Oregon Cam #346 - questions

csheehy said
@Jim Kueneman - from my opening "Most of my driving is twisty and hilly back roads at about 40 to 50 mph The other 40% of my travels are highway 65-70." In hindsight, I was clearly missing some details...

I'm not sure of what RPM range I'll be in with the gear change, but like you, I'm not a racer, and don't wind-up the engine, nor do I do donuts - although I may spin a tire now and then - I'm not going to do long-hard burnouts. I'm looking for a stout (torque) street engine. This is a toy for me that doesn't see snow, but I will take it out in the rain.

Ok so your requirements to get the most fun out if it driving and a lumpy cam are at odds. You will loose a some torque where it makes me smile just driving through the country and stepping on it if you want a lumpy idle. Here is just my opinion on what you asked:

OG 346 or 2106 which will not give you a lumpy idle but at minimum 20 ft-lbs loss of torque in the normal grocery getting power band
Modeling says if optimizing for low end torque and using the above cams then you run out of cam before you run out of CFM if you have around a 350CFM carb setup and for low end torque error on the low side
6:1 header.. What is the tube distance from the port to the collector? What is the tube inner diameter?
9.5 vs 9.7 compression ratio is barely a tickle on the graph. The gain is getting it from 7.0 to around 9.0
Larger valves... I did it... would I do it again now I know more? Likely not... It is fun to throw around at car shows but again with a torque cam you run out of cam before you run out of valve for the most part
Lighter valve train can be modeled in the software but it is a second order effect at the RPMs for a torque motor... if you had a 170 with a hyper pak running at 6000 RPM then it may be worth looking at but otherwise better places to spend resources
Torque Converter: if your are not drag racing what does it matter? If you build a torque motor it will come in around 2000-2500 RPM. The factory is what 1800 RPM? I can really feel it turn on at around in that 2000 RPM range so maybe it would be more fun launching it if I had a bit higher stall speed converter but I don't really plan on racing it so the more efficient 1800 is fine for me

The cam, exhaust, get the 7:1 compression up to around 9:1 and a bit more CFM in the carburetor are all you really need to focus on for a torque engine in my opinion based on all my simulation work.