[n2oracer]

If you were tuning a new engine that had not been on a dyno, where would you start ? Jetting, timing, or shift RPM?

 

[Tanner]

I would set all in timing to 36 degrees as a moderate setting. Choose a shift point (didn't give cam info to determine valve float point), and from that point keep these two variables constant as I jet the carb for best mph.

After carb sweet spot is pin-pointed, I'd see if I could make anymore power by increasing the timing 2 degrees at a time, but better to be safe in this area. Back it off if you start to lose mph, see flecks on the plugs, or hear any detonation.

I personally have always kept my shiftpoints low, say around 6,500 or so. I don't feel I'm losing more than a hundreth in ET, but hopefully helping my motor's longevity in keeping the rpm's down.

Good luck, and have fun!

-Tanner

 

[Butch Kemp]

36 degrees would burn my engine to the ground.

 

[ROB]

36 degrees would burn my engine to the ground.

Exactly.

Don't ever pull a number out of the thin air for spark advance requirement of a cylinder head that you are lost with.

What head is on the engine?

What is the compression ratio?

How big is the cam?

What are the valves made of?

What is in the lower end?


You can't ask for a recommendation without providing any critical information up front.

 

[n2oracer]

Thanks guys. Here's a little more info.

482" BBC
990 rect heads
12.5:1
276/287 .790/.731 110LSA
1050 dominator

jetted 92 square no PV
38* timimg
7200 shift
approx 600 HP
3350 lbs

1.41 60'
6.43/105.96
10.16/130.96

 

[farrigno]

big diff between your butch's head and 990 rec ports,i'd say where you are is a very safe start........been there done that.

 

[n2oracer]

How much timing did you end up running when you had the 990 heads?

 

[farrigno]

with the big domes i had,38-40,depending on the air quality.

 

[n2oracer]

The car has a glide w/ a transbrake. The converter flashes to about 5400. The shift recovery point is 5900. I think I'm about 4-600 low on the flash RPM from where it needs to be. The builder was looking for about 5800. I guess the big cam killed the midrange and it ended up flashing a little lower. I plan on having it adjusted after I get it tuned a little better.

 

[farrigno]

are you gonna spray it??

 

[farrigno]

also why do you run a glide?who makes the conv.?

 

[n2oracer]

The converter was built by Cameron @ Torque Converter Services in Columbia, SC.

I plan on spraying the car eventually. I have another converter that was built for nitrous. I really want to get the car into the high 9's on motor. I just got back in the seat after a 7 year break. My last car ran 11.40's, so this has been a blast.

 

[farrigno]

not familiar with the converter guy, i would lose the glide, go to a t-400 maybe try a diff conv, you seem to have enough power to run in the high 9's on motor...all this is just my 02.

 

[n2oracer]

Just a little update. I reached my goal last October. Here's a rundown of the pass.

60'.......1.35
1/8.......6.30/107.5
1/4.......9.98/132.5

 

[Looey]

...did you ever try shifting at a lower rpm, say 6500-6800. Is it pulling hard to 7200? It just seems like a lot of rpm, and if the engine hasn't been dyno'd you wouldn't really know where it makes its peak hp, who knows you could be going 500rpm past the peak power, which just uses up track.
Just my .02 :-D

 

[farrigno]

Just a little update. I reached my goal last October. Here's a rundown of the pass.

60'.......1.35
1/8.......6.30/107.5
1/4.......9.98/132.5

see, nice numbers,where was the timing?
and jetting!how about shift points??

 

[n2oracer]

All of the tune was the same ... 38*, 92 square, and 7200 shift.

On the shift point, I gained 1.7 MPH going from 7000 to 7200.

 

[n2oracer]

I didn't make any changes to the engine tune. I chased an intermitent miss and not starting problem through out the year. I put in a new battery which seemed to help, but the car would still not fire at times. I eventually changed the coil and problem solved. I also added an alternator. First pass after those changes was the 9.98/132.50 but that was in cool fall air also.