Skinny Neb

iTrader: (2)

I feel like my car is leaving a good amount of time on the table on the launch. It seems to plant great, actually good enough that I cut a better 60' with street tires. I have a 3400 stall and 4:10 gears with a 700R4, and can only foot brake it up to 2000rpm before the car starts moving forward. The car runs 8.2 @86 on street tires with a 1.89 60' at 4500DA. The question is..

How can I launch at a higher RPM without installing a higher rpm stall or trans brake? I drive the car on the street as much as possible, so I can't have a massive non lockup stall. Any ideas would be much appreciated!

project89

iTrader: (1)

ur sig says 3400 stall , so im assuming the brakes just wont hold , try using the ebrake while footbraking as well , on my car i can go wot without the car moving like that.
also get a line loc for the front for doing ur burnout this will keep the rear brakes cool and they will hold better on the line
edit
could have sworn i just looked at ur sig and it said 3400 stall

AlkyIROC

The vehicle brakes will never allow you to launch anywhere near what the stall speed of the converter is. If you launch at 2000, the converter will flash to 3400 as soon as you take your foot off the brake.

I have a 6000 stall converter and I can't even launch at 4500 without using the transbrake.

The only proper way to get a higher launch rpm is with a transbrake

Skinny Neb

iTrader: (2)

I do have a 3400 stall, I edited my sig right after I posted the thread to get rid of the old engine details.
My brakes very well may not hold much. I shouldn't be pulling much vacuum seeing that I have a pretty large cam.

I have toyed around with the idea of an adjustable proportioning valve. Adjust all the way to the front for the burnout, and most of the way to the back before staging.

Does anybody make a transbrake for a 700r4? I like my overdrive, and those gearvendors are a little out of my price range. Otherwise I'd love to have a th350 with a brake. The car just gets driven too much at highway speeds to get rid of my overdrive in favor for a brake.


I appreciate the ideas guys, I'm willing to try anything!

project89

iTrader: (1)

2004r with a stage right manual brake , it engages the transbrake when u move the shifter into 1st gear , and rleeases when u shift to 2nd to launch it
other option is a 4l80 and brake

im doing a th350 and brake in my car this weekend the only plus side is being a turbo car i run a low numerical rear gear so i can still go down the highway at a good rpm with the 3 speed

DIGGLER

iTrader: (1)

What is your 60 foot when you leave from an idle? Are you gaining anything by stalling it up?

Wolfster14

The proportioning valve idea sounds like a lot of grief. To try to turn the valve all the up and down between your burnout and staging will be difficult and just and another thing to your screw with you consistency.
Diggler asks a good question are you sure you need more RPM?
And I have to agree with Alky 100%.
Its a tuff spot to be in. keep it very street able, or start making changes towards full racer.

FRMULA88

A trans brake for a 1.89 60' on a car you enjoy to drive on the street ?

A 'brake is pretty useless unless you have a manual valve body to control the shift point. and 2 step rev limiter to control the launch RPM.

Any seasoned racer will tell you the difference in 60' times between foot-braking and a 'brake is marginal if the car is setup right.

All the 'brake does is give you more consistency at the starting line since it will leave at the exact same RPM every time because of the 2-step

by the time you spent the money on good 'brake, a manual valve body trans, 2 step. reverse pattern shifter, new driveshaft, etc. etc . you still have a 86 MPH car. (1/4 mile or 1/8)

A healthy 383 should be in low 12s.. high 11s. something else is amiss with your build/setup or your driving technique.

Back in the day I ran 12.16 @ 111 in the 1/4 ( 1/8 was 7.75 @ 88.5 ) with a 383, 700R4 trans 3.70 rear gear, & Nitto Drag Radials. on 1.65 60' Foot braking to 3000 RPM.

a 700R$ will really benefit from a governor recalibration kit, at WOT you want to see your shift point at 6000-6400 to stay in the sweet spot of the power band, To keep costs down and be consistent
I calibrated my governor to shift at 6000 at WOT and simply left the shifter in D... manually shifting without a manual valve body is waste of time as the trans will always hesitate between shift..

