[PHILLYGOAT]

You said flow was increased but was that ONLY on the intake side? If exhaust side is weak compared to intake wouldn't any improvements on intake side(flow/lift/duration) not help but possibly hurt due to exhaust possibly plugging everything up? Was the roller cam exhaust duration longer than the solid? Did the non-mandrel bent "x" pipe system also have 3" pipes? It may flow as well or better than straight 3" pipes even with 1 7/8" headers.
I think fuel system/carb needs to definitely be checked to be sure it is up to the task. Does fuel pump have big enough cable/ relay set-up?
How much does your car weigh? 10.20's seems like you are already flying with those dumb ol' D-ports!!!

PHILLYGOAT

[Thumpin455_GTO]

What gears? Converter? Tire size? Weight? If you have too much gear you wont improve even with more power, are you maxed before the finish line? Make the engine work more, drop down some, like 4.56 down to 4.11 or whatever you have... Its an idea...

Or can you go the other way? More gear if you have rpm left over?

[torqjunki]

The exhaust on the heads flow about 70% of the intake. Solid was 271/279 @.050 and roller is 276/284 @ .050. Lobes are .440 very aggressive. First exhaust system was 1 3/4" headers into 3" X pipe and back to Ultra-flow mufflers. Current set-up is 1 7/8" headers with straight 3" pipe back to same mufflers in same location. I have also tried running the car open headers with short extensions and found no gain. Race weight is 3350lbs. Gear is 3.73 with 28" tire. Crosses finish line at 6100rpm. Car seems like it needs one more gear. It gets into 3rd well before the eighth. Converter goes to 4600 outa the hole off foot brake. Best 60ft has been 1.42 with average around 1.47 I think something is wrong in the carb. In the past, a few jet sizes showed on the time slip. I think the intake needs some porting as well.

[slowbird]

If you find out what it is please post what you find. I feel like it might be a reversion or over scavenging issue. The fact that jetting does nothing leads me in that direction. I would try playing around with rocker raio, try more on the intake like 1.65in and 1.5ex, and then go the other direction and see what that does. Playing around with lash might help also.

[screamingchief]

I dont think this has much to do with the jetting issue,but it does sound like you car is moving thru the gears to quickly and not staying "on the convertor" as much as it could.

If the car were lighter I'd say it was time for a glide.

Instead you might consider a 2.10 low gearset to try and do the same thing.

This will allow you to keep it in the lower gears longer and keep it "on" the convertor longer allowing the torque multiplication to be greater and move the car thru the first part of the track quicker.

I would most likely change the rear gear and tire size also as part of this change.Use a taller tire(say 30")and slightly more gear(say 3.90-4.10)to keep the SLR where it will still "hit" the tire well on the launch.

These changes would be to keep the trap RPMs in the same area as they are now.

The taller tire offsets the gear increase without negatively altering the SLR and allows for an increase in contact area for the tire adhesion.

This also gives more sidewall to "work" with.

This would likely help pick up the 60 foot numbers some.

As long as the traction is there and the motor makes enough torque to pull it.(and we all know these pontiacs make LOTS of torque to begin with)

This all would help pick up the ET's almost certainly too.

Just some thoughts to consider...

[torqjunki]

Thanks Chief...I have been thinking these very things. However if the Wenzlers find their way on the car, everything will change. I may likely need more gear, a break and possibly more converter. I should have some flow numbers today and will see how it plays out. Either way, I plan to try another carb.

[fasteddy]

TJ, ever consider the Hoosier Radial slicks? I loved mine until they wore out. Picked up .3 in the 1/4 and .08 in the 60 foot. 30 x 10.5R 15s

I had to put my old M/Ts 10.5Ws back on because of $$$. Back to the slower times again. FWIW

[Thumpin455_GTO]

Just try a taller tire, rejet it and see if it picks up. If a 29 or 30 runs faster then you can drop a gear (like 3.55) and try again. Your ride sounds alot like mine, except I have 330cfm E heads and only a 3600 stall. Hopefully tonight I will be able to post up some 1/8 mile and 60ft times.. if it ever hooks...

