Degrees of total timing for peak horsepower

[Mark Aubele]

Thought it would be interesting to have a thread where people could discuss what total timing they arrived at through dyno testing, or track testing to arrive at maximum horsepower for different cylinder head applications. For example, on my old P headed combo we saw nearly no difference in peak or below the curve between 32-36 degrees of total timing, so we of course decided to run it at 32, and could actually get away with 87 in the tank every once in a while. My current TW headed combo seems to like a bit more timing, and is very sensitive to changes whereas the P heads really didn't care over a very wide range. Unfortunately, an issue with the summit balancer not discovered until I was at the dyno already prevented me from knowing the exact number the car made 347 hp peak at (stock short, N91, TW's, Victor jr, 750DP, and the wrong plugs, too short, I am an idiot) we just had to get close an move it back and forward until we arrived at a number. Anyone have any data they would like to add? Not too interested in initial, the standard "pull the spout and set it at 14" has been discussed many times.

[Killercanary]

My current 9:1 AFR 185 comp headed 331 makes peak at 36*. We tried pulling it down to 34* and it lost HP and TQ. My dad's NA 347rwhp 302 made peak at 36* as well.

[somethingclever]

36 deg on an iron headed (C8VE) BBF. Made no additional power at 38deg...lost 10 at 34deg. Bore is 4.36" and CR is 10.5:1.

[97LaserRed]

Yes I'm very curious what these 5.0 run. Timing wise.

[Martin0660]

Here is a capture of my table ... remeber it's a big boost, 140 cubic inch, iron head combo :laughing1:

[sutyak]

Bob what's your compression ratio?
Mine's 10.1:1 and with 10psi I can only run about half that amount of timing before I get deto.

[Martin0660]

Bob what's your compression ratio?

Mechanical is 8.0:1


Mine's 10.1:1 and with 10psi I can only run about half that amount of timing before I get deto.

For sure, and remember you have a MUCH better head design ... I am pretty good at 25 psi on pump gas with that compression, seems that going to 9.0:1 would boost limit me to about 20 psi with some assumptions. I could only imagine 10.X:1 With the new fuel capabilites (80# injectors) I will be playing with more boost and see if I need to take away timing.

EDIT: sorry guys, just saw this was in the pushrod section, didn't mean to jac your thread.

[Mark Aubele]

No thread jack, very interesting post!

[yeahloh95]

my friends 93 stock short block liked 10 deg. initial we had it at 16 and kept backing it off on dyno and making more power , this was with tw track heat heads

[Mark Aubele]

My present combo oddly likes a ton of timing. I'm at 38 degrees total now. Will be ghetto tuning tomorrow morning by trap speeds at the hillclimb this weekend.

[Balaska347]

My TW headed 347 na with 10.25CR likes 33-34 didnt make any more power on the dyno by increasing the timing.