GR650 cam duration specs vs GS400C vs GS500

[Chuck78]

Does anyone know the differences in cam timing/duration on GR650 cams vs GS400C or GS500E cams?

I know the 650 has the highest lift, but I wondered how a GS425 or GS450 would respond with the stock gr650 cams vs the GS400C (highest duration if the 400+ twins' cams so rumor has it).

The 400C cams are allegedly the hottest for high rpm horsepower out of the 400/425/450 cams.

I think the 500 has less duration but a bit more lift, & I know the gr650 has the highest lift of all via mekanix's GS Twins wiki. No valve timing specs have been comoaritively posted here, however.

 

[Chuck78]

I'm slated to build up my GS425 into a modified road racer, but I'm torn on how far to take the engine. I have a spare engine, & I considered trying just some Wiseco gs750 844cc pistons out in one for a 449cc 10.55:1 with GR650 cams and 2 into 1 MAC exhaust and Kerker System K muffler.

The real plan was to build a custom CP piston'd 489cc or 502cc build with resleeved block, ported head with +1mm oversized valves, & Megacycle .380" lift or Web .395" lift cam regrinds on GR650 cores and shim under bucket. GS500 spec Keihin CR33 smoothbore carbs.

That could get quite pricey but that is the ultimate dream there. I could go 475cc JE pistons (re-order of a friend's 894cc gs850 design) to bore straight into the stock sleeves, but if going custom pistons, may as well go as big as the block and cylinder spacing lets me. I may throw together the spare engine with wiseco's or GS850 pistons in the meantime just to see how much performance I can squeeze out of one of them on a budget.

Opinions?

Cam timing specs on 400 vs 450 vs gr650 vs gs500, anyone???

I've heard that the 650 had less duration ascites was more of a cruiser, but had high lift for more torque.