Compression ratio question.
2nd Gear Member
Joined: Mar 2004
Posts: 392
From: Arizona Desert
RE: Compression ratio question.
I believe the big advantage to dished pistons is that you can push the compression a "little" higher while still maintaining a good valve clearance.
[sm=gears.gif]
Pro. B.S. caller outer
Joined: May 2004
Posts: 9,644
From: IL
RE: Compression ratio question.
ORIGINAL: Soaring
OK, makes sense, but why do most hot rodders prefer the flat tops?
OK, makes sense, but why do most hot rodders prefer the flat tops?
2nd Gear Member
Joined: May 2004
Posts: 349
From:
RE: Compression ratio question.
The main reason flat tops are popular today is poor gas. Back when I started fooling with cars you could get good gas like SUNOCO 260. Back then pop tops were king and people were running 12.5:1 compression. Those high compression engines would go from idle to wide open and back to idle almost instantly. Those were the days. You can't run todays gas in one of those engines. 11:1 is about as much as you can get away with today.
Thread Starter
I ♥ Acer
Joined: Oct 2004
Posts: 17,565
From:
RE: Compression ratio question.
ORIGINAL: 67coupe
The main reason flat tops are popular today is poor gas. Back when I started fooling with cars you could get good gas like SUNOCO 260. Back then pop tops were king and people were running 12.5:1 compression. Those high compression engines would go from idle to wide open and back to idle almost instantly. Those were the days. You can't run todays gas in one of those engines. 11:1 is about as much as you can get away with today.
The main reason flat tops are popular today is poor gas. Back when I started fooling with cars you could get good gas like SUNOCO 260. Back then pop tops were king and people were running 12.5:1 compression. Those high compression engines would go from idle to wide open and back to idle almost instantly. Those were the days. You can't run todays gas in one of those engines. 11:1 is about as much as you can get away with today.
I also dug up a simple mathmatical formula to figure compression ratio. Simple algebra.
http://e30m3performance.com/myths/mo...comp_ratio.htm
1st Gear Member
Joined: Jun 2004
Posts: 83
RE: Compression ratio question.
Hey cool, that was the concept I posted earlier (now I have the algebra). I believe the difference in the fuel from yesteryear was the octane rating. If I recall correctly '60s fuel was around 120 for an octane rating where today it is usually under 97.
2nd Gear Member
Joined: May 2004
Posts: 349
From:
RE: Compression ratio question.
After all the smog equipment was added and compression ratios dropped in the mid 70's there was no need to make the higher octane fuel anymore. You can still by racing fuel at the track or speed shop, but it's about $4.00 a gallon.
Thread Starter
I ♥ Acer
Joined: Oct 2004
Posts: 17,565
From:
RE: Compression ratio question.
ORIGINAL: 67coupe
After all the smog equipment was added and compression ratios dropped in the mid 70's there was no need to make the higher octane fuel anymore. You can still by racing fuel at the track or speed shop, but it's about $4.00 a gallon.
After all the smog equipment was added and compression ratios dropped in the mid 70's there was no need to make the higher octane fuel anymore. You can still by racing fuel at the track or speed shop, but it's about $4.00 a gallon.