[Stan Weiss]

Originally Posted by 78w72

Great advice here & applies to my set up that also has traction/launch issues, engine is similar but less than the OPs car.

My setup is a 72 firebird, 467 stroker kit with stock unported 72cc E-heads, SD old faithful roller cam, Cliff built Q-jet & SD ported cast iron/HO intake. TH400, continental ~3200 converter, 3.23 gears. Has the same PTFB dropped front/rear springs & subframe connectors, using cheap summit 3 way drag shocks, no traction bars. Runs 11.3-11.4 at 119 with ease in any temps, best is 11.2s at 121-123mph.

I was very surprised & happy at the times & speed, expected mid to low 12's, but upset at the traction issues, I have to launch off idle too & it has some fuel starvation issues on good runs using a robbmc 1100 pump & 1/2" pickup. Those 2 things are holding it back but happy with the car since its more of a street/strip/light auto-x car.

I will 2nd or 3rd the wheel/tires, the 17" wheels are cool but heavy & hurt traction since theres much less sidewall, I bet just going to a 15" wheel/tire like some draglites makes a big difference in speed & launch. I have the older M/T drag radials but plan to go to the newer compound or the 275/60 Pro bracket radials that Ive read are the best radial tire option today. Also electric fuel pump to eliminate the starvation issues. With those issues fixed im hoping for a 10.9x or better.

With 340 heads, bigger cam & 1300 FI that car should easily be in the low 11s or high 10s & 120+ mph, like myself or many other street/strip cars, there is a lot more in it if it can be dialed in more.

Since the first 60 foot can make or broke a run. What were your 60 foot times?

Stan

[78w72]

Agreed. I will have to check some time slips to say for sure, but they were pretty crappy like the OPs, I think most are around 1.6, maybe a high 1.5.

Even with decent track prep I have to launch off idle & kind of roll into the throttle otherwise the tires spin like crazy. Have tried foot braking to about 1600-1800 but just seems to make the tire spin worse or lower 60ft times. Most people have said off idle hits the converter harder for better launch, but with zero traction aids & a stiff suspension its hard to get a good launch. Typical street car problems if you want handling performance too.

[prostreet64]

78w72, if you are trying to avoid using traction bars then several things you can do if you haven't already, is to clamp the leaf springs to avoid 'wrapup' on the launch and use a pinion snubber to make sure the pinion angle cannot go positive. Also a good set of adjustable rear shocks is a huge factor. Before I added the Assassin bars I was doing these 3 things and the car would hook about 50% of the time.

[VCho455]

Originally Posted by yellow1098

That makes sense about the PTFB suspension….what changes would you make to gear it more towards drag? Aside from the slicks …Dave suggested those anti squat brackets specifically instead of Caltracs

Also what would suggest to pull more on the top end?

Thank you again everyone….all great info indeed

I am assuming you have the dual adjustable Viking shocks? If so you want to try and mimic the action of a 90/10 front drag shock by reducing the rebound rate as much as possible so the front end will rise up quickly on launch to help plant the rear tires.

Then try raising the compression rate on the passenger side rear to counteract the axles tendency to lift the right rear tire. You may have to play with this a fair amount before you find the best combination. Some people will unhook the front swaybar mount on the drivers side to help get the front to rise and put more weight on the rear tires.

These days recordings of the rear axle movement are easy to obtain and watching them at different playback speeds can be very revealing allowing you to make informed changes. Investing a a good gopro type camera would be worth more than buying parts on bad information.

[78w72]

Originally Posted by prostreet64

78w72, if you are trying to avoid using traction bars then several things you can do if you haven't already, is to clamp the leaf springs to avoid 'wrapup' on the launch and use a pinion snubber to make sure the pinion angle cannot go positive. Also a good set of adjustable rear shocks is a huge factor. Before I added the Assassin bars I was doing these 3 things and the car would hook about 50% of the time.

Thanks for the suggestions, I did make an extended pinion snubber, didnt make much of a difference, may have helped a little but wasnt really consistent.

Im not really avoiding traction bars, but being mostly a street car i just havent invested in them yet playing with the car at a couple test & tunes per year... need to fix the fuel issue & get a stronger driveshaft if I want to go faster. The PTFB rear leafs are stiffer/stronger than stock springs and dont seem to wrap up much. How/where do guys clamp leafs?

I have looked at the assassin & cal trac bars. I have cheaper 3 way adjustable drag shocks front/rear, seem to work best at 50/50 rear & 90/10 front, I remove the front sway bar too for drag use.

[yellow1098]

Originally Posted by 78w72

Great advice here & applies to my set up that also has traction/launch issues, engine is similar but less than the OPs car.

My setup is a 72 firebird, 467 stroker kit with stock unported 72cc E-heads, SD old faithful roller cam, Cliff built Q-jet & SD ported cast iron/HO intake. TH400, continental ~3200 converter, 3.23 gears. Has the same PTFB dropped front/rear springs & subframe connectors, using cheap summit 3 way drag shocks, no traction bars. Runs 11.3-11.4 at 119 with ease in any temps, best is 11.2s at 121-123mph.

I was very surprised & happy at the times & speed, expected mid to low 12's, but upset at the traction issues, I have to launch off idle too & it has some fuel starvation issues on good runs using a robbmc 1100 pump & 1/2" pickup. Those 2 things are holding it back but happy with the car since its more of a street/strip/light auto-x car.

I will 2nd or 3rd the wheel/tires, the 17" wheels are cool but heavy & hurt traction since theres much less sidewall, I bet just going to a 15" wheel/tire like some draglites makes a big difference in speed & launch. I have the older M/T drag radials but plan to go to the newer compound or the 275/60 Pro bracket radials that Ive read are the best radial tire option today. Also electric fuel pump to eliminate the starvation issues. With those issues fixed im hoping for a 10.9x or better.