[torqjunki]

About 2 years ago when the car was heavier, had a solid flat tappet cam and less head flow and running 10.20's and 10.30's, I brought two sets of tires to the track. Some 30" tall and 28". I back to back the tires and found very little difference in the times and mph. That is the thing that upsets me most that the car ran 10.25 two years ago at 3500lbs with a solid cam and 258 cfm of head flow and I have made several nice improvements and can't find the payoff.

[Torment]

Jetting not effecting anything could be a fuel supply issue. Pressure and volume are related but you shouldn't rely on pressure alone. Mine picked up nicely running two 1/2" lines to the front rather than one 1/2" line with two pumps. Both systems gave solid pressure reads, but not the same performance. Over jetting now effects my car, where it didn't before. And my car has 4 bowls to work from at the start.

[Lee]

Dave,

Might there be a problem with your converter? You are over a second quicker than myself, but your 60' times are only about a tenth different - and I'm heavier, less gear, alot tighter on the converter and on DOT's. I would have expected you to be deep into the 1.3's with your performance.

When I experimented with some converters a few years ago, the really loose ones gave me consistently performance - slower, but consistent!

Lee

[gem66]

Lee,
I was going to say the same thing. I have seen a converter 'eat' a considerable amount of horsepower on the chassis dyno. If the chassis dyno was a Dynojet there are a couple of graphs that can help determine if this is the problem. The first is gear ratio. It is a calculated figure based on RPM and MPH. If it is a steep ramp and never settles, I would think the converter is failing. The second graph is RPM vs MPH. There are some calculators on the net to tell you the slippage percentage based on the graph numbers you get. Does any of this make sense? I saw a 72 Nova (repeat customer) make meaningful changes, that made no difference in dyno pulls, until we noticed the converter stalling higher, and effective gear ratio changes. I have no explanation for 10 (?) changes in jet with no change in AFR, thats a whopper. Seen it once, when a car was smoking bad with blowby...

[screamingchief]

Lee,your kind of showing what I was trying to get at in my earlier post.

By virtue of a lower rear gear ratio you probably are pulling your car longer in the lower gears and lower rpms forcing it to stay "on" your convertor longer thus multiplying the torque more which is picking up your 60 ft. numbers.

The fact that your's has a th-350 still keeps the SLR numbers reasonable for a good tire "hit" on launch,and helps "make up" for the rear gear slightly.

This helps keep your overall gear ratio reasonable, and it also will keep you in the rpm range where your convertor can take advantage of it best in the lower gears.

This would tend to show that he is making up the bulk of the difference in ET when his car is in high gear dropping his rpms enough to put it back "on" the convertor and back to multiplying the torque some more.

More torque will always mean a somewhat higher stall from a given convertor,and if the changes added more torque and not much horsepower,the overall changes could have been lost due to it moving too quickly thru the exact rpms it would help him the most.

I feel he needs to put more of this torque to work in the first part of the track hence my earlier post's suggestions.

With his combination his peak trq/hp numbers are naturally at a higher RPM so he needs to keep the stall around where it is for the sake of maximum yeild on his power.

And he needs to maintain an overall gear ratio to accommodate this and maintain a reasonable maximum rpm also.

The tire diameter can help do that.

So it seems only natural to me to use the transmission ratios to keep it where it can do the most good in the lower gears only.

And still maintain a good SLR with respect to the rear gear ratio.

Again these are just some thoughts...

[Nine Ninety]

have you or can you check battery voltage during a pass?

i have experienced a case quite a while back where the car wouldn't respond to tuning changes. i wasn't running an alternator at the time and it turned out that I had a bad battery (shorted cells) and the voltage was dropping under 10 during a pass.

[SupergasDil]

Have you checked the resistance in your spark plug wires?

[Skip Fix]

EGTs don't always give an exact indication of AFR as timing an other variables can affect EGT(firing out in the tubes) wide bands give alot more accurate numbers.Might be good to go to a chassis dyno with a AFR meter,new shop that does mainly EFI cars up 290 HPE has one, had a "new" GTO dyno session there Saturday. I think the Mustang's use the LM1 standard, you can pick one of those up separate and log runs at the track on it also.