Ive been having this problem ever since i did my hot cam. I cant get my car to launch any higher than 1800 off the line. If i brake torque it any higher than that i trip the tree and start rolling through early. I imagine i should be able to launch it quite a bit higher than that since i have a 2800 stall.

Is it as simple a fix as getting a brake upgrade or would a line lock work? Or should i be looking elsewhere first to see what the problem is?

I just dont know much about line locks, so if anybody could shed some light on this problem i am having that would be great. Thanks

 

I am getting a line lock for this exact reason, plus you can burnout in the wet box much easier. However, I am a m6 but same basic reason. I want to be able to control my breaking with a flip of a switch.

 

well, here is another question then... isnt a line lock only as strong as your brakes? I mean if foot braking cant hold the car still, how will a line lock fair any better?

Maybe i just dont understand line locks all that well... anybody wanna shed some light on this topic?

 

I'd inspect your brake system.

A line lock system allows you to "lock" the front brakes, leaving the rear brakes "off" to allow you to perform a burn out. It also frees up a foot for the M6 guys so they can have one foot on the clutch and one on the gas while the line lock keeps the car from rolling.

 

Only real way a line lock is good is for your burnout, and if you run a transbrake to help lock the car in place once you activate the tbrake to prevent car from minor movement from suspension settling.

Anyways, your right, the LL is only as good as your front brakes, right now footbraking you have pressure to all 4 corners and your pushing through at 1800....by using only a LL on the front tires you will push through just as easy if not easier since your only using 2 tires to hold car in place. Also what will happen and I've seen it hundreds of times, once you bring the rpm up with line lock enguaged, it will literally push the locked front tires through the beams.

The heart of your problem is the convertor. Just becaue it's rated at 2800, does not mean you can pwr brake it to that rpm. For one ratings are a general window of what it should flash to. Best way for you to see what your convertor is actually flashing to (should be 2800 or real close) is looking at the tach when you launch and see where the needle goes. It should hit the flash point and hold there until car speed reaches engine speed and it will then start to gain rpm. Only way to get a looser convertor to pwr brake higher is to send it back in to manufactuer and have them cut it open and tweak the fin angle. It will build a lil more heat like that, but will allow you to pwr brake it higher. Same goes with installing a hwy gear out back, if you go from 4.11's to 2.73's the convertor will pwr brake higher since the mechanical leverage is'nt there to help overpwr the brake system.

 

thanks a lot IHI... helped me out. I didnt think a line lock was gonna be able to solve this problem.

So really my only true way to solve this is to have the converter sent back? I mean, what about getting better pads? Or upgrading to the LS1 set up since it is 2 piston calipers compared to the LT1 one caliper design?

Also, i am going to a 3.73 gear ratio from a 2.73, so will the converter power brake lower then? If so, that might help me out too, right?

Help me out, its really frustrating.

 

Senind convertor back to have it tweaked is the only correct way to fix the problem of rolling through, or just dont try and bring rpms up so high.

better brakes will help and make stopping better so it's a good investment no matter what the problem since it's a safety issue. BUT your brakes can only hold so much and then it's going to boild down to rear tires are going to try and push the front tires across the top of the race track and your back to square one again so that in itself is a wash.

better gearing will help performacne big time over what you have/had in the 2.73, but again, increasing gear reduction is going to make it worse since mechanically your making it easier to over pwr your brakes and push the car....right now with the 2.73's you should be able to get quit a bit of pwr brak rpm since mechanical gear reduction is soo low it's harder for the car to psuh through the brake system...I hope that all makes sense so I dont hve to type out a big example

boils down to, see where your at with the better gearing, you may find your able to reduce staging rpm so as not to push through the lights and still get proper performance. FWIW, I 60' the best off the transbrake leaving at 4600rpm, but I actually ET the same and mph more leaving at a dead idle....transbrake is designed more for consistant R/T and chasis tuning....they do absoultly nothing to make you faster. My normal staging rpm was 3000K, a few yrs ago with my old 12/13second 355cid 2800rpm was where I staged at. RPM is not everything and trying to take it to the extreme will not get you the gain I think your trying for....trust me I've been there done that and have tried many different leave combinations with this car to test theories.

 

thanks, that does make sense. Im just so perplexed because after i did the hot cam kit, the gains i got were not all that satisfying and the only thing i could come up with is that i wasnt able to launch the car at as high of an rpm as before the hot cam.

As is with my mods, im still in the deep 13's which is very disappointing. Because i see some guys on here with no cam doing high 12's. I know every car is different, but it just pisses me off.

