A few tuning ?s for a twin-supercharged Olds 455

oldskool442 · Newly Aquired Joined: 26 Feb 2008 Posts: 6

Hey guys

I was looking for some insight on getting my '65 Olds 442 running better. I recently got the car together, and have been trying to get it more driveable for street use (for now anyway).

The engine is a 468 c.i. big block Olds, with a built bottom end, heavily ported iron heads (305cfm on the intake), and a large solid roller cam (.670" lift). The induction consists of a custom twin Vortech A-trim setup, twin throttle bodies, and a heavily modified Edelbrock Torker intake. It's got your standard TEC3r with full sequential and the coilpacks. To get a baseline on the engine, it was dynoed with just an untuned carb and made 520hp / 540ft*lb at the flywheel. I'm assuming with the blowers making 6-8 psi it should be in the 700 hp area.

My first questions are with the fuel. The Wizard calculated a UAP of 21, and it seemed to like a -1.5 POT at idle w/ a UAP of 23. With an idle at 4 inches of vacuum, I have the TPS/MAP Blend at 60% and fades to 0% by 2000rpm. Idle VE's of around -20 give me an AFR around 14.2-14.5. Cruising around I'm aiming for 13.8-14.0 AFRs, but under low RPM light acceleration the AFRs shoot up to 16 or so (as it begins to sputter/pop, no power). Should I have the TPS/MAP fade off sooner, so it only has effect on my idle? I think the stumble is due to the MAP being modified by the TPS at such low rpms, so the computer can't understand/see the changes in engine load at low rpms. I tried conservatively playing with the ACE4 & ACE5, but the problem still exists. Maybe I should play with the Accel Enrichments some more?

Also, the timing is at around 14deg idle, and gets to 36 by 3000. I noticed while cruising the timing is around 35 deg, and the EGT gauge is showing 1300. Does this seem high for a supercharged engine? Under acceleration it seems to be creeping up to 1400 degrees. I haven't noticed any detonation, so I'm tempted to bump the timing up to 40 deg to see if there are any changes. Any thoughts on if increasing the timing beyond 36 deg is the way to go?

Thanks in advance for you help guys, I can't wait to get this thing running right!!

oldskool442 · Newly Aquired Joined: 26 Feb 2008 Posts: 6

Little update on the car, now that I've been playing with it some....

It seems as though the acceleration stumble is going away, just by playing with the acceleration enrichments a little. I took the car to a show today that was 75 miles away, and it ran great. AFRs stayed around 14.0 on the highway, and I calculated from the fuel useage rate and mph and it's getting around 16 mpg (which I think is incredible for an untuned twin supercharged 468 c.i. engine).

As for the timing, I bumped it up to around 40 degrees, and the EGTs have gone from approx 1300 to slightly over 1200. I played with it a little to hear for detonation, but if it's detonating it's not anything audible. I'll be installing the knock sensor soon to verify this.