73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: micahadams on October 04, 2009, 11:43:50 PM
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Anyone know what the stock stall speed is for a 454/400 combo? Mine seems high for what I think stock should be
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1500-1800
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Thats what I though it should be at. I am getting 2100 right now. I am thinking maybe someone put a converter for a small block.
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wouldn't that make it around 800 if its for a small block, maybe its a stall someone put in
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How did you check your stall speed? Why do you think yours is high?
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I just pressed the brakes so they didnt spin the tires and floored it. I think its too high because the full throttle shift points are 4k and with a truck that is meant to haul/tow... Plus with a non locking converter that is building a lot of heat for the trans.
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Do you usually haul/tow at full throttle?
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Your shift points sound about right to me! My 86 k10 305/350 combo shifted at 5100 wot
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Stall speed doesn't control your shift points. If you are towing you should have an auxiliary cooler. If you want to change your shift points get an adjustable vacuum modulator.
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Would a adjustable vac modulator help shifting at wot? Vac is at 0 right?
My point is the motor is done making power at 4k, and will 4.11 gears and a high stall it makes a very limited range of speed. At 65mpg im turning 3k rpm. I just think that if it had a stall speed of 1500-1800 it would make a lot more use of the BBC power band
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No, vacuum is not at zero at wot. When the throttle is quickly opened it will drop to zero but if it stays there you might want to check for a plugged exhaust. If your engine is done making power at 4k it's not your torque converter. I'd check for restricted exhaust, correct ignition timing and correct cam timing. Something's not right.
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micahadams, what are you trying to accomplish? Lower the cruise rpm? Fire-breathing drag truck? long distance tow-monster?
One of your earlier posts you had asked about shift points, consensus seemed to be that everything was about right for your trans. How are your part throttle shifts? (hence the question "Do you usually haul/tow at full throttle?")
If you tell us what your looking to do, these fine folks can help. :)
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My goal is trying to make this truck more driveable. Imagine driving a truck with 5.13 gears. 1st gear is good for 25 mpg, 2nd for about 50mph. Just seems like a low mph. Im not looking for a hotrod, just soemthing with a better range of speed. 70mph tops sucks.
Vacumm at wot is 0. Unless you had a extremly small induction system. When I say zero, I mean less then 1 inch.
Part throttle shift are fine, just really short. I can be in 3rd at 15mph with light throttle.
A motor/trans combo with a high stall is fine if your motor has a high rpm potential. A buddy of mine has a nova with a 4000 rpm stall and its a blast because his powerband is high. Low powerband, highstall and high gearing makes it a turd.
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5.13... wow, no wonder. I think you would be extremely happy with a 3.73. I remember my first truck had a 4.56 rear in it and at 55 mph the tach showed 3500 rpms. Yours has to be screaming at 70
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Ditto on the 5.13's. How tall of a tire are you running?
4.11s and a 30" tall tire (245/75-16) in my truck put me 3000rpm@65mph. I don't have the big block torque, or do much highway driving so for me it's working.
If I were in you shoes, I'd be looking to get the final drive lower. By using an OD tranny, different rearend gear, or taller tire.
From what I understand, a stall converter just allows the engine to operate in it's optimum rpm range.
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I typed that wrong. I have 4.11, but with the high stall it feels like having 5.13
Im the same as you Donut, 3k @ 65mph and I think thats too high for a big block.
A stall converter is just another name for a torque converter.
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IMO, if you don't like the rpm range, you should look at lowering it. Taller tires, lower numerical gear, OD trans, or a combination.
I don't believe the converter will affect your final drive.
I did have the fun of driving an old furd SD with a real steep gear. Above 55 all it would do is make noise. At low speeds it would pull just about anything as long as you could keep traction. (460, auto with OD)
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The only time a converter will effect rpm at certian speed is if you have a very large converter and the stall speed is higher than your cruise rpm. Like having a 3500 stall and your cruise rpm would normaly be at 3k but the converter will not lock in untill you reach 3500.
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Because this converter does lock up it does change your final drive ratio. When I say lock up I mean like a locking converter style. With out a lock up converter, your non locking converter will always be slipping. The more load you put on it the more it will slip.
