255 pistons quickie
- Thread starter 80Stang
- Start date
rickwrench
Famous Member
Stock 255 pistons are 1.5cc.
Rick(wrench)
Rick(wrench)
rickwrench
Famous Member
Silvolite lists the piston as 1.5cc "dish" so I think its for the entire piston.
http://kb-silvolite.com/index2.php
Go to the Silvolite products tab --> pistons and look for the engine or diameter (3.68"). Lots of other pistons to look at and bench build engines with.
Rick
http://kb-silvolite.com/index2.php
Go to the Silvolite products tab --> pistons and look for the engine or diameter (3.68"). Lots of other pistons to look at and bench build engines with.
Rick
80Stang
Well-known member
Thanks. Just looked at one piston in the morning and actually there are two smaller reliefs and two bigger ones --- I'll measure to be sure.
I'm at the edge of spending $200-250 on the dishes, unless somebody convinces me that 11.60 CR is great thing to have --- or does 10.80 make any difference anyway...
Being more analytical; save the dish-work money, and boost the octane instead with t________ which I have access to. Costs 2x gasoline, used 4% in the mixture means about $5 more cost per 100km (61mls), so the dish-work price will be zeroed in.....4000-5000km. Being a hobby vehicle, that would be one season only.
Result: it is worth lowering the CR to level suitable for our best pump gas, but maxed out. About 10.80 is my goal.
I'm at the edge of spending $200-250 on the dishes, unless somebody convinces me that 11.60 CR is great thing to have --- or does 10.80 make any difference anyway...
Being more analytical; save the dish-work money, and boost the octane instead with t________ which I have access to. Costs 2x gasoline, used 4% in the mixture means about $5 more cost per 100km (61mls), so the dish-work price will be zeroed in.....4000-5000km. Being a hobby vehicle, that would be one season only.
Result: it is worth lowering the CR to level suitable for our best pump gas, but maxed out. About 10.80 is my goal.
The pistons I cc'd several years ago measured right at 1.5cc, confirming the Silvolite info. A dish would be good, but it would have to be a big one. Opening up the chamber and fully relieving those valves would be a better way to enhance breathing and gt the CR down to a reasonable level while maintaining quench.
scare bleu! I know lots about Tolulene. It's a Benzene base chemical thinner which has been used for years as an octane booster. In my opinion, its worse than tetra etyhl lead in terms of environmental risk. Over here in New Zeland, our aromatic hydrocarbon level is so high, a four gas anayliser goes of in any busy street in my town.
Despite my philosphical dislike of the stuff (born through three years as a tar macadam/Bitumen/emulsion technician), I think compression ratio increases are okay as long as the engine is optimised to suit. All tests on conventional GM V8 engines show that increase in compression with no cam optimization causes a loss in peak power. Past 10:1, volumetric efficeincy drops as CR goes up, if the cam isn't optimised to suit. In the case of an old dunger postwar car, going from 6.8:1 to 7.8 or 8.8:1 gives half the % increase in power. Above 10:1, you must optimise the engine to suit, and you don't see those increases unless you add camshaft duration, lift and overlap.
The reason is that if he engine is on the cusp of detonation at 8.8 or 9.8:1, then at 10.8:1, you'll be right on to it, even if you octane goes up from 96 to 105 by the addition of tolulene. To use 10.8:1, you've got to retart cam timing to get cold cranking compression below 190 psi. Then you may have to fiddle with ignition timing.
The plus is that any engine with any compresion increase always yields significantly better part throttle fuel consumption.Peak power may flat line, but part throttle economy goes up.
Despite my philosphical dislike of the stuff (born through three years as a tar macadam/Bitumen/emulsion technician), I think compression ratio increases are okay as long as the engine is optimised to suit. All tests on conventional GM V8 engines show that increase in compression with no cam optimization causes a loss in peak power. Past 10:1, volumetric efficeincy drops as CR goes up, if the cam isn't optimised to suit. In the case of an old dunger postwar car, going from 6.8:1 to 7.8 or 8.8:1 gives half the % increase in power. Above 10:1, you must optimise the engine to suit, and you don't see those increases unless you add camshaft duration, lift and overlap.
The reason is that if he engine is on the cusp of detonation at 8.8 or 9.8:1, then at 10.8:1, you'll be right on to it, even if you octane goes up from 96 to 105 by the addition of tolulene. To use 10.8:1, you've got to retart cam timing to get cold cranking compression below 190 psi. Then you may have to fiddle with ignition timing.
The plus is that any engine with any compresion increase always yields significantly better part throttle fuel consumption.Peak power may flat line, but part throttle economy goes up.
80Stang
Well-known member
This old topic relates to another topic
http://fordsix.com/forum/viewtopic.php? ... highlight=
which highlights my plans more. Now when we are done with cc'ing the reliefs here I'd say we continue there...thanks!
I'll post there the new thoughts.
http://fordsix.com/forum/viewtopic.php? ... highlight=
which highlights my plans more. Now when we are done with cc'ing the reliefs here I'd say we continue there...thanks!
I'll post there the new thoughts.
Similar threads
All Small Six
1962 Falcon - Swapping a 170 for a 200 plus C4
