Alky Injection Question

[Mike Lawless]

I think I've been missing the boat on my tune up. Do most of you guys tune fairly rich to help with launch torque, then use a high speed to bring it back for higher rpm?

First a little history...

I've been running without a high speed since I first put this thing on MFI and alky. It's been working pretty good till now. Recently, I put on a really b!tchin' set of heads, and we picked up over 25HP on the dyno. I know that's not a lot to you V8 guys, but going from 260 to 288hp out of 142 cu/in is a pretty stout increase.

The trouble is we're not seeing the results we should on the track. The bottom half of the track numbers are soft, and the big end numbers are bigger when tuned for the highest MPH. I also had to turn the wick up on the launch rpm to get the thing to leave cleanly without bogging. (Stick shift and a clutch) Added up, it's ETing about the same, maybe only very slightly better than before the head switch.

OK, now for the question...

Would I be on the right track if I were to fatten up the main bypass a couple numbers and start using the high speed to bring 'er back on top?

[DALE TAROS]

MIKE,
I TAKE IT YOUR 60' TIMES ARE DOWN,ARE YOU SURE ITS NOT TIRE SPIN = MORE POWER. OR PULLING THE FRONT WHEELS UP OUT OF THE BEAMS QUICKER, ALSO MORE POWER? MORE MPH IS DEFINITELY MORE POWER. MAYBE THE POWER IS UPSETTING THE CAR ON THE BOTTOM END AND NOT JUST WEAK IN THE TUNE-UP AREA. JUST A THOUGHT.
GOOD LUCK
DALE

[Mike Lawless]

Thanks for the reply Dale.

Upon reviewing video and talking to observers, what I get is a "dead hook", and it jerks up the front, (it's always been a wheelie monster), but instead of carrying the front wheels as it has before, it just jerks 'em up, plops 'em down, recovers then goes.

Typically before the head change, I could vary the two-step between 7200 and 7800 rpm to launch, which would allow me to dial in the reaction time and compensate for track conditions. I now have an 8000rpm chip in it just to bring the 60s back close to what they were before.

I'm just wondering if you guys that run high speed valves have the bottom relatively fat to help with the launch

[James]

What about your timing. Alcohol likes more timing than gas. Timing= ET fuel is your MPH. I have found that it is best to not use the high speed until you are running right close to where you want to be then start using it in small increments and small shims at a time. Otherwise you throw in too many variables and do not know which one is helping and which one is hurting.

[Mike Lawless]

It was a well sorted combo before the head swap. I guess this is a case of too much information. I reckon I shoulda just asked the question without embellishment.

Thanks guys

[Ron Gribble]

For what its worth, those symptoms are the same I had running a hilborn stack injected 351W on alky. It ran best for the low gears tuned fat, but mph needed a much leaner tune. I was advised to add a high speed, but I lost a rod before I put one on.
Ron Gribble
Have you tried asking Kinsler? I have not called in years, but thier tech help used to be really helpfull.
Please let us know how it works out.
Ron

[Mike Lawless]

Thanks Ron. I reckon the only way to know is to try it. I need to send my pump in to get it tuned up anyway, so getting some flow/pressure figures at various RPMs would help me determine a jumping off point.

[James]

If the new heads are that much better flowing than the old ones Im sure the volumetric efficiency has gone up. Therefore to keep the best air/fuel ratio of 5.2:1 you would indeed have to go to a larger main jet. The idle bleed off and barrel valve leak setting would be where I would start by looking if the problem is only on the launch.