FRMULA88

Simply raising the shift point will go long way to improve the ET & MPH..

Skinny Neb

iTrader: (2)

The only time I left from an idle on the track, my 60 foot was down about half a tenth. Being more on the street and no prep clocks off races I always have it stalled up so I'm ready for whenever the light comes on.

I feel it needs more RPM out off the initial hit. I actually bog down for a second on old 26x10.5x16 ET street bias ply tires on 12psi. The more rpm should end up with a harder launch and fix my bogging problem, correct?

Skinny Neb

iTrader: (2)

This 383 is not the meanest thing that anybody ever built, it made 326/319 at the tires on a mustang dyno. I shift at 6300-6400 and cross the 1/8th just after I get into third (4.10 gears).

The only time it was at a 1/4 mile (we don't have one around here) the engine was slapped in the car earlier that week and we were still fighting issues. It ran a 13.6 @84 lifting at around the 1/8th (fuel was boiling before it hit the carb, was misfiring, didn't feel like blowing up a fresh build).

I've never looked into messing with a governor on it, I just always manually shifted when I was racing.

Wolfster14

I feel it needs more RPM out off the initial hit. I actually bog down for a second on old 26x10.5x16 ET street bias ply tires on 12psi. The more rpm should end up with a harder launch and fix my bogging problem, correct?


Not necessarily. The bog could be from lack of fuel. Carburetor adjustments. Jetting. timing.

Skinny Neb

iTrader: (2)

I had the car dynotuned before I put it on a track.

Wolfster14

I have never had the opportunity to use a dyno. I am not sure that would duplicate the launch at the track. Maybe one of the other guys could verify.

You said you 60td better with old street tires than slicks. Were they the same size tire ?
Like some of the others have said could be something not working with the rest of the combo you have .

DIGGLER

iTrader: (1)

if everything else is working correctly on the car, i can only assume you need a different converter. adding extra rear brake on this type of car would be goofy and shouldnt be needed.

Skinny Neb

iTrader: (2)

The street tires are 275/40/17 BFG sport comp 2's. The cheapest tire I could get in that size. 1.89 60'.
The other ones are 26x10.5x16 MT ET street bias ply tires. Best 60' I could cut with these was 2.08, and I was also down ~7mph at the 1/8th. Maybe more air would help? I've only ran them at 16psi and 13psi (16 was on the street first time I tried them with the old setup).

I guess it's also worth noting that the car will be getting 150 shot of spray this month.

pancherj

How is a 383 with AFR heads and good compression only making that RWHP? In addition, how can it bog on street tires?

I'd visit another tuner. There has to be more in that combo unless it is a stock cam.

Skinny Neb

iTrader: (2)

It doesn't bog on street tires, it bogs on the ET Streets. It hazes the street tires off the line.

It's likely a poor cam choice. I bought the engine second hand from a local (idiot in my opinion). Take for instance the engine has a small dome piston with 75cc straight plug heads. I guess I just don't understand the choices he made on some of the parts..

I also have a weiand Xcelerator intake on the car to clear the factory hood, I'm well aware that it kills some power, but I can't tell people its a pooch when I have a large cowl hood to clear the filter. If my plate requires me to make some clearance that'll be enough for me to warrant buying a taller/better intake.

Here is a link to the cam specs. Part number 12-368-4. It's the largest hydraulic flat tappet in the Xtreme fuel injection line up from comp.
http://www.compcams.com/Company/CC/c...?csid=123&sb=2

I'd love to put a custom grind solid roller in the car, just didn't have the funds at the time the engine went in.

AlkyIROC

I didn't install a transbrake on my car until I was in the low to mid 11's. I also swapped out the 10 bolt for a 9" at the same time because I knew the 10 bolt wouldn't last with the transbrake.

pancherj

That cam should make plenty of power. You should be obliterating street tires. The intake is probably holding you back some, but I would still expect 400RWHP or close to it.

