['69ragr]

I had the car out a couple of week end ago, ran 11.6 at 117 mph, 1.70 60 foot. The 69 GTO convertible with 6 point bar wieghs 4250# race ready. 535 cu. torqer with 1000 HP, dynoed 620 hp at 5600 rpm and 665 # torque at 4300 rpm, Comp cam 254 duration , .640 lift solid roller. Ford 9" with 350 gears and turbo 400. Improved from last fall run 12.2 at 114 mph and 1.85 60' time adding the bar (twisted alot) ,added anti roll bar and playing with suspension. Running MT 275/60 radial street ets. I would like to get into the low 11's or better, and am told to change cam ( told it was old style), change rear gears, or change torque converter to higher stall and right now it is 2800 to 3000 stall. Would appreciate opinion from guys with similiar set up and heavy cars, ANY IDEAS as I am a bit confused.

Thanks

[fasteddy]

Continental 9 inch to 4500, 4.11 gear or a 3.90 and a 2.75 low gear TH400. If you can hook up and get the 60s in the 1.5s you should see 11.0s or 10.9s. That is a torque monster. It takes power to the ground to get a 4200+ barge going. Maybe Troy (60man) will chime in here. He has alot of experience at this.

['69ragr]

Thanks Fast Eddy, of the three you mentioned which one will give the biggest impact?

[fasteddy]

Best for the buck and easiest is definitely the 4.11 gears. What is your RPM through the traps now? You may need some taller tires.

[estep455]

my biggest gain when i switched to my 535 was in the converter. picked up 1/2 a sec. by changing the stall.

['69ragr]

Estep455 what do you have in the 535, if it is in the car in your avatar it must be very healthy. What converter stall you using. Fast Eddy I am running 28" tires. Doesnt increasing the tire size decrease the rear end ratio?

[60man]

Originally Posted by '69ragr

Thanks Fast Eddy, of the three you mentioned which one will give the biggest impact?

Boy!!!...is that a loaded question
I would go gears and hope you can still hook ?!
To be truthful....they all play a roll in performance..
Got a coin ??
First off..your cam...254 @ .050 or adv. duration.?? Old style ??
What is your compression? Don't want to go to big on cam if CR is not there.
Mine is 13-1 and I run a 284/288 @ .050 with .740/.690 lift. I think it's too big for 13-1?? I'm ready to try a smaller cam.
I also spent a fourtune on rear suspension over last two years..can finally launch at full power and 60's are at mid 1.4's . Now run a 5k PTC converter & 4.10 gears w/29X10.5WX15 slick.
By all means work on the 60' first....got to get that mass moving at all costs..
Oh ?? is this just race only..,
Just my

[68WarDog]

My 70 GTO race weight is 3968. We need TORQUE to get these heavy cars moving. I run a 4400 PTC stall/12 bolt 31 spline axles/ 4.10 spool. Don't cheap out on a good stall.1/8 mile best time has been 6.6 @ 102. 1.47 60 footer. My cam is a bit larger than yours,270/280 @ 0.050 .660 lift.

[GTOLou]

Good to see other guys running fat boats. I run a 69 gto vert also, it is a HEAVY sled....And I am very impressed that you can hook up w/ the MT drag radials.



My car is similar, 69 vert. w/ 535 (new this year). I've got a FOUR SPEED and it is a real trick getting 60' foot times. Add in that my driving prolly sux....lol. Last night was very crowded at my track, 90+ degrees when I first got there, only ran three times and got a 1.86 60'. Terrible traction w/ MT ET slicks 26.5 x 10. I've only got a 3.42 gear, hence the shorter tire. The best sixty was w/ 17lbs pressure.



I've even built the thing w/ a fairly small HR so I make power at low RPM and don't have to load 650hp in 2 tons at 3500rpm plus.


I don't have much in the way of advice - maybe weight? I run a glass hood...I just put some smaller skinnies on the front...have toyed w/ the idea of a glass (endura-style) bumper, etc...

Good luck

[60man]

Originally Posted by 68WarDog

My 70 GTO race weight is 3968. We need TORQUE to get these heavy cars moving. I run a 4400 PTC stall/12 bolt 31 spline axles/ 4.10 spool. Don't cheap out on a good stall.1/8 mile best time has been 6.6 @ 102. 1.47 60 footer. My cam is a bit larger than yours,270/280 @ 0.050 .660 lift.

Nice 60' !! what motor/tires ??
NO substitute for torque with Barges!!
Amen on converter..I may to tighten mine up a bit

[estep455]

Originally Posted by '69ragr

Estep455 what do you have in the 535, if it is in the car in your avatar it must be very healthy. What converter stall you using. Fast Eddy I am running 28" tires. Doesnt increasing the tire size decrease the rear end ratio?

it is in the car in my avatar. i have a 5ooo stall, run basically the same cam as 68wardog. when i first got the converter the stall was off,car did not like it, sent it back in and got it right. 500 rpm made a huge difference in the 60ft times. now its 1.20 with 4.56 rearend and 1.27 with the 4.10 gears.

