The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by blazedogs, Jan 23, 2020.
Sadly that's not the problem right now, I'm at work
Use a stock "big" Vega converter , around $100
Size of the motor and the torque that it makes converters stall / slip @different rpm, Unless you custom order a specific converter for your application,
Big Vega Will not pull when @ a stop , will start to pull around 1,200 rpms full lock up 1,800-2,00 rpms . " mild cam up to .530 lift 350 sbc.
Or a small Vega will lock up around 2,800-,3,200 rpms.
I have a few custom converters that range from $1,500-2,000.
I run a stock small Vega in my 30 Sedan.
427 sbc over .600 lift roller 3:42 gear 30 tall tire 350 trans . 6 inch wide Bridgestone radial tire, S10 rear , short shift @ 6,000 rpms , over 100mph in 1/8 . 2,800 pounds .
It would run faster with a 3,500 stall , but why ,
No tires traction anyways & s10 rear , junk china 4 bar , It would break with set of tires .
600-800 rpms why ? If you wanting to hear the over lap install the wright cam shaft for yr combo and tune the combination.
Stock initial timing is to low even if it was a stock 327 365 , start with 15 degrees of initial timing, ( it might like more ) I have ran as much as 22 degrees of initial timing .
keeps plugs clean .
Even on a bone stock two barrel Engine ,I play with the timing.
play with your total timing 36-45 . I set all my combos idle speed 1,000-1,200 rpms, stick or auto .
There is so much little things that need to be done for the engine to run efficient and correct.
I read all the time guys can not get a carb to idle correct ,in gear or park , there is more then mixture screws , jets and the Idle screw .
To tuning a carb or carbs .
Most Of the time people install camshaft that requires holes drilled in butterflies to idle correctly ,or adjust secondary butterflies with more of a airgap ,if not done ,butterflies are pass the transfer slot in the carburetor, No mixture adjustment & hight idling RPMs.
""Seat Of Your Pants Will Lie To You""
The rated stall speed is really more of a guess, the actual stall speed will vary depending on the actual car it is installed in, and things like weight are a part of that. A 2000 rpm stall speed converter might stall out at 1500 - 1800 rpm in a very light car, like a Model A hot rod. If it's driving through the brakes, the RPM that it drives through the brakes IS the actual stall speed.
My first guess is your brakes are bad. Stall converters are used a lot to spool up turbos so they will be up to power when you leave the starting line.
In brief, the torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. It is responsible for pressurizing automatic transmissionfluid, a pressurization that supplies the force necessary to shift transmissiongears.
Most modern drag race cars use an automatic transmission. Selecting the right torque converter for your automatic transmission can make all the difference in how your drag race or street/strip vehicle performs.
A performance torque converter can help you to:
Improve the performance of your vehicle
Get better speed
Get better acceleration
Idle better in gear
Leave from a stop harder
The torque converter is an integral part of the total vehicle combination. While many vehicle combinations and applications are very similar and the best torque converter may be an off-the shelf buy, it is normally a wise step to consult an expert for your specifications, and choose the best torque converter for your particular application. It is extremely important to communicate with your converter builder in order to get the right torque converter for your race car.
For many quarter-mile racing enthusiasts, and especially backyard mechanics, there seems to be a mystery about an automatic transmission's torque converter. Many people do not understand how it functions, let alone how one can work to your advantage when trying to improve a car's performance and efficiency. The torque converter is really not all that complicated, once you understand how it functions. This adaptable coupling between your engine and your drive-train can be modified or reproduced by transmission experts to increase your transmission's use of the supplied engine horsepower. But, before you go out get an expensive new torque converter, we believe it's important to understand what you are spending your money on.
OP what the specs of your cam shaft ?
What size is your carb? ,
then when can give more accurate help ,
I can not Believe your brakes are that bad or out of adjustment, But maybe !
I've had exactly the same problem with 2 hotrods - fairly mild smallblock, auto trans and a light car ('32's). Drove normally but awkward at stoplights but the worst was when the choke was on and trying to maneuver in tight spots, eg getting out of garage with obstacles to avoid. Gravel driveway just added to the problem. A real fight - sometimes scary. There were some other non Hamb friendly factors in play as the engine really did have a mind of it's own!
I installed I think a B&M (now TCI?) Saturday Night Special (something like a 2000 rpm stall?) and the transformation was instant. The car 'creeped' but gently and controllably, just like any ordinary auto car does. But the huge bonus was that the already pretty good (or so i thought!) performance was similarly transformed. No obvious downsides.
Does the OP's car when stationary kind of bang/bump/lurch when changing through the gears, ie P into R, R into N, N into D? And worse if the brakes are firmly applied. Mind did. Now doesn't, and is now a joy to drive - been that way for getting on for 20 years.
Try either removing the vacuum advance or connecting it to ported. I remove them and raise the initial since I have a low compression motor..
I like my idle as low as possible so when I put it in gear it doesn't bang (TH-400).. I usually flip it into neutral at red lights. I manual shift my automatics.
This is what a mildly higher stall speed converter will do. If we're interested in answering the original question, here
Built a Model A back in the 70's with a 327 and 400 turbo and had to change the converter after I built it. When you dropped it in gear it felt like it was going to turn the car over.
I wasn't going to open this thread for the very reason that Gimpy pointed out. The terminology is "High Stall".