Skinny Neb

iTrader: (2)

The tuner told me my carb was holding me back 15-20 at the tire(holley 750 vacuum secondary), the intake has to hold me back close to 30 from one matched to this setup. The converter was locked and it was on a mustang dyno (roughly 30-40 lower on average from local dynojets).

I'm also unsure how the person who built the engine degreed the camshaft. It's range goes to 6800 and power starts going downhill after 6200.

pancherj

The 750 vacuum probably limits your transition from part throttle to WOT (such as launching the car). I have never had good luck getting them to work like a double pumper. But, they flow the same CFM as a 750 double pumper, so I doubt it its limiting your HP at all. The intake certainly is and 30hp is probably a good guess.


I would also agree that the cam should peak around 6200 and you should be shifting in the 6500-6800 range. Be careful though! The lobes on that cam are aggressive and valve float can happen quickly. Your springs need to be up to the task and I would get some Ti retainers and good pushrods.


I think there is a ton left in this combo. I may just take some experimentation to extract all of the power. What headers are you using? Exhaust system? What does the timing curve look like? What about the air cleaner and air intake system?

AlkyIROC

Trouble with both DP and Vac carbs is that you're trying to launch at anything above an idle. Not quite sure on the Vac carb but with a DP, you're already partially through the pump shot just bringing the rpm up. When you go to WOT, the engine may not be seeing enough fuel in that sudden lean condition.

With a DP carb, it's easy to change the accelerator pump cams to fine tune the pump shot. I'm not sure what can be done with a Vac carb.

FRMULA88

that's over 400 HP at the flywheel! My 383 made 465 HP.

A healthy 383 should be in low 12s.. high 11s.

Like I said, something else is amiss with your build/setup or your driving technique.

FWIW for 1/8 mile racing 4.10 is too high of a gear, even with a 26" tall tire.
If you are serious about 1/8 mile racing you want to be crossing the finish line ideally with your RPM at max. this is after all an acceleration test.

my 1/4 mile car has a 4.30 with 28" tall tires which is equal to a 4.10 with 26" tires. I am going twice the distance down the track so this is an ideal gear for me.

You want to be "all done" by the 1/8 mile. you don't need the gear to take you a full 1/4.

If you upgrade to a Ford 9" you can have a carrier set up for 1/8 mile racing and another with a street gear when you are not racing.

swapping carriers takes about an hour if you know what you are doing. OD is nice but why run a tall gear all the time if you don't need too.

pancherj

OP, just as a reference, my stock L98 shortblock with old AFR 190 heads, a similar cam but the hydraulic roller version, same gears, same trans, same converter and a 750 double pumper on an RPM airgap would routinely go 11.90-12.00 at 115MPH in 3000DA. This is why I am sure your combo has more in it.

FRMULA88

A purpose built 1/8 mile car with a 6400 RPM redline thru the traps

and 465 HP would like at least a 5.44:1 rear gear with 26" tall tire.

7.31 ET @ 91.05 MPH.. (assuming 3600# car w./ driver )

This would make a miserable 1/4 mile or street car even with OD.

In OD the 5.44 * .7 = 3.80 not too shabby but not enough gear for the quarter mile and on the street MPG & MPH will suffer with a 3.80

Which is why I dislike 1/8 racing... I understand not all these tracks have the real estate for a proper drag-strip but If I can choose I will always run full track vs half..

Skinny Neb

iTrader: (2)

I'm gonna try to answer all these with one response, I may miss something.

It has hooker long tubes, had to dink the one primary to clear a spark plug, but otherwise untouched. 3" crush bent duals with magnaflow 4" bullets and turndowns.

Total timing is set at 38*
Air cleaner did not affect power or torque at all. Exact same curve and numbers back to back. The air cleaner comes off at the track anyway.
Valve springs are matched to the cam.

1/8th mile is the only track we have around here, the car is mainly raced ~1/4mi on the street. I only bring it to the track to see any improvements my car is making.



