Rage

What is the optimum A/F at WOT for a naturally aspirated EFI gasoline marine engine running 87 octane to get maximum HP with out detonation? The 496 versus 502 BBC are the two engines of primary interest.

TylerCrockett

iTrader: (1)

If you have aluminum heads you can get away a little leaner. But over all I like to see 12.8 to 13.2 to stay safe. we run are blower motors at 11.8 to 12.0. You could also look at cylinder temps with the air fuel to double check yourself.

Rage

Thanks for the info.

How does one check the cylinder temperatures and what are the temperatures that indicate bad fair good best?

TylerCrockett

iTrader: (1)

Livorsi makes a EGT gauge.

articfriends

iTrader: (1)

I had gaffrig/livorsi egt gauges with temp probes on my lightning headers and they read 200-250 degrees HIGHER than actual temp,hopefully they have straightened that out but mine were about usueless,Smitty

Rage

What should the exhaust temperature range be?

articfriends

iTrader: (1)

1150 to 1250 is what I have always heard,1330 is melt down. My gaffrig egts read 1500-1600 degrees all the time on my old blower motor so it was obvious they were useless,Smitty

2112

On a closely related topic, does anyone know the formula to determine the amount of fuel needed for a specific horsepower? Trying to determine GPH of fuel pump. I have alway just gone overkill in the past.

MYSKATER32

EGT Temp. vary wildly depending on how far the prob is away from the exhaust valve.On a dyno the probes are usually 6 inches from the valve.This is hard to do on a marine water jacketed header. I had mine in the exhaust port next to the header flange,i saw temps in the 1700*range.The dyno showed 1300*with the probs 6 inches downstream !

Rage

To be blunt, given the variability of EGT measurements emntioned as a function of the distance from the combustion chamber, it would seem that all it is good for is cylinder to cylinder EGT balance check. Are there EGT numbers for that?