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Old 03-30-2013, 08:04 PM
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Converter does not stall very high

I know vague statement.

Long story short, This afternoon I changed out my transmission (700r4) in my 77C10 that was burnt up for another good/working r4. I also changed out the converter to a 2600 rpm summit racing stall converter. While I was there I changed out the 10 bolt that has 2.73 gears to another 10 bolt I had that's from a suburban with 3.73's. The installs went fine but, after checking for leaks and what not I tried a small burn out. To my surprise it wouldn't. I held the brakes and the throttle but all it would do is try to push the truck. I couldn't get the rpm above 1600-1800 while doing it. I figured being a 2600 rpm stall it would stall higher then that. But I'm not sure about stalls. From a dead stop, if you just floor it, it is like a dog off the start but it picks up a lot above 2500rpm. I'm at my wits ends here. I have spent 2hrs trying to figure it out today. Can anyone recommended a plan of attack for me. Tomorrow i might pull the after market converter and go back to the stock unit to eliminate that as the cause.

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Old 03-30-2013, 08:31 PM
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Your engine doesn't have enough torque to efficiently use the flash stall of the converter!

Jester
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Old 03-30-2013, 08:34 PM
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Originally Posted by painted jester View Post
Your engine doesn't have enough torque to efficiently use the flash stall of the converter!

Jester
What would you recommend?

Also the reason i went with the 2600 stall is due to the cam card said it needed a 2500rpm+ stall.
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Old 03-31-2013, 06:11 AM
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If you didnt perform any other mods to the engine other than the cam, it might be lacking the compression ratio to run the cam , hence the low end would be doggy.
What does your engine consist of ?
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Old 03-31-2013, 06:30 AM
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Motor is a 355 stock compression, 195 64cc procomp heads, comp mutha thumpr cam 235/249, rpm performer intake, edelbrock 1406 carb, the usual long tubes and 3 inch exhaust. Very mild motor.
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Old 03-31-2013, 06:32 AM
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Originally Posted by Slammedsi View Post
Motor is a 355 stock compression, 195 64cc procomp heads, comp mutha thumpr cam 235/249, rpm performer intake, edelbrock 1406 carb, the usual long tubes and 3 inch exhaust. Very mild motor.
Forgot to mention that it was fine before the stall and other mods. I could atleast foot break a burnout. It didn't want to spin the tires from a dead stop. But was better on the top end.
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Old 03-31-2013, 06:39 AM
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Motor is a 355 stock compression, 195 64cc procomp heads, comp mutha thumpr cam 235/249, rpm performer intake, edelbrock 1406 carb, the usual long tubes and 3 inch exhaust. Very mild motor.
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Old 03-31-2013, 08:21 AM
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You have one problem defined two different ways. A common mistake I have seen for decades

The camshaft is too large for the convertor or the converter stall is too low for the camshaft. Same results for two different combos.

Most converter shops rate stall speed with a 450 CID engine. You are 100 CID light on the stall converter

You keep repeating "stock compression" Stock for what? That camshaft needs a real 10 - 1 compression to function well IMO

You point out the problem when you say the engine runs well when you get it wound up..... the engine comes up on the camshaft and runs
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Old 03-31-2013, 08:23 AM
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Big cam, low compression...thats why it has poor low end.
probably could have went with a 3000 converter.JMO
Crosley beat me to it.
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Old 03-31-2013, 08:33 AM
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Thanks guys and sorry for the double post. I will start another thread in the engine fourm about specing the correct cam for the motor.
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Old 03-31-2013, 11:15 AM
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With camshafts on the street , it is a situation where : " less is more"

Less duration is more better usually in a street application

I built my first hot engine when I was 16 (1970) ... I had compression (12-1), I had big valve springs, 2.02 heads... yada - yada

I bought a used Sig Erson 990C camshaft and the used lifters. Both mistakes, too large of cam, used camshaft & lifters.

the engine was a turd till about 4000 RPM, then you had better hang on till 7500 RPM.

ahhh, the good ol days
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Old 03-31-2013, 01:04 PM
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His previous TC did fine though, this new 2600 "performance" TC doesnt cut the mustard. This tells me that his previous TC must have been a "looser" TC than his current one.

SLAMEDSI, do you still have the original TC around? If you do, take a peak at it. Look for s paper sticker that is located on the side that the snout is on. There should be a 4 digit alphanumeric code on itlike DCLF or DBHG or something like that.