One thing I'm questioning is could my converter be holding me back? Not necessarily the stall speed itself, but the quality. It's a RevMax 3200-3400 lockup stall. It's only a few thousand miles old, But I'm not sure if converter quality can hold back my 60' times?

AlkyIROC

Based on your cam grind, your converter should work just fine for street/strip. For full race, something in the 3800-4200 rpm range would be better but then it's too high for street use. Stall speed however is not an exact science. You can have a loose and tight converter that both stall at the same speed and they'll perform completely different from each other.

With torque converters, you really do get what you pay for. An inexpensive converter is inexpensive for a reason. They may all look the same but the quality of the parts inside can make a huge difference in cost. My 8" race converter was $1200-$1500

Since your converter is close enough to match the camshaft, the rest of the car now needs to match the powerband that the camshaft and converter work in.

Skinny Neb

iTrader: (2)

What would be your go to suggestion to better my 60' times besides more power? I know the nitrous should help, but I feel like there's something holding me back down low.

AlkyIROC

Traction and torque

Leave the street tires at home and use slicks at the track. If you spin off the line your 60' time will suffer. Street tires at the track will never hook up like a slick. Even though it may feel good, you're probably spinning the street tires. Your 700R4 and 4.10 gears are already making a huge torque multiplication. If you're worried about breaking something with slicks then you'll never get better 60' times.

3.08 first gear x 4.10 equals a multiplication factor of 12.628. Multiply by the amount of torque the engine makes and that's how much torque is getting you moving off the line on a 26" tall street tire.

My race car engine makes a huge amount of torque. With a 1.76 powerglide through 4.86 gears, my torque multiplication is only 8.55 getting me off the line but I'm also powering 32" tall, 16" wide slicks. With all the torque the engine makes, when I get on a good sticky track, I put the car up on the back bumper (got wheelie bars installed now). A moderately sticky track and I usually carry the front end a couple of feet off the ground to around the 60' mark. A slick track and street tire cars are spinning off the line and I can't get my front end off the ground but can still power my way down the track with the big tires.

FRMULA88

Reduce unsprung weight and improve the weight transfer to the rear tires when you launch.

use front runners and remove the front sway bar
front drag springs
front drag struts
rear drag shocks
the non-adjustable Lakewoods are just fine... I used 90/10 drag struts on the street with no issues..

use purpose built rear tires:
DOT drag radials
slicks

FWIW at your power level Drag radials are a great choice... you will see no major improvement with a small tire slick.

There are guys running in 8s in the 1/4 on small tire drag radials..

no green

It could be, but I think it's a fuel or acc circuit issue, if it's bogging. A dyno wont show this. Also, if you have a fuel issue (and dont know it), putting it on the bottle will make it painfully obvious... I changed gears, converters, timing, all kinds of stuff, and i finally moved my pump behind the tank down low, and all my issues went away. FWIW, i had a 3400 with slicks and 4.11, with a TH350. My fueling issue cropped up about the same 60' you're at. It would bog and go 2.00, the next pass be ok and go 1.75... after the swap it was low 1.7x.

You have it at 38* total, what's the initial, and what springs are in it?

Also, it wont help your bog, but i found that staging position means the world when you're foot braking. When i went from foot brake to transbrake, the difference in 60' wasn't that much.


^^ case in point...

Skinny Neb

iTrader: (2)

Well, tested a couple times on the street with the ET Streets. I think they're just too old and don't have anything left in them. Both videos are of me going WOT immediately, no modulating of the throttle, just to see what happens.

First we tried 15PSI and a 1000rpm launch (sorry for the vertical then sideways video). The car just blew the tires off, then set off a car alarm a quarter mile away.


Then I decided to listen to some advice given on here and some friends to take my front swaybar off. We tested again, about the same temperature but at 12PSI in the tires and a 2000rpm launch. Now the front comes up right away, then blows the tires off about a foot out. Upon further testing the car does seem to launch much harder at 2000rpm than idle, or 1000, 1500 etc.

Very poor quality video, but it shows what it needs to.


We were going to test some 275/60/15 hoosier drag radials, but...