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http://en.wikipedia.org/wiki/Torque_converter (http://en.wikipedia.org/wiki/Torque_converter)
If it in fact does change the final drive ratio (noticeably) Couldn't the OEMs get rid of that pesky OD?
My redneck understanding of a torque converter is that it's nothing more than a hydraulic "clutch", lock-up converters quit slipping and helped give you 1-1 on the final drive. Lock up and stall converters are 2 different animals (IMO) I briefly looked into a different converter for my truck, a lock-up wouldn't help me off idle, which is where I plow, a high stall would be slipping at that low of an rpm. The stock converter fit me OK, probably not the best, but a fair compromise across the board.
I maybe all wrong. If someone could correct me please do, it may make a good blurb for the tech-pages.
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A lock up converter has nothing to do with final drive ratio. The only purpose of a locking torque converter is better fuel economy during the coupling stage.
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lock-up converters quit slipping and helped give you 1-1 on the final drive.
Right.
It doesnt effect your final drive "ratio" but it does effect drive rpm. Thats what I am interested in. All torque converters slip, the more stall rpm, the more they slip. If you have a lock up style then its 1:1 once it locks up.
My point is take 2 vehicle all other things being equal. 1 has a high stall converter, and the other is low. Cruising rpm will be different.
Anyway, I have a approx 1500 rpm converter coming from Hughes this weekend. I am going to put it in and report my findings. Any predictions?
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I predict it'll take longer and you'll drink more beer than previously budgeted.
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im running a 2400 stall in my 75..
4.10/285/75/16 (33") 70 is ~3000
looking at going to 35" tires
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My 86 has a 2800 stall. With 3.42s and 31s
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...Anyway, I have a approx 1500 rpm converter coming from Hughes this weekend. I am going to put it in and report my findings. Any predictions?
I predict (everything else being good) that you could slow down 5 mph and get the same results cheaper.
Isn't a 1500 rpm converter essentially a stock replacement? I believe Captkaos posted that stock was 15-1800 stall.
I am curious to see your results. I actually hope my prediction is wrong, and you get what your looking for.
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UPS says it will be here tomorrow around 4pm. I am curious too.
700 rpm reduction at stall probably is only a couple hundred rpm reduction at cruise throttle position(because of lower hp input into the converter) Thats my prediction.
Screamin 86, do you remember your 65-70 rpm?
I would be curious to drive the same truck with 2100 rpm stall and something real low, like 1100. Keep in mind this isnt my daily hotrod, its manly a hauler.
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Your converter should only stall on a launch or climbing a grade, passing uphill etc not at cruise. Cruise is trhe coupling phase of the converter. A lower stall speed may help you with around town fuel economy but if you are looking to reduce cruise rpm don't expect any miracles.
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^ Right, doesn't a higher-stall converter still behave like a low-stall converter at lower RPMs and/or lighter throttle input? Meaning, if you have a 2500 stall converter and putter around town at say 1800 RPM, that doesn't mean that your converter is slipping by 700 RPM at all times. If you stomp on it though, it should flash to about 2500 and go, right? Camshaft profile, tire height and gear ratios can affect how your converter behaves as I understand it.
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Tires gears tq your engine makes ect all will play a factor. I have a 9.5in 3500 stall in my 82 ta and its not too loose to me but you can feel it slip until you are cruising at an rpm above 3500 then it will completelty lockin. I had the 2800 in the car b4 thats now in my truck and it would flash to 2200 and footbrake to 1900 and i barely felt any slip with 3.42 gears then 3.73s with 26in tall tire. The 2800 i have is a 12in converter. I havent been able to drive my truck yet with the 2800 verter since the weather has been bad and ive had a cold and havent been able to finish putting everything back together. My only reason for putting in that converter is to insure good idle in gear and well i had it already so why not ;)
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It's been a couple of weeks. How did you make out? Any results?
I'm curious. If it worked out for ya, if so I'll be looking for an upgrade in the spring.
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They sent me a converter for a power glide by mistake.
Up untill that day I havent pulled my toyhauler yet so I decided to go out for the weekend. On the way I had a bunch of problems I need to take care of. Overheating, and major lack of power. Swapng the converter is on hold
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Sorry about the run of luck, keep us posted though.