[blueghoast]

Pump gas and compression; With these big cams there is a lot of bleed-off
from the high percent of overlap which in turn lowers compression and
with the alluminium heads which you can run more compression makes it
able to get away with the higher compression if that makes any sense.
All I kmow is that it works for me and a lot of my friends in the same situation
I've always used race gas when dynoing my motor for the ease of reading
the plugs, they stay cleaner but the next time I use the dyno I'm going
to run pump gas first and the race gas and maybe even E-85 just to see
what kind of power it makes over gas.
And some thing I've found that usually any thing under 200LBS of
cranking compression is usually safe for pump gas. I hope this helps
any one trying to run pump gas and higher compression.

GT

[Dragncar]

Originally Posted by blueghoast

Pump gas and compression; With these big cams there is a lot of bleed-off
from the high percent of overlap which in turn lowers compression and
with the alluminium heads which you can run more compression makes it
able to get away with the higher compression if that makes any sense.
All I kmow is that it works for me and a lot of my friends in the same situation
I've always used race gas when dynoing my motor for the ease of reading
the plugs, they stay cleaner but the next time I use the dyno I'm going
to run pump gas first and the race gas and maybe even E-85 just to see
what kind of power it makes over gas.
And some thing I've found that usually any thing under 200LBS of
cranking compression is usually safe for pump gas. I hope this helps
any one trying to run pump gas and higher compression.

GT

When you dyno it next time, what do you think about running race gas first and get you max power number. Then switch over to pump gas. If my theory is right your power should be the same or go slightly up if you are not detonating.
E85 you are going to need a different carb unless you want to do a bunch of work on dyno time. It would be cool to compare it all.
I am a pump gas guy and my High Port 461 is 11.5-1 static CR. I have started out with 99 octane mix and will go to a 95 mix, Finally 92 all pump gas if everything looks good.
It cranked 175 psi, but that was before the engine was ever started. It might come up a tad with broken in rings.
Can you post a cam card ?

[Skip Fix]

My RAIV 400 I was racing in the old NMCA Top Stock had no audible detonation on pump gas but picked up 8 hp on race gas at it's 10.25:1.

[tom s]

If it picked up HP it NEEDED it!Tom

[ponjohn]

Originally Posted by blueghoast

Pump gas and compression; With these big cams there is a lot of bleed-off
from the high percent of overlap which in turn lowers compression and
with the alluminium heads which you can run more compression makes it
able to get away with the higher compression if that makes any sense.
All I kmow is that it works for me and a lot of my friends in the same situation
I've always used race gas when dynoing my motor for the ease of reading
the plugs, they stay cleaner but the next time I use the dyno I'm going
to run pump gas first and the race gas and maybe even E-85 just to see
what kind of power it makes over gas.
And some thing I've found that usually any thing under 200LBS of
cranking compression is usually safe for pump gas. I hope this helps
any one trying to run pump gas and higher compression.

GT

Could you, run lower static compression, smaller cam to build more dynamic and end up at the same place, power wise?

[Tim Corcoran]

With a longer duration cam the valves are open for a longer period of time allowing more complete cylinder filling and more time for exhaust scavenging which increases volumetric efficiency (VE). With both valves being open longer during overlap allows the gas discharge to speed up and creates a super charging effect which further increases VE especially at peak torque RPM. Also the more compression the more VE. With a smaller cam and lower compression all these properties decrease so to answer your question, NO.

[65madgoat]

Black Friday sale will have them at 40% off. Get on it.

[Tim Corcoran]

Originally Posted by 65madgoat

Black Friday sale will have them at 40% off. Get on it.

What is 40% off?

[65madgoat]

Speedmaster parts(heads etc)... what title of thread is

;-)

[Tim Corcoran]

Where are they 40% off? I looked at Summit and they are more than eheads

[65madgoat]

Friday on Speedmaster website

[blueghoast]

I'll get that info up soon for everyone.

GT

[Johnny406]

Sale is on now!!

[performerrpm]

i just ordered a set of the bare cnc 78cc heads and guide plates.....shipped total was under 1400. with the money saved i can put good valves and springs in.

[mrennie]

Sale is on the Speedmaster site.

[Skip Fix]

The HR springs that came with mine were OK. Machine shop did not like the locks though but retainers were OK.

[65madgoat]

CNC 78cc for later reference when guys who buy them today try to sell them for more later. ha

[performerrpm]

it dont seam like the sm heads carry a good resale value like the eheads and kre's. i think its best to buy those if you know you can use them and get your monies worth

[Skip Fix]

Black Friday on 9" pumpkins too.

[Tim Corcoran]

I just placed an order for a set of the 78 cc bare heads and guide plates. I could not resist the black Friday price, I guess this will be my Christmas present to myself. I should buy 10 sets and let them sit for a couple years then re-sell them.