Dead on top end.

ChuckZZ

Member
Just rebuilt a flathead that has run very well in the past. 07-03 cam .006 lash 30* timing .049 jet. I am testing it on a water brake dyno (analog) that I have never used before. No smoke, no blowby. Low end seems stout, 9.3 ft lbs torque @ 4200. The dyno says it is dead @ 6500 with only about 3 ft lbs of torque. My best guess is I messed up the timing or it has slipped. Can anybody think of anything beside timing? After posting I am going to put on a known quality animal for testing for comparison as I do not have another flathead. I set the timing with a degree wheel and then find a key I can tap in, in this case I used a #6
 
Last edited:
Valve springs @ 18 seat pressure. My intent was to set timing at 30 but I failed to make a mark on the flywheel using a timing light. This motor sat for at least ten years never being run. Used it last year and it ran great but the rings got wiped out from rust. Even with bad rings it rad well but with lots of blowby and would foul plugs. I set timing with a degree wheel and then fit a key to tap in so I doubt the flywheel slipped. It was a #6 key. Even though I have my best flowing carb on it I think I will try another one before I attempt to re-time without removing the head (just used my last head gasket). Any, and all input is certainly appreciated.
 
Springs sound soft for a stocker that you want to turn up in rpm. Try something like 21.5# IN, 18.5# EX and see if that helps.
07-3 is a real finicky cam on set-up. I've found some engines like tons of ignition advance and others very little. I've also seen 0.5* totally wake up an 07-3 cammed engine on the dyno. You're going to have to experiment some on your own, but for sure, I'd bump up the spring pressures.

🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Back
Top