[D. Miles]

I'm along the lines of estep455... I can't tell guys enough CONVERTER CONVERTER CONVERTER!!! Years ago, I had a 67 Ventura with a .030 455 the first set of heads I ever ported (needless to say I had NO experience, I'm sure they weren't right) they where # 62's that probably flowed maybe 230 I had a flat tappet solid Lunati cam that was 262/272 @ .050 .575/.578 lift on a 106 LSA. It had a Torker I intake with a 750 DP (under carbed) a set of 1 5/8 headers (too small). The trans was the factory T-400 with a B&M trans-pak. The kill-joy was the odd-ball Pontiac rear that no gears were available for, one of those 10 bolt cover - 8 1/2 ring gear 12 bolt carrier with the almost 2" pinion. The only way I could get gears for this deal is if I could've talked someone out of their 3.90's from a Catalina 2+2 or 67 Grand Prix, anyway, I was stuck with the stock 2.73's. But stuffed in between the 455 and T-400 was the ATI 8" 5600 stall converter from my race car which was parked for a while (I missed the street scene) I left the line at 2400 shifted at 6200 went through the traps around 6000-6100 in second gear, the best 60' was a 1.79 and the best 1/4 was a 12.43 @ 109 mph.

Don't get me wrong, everything else does play a VERY important part in the combo, as mentioned before you could use more cam, a more aggressive more modern design, with that 535, it'll take a lot of cam before you start to hurt torque, I'd say in the mid to high 270's @ .050. 3.90 or 4.11 gears will help but not nearly as much as the converter but will play a part further down track.

I'm sure some guys will disagree and beat me up on the converter thing but it's what always made our cars run, from basically stock motors with small hydraulic cams to steel rodded bottom ends with .720 lift roller cams we don't go anywhere unless there's an 8" donut on the front of that tranny... Thanks D. Miles

[ponjohn]

Originally Posted by estep455

it is in the car in my avatar. i have a 5ooo stall, run basically the same cam as 68wardog. when i first got the converter the stall was off,car did not like it, sent it back in and got it right. 500 rpm made a huge difference in the 60ft times. now its 1.20 with 4.56 rearend and 1.27 with the 4.10 gears.

Estep- what did it 60ft with the lower stall?

[DiamondJim]

This is a good topic that inspired a thought. Typically, what would help 1/4 mile performance more, a 10% lower gear (say 3.73 to 4.10) or 10% more stall (say 3500 to 3850), this of course based on the assumption the trap rpm remaining optimal, all hypothetical of course. My guess is the added stall if the tires hook. Comments or experiences? ? Thanks -Jim

[Half-Inch Stud]

CONVERTER is key to getting the "over-cammed" motor into the HP range quickly.
Pretty good idea for the rightly-cammed motor too.

11.0 Signature would be the Rightly-cammed with an off-idle launch. Converter was 3200 stall. Seems the over-cammed motors would NEED more stall or/and more gear to get better 60foots.

I gots no experience with the Trans-brake folks' rules-of-thumb for cam//converter//gear.

[BruceWilkie]

3100 stall to 5200 stall behind my old 440 combo netted me 3 tenths in 60 ft time and eventually 8 tenths in the quarter once i upgraded my fuel system. 1.81 best to 1.52 best (and consistant) 60 ft 12.62 109 to 11.74 115. Prior to convertor changed to 4.10's from 3.23 went 12.98 102 to 12.80's 104. Made engine changes between convertor and gears(bigger solid cam 255/264 110 LSA 1 point more compression, 6700 shift vs 6000). staging weight 3910.

Agree with Miles convertor was my biggest single gain. FWIW ft braked to 2500 was still my best launch with either convertor and I had to adjust my reaction time due to time difference to hit flash and actually move the car.

[estep455]

Originally Posted by ponjohn

Estep- what did it 60ft with the lower stall?

1.41 60ft with the lower stall. even tried a buddies conv. that stalled 5500 and the car was almost the same as with the 4500 conv. got it right and down it came.

[screamingchief]

Originally Posted by DiamondJim

This is a good topic that inspired a thought. Typically, what would help 1/4 mile performance more, a 10% lower gear (say 3.73 to 4.10) or 10% more stall (say 3500 to 3850), this of course based on the assumption the trap rpm remaining optimal, all hypothetical of course. My guess is the added stall if the tires hook. Comments or experiences? ? Thanks -Jim

My thoughts.

Combo wins everytime.

There's absolutely no reason to run a converter that stalls a whole bunch higher than peak torque,so the torque converter situation will eventually reach a point of diminishing returns,but no doubt till that point is reached,manipulating the converter situation can make a huge difference as others here have testified to.

Rear gearing is sorta the same deal,but it also affects other things like starting line ratio,and the abillity of the car to hook well initially,as well as trap RPM,and RPM drop on the shifts,so one should always be somewhat careful using this option.

Also the rear gearing choice will affect the operation of a given converter as well,and vice-versa,the two are very interdependant on each other,so it's often just not simple enough to say one specific choice will always give the better result for all combos.

