you know it does seem odd that it works that way and the new 450 with 12-1 that will run pump gas

 

If you guy's may have read some of my previous posts the Compression ratio is off on most of these pistons. The Samcoe 12:5:1 piston is actually more like an 11:1 piston and So on and so on. With maybe the exception of Mr. Horsepower, no one has actually CC'ed the these motor's with the new piston. Turn's out with the a 12:5:1 compression piston you have to deck your head .030 do get it at an actuall 12:5:1 ratio. All this info was provided thru COpe Racing out of Florida, they are the Shiznit like Vance & Hines in Motorcycle engines. They did some work to Big Baja's bike and this is what they found on his setup. I always wondered why I could always get away with running 101 octane with out worrying about it.

 

Does that then mean the my 11.5 is really 10.5? how about the stock 9.7 or what ever? is that accurate? with that said could someone run a 12.5 and be fine on pump gas as it would only be 11.5 in reality?

 

I am not exactly sure about the Ron Woods stock bore piston or TVI's but I know at least with Samcoes's piston you probably could. I ran 101 in my stock bore with a 12:5:1 TVI piston and according to Dcryder he said there were some small pits in the intake side probably from Detonation. If that is the case than I would say that TVI has the closer to true Compression numbers. And you wouldn't want to run lower than 100 octane with that one. If you could afford it that VP Ultimate 4 would be good all the way up to 12:1 ratio. I think we should get some more input from RWR ANd TVI and find out if they CC'ed there engines with these new pistons, because I know Samcoe hasn't.

 

what is the Piston to valve clearance on the 14:1 piston with stock valves?? anyone.






Bigger.

 

My 14:1 is the 1st gen and its probably a lot more close to 14.5:1 than 14:1. However, I'm pretty sure that the 2nd gen is pretty close to 14:1.

 

Marky, how do you know? I mean what is your PSI? I would think it should be up around 290/300lbs.



Bigger.

 

my new piston is about 13-1 but i couldn't tell you what the pressure is but man did it wake things up, i think these builders with the higher compression are onto something, i want to see how that 16-1 seals i bet it is insane on power,

 

I checked a 12.5 piston today and it had 5cc of positive dome and pin heighth would set it at zero deck. After doing the math this comes to a grand total of 10.1:1 actual compression ratio with a stock unaltered cylinder head.


I think compression ratio should be given using the cc's of a stock unaltered head with stock valves at factory seat heighth. Anything other than that would be speculation.


MrHorsepower

 

So (ahem) what do you think the 14:1 is?