTW, it's going in a 69' IRS Bug.

I'd say 42 x 36 just like a stock 2.0 .

The "old rule of thumb" is small valves make torque and no rpm and large valves make HP and high rpm. It is a matter of increasing the volumetric effeciency of the engine.

I do know that if you only change the valves, you aren't doing the total job as you have to take into consideration the modification of the entire intake and exhaust tract to realize the full potential of a valve change - Can you say MONEY!!!!!

Even the 2.0 had larger intake/exhaust tract diameter than the 1.7/1.8 to take advantage of the larger valves.

Stock 74 bus heads are what you want to use 021.101.371H 41 x 34 these will give you more comp. with the dished pistons you are running. With flat top and .035 you are at 9.2 to 1 even with the RX-7 oil cooler I put on Bills Bug ( this is my old Bug that I got from Bill Culver a WW-2 P-51 Pilot and a really nice guy who passed away in 1995, He bought the car new and then gave it to me when he could not drive anymore. When I had it I always called it Bills Bug As In the Surfs up let go to Malibu I will drive Bills Bug). I would use .045 which is 8.9 to 1.
Call Rick Conemac he has a set. Steve


For Engine Capacity and Compression Calculator

http://www.aircooled.net/gnrlsite/resource/specgeninfo/calcs.htm

You might also want to buy the Engine Analyzer Plus software (or the Professional version) to help design your motor. It's fun to play with and with the Plus version you can even enter full flow curves for the head ports.

I already bought brand new unused heads, flycut for 1.8/2.0, with 39x33's.

At this point I'm at the point of no return for deciding to go 1.9 or 1.8...