Power vs timing

[FreeBeeTony]

A little disappointed in the wot of my rebuild. Seems very torquey around 4K and stops at 4400.
seems like there is more in there! Can I increase the timing?

 

[greno]

Depends on what cam you put in there.

 

[FreeBeeTony]

Otd a comp cam XM270HR

 

[greno]

With that cam you're going to need about 16 degrees of initial timing. And you should have about 32 degrees all in.

 

[greno]

Run 93 octane while you're getting it dialed in. A little extra protection against detonation. Once you're close then you can go back and run 89 or 90.

 

[greno]

Set your advance curve on your distributor spring-weights / MSD module / or ECU to be all in by about 3K. You can play with this for a little sooner but just keep out of detonation under full load.

 

[FreeBeeTony]

Went down to the boat tonight.
Found the carb secondaries were not totally opening, adjusted appropriately.
Also checked the timing.........hadn't checked it since I had it running outside the boat, was only set @ 6* BTDC, adjusted to 10*........too choppy to take a ride.
Will check tomorrow and report.

 

[greno]

That cam, dialed in, should work real good for you. I put a very similar cam in mine years ago and was very happy with it.

 

[FreeBeeTony]

Went fishing today...........got skunked!
Checked WOT and I'm at 4700RPM now that carb is fully opened and timing adjusted to 10*BTDC.
Really want to go up in pitch on the prop,,,,,,currently at 17", would like to try a 19".

 

[Bondo]

currently at 17", would like to try a 19".

Ayuh,...... I'd stick to what you've got,.....

4700 rpms is 'bout ideal for power, 'n efficiency,....

Yer below peak by 100 rpms,.... bigger prop will lower the rpms, 'n probably not raise mph,.....

 

[FreeBeeTony]

Tried the prop from the donor boat, also a 17P........stainless steel.
Picked up 3-4MPH mid range and lost ~300RPM at WOT.
WOT now 4400RPM..........going to leave it like this......never run @ WOT......usually 3800-4000.