Hey guys, I have a 1985 Corvette with a Miniram, 58mm Throttle Body, flat tappet ZZ409 camshaft, (specs are 224*/224* duration, 0.528"/0.258" total valve lift with 1.6 roller rockers, 112 LSA.), AFR 195 Eliminator Heads, Hedman 1 5/8" Long tube Headers, Dynomax true dual 2 1/4" exhaust, Dynomax Ultra Flow Mufflers, 3.75:1 rear gears, MSD 6AL2 ignition box, D.U.I. Distributor, 1.6 Roller Rockers, K&N Air filter, Air lid cut, descreened MAF, Heated O2 sensor conversion, EGR delete, AIR delete, MSD 8.5mm low resistance ignition wires, AFR Gauge and Wideband O2 sensor, Speedometer calculator, American Eagle 2 Row 1" tubing Aluminum radiator, 180* Thermostat, running on 10:1 Compression, Autolite 3924 spark plugs, 28* of total timing I believe.

WOT AFR is 12.7:1, I'd like to go to 13:1 though but I don't think it's going to make much of a difference.

So what happens is, the other day before I got my new tune, it was very powerful, very torque-y.

Today with the tune, power picks up at around 4000 RPMs and pulls pretty hard, but not as hard as I think it should.

I used to be able to light the tires up at any RPM in first gear before I did the heads, but I don't seem to be able to do that anymore, it sorta just hooks now.

Any ideas on what's going on?

It doesn't sound like it's misfiring, but it just doesn't feel like it's giving everything, or close to everything that it's got.

Thanks!

 

Put it on a dyno with afr.

 

You need to match up the torque converter (if auto) to the modified engine.

 

Oh no...not the old peel-o-meter.

Put on a dyno or take it to a track. You need objective data. We can't really give quality help with worthless references.

 

Try adding 4 to 8 more degrees to the timing.

 

It probably needs more timing. I would try at least 34 degrees total timing with your combo.

 

When you went from the stock TPI to the Mini Ram you lost low end torque and gained upper end horsepower.

 

Try timing as stated.

 

Yes,

as others mentioned; put it on the track; see what it does; MPH (1/4 mile track) is an important factor since it will give a good measure on HP;

Then take it to a chasis dynometer facility and get your HP/TORQUE curves /AFR ratios measured with a wide band in place....examine what is doing and at what RPM.....

Then play with timing/AFR's..........

Spinning the tires in first gear at any RPM means nothing........

 

Changed the ignition wires, and changed the spark plugs. Went from Autolite 3924 to NGK NGK BKR6E along with changing the spark plug gap from 0.035" to 0.055" as recommended by my ignition manufacturer.

Has tons and tons and tons of power now. Spun the tires in 2nd gear at 2500 RPMs which is way out of my power band. I can only imagine the power it has when I get it to hook up in 1st!

Thanks for your help guys! Engine idles smoother, exhaust sounds smoother and better, and no more exhaust popping!

 

Coulda been just the wires, if your ever at a track try diff gaps.

 

Go to the track and post the results.