My 2nd vette is a 1980 with a rebuilt CA 305 and a small cam on it. I have NO info on the cam installed; it was done by previous owner (2 ago). My mechanic is telling me that I HAVE TO HAVE a stall torque converter. He isn't selling anything because his shop doesn't do trannys anymore....he just SWEARS that I need one.

I have used this mechanic for 20 years and have a really hard time letting anyone else touch my cars...

Someone else told me that the ONLY REASON for a stall torque converter is for drag racing.

Glad they don't know each other! ...they both said the same thing about each other...and it went something like "he's a dumb$&%"....

I have been looking at a lot of posts on this website but nothing I have found really matches my dilemma...

I do not have all of the specs about my "new" car like so many folks do on here. We have found that there is a formula for figuring out your lift and duration of your cam by going through the gears if you don't have the specs...I do know that I have the 3-speed 350 auto tranny, and that the rebuilt 305 has about 25K miles on it.

I trust my mechanic; but am not sure why he says the stall torque converter is mandatory or it will mess up the engine/and or/tranny if not installed...with the 25K miles it already has on it.

I am thinking that previous people went more for the hot-rod effect; while this is my daily driver. This car will not be raced or hot-rodded in any manner...I gave up racing like a crazy person 20 years ago...(no offense...still love it..just too old for it!!) i just like to stomp it once in a while from a dead stop.

I have been reading a lot of posts about it wanting to lunge while at a stop. The car did do that (which is why this subject came up) but after some adjustments by mechanic; the car sits, at a stop, in drive, with AC running, at 700 rpm. Sounds pretty stable to me.

Plus I love the LOBE........


Any advice would be truly appreciated!!!



TANYA

 

I've always heard stall converters were for high-horsepower motors only.

 

If it doesnt drag the motr down at an idel and accelrates well for you leave it alone. Every mechanic is some kind of ex Nascar race expert just ask them.

 

you don't need a higher rpm stall converter.just make sure to prevent any vacuum leaks and keep your brakes working properly.

 

No. You dont need a higher stall converter until you really start playing with moderate to wild cams. Imagine your 'stall speed' on an automatic transmission as the same speed where your clutch hooks up on a manual.

An increase of just a few RPM'S (say 100-200) you arent even going to notice. (Waste of money)
Go to a much higher stall speed and and your start offs will become, well, unfriendly for the kind of driving you say you do.

 

Converters are generally matched with the cam you have .... it takes more RPMs to get the car moving ..... bigger cams require higher RPMs at idle and assists in getting into the torque curve quicker ..... you;ll also experience more clutch slippage in the tranny ... reducing life .....
From past experience, if this a more of a DD, you'll not be happy with a converter other then one in the OEM range ..... so ... if it ain't broke ........

 

excellent info

 

If the drivability is good now - accelerates well from a stop, will idle without bogging down, and not trying to run away from you at an idle - don't worry about it. Some more radical cams idle higher than the speed at which the stock converter locks up, and dont make power until the RPM is up. For a daily driver you would be better served by a stock converter if possible.

 

A Stall converter and a torque converter are the same thing just different names. If you have an automatic transmission, your car already has one which is basically a fluid coupling device between the motor and transmission.

The term stall converter is generally used when changing the rpm rating that the converter fully engages. Where stock may be 900 rpms an after market can be 2800 rpms. The effect can be like riding the clutch on a standard until you hit 2800 rpms.

Why does your mechanic think you need ANOTHER one so badly? What symptom is he trying to fix and why did you take the car to him in the first place, what issue?

My opinion is that unless you have a converter failure or some other driveability issue I would not change it.

If your current converter is failing, you just need another converter. The transmission would slip I would think.

If your cam is too large for your current converter, the motor will have to idle up and will push hard against the converter. So when you are at a stop light, you will have to hold your foot on the brake to keep the car still.

I would ask him why exactly are you recommending a different torque converter.

 

Ask him. If you trust him, follow his advice after he explains his line of thinking.

 

Your mechanic may be guessing that you have a high duration cam with the lopeing of the engine that you described. If that is the case then the higher stall converter helps get the engine into the operating range of the cam optimally without lugging at low rpms. The rear end ratio is also going to make a difference. A 3.08 is going to lug more than say a 3.55 or 4.11 rear end.
So if you have a 3.08 rear end with a high duration cam that does not hit it's power band until 2200 rpm then the engine is lugging/grunting until you get to that 2200 rpm. A stock Converter will brake stall around 800 rpm. In the case I illustrated that means from 800 to 2200 rpm the engine is not producing much torque for that 1400 rpm range and is slow to accelerate. So now if you put a 2200 rpm stall converter in you will allow the converter to slip more until 2200 rpm which allows the engine to quickly get into it's power band range and accelerate better. Then factor in the 3.08 rear end and perhaps you would want more torque (higher up in the rpm range) due to the high gear ratio and have something like a 2800 stall converter. This makes the engines job easier until 2800 rpm is reached allowing torque to be built to overcome the high gear ratio of the rear end.
If you install a high stall converter, due to the slippage it will create more heat until the stall speed is reached. To dissipate that heat it is a good idea to install and additional heat exchanger for the transmission fluid.
I have a 2400 stall torque converter on my stock 77 right now. It is not well suited to the stock motor and I plan on changing that soon. I do notice that the car accelerates much quicker when I get on it and at the same time requires more throttle deflection at low speeds to get it moving, particuarly when pulling a hill. No note-able change in fuel economy. I kind of like it now, it gives my side pipes a chance to make noise even at low speeds.

 

Bad thing about a bigger cam in a 305 is like night and day compared to the same cam in a 350.
A Edelbrock Performer cam might sound stock in a 350 but a 305 it will have a slight lope and rumble.
If sitting at a stop light and the car is surging with the brake on it needs a stall.
Also your trans fluid and water temp is going to be hotter because of the surging.
You can call www.ptcrace.com and tell them what you have and they will get you what you need.

 

Lane is the guy to talk to.

 

can you drive the car with one foot at a red light?.....and at 500 rpm`s?

 

Thank you all for your input! I am thinking it doesn't need to be changed out...I can sit still a light without it taking off...and being a daily driver and me a slow poke...I don't need it to take off like a bat out of hell!

 

I still think you need to understand why this mechanic is saying you NEED one.

 

enjoy your car, if its not broke and you like the way it is, dont fix it

 

Bingo. Cruise and enjoy.

 

I am taking the car in Monday for a new radiator and heater core. I will ask him why then and get back with you. My understanding of what he said was that any vehicle with a cam needs one, period. Also, the car was trying to lunge while stopped but he has adjusted the distributor and timing and it does not try to lunge anymore. I believe that was why this came up in the first place.

 

Tanya. I'm guessing you are a female. Take the biggest, hairiest back guy you know in next time you talk to your mechanic.