CR ratio and performance

[Anonymous]

hi guys, i have a question refering to aussie 170, its compression ratio and performance, the aussie 170 had 101 hp@4400 rpm and 8.7:1 CR with a top speed of 98 mph (maybe i´m wrong, dont remember now), 17 sec 0-60 mph and 20 seg 1/4 mile.

mi argie 170 had 101 hp@4400 rpm and 7.2:1 compression ratio , 87 mph top speed , 20 seg 0-60 mph according to 1965 tests.

i dont know why producing the same HPs, one have more compression ratio and runs faster than the another (ok, both cars doesnt have same gearbox and diff relations but my question is about CR ratios), if i work on the head to make 8.7:1 CR i dont think that´ll be good for pistons also i´m worried about detonation with regular fuel and that level of CR...

 

[addo]

Yayo, I would be suspicious about the numbers for the Australian motor. Don't use it as a reference source. Raise your compression a little; depending on what grade of fuel you can afford. Duraspark ignition will help it, too.

 

[Anonymous]

thanks for your answer, here we have 97 oct fuel, and 100 oct too... can i raise un point of compression?? from 7.2:1 to 8:1 or 8.2:1...

 

[Asa]

there are a couple guys here are running about 9:1 and are getting by with pump gas
our highest is about 91-93

it might be possible that octane ratings down there are determined differently

 

[addo]

I assumed that fuel in Argentina is like Australia - often illegally diluted with cheap additives. That would suggest that even though you can get 97 rating, treat it like 93, and not more than 9.3:1 compression. If you aim for 9.2, then you have a little room for mistakes.

Will you be using the standard cam? How many km on the timing chain? The factory ones stretch badly with use, and this can alter your effective compression. There is probably a local improved one available; it would cost about 320 Pesos to import an Aussie set.

Regards, Adam.