With 340 heads, bigger cam & 1300 FI that car should easily be in the low 11s or high 10s & 120+ mph, like myself or many other street/strip cars, there is a lot more in it if it can be dialed in more.

That is exactly why I wondering what was holding me back so much because of the 340 heads and bigger cam and 1300….I was figuring I just be in the low 11’s or high 10’s also….but Im thinking after all this great advice its definitley getting choked out by the 2.5 inch exhaust and the timing needing to be dialed

and for sure those 60 foot times

Maybe me weighing 260lbs also hahaha

[78w72]

forgot to mention im using a full 3" pypes kit with an X pipe. & probably too big 2" hooker super comp headers. stock hei but set up by member "suntuned" to match the combo, think its like 34 max. never played with it on the dyno or at the track.

Ive heard of & seen cars with a good 2.5" system doing low 11s & faster so im not sure its all exhaust on your car, im thinking its traction & launch more.

[prostreet64]

Sounds like you have it pretty well thought out. And you are right about making sure fuel delivery is not an issue. Are you already running 1/2" fuel line? Even on my son's Bird with the 400 we had to go to 1/2 line and a 125gph electric pump to get the job done. Your leaf springs may not be an issue at all but if you do clamp the leaves just the front half of the spring at the overlap point of each leaf to keep the front leaves from separating. Behind the axle you actually want the leaves to separate.

[prostreet64]

By the way, your car is running really strong for the limitations that you are working with. And I just saw in your earlier post that you have a Q-jet. Great carbs ! I ran one built by Cliff on my 403 and it was flawless but Cliff will tell you that because of the relatively small float bowl compared to a squarebore double pumper, it is more important than ever to make sure fuel delivery is up to the task.

[Probird]

Those heads are capable of running in the 9’s easily with the right matched parts. Looser converter, more gear, and a bigger cam. But making more power won’t help much if you can’t get it off of the line without blowing the tires off. I run ladder bars with my leaf springs with housing floaters. It’s an old school setup but works great. Most of the guys run cal tracs and mono leaf springs. Get a set of drag radials. Loosen the front up. Once you get the traction under control them put 4.11’s in it and about 4800 stall built for your engine. Put a cam in there that can take advantage of the 340’s. A good cam that I used to run that got me into the 9.30’s-9.40’s is the 280/284 @.050 with the .440 high torque lobe. That was with E-heads that flowed 328 and a race weight of 3275lbs. Then you will be making some top end power.

[78w72]

Originally Posted by prostreet64

By the way, your car is running really strong for the limitations that you are working with. And I just saw in your earlier post that you have a Q-jet. Great carbs ! I ran one built by Cliff on my 403 and it was flawless but Cliff will tell you that because of the relatively small float bowl compared to a squarebore double pumper, it is more important than ever to make sure fuel delivery is up to the task.

Thanks, Im very impressed with it for what it is, stock E-heads & 3.23 gears with a factory but ported intake & Q-jet, main reason for that was the formula hood clearance issues, using a factory 76-79 TA type drop base air cleaner.

Cliff built this carb & the one on my mild 400 78 TA, both are 78 TA carbs and run excellent out of the box, minor choke & idle screw adjustments is all thats needed.

I do have 1/2" line from tank to pump, -8 braided from pump to carb, high flow filters, the robbmc pump works great but on about half of the good low 11 runs it will cut out, plan to verify psi on a run with a gauge soon. but future plan is to go intank pump in a baffled tank... just takes $$$ to go faster but it runs so good as is im somewhat content for now.

[prostreet64]

On both of our cars we added a sump to the factory tank and mounted the electric fuel pump as close to the sump as possible. On a hard launch with 1/2 tank or less you will probably uncover the factory pickup. With the sump we can run down to at least 1/4 tank before it becomes an issue. It is asking a lot for a mechanical pump at the engine to pull sufficient fuel for a car that can run in the low 11s or high 10s.

[yellow1098]

Originally Posted by Probird

Those heads are capable of running in the 9’s easily with the right matched parts. Looser converter, more gear, and a bigger cam. But making more power won’t help much if you can’t get it off of the line without blowing the tires off. I run ladder bars with my leaf springs with housing floaters. It’s an old school setup but works great. Most of the guys run cal tracs and mono leaf springs. Get a set of drag radials. Loosen the front up. Once you get the traction under control them put 4.11’s in it and about 4800 stall built for your engine. Put a cam in there that can take advantage of the 340’s. A good cam that I used to run that got me into the 9.30’s-9.40’s is the 280/284 @.050 with the .440 high torque lobe. That was with E-heads that flowed 328 and a race weight of 3275lbs. Then you will be making some top end power.

Great comments and info…..Bigger cam, looser converter, and more gear as well as get the power down…..makes perfect sense ..thank you for the details

[78w72]

Originally Posted by prostreet64

On both of our cars we added a sump to the factory tank and mounted the electric fuel pump as close to the sump as possible. On a hard launch with 1/2 tank or less you will probably uncover the factory pickup. With the sump we can run down to at least 1/4 tank before it becomes an issue. It is asking a lot for a mechanical pump at the engine to pull sufficient fuel for a car that can run in the low 11s or high 10s.

I considered the sump option early on, cliff suggested that & that its better to push fuel than pull it... but being mostly a street car I chose a stock tank with a 1/2" pickup & keep the tank 3/4 full at the track. The external pumps are nice but most are loud & not very reliable for street use. If/when I go electric pump I will get a tanks inc set up or other in tank pump module, the tanks inc has a nice internal baffle in the tank. Thanks for the advice.