If you have a bunch of torque,a really heavy car,and a ton of SLR,well your likely gonna just end up running over the sidewalls as they ball up on the initial "hit",and trust me that does'nt work very well at all either.

Now there are ways to adjust for that,but as most folks know (or learn),that can be very tricky to master,stiff sidewall slicks or drag radial/radial slicks will help here some,but they wont always compensate for the root problem completely,there may still be some lingering inconsistency in the combo.

Suspension better be top-notch,or you wont stand a chance of hooking a car like that.

And as alluded to earlier,rear gearing works together with the converter going down the track as well,that affects the RPM drops on the shifts,and how the converter is loaded by the drivetrain,and thus that affects the converter's slippage numbers.

Personally,I'd like to know a little more about the engine in this car to make specific recommendations or such,but were it my car,and money was not an object of any concern,based strictly on the stated dyno info,I'd likely end up with a 3.89 rear gear,a nice tight converter around 4200 to 4400 flash stall,and I'd use a 2.10 low gearset for the TH400.

That way the initial "hit" is tamed slightly from the current combo,and that lets the tires hook well initially,the "new" converter will get the combo to peak torque faster (and thus it should 60' better),and the rear gearing should keep the RPM drop on the shifts in check,without putting the trap RPM too high.

With an appx. 28" tall tire (275-60-15),and 620hp that should easily net a low 11 second ET,and it should go thru the traps right around 6000 to 6200 RPM (just above peak HP) @ between 123 to 125 MPH.

Cruising RPM should be liveable as well at that ratio (3.89/28" tire),should be right @/around 3000 RPM at 60 MPH.

Any higher in the rear gear department and that situation will suffer some IMO.

A few simple concepts to remember are thus,we want the stall right @ or just slightly above peak torque,and the rear gearing should put the engine right @ or just above peak HP thru the traps for best results,this is pretty much common knowledge/theory.

The 60' game all depends on getting traction,and that is where most folks struggle.

I know some folks will argue the logic on my 2.10 low gearset recommendation,likely saying that one needs as much low end gearing as one can get to help get this sorta heavy car moving,but IMO a high SLR/heavy car combo makes it harder to hook an already difficult to hook car,I say if one already has ample torque output from the engine,manage it wisely from that point on,and all should be OK.

Some might even lump this line of thought into the "tractor mentallity" school of thought.

Remember,if you have 665 lbs/ft @ 4300 RPM,until the converter reaches full stall that converter is multiplying the engine torque output by a factor anywhere up to (and often over) 2.0:1,now compound all that torque (say 1320 lbs/ft) at the input shaft by the trans and rearend gearing and I assure you,you already got plenty of torque to get that big car moving,you just need to get all that power to the ground without spinning the tires in the process,and when all that torque is fighting to get that heavy car moving off the line,something is gonna give,and often it's the rear tire traction that suffers in that pursuit.

Moser engineering has a nice little calculator to figure that driveline torque situation out,but even that calculator does'nt take the converter's torque mulitplication factor into account.

http://www.moserengineering.com/Pages/axletech.html

But even just taking into account the trans gearing (2.48 stock) and rear gearing (3.50) with 665 lbs/ft,you'll have 5194 lbs/ft at the rear wheels,assuming a .90 % frictional loss factor.

Now try plugging that 1320 lbs/ft from above into that calculator...

Uhhh,,,10,311 lbs/ft!!!

You got plenty of torque.

It's the cars with lesser torque output that can benefit from the 2.75 low gearsets and higher numerical rear gears,say an NHRA/IHRA stock class car,or a pure stock drag deal.

At least that's how I see this.

As far as the cam situation,would need to know specifics,exactly what cam is in there now,what bore/stroke is being used,what heads (cfm #'s) are on there,what the SCR is,what intake/exhaust tracts are in use,all that sorta info.

Without that info,any input would likely be useless.

[68WarDog]

Originally Posted by 60man

Nice 60' !! what motor/tires ??
NO substitute for torque with Barges!!
Amen on converter..I may to tighten mine up a bit

Troy, I run a Dale Nichols built 11.8:1 474. Marty Warden race ported E's.Tight 8" PTC 4400 stall. My new tires are 28.5 MT/ET street,which has effected my 60's(1.52) from my old 29.5 MT slicks(1.47). I had to move from a "racing slick" to compete in our local "street legal" class as well as reinstall my rear wheel well trim.(just for looks of course)

[60man]

Originally Posted by 68WarDog

Troy, I run a Dale Nichols built 11.8:1 474. Marty Warden race ported E's.Tight 8" PTC 4400 stall. My new tires are 28.5 MT/ET street,which has effected my 60's(1.52) from my old 29.5 MT slicks(1.47). I had to move from a "racing slick" to compete in our local "street legal" class as well as reinstall my rear wheel well trim.(just for looks of course)

Thanks...just comparing notes..
For possible swap to a "smaller cam"...
I once removed my front bumper to save weight...looked like chit so i put it right back on..for looks of course..