ou812 wrote:David Vizard wrote:[color=#0000FF]A:- Agreed, but I am running 10/1 plus with moves that make the engine less demanding of higher octane fuel.
If I may ask, what moves do you make to achieve an engine that's less demanding of higher octane fuel? Our here in Ca., we have really poor fuel with 10% ethanol. I've been wanting to experiment with 87 octane fuel but not with customer's stuff....
Just got to your post here. lets see If I can do a quick answer before I have to hit the road.
#1 chamber designs that scavenge better than average. This gets rid of more hot exhaust residuals and allows for a lower temp charge at the time of ignition.
#2 Assuming the right spark plug the exhaust valve is the # 1 cause of detonation. Thermal barrier coatings on the face cut valve temps. So do sodium cooled valves and coated sodium cooled valves are even better yet.
#3 Minimize exhaust valve stem clearances just short of what will seize for sure as closer clearances dump a lot more E/valve heat into a bronze guide.
#4 Use bronze guides not iron.
#5 Use aluminum heads not iron.
#6 The intake valve absorbs more heat than the exhaust valve during the combustion cycle because it is of greater area. that heat is then transfered into the intake charge which is not good. Coat the Intake valve face as an absolute minimum.
#7 Use a good thermal barrier on the intake port and manifold runners
# 8 Better fuel atomization is needed with thermal barrier coated ports. Dyno test alternative boosters in the carb if the atomization is too coarse.
# 9 if the fuel atomization is at or near optimal the spark timing needed will be less. This means the end gases (which is the part of the charge that is last to burn and most likely to detonate) will have received less radiated heat. This reduces the temperature and increases detonation resistance.
#10 Use an intense spark (Might want to read what I have on this in my Holley book ref Amozon.com)
Run the engine block at no more than 170 degrees F.
#11 If it is convenient run reverse cooling
#12 draw in cold air from outside the engine compartment
#13 I am sure there are still more little details I/we do but off hand I can't think of them.
As it happens all of these moves also increase torque.