[sheetmetal]

how does one come up with the correct stall speed. ive heard so many rpm over peak tq, match the peak hp. under the each???? converters are a bit expensive and a wild a$$ guess just dont cut it. right now the playback says im launching at about 4800.seems a bit light. the cam is 251-262 solid roller. the card is callin for 5000-5500 stall. i have no real clue where the peaks are. the card says 4800 pk tq ,6200 pk hp. im thinkin coan might be able to help me out but thought id check with the masses first. thanks Dave

 

[FourEightyNine]

I would just run the exact same converter as John Wilson(you guys are buddies if I remember right). Better to buy a converter that you know will go low 9s and only buy one, than buy multiple converters on your way down there.:yes:

 

[trmnatr]

Usually your converter stall on the transbrake you want at peak TQ to +200rpm as if your transbrake stall is 5,500rpm and peak torque is 5,500rpm, If you stage at 5,200rpm for an example your right in the torque range and when you release the trans brake the converter will hit about 300rpm higher than it did on the brake for a great launch

This is how we get converters for small block high rpm engines in our cars

 

[sheetmetal]

Butch, this is a foot break car, launch rpm is 1500. Dave

 

[trmnatr]

Then you want the rpm to flash about 300-400rpm past peak torque because it will flash as soon as you hit it from 1,500rpm which i assume is darn near idle, if the car hooks the rpms are gonna have an initial drop of about 300-400rpm, this is why you want it to flash beyond peak tq so it flashes above it and as its hooked off the line the rpms do drop a hair, your still at or around peak TQ, If it spins the rpms go up, it hooks the rpm's go down thus needing the extra RPM's on the flash point

If you have a 5,500rpm stall {footbrake}, you will see it flash 5,500rpm and drop a couple hundred then accelerates up on a good run, the rpm's dropped right after the flash, if it spun the rpm's would not drop

Note: It takes a play back tach to see it or Data Logger

 

[sheetmetal]

Butch, i have the play back tach and at half speed i really cant see the drop or fall back. it just slows down at 4800. and the car generally hooks ggod. Dave

 

[trmnatr]

So the tach jumps to 4,800rpm off the line? Where does the engine make peak TQ? For it not to dip down you may be perfect as it flashes up right at peak TQ

With a Transbrake you can have a 4,800rpm stall on the brake and it will flash above the transbrake stall then drop a little, This may be why Transbrakes usually run more MPH and 60'

With the streetable cam in my car ET didnt change much from footbrake to transbrake but 60' dropped almost .2 on the transbrake, If we had our old cam in it the better 60' would have been a good run

Most stuff we run has a transbrake, Our old combo had a 283/291 @.050 in a 331cid so we needed a transbrake and a BIG converter

 

[sheetmetal]

not real sure Butch, the cam card says pk tq 4800, but calls for a 5000/5500 converter. the old HR cam made pk tq at 5000 on the engine dyno.

 

[trmnatr]

What are the specs on the engine? What are the cam specs too?

 

[sheetmetal]

383. ported afr 195s flow 304 at 700. 251-261 sollid roller on a 107.5 734 gross lift. 10.7 cr, ,super victor

 

[trmnatr]

Im gonna guess about a 5,800rpm for a footbrake car, if you put a transbrake in i would use a 5,500rpm

 

[trmnatr]

The reason i say that is if you take a 5,800rpm flash {Footrake stall} converter and throw the brake on i bet it would go 6,200rpm so it would run cooler if on the street with a transbrake because you could run a converter that gives you your X,XXX stall at the track but its actually is a little tighter

ATI is a good converter but most of the time they build them a little too tight, some times they are dead on, I have never seen ATI do a converter too loose

 

[trmnatr]

Dave, here was my converter from ATI, listen to my video on this run, The exhaust was off with the streetable cam in it, about the size of yours but 331cid, you can hear the converter is too tight, the cam is a 260/268 @.050 .630/.630 110° lobe center which kills the TQ off the line in the little engines, shifted at 8,000rpm on that run {light set at 7,600rpm}, Our old 106° cam is worth 1.0 drop in ET

Video your car, video will tell alot, almost as much as Data

Here is the link, its under trmnatr

http://chevelledotcom.com//video/

 

[sheetmetal]

ok i listend to the vid. mine dosent seem to lug as much right off the line but the rpm does start to rise about 30 out

 

[trmnatr]

ok i listend to the vid. mine dosent seem to lug as much right off the line but the rpm does start to rise about 30 out

Thats where ATI and i butted heads, they said the converter was fine, I told the ray charles could see the car slow down after the launch ! After a little talking they repaired it and its all good

 

[trmnatr]

ok i listend to the vid. mine dosent seem to lug as much right off the line but the rpm does start to rise about 30 out

If yours has a lug/lag like that off the line it needs more converter, mine needed 1,300rpm more to correct it, You can judge how bad the lag is on yours, i bet its gonna put you 5,500rpm but watch your gearing when you adjust the converter, make sure you wont run out on the big end

On your playback tach, it jumps to 4,800rpm, where does the tach start moving faster? 5,500rpm? Does the play back show a slow acceleration spot in the RPM's?

 

[sheetmetal]

im running a ati now but with all the bad press ive read as of late i dont think ill get it restalled buy them. thinking about going with a new coan. just not sure about the stall.

 

[trmnatr]

im running a ati now but with all the bad press ive read as of late i dont think ill get it restalled buy them. thinking about going with a new coan. just not sure about the stall.

How old is the ATI ?

 

[sheetmetal]

Butch, ill have to take a look tomarrow at it. it goes kinda fast to 4800 then slows down. not real sure if it moves at a faster rate after anywhere in the run after that

 

[sheetmetal]

the converter is about 5 yrs old. not even 100 passes.