But the real problem is that there is too little information supplied which causes a bunch of half baked opinions on how to "FIX" it.
The OP states that the motor 'idles down'. What is the idle RPM in neutral with the engine and transmission at operating temperature? Until you know this, everything else is a stab in the dark.
The things I have learned from this thread are:
Most guys don't know how a torque converter works.
Most guys don't proof read their posts.
But, most important I learned a new word, "Pedantic". Thanx Gimpy.
He's pretty good at it.
but then...I tend to be that way, myself. I'm trying to get better, though.
Pretty soon I'll have to look up every word you guys say just to have a conversation with you. Lippy
It's been mentioned several times in this thread that the car's weight affects the stall speed.
Can someone explain to me how weight affects the stall speed of the torque converter?
I understand that a higher stall speed can be effective in getting a heavier vehicle to accelerate from a stop a little quicker due to higher engine torque being available at the higher stall speed, as well as the torque multiplication of the converter, but as far as weight actually affecting the stall speed, I doubt that it does.
If you swap the engine and transmission from a featherweight Model T into a 1940 LaSalle Hearse, the stall speed doesn't change, does it? It just takes longer for the corpse carrier to ooze away from the crematorium stop sign.
Vehicle weight does not affect the stall speed of the torque converter. It does affect the driveability of the car, hence it affects what converter you want to buy.
It’s my opinion you are totally wrong with this statement. Vehicle weight does have an affect on stall speed.
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High stall converter science is all witchcraft! A lot of it is kind of backwards of my normal thoughts. So I admit that I do not understand it. A high powered car needs one so it can idle in gear and get to power on take off. A heavy vehicle with a low powered engine needs one so it can get up to power to pull out. Two different needs that have the same solution.
Of course the weight effects the stall speed. It has to do with pressure vs resistance. The combination of the elements inside the converter, the impellor, stator & turbine, creates the characteristics of the converter, how it converts rotational energy from the engine and transmits it to the transmission input shaft. If you take a power train out of an Impala and stick it in a Model A, the stall speed will be lower. That's because the same converter in the Impala has more weight it has to move, which requires more pressure from the converter. Put that same converter in a Model A and less resistance is required to get the car moving, the torque rise from the converter will overcome the resistance to motion with less pressure. Reverse the situation, take the converter from a 6 cyl Nova and put it an Impala, and the stall speed will increase, it takes more pressure to get the car moving. This is well established.
Incorrect, a heavy vehicle with a low power engine needs a low stall speed converter, because the converter is already going to slip trying to build enough pressure to get the vehicle moving. Think pressure vs resistance.
Convertors are, in simple terms, 'torque reactive' components. High stall convertors are akin to nitrous HP ratings. They're figured "x with y" and set accordingly, so if you buy a 2500 RPM convertor then what is that installed in? I'd bet my 39 Ford that if it went into a 350/350 HP combination and gave close to the 2500 figure and then it went into a 454/500 HP engine it would be more like 3000. Now any keyboard experts out there can shit all over this if you like but I've backed this up on street racers and drag cars for decades. Want more? Call someone like Hughes, Continental, Art Carr, ask for a convertor. They want wt, CID, compression ratio, cam specs, rear axle gearing, dyno figures (if you have them) and probably blood or semen samples just to be sure they build the right part. True enough, any looser "off-the-shelf" convertor will net some improvement, but it's important to know what basic engine combination, or indeed torque output, they used to get that rating. That means if you need something loose in a nervous little 283 with a high RPM power/TQ curve that off the shelf spec needs to be chosen much looser than something like a 350/350 or a basic street big block. Does this help? It's as simple as I can keep it. Carry on...
Stall speed is measured with the brakes applied, so the vehicle is stationary. This is the definition of the term "stall speed". There is no way that vehicle weight can affect the stall speed of a torque converter.
But how the vehicle reacts after it starts moving, definitely is related to vehicle weight. So, if you have a light vehicle, you probably want a higher stall speed torque converter, than if you have a heavy vehicle.
For a given engine torque and associated torque converter, there is an absolute stall speed at which the engine can not attain higher RPM. This stall speed is not affected by vehicle weight. It is a stationary measurement.
The stall speed of the converter you CHOOSE should be based on the weight of the car, engine torque, gear ratios, etc, but the weight of the car does not affect the advertised stall speed.
I don't recall if there has ever been an instance where the same torque converter has been advertised as having different stall speeds based on vehicle weight.
Jim is correct, as is Ebb's . They are talking about stall rating, in which case the vehicle is stationary.
Yes, vehicle weight does play a part on how a converter "acts" though it's acceleration curve.
It's always made me crazy when someone uses the term "stall" converter. I want to see somebody drive a car with a "no stall" converter.
A transbrake will tell you what the true stall speed is in a torque converter.
They do make lockup torque converters, just don't have it locked up when you come to a stop.
this is about the time when I should bring up variable stall speed ("switch pitch") torque converters, eh?
My favorite transmission feature from the mid 60's.
I had one once, in an O/T vehicle with a 2004R transmission. It worked normally again once I replaced the lockup solenoid.
Then you would have a 0000 rpm stall!
It's also related to how much power you have isn't it? Just because the box said "3500 rpm" doesn't mean a stock small block is gonna push it to that?
yes, stall speed depends on available torque.
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