I know the better gearing will get me into the 12's, if it doesnt, then this car has a major issue somewhere. But i just keep thinking that if i can launch it above 2000 rpm i can get a better hole shot, better 60', better 1/8 mile etc. etc.

 

Every convertor and drivetrain combo is different, but I've seen a great many cars (faster type cars) actually get better 60' times leaving at a dead idle. What happens is the car gets a run at the convertor and hits it pretty hard...with my car from a dead idle was only .04 slower than t braking at 4600 just so you understand what I'm saying. Good 60's are not always dependant on trying to get crazy. Think about it like this also, when your pwr braking waiting for the light, think about how much pwr your wasting binding up your supension preloading the car that is already wasted energy at that point. Wasting pwr is not going to get you anywhere fast.

Which brings up a valid point of why I rank convertor #3 on my list to go fast "effeicently" your torque convertor is the KEY element to transmitting everything your engine has to offer and "converting" it into the ground so you can go. a mismatched convertor will kill a combination and is usually one of the last areas people look at when wondering "why is my sheeot so slow" or "why is'nt my car doing this or that". Many issues are tuning, but once you know tune is right and the performance still is'nt there, the convertor is usually the biggest culprit. Take a stock car but put in a hot motor-making it a combination that does'nt work together even though you have say 500hp under the hood. Now take a car with that same 500hp but has a convertor, gear and tire size to match to complete the perfect combination the answer is obvious who's gonna win. convertors need to match the cam which dictates the pwr band so you can use the available power to get you moving quickly/effeciently.

convertors are not one size fits all, and dont expect to get a great convertor cheaply either if your looking for a bullet proof piece that works as it should. I dont know what your current cam specs are nor your current stall rating or what it actually flashes to, but obviously someting is amiss. Only way to honestly see what convertor flashes to is with a transbrake and pulling out the rev limiter pill and flashing it at WOT with Tbrake enguaged for a split second and seeing where the tach goes. If no Tbrake is used, next thing is to take the car to the track, stage and when the light turns green stare at your tach and see where it flashes to on the hit (WOT) this will be your flash point (more/less) or if you have a manual valve body put the car in high gear and go WOT and see where the tach goes....this can be done rolling at 5-10mph, but if the transmission kicks down there is no way of knowing since obviously rpm's will jump.

As for your tune, dont feel bad it takes time. When I first brought out this combo I thought I could at least hit 11's....I was running consistant 12.00-literally 12.00 all day long, I raced 2 events and won with a 12.00 on the window. I took some smarter guys than me to come over and help diagnoise the problems which turned out to be a bad MSD dizzy that missed some bushings, 1 glide was missing, a lil too much end play and advance curve was goofy. I installed a brand new MSD with a different curve and 1st pass off the trlr was an 11.21 so I had .8 buried in a crappy distributor that honestly I dont think I would've picked up on myself so thankfully I have smart buddies

Keep pecking away and you'll get'er to come around and make all this trouble now seem worth it, plus you'll have all this experience under your belt for next time...a journey I know all too much about

 

Now, what do you mean by "where it flashes at"? So at the track if i am just sitting at idle waiting for the light to go green, when i hit it (WOT) wherever the tach goes is my flash? If i go WOT, wont it just jump up and start taking off? Or is my flash where the tach first jumps to?

Im not sure i understand. Im trying to find out more and more about the inner workings of a converter.

This is helping me out so much, i dont know what my specific cam specs are, but they are the normal hot cam kit from GM, not a custom ground cam.

 

You've got the jist of it. Assuming your at the tree and lights coming down, then you go WOT with 100% traction, your tach will instantly go to the convertor flash point (since convertor will be slipping it allways motor to rev upto the rpm point of the convertor) and it will stay at the rpm until it starts to fluid couple and not slip then tach needle will start to rise again. This is why it's important to have a good convertor since you need it to slip enough to get your motor revving into your ideal tq/rpm band for max effort off the line performance, but not slip soo much your not going anywhere.

The convertor is acting like a clutch in a manual transmission. Say your motor makes peak tq at 4500rpm. If you have a stick shift you'd want to let out the clutch keeping your revs at 4500 and slipping the clutch manually to maintain that 4500rpm sweet spot until the car is up and running before you fully let off the clutch and let the car eat. Very vauge/rough example, but I hope it paints a picture of what the convertor is doing. and that is why you want to match the convertor to cam specs since that is a very important part of the equation dictating where your peak pwer is in the rpm band.

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http://oldanimotorsports.20megsfree.com/custom2.html