Timing recommendations for 12.2:1 E85 408

[dstemmerman]

Given altitude of 6,000 ft (Denver) and my specs of 408 Ohio Crankshaft forged internals, H-rods, JE pistons 12.2:1 compression, custom solid FT 248/255 106lsa, Air-Gap intake, Holley XP 950 running E85 with the new Trick Flow Power Port 190 heads, where would you put timing? We have it at 36, but think we can get more out of her, but don't want to detonate obviously. Any thoughts from experience? We have it fired and it sounds pretty nasty, just haven't made the maiden voyage yet due to tranny linkage. Thanks for your opinions as always FABO!

 

[Willyrd]

Given the altitude, I wouldn't push it more than a few more degrees

 

[yellow rose]

Only way to know how much timing it wants is to look at the plug. Everything else is a guess at best.

 

[B3422w5]

At high altitudes you are losing effective cylinder pressure. It stands to reason the motor would like more timing in the thinner air
That all being said, if i were a betting man and the car was raced at a more “ typical” altitude, wouldn't surprise me at all if somewhere around 32 was where it ran the best

 

[flyfish]

My old 410 combo (almost identical to yours except ported Edelbrocks and less compression and a 750dp) liked 34° the best. That engine ran 10.8's most of the time during the summer.

My current 408 on e85 likes 34° (13:1, ported Edelbrocks, Victor, solid cam with 264/268 duration @0.05, XP 950 e85 carb)....granted, I have not tried giving it more yet. New motor runs 10.4's in the heat (hitting my rev limiter)...hoping for 10.1's in the fall once I replace the rev limiter chip.

 

[anitrowarrior9]

Given altitude of 6,000 ft (Denver) and my specs of 408 Ohio Crankshaft forged internals, H-rods, JE pistons 12.2:1 compression, custom solid FT 248/255 106lsa, Air-Gap intake, Holley XP 950 running E85 with the new Trick Flow Power Port 190 heads, where would you put timing? We have it at 36, but think we can get more out of her, but don't want to detonate obviously. Any thoughts from experience? We have it fired and it sounds pretty nasty, just haven't made the maiden voyage yet due to tranny linkage. Thanks for your opinions as always FABO!

You can advance timing at altitude, typically around 1degree for every 1000ft. I've advanced the cam some too.

 

[RustyRatRod]

I wouldn't go more than the 36 total. Is it locked out? If not, you can give it more initial and limit the total to 36. Either way I think 36 is probably enough.

 

[Toluene56]

I'm at about the same altitude, 4800-5500ft within a few miles in the same city. Right now I have about 34* timing in, locked out. Seems pretty happy at it.. haven't really tried too much more than that.

 

[furrystump]

I would start at 30 and make a run. advance it 2 degrees and make a run and continue until you lose mph, then back it up 2 degrees. Wait so you are happy at 36? I would start at 34 if you pick up mph at 34 go to 32. If you lose mph go to 38 if you lose mph at 38, then you know 36 it is. Then you can try 1 degree changes, but you really need a couple of runs at each to see any real change. At 1 degree there are just to many variables that can throw you off. Most dampeners are not that accurate so trusting the exact number can be troublesome.