+4 timing advance recomended ?

[yamaha4life45]

I got a welded crank, drag port, cool head with 19cc domes, vforce 2 reeds, shearer pipes and filter with stock airbo. Could i adjust the timing and still run 91 octane fuel or would i have to run race fuel and if i did have to run race fuel would it make a significant difference with the timing advance ? Thanx in advance !

[shee2000]

u should be fine

[toytech]

have you done a compression test? anything over 150 should run race fuel.

[yamaha4life45]

Yea ive checked it and its around 145. So i should b good aslong as my compression is under 150 to run pump gas ?

[georgie]

Yea ive checked it and its around 145. So i should b good aslong as my compression is under 150 to run pump gas ?

 

If your plugs start to back up, then you got detenation going on. you'll need a 50/50 mix with race fuel.

[toytech]

Yea ive checked it and its around 145. So i should b good aslong as my compression is under 150 to run pump gas ?

 

with +4 timing and 145 comp you should be ok

[mopar1rules]

have you done a compression test? anything over 150 should run race fuel.

 

i still get a kick outta guys that think compression testers are what's used to determine the octane needed for a motor. you need to compare total volume in cylinder (full stroke volume + deck height volume + head volume, which is all volume above the piston, when its @ BDC) to the trapped volume (all volume above piston @ TDC) to determine octane required. there's a few more little factors, but that's the main one.

[Sandfrk33]

i still get a kick outta guys that think compression testers are what's used to determine the octane needed for a motor. you need to compare total volume in cylinder (full stroke volume + deck height volume + head volume, which is all volume above the piston, when its @ BDC) to the trapped volume (all volume above piston @ TDC) to determine octane required. there's a few more little factors, but that's the main one.

Is there a way to figure out the compression ratio if you know bore/stroke/dome size? Or does it have to be apart to figure a correct ratio