What stall converter do I need?

michael_cini

Well-known member
I have a '75 250 engine with OZ head and 350 Holley. I have a Clay Smith 264/274 110 lobe center cam with C4 tranny. The car does not idle well, I adjust the carb and timing with the car in park and idles fine. But once the car is in drive the idle gets rough. The stall converter is stock. What converter do I need to put in the car?
Thanks.
Michael
 
8) start by setting the timing and carb with the trans in drive, as per factory requirement. it sounds like the idle speed setting is too low.
 
thanks for the tip. i have done this, and it idles better, but never as good as it does in park. and then when it is in park the idle races. isn't switching the stall converter the correct fix?

rbohm":d632ft9i said:
8) start by setting the timing and carb with the trans in drive, as per factory requirement. it sounds like the idle speed setting is too low.
 
Yes you are correct , you need something advertised to be in the 2500-2800 range ( it will stall lower than that because you only have 250 cubes and the standard for most mfg's is an all stock 350)
 
FalconSedanDelivery":zgsliyjo said:
you need something advertised to be in the 2500-2800 range

Where would one find such an animal for a small six with a C-4?

Crap, the 250 uses a different setup than the 170/200, right? :banghead:
 
Yes and for you ( and Me as well ) its a good thing , as they take the common C-4 converters as used behind the V-8's , But just as I stated above , you want something that will ( be rated ) at 2500-2800 as with a 250 it will be at least 500 lower than advertised
 
that is a good question, i was going to ask too, but you answered it. the 250 takes a v8 type converter, good. any suggestions on where to get one? is it advisable to get a used converter? what all is involved in changing converter? I assume in order to change the converter, i would need to disconnect tranny and move it back slip in new converter and reconnect?
michael
 
I personally wouldn't use a used converter...new ones are not that expensive. I am using a 2800 stall from Roadrunner converters but there are many vendors that can supply you with a converter. You can check Summit and they sell a variety of converters. To change, just remove the converter inspection plate and disconnect the nuts that bolt up the converter to the flex plate. Then disconnect tranny and pull tranny back so you can remove the converter. Slip on the new converter making sure it properly engages to the tranny input shaft...then re-install in the reverse order. BTW, I have the classic inlines 278 cam with a 110 centerline and it idles in gear nicely around 700 rpm...almost seems like the stock cam...but it doesn't run like it has a stock cam in it!!! :D
 
thanks for the info gene. i took a looks at the roadrunner website, and strangely enough, they do not have a c4 converter listed. just aod's.
http://www.roadrunnerconverters.com/ford.htm

Gene Fiore":3mapnoem said:
I personally wouldn't use a used converter...new ones are not that expensive. I am using a 2800 stall from Roadrunner converters but there are many vendors that can supply you with a converter. You can check Summit and they sell a variety of converters. To change, just remove the converter inspection plate and disconnect the nuts that bolt up the converter to the flex plate. Then disconnect tranny and pull tranny back so you can remove the converter. Slip on the new converter making sure it properly engages to the tranny input shaft...then re-install in the reverse order. BTW, I have the classic inlines 278 cam with a 110 centerline and it idles in park nicely around 700 rpm...almost seems like the stock cam...but it doesn't run like it has a stock cam in it!!! :D
 
8) i will say this, before you go to the expense of installing a new torque converter, make sure you dont have any vacuum leaks that are causing you to have to run a higher idle speed. also make sure the carb is not leaking fuel into the manifold as well.
 
Gonna go out on a limb here but have you checked the vacum modulator on the trans?? I was having idleling issues and such with my old truck (300-C-6) a friend help diagnose the problem swapping out the modulator solved the problem also you may have adjust it to get the tranny to shift right to your liking.I noticed especialy when I changed gears in the rear end went from 2.70's to 3.55's that the shift rpm changed afterwards especialy when run the 1/4 mile. might not be the answer but might be worth cheking into aswell.
 
how would this effect idle quality in gear and not in park. wouldn't it effect both?

rbohm":zzzz4s0a said:
8) i will say this, before you go to the expense of installing a new torque converter, make sure you dont have any vacuum leaks that are causing you to have to run a higher idle speed. also make sure the carb is not leaking fuel into the manifold as well.
 
how would this effect idle quality in gear and not in park. wouldn't it effect both?

82F100":18yul04z said:
Gonna go out on a limb here but have you checked the vacum modulator on the trans?? I was having idleling issues and such with my old truck (300-C-6) a friend help diagnose the problem swapping out the modulator solved the problem also you may have adjust it to get the tranny to shift right to your liking.I noticed especialy when I changed gears in the rear end went from 2.70's to 3.55's that the shift rpm changed afterwards especialy when run the 1/4 mile. might not be the answer but might be worth cheking into aswell.
 
8) when the throttle plate is open enough, you can get a decent idle with no load on the engine, because at that point the vacuum leak isnt affecting anything except that you need to open the throttle up enough to get the engine to idle smoothly. when you put the load on the engine, the vacuum leak will rear up and bite you.
 
thanks for the explanation. how do i make sure i don't have a vacuum leak?

rbohm":17czyx52 said:
8) when the throttle plate is open enough, you can get a decent idle with no load on the engine, because at that point the vacuum leak isnt affecting anything except that you need to open the throttle up enough to get the engine to idle smoothly. when you put the load on the engine, the vacuum leak will rear up and bite you.
 
8) put a vacuum gauge on and see what vacuum reading you get. it should be around 18-22" and the needle should be steady. if the reading is lower, or the needle jumps up and down substantially, then you have a vacuum leak. you can also spray a little wd40 around the gasket areas, especially check the carb adapter to manifold gasket as people tend to forget that gasket needs replacing from time to time.
 
btw when spraying wd-40 or carb cleaner which for me works best at pinpointing vacuum leaks . when spraying the mating areas the engine revs up then there is the problem. also check your carb screws and gaskets. remember there is a venturi inbetween the throttle blades and choke that is mated together with 3 large phillips screws from the underside of the carb. If u have a leak inthat area i suggest a new gasket and check for straightness. if all else fails check all hoses and connections. and the vacuum advance line. do u have it plugged into manifold or ported? if ported connect direct and see if that helps ." the vacuum advance and vacuum leak seem to be the culprit according to your desciption of the problem".
 
i think you should get one with a lower stall than that if it is going to be a street car, think about when you backing up, the rpm would have to build up to 2500 and it would punch into gear with almost the full torque of the engine.
 
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