Skinny Neb

iTrader: (2)

No Green I honestly can't remember, I think it was at 18* initial if I remember right, but I can't be for sure. Which springs are you asking about? I have a holley mechanical fuel pump on the car, shouldn't be having any fuel delivery issues anymore.

Also thankyou again everyone for taking your time to give me advice.

Skinny Neb

iTrader: (2)

Did some testing this weekend at the track. Had the opportunity of making back-back-back runs on the same night with 3 different tires, but throwing the water pump belt cut my time short. I'm convinced my slicks are just worn out. I'll try grinding them down a bit to reach fresh rubber and if that doesn't help I'll purchase new.

Started off with the slicks, spins off the line, 8.28@84.6 with a 1.98 60'

I showed that Dart who the boss was.

Swapped over to some 305/35/18 Nitto NT555R Drag radials at 20psi and had zero traction. Spun through the 60' if I didn't pedal it. With a couple blips for traction the best I managed was a 8.49@86 with a 2.11 60'. I don't have a video for the runs with the DRs, but I did manage to beat and **** off the owner of a 2014 ZL1 Camaro.


Side note, ZR1 wheels look killer.

no green

I'm asking what advance springs you have in the distributor. You have 18 initial and 38 total, right? What distributor, coil, wires, box? When you're foot braking, the advance curve can make or break your 60' times. Fuel curve, too, that's why someone mentioned the squirters in the carb before. You're not leaving the starting line at WOT, so you have to tune the RPM sweep between your launch RPM and WOT. That's the trick, the engine is trying to pull up to WOT, but if your not giving it the fuel and timing it needs, it's not getting there as fast as it could.

Believe it or not, I knocked 1/2 second off my car for less than $10 and some track time playing with the advance and pump circuits. On mine, going from 16 degrees initial to 26 initial showed the biggest gains. I also put the lightest advance springs in i could without the timing jumping around on the timing light. I eventually locked it out, but since you're street driving this, you'll need to find the sweet spot between et and drivabilty you can live with.

Fuel "shouldn't" be a problem, isn't the same as saying fuel "isnt" the problem...


And something I'm just now realizing on tires, that tread is only 1/2 of the equation, and the sidewall is equally important. The tread has to be on the ground to hook up, and the suspension has to work to hook up, but what's the link between them??

Skinny Neb

iTrader: (2)

The distributor is a billet HEI Street Fire with stock springs (that come with the distributor), and the block off plate that comes along with it. Also has Street Fire wires on it. I've heard some people saying I'm leaving a lot on the table not going with an MSD distributor/coil/6AL box, but I've heard just as many people saying I won't gain anything.

New tires are ordered and will show up early next week. Trying out a 295/50/16 Hoosier drag radial. The spray will be going on shortly after. Going to be hitting 150 on a button, or more if the car handles it fine.


I found some cracking in the excuse of tread in my ET Streets, safe to say they're trash?

no green

I think you'll have better luck with some more initial, than changing a bunch of parts. I ran a Malory HEI & budget wires for a long time.

Is the bog gone, now? If it's not, the nitrous wont help, it'll be worse.

Make sure to go to a colder plug and pull lots of timing with the spray. It's easier to start with low timing, and add in a few degrees at a time, than it is to change pistons. Ask how I know.

And, invest in a window switch.

Skinny Neb

iTrader: (2)

The bog does seem to be gone, I'm wondering if the 5500DA the times it was bogging had to do with it.

Setting total timing down to 34*, adding some 110 and going some reduced resistor NGK plugs a heat range under what I have now. It's also going on the dyno so I can make damn sure my AFR is where it needs to be since I don't have a wideband.
I know what it's like to lose a piston too.. Not from spray, from an exhaust valve breaking for no reason.

no green

Ngk has great tech help via their website & email. I've emailed them a couple different combinations for stuff, and they were quick to come back with base line recommendations. It'd only take 5 minutes to see if what they say jives with what you're planning.

Good luck with it!

Skinny Neb

iTrader: (2)

Thanks for the tips no green!