Since you went from 2.73's to 3.73's, that should help your burnout ability, but because the higher gearing is loading the TC less, you will realize a lower flashstall rpm, all else equal. So when you are at a light, then let off the brakes and go to WOT, you tach will read lower as the vehicle begins to move. If you still had your 2.73's, you are effectively loading theTC more, thus when you launch at WOT, your tach will read more rpm as the vehicle bgins to move. This is the "flashstall" rpm of the TC.

Is it possible that the rear you swapped in has brakes that are setup better than the rear that you removed. If you old brakes were not setup tight, which is very common, brakestand using the brakes would be far easier than tryiong to do a brakestand with brakes that are setup properly.

Since you havent changed theengine in any way, you must have had a higher stalling TC in your truck before, and the TC you have now is lower stalling than the original TC.

Since you have a 700r4 trans that is equipped with a TCC(torque converter clutch) you can be more agressive with youyr stall speed selection because once the TCC applies, the torque converter stall speed, is taken out of the equation as a locked TCC forces the TC and the trans input shaft to spin as 1 with no speed difference at all. In a trans without a lockup clutch, you would have that difference of speeds happening all the time, leading to increased engine rpm and trans heating.

I get about 2800 rpm of brake stall(this is the rpm at which the tach reads when you are holding the throttle WOT without the output shaft of the trans turning-hard to do as usually the rear brakes are overcome by the engine torque-in high torque apps-braksestall is most accurately attained via a transbrake). I am using a TC from a 1995+ S-10 with the L35 4.3 V6, TC code DBLF. The "performance" stock equivalent for your truck would be the Corvette TC the same year as your 700r4 trans. But I think you would be far better of by getting a quality 3000-3500 rpm stall TC.

Let us know about the TC you removed, I'm interested if its an aftermarket TC or not. If its a stock TC, then that "performance" TC from Summit must be quite the tight TC.

peace
Hog
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Old 03-31-2013, 02:16 PM
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Quote:
Originally Posted by Hogg View Post
His previous TC did fine though, this new 2600 "performance" TC doesnt cut the mustard. This tells me that his previous TC must have been a "looser" TC than his current one.

SLAMEDSI, do you still have the original TC around? If you do, take a peak at it. Look for s paper sticker that is located on the side that the snout is on. There should be a 4 digit alphanumeric code on itlike DCLF or DBHG or something like that.

Since you went from 2.73's to 3.73's, that should help your burnout ability, but because the higher gearing is loading the TC less, you will realize a lower flashstall rpm, all else equal. So when you are at a light, then let off the brakes and go to WOT, you tach will read lower as the vehicle begins to move. If you still had your 2.73's, you are effectively loading theTC more, thus when you launch at WOT, your tach will read more rpm as the vehicle bgins to move. This is the "flashstall" rpm of the TC.

Is it possible that the rear you swapped in has brakes that are setup better than the rear that you removed. If you old brakes were not setup tight, which is very common, brakestand using the brakes would be far easier than tryiong to do a brakestand with brakes that are setup properly.

Since you havent changed theengine in any way, you must have had a higher stalling TC in your truck before, and the TC you have now is lower stalling than the original TC.

Since you have a 700r4 trans that is equipped with a TCC(torque converter clutch) you can be more agressive with youyr stall speed selection because once the TCC applies, the torque converter stall speed, is taken out of the equation as a locked TCC forces the TC and the trans input shaft to spin as 1 with no speed difference at all. In a trans without a lockup clutch, you would have that difference of speeds happening all the time, leading to increased engine rpm and trans heating.

I get about 2800 rpm of brake stall(this is the rpm at which the tach reads when you are holding the throttle WOT without the output shaft of the trans turning-hard to do as usually the rear brakes are overcome by the engine torque-in high torque apps-braksestall is most accurately attained via a transbrake). I am using a TC from a 1995+ S-10 with the L35 4.3 V6, TC code DBLF. The "performance" stock equivalent for your truck would be the Corvette TC the same year as your 700r4 trans. But I think you would be far better of by getting a quality 3000-3500 rpm stall TC.

Let us know about the TC you removed, I'm interested if its an aftermarket TC or not. If its a stock TC, then that "performance" TC from Summit must be quite the tight TC.

peace
Hog

Thanks Hog. The burned up R4 I took out was from a 86 burban, I do know the converter was blue. But don't recall any codes. I will look as I stuck it on a shelf sense i felt it was still good. The transmission i replaced it with is a R4 from a 90 Burban. So i had to convert it back to mechanical speedo. also went from a 27 spline to a 30 spline while doing so.
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