Torque converter Help
Thread Starter
Pro
Joined: Feb 2007
Posts: 548
Likes: 1
From: Victoria VA
Torque converter Help
So let me get started I have a 77 Corvette with stock engine bore. I have a comp cam 270H
Operating Range:1800-5800 RPM
Duration Advertised:270° Intake / 270° Exhaust
Duration @ .050'' Lift:224° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers:.470'' Intake / .470'' Exhaust
Lobe Separation Angle:110°
L98 aluminum heads reworked with stronger springs was told will take. 510 lift. With steel head gasket. Figure my compression is around 10.1 I have 1.6 rockers do I'm around .501 lift now. A Edelbrock intake with 750 Holley dual feed double pumper mech carb. It has aTH350 and stock converter I'm running a 3.73 gear. I needed some advice on a converter don't really want a expensive one just a street car I take it to cruise ins. It runs really well now just not coming out of the hole like it should with out braking it. I hope for your in put.
Thanks
Operating Range:1800-5800 RPM
Duration Advertised:270° Intake / 270° Exhaust
Duration @ .050'' Lift:224° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers:.470'' Intake / .470'' Exhaust
Lobe Separation Angle:110°
L98 aluminum heads reworked with stronger springs was told will take. 510 lift. With steel head gasket. Figure my compression is around 10.1 I have 1.6 rockers do I'm around .501 lift now. A Edelbrock intake with 750 Holley dual feed double pumper mech carb. It has aTH350 and stock converter I'm running a 3.73 gear. I needed some advice on a converter don't really want a expensive one just a street car I take it to cruise ins. It runs really well now just not coming out of the hole like it should with out braking it. I hope for your in put.
Thanks
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
You can take a torque converter rated or advertised at say 2600 RPMs. Put that unit behind ten different engines and you will get ten different results. Having said that, maybe call some of those 800 numbers of your favorite company and see if all the tech guys have a common denominator. They will need to know what you just wrote: axle, duration, LSA / Dur and maybe tire diameter. Plus your driving intensions and power band area (RPMs).
I have a 10" B&M HoleShot, 4:11s and 284 duration, 3000 stall speed. (But it seems more 32-3400) It is a blast to drive.
Anyway, I would highly recommend a small trans cooler out front too !
I have a 10" B&M HoleShot, 4:11s and 284 duration, 3000 stall speed. (But it seems more 32-3400) It is a blast to drive.
Anyway, I would highly recommend a small trans cooler out front too !
Last edited by HeadsU.P.; Mar 1, 2020 at 12:06 PM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Well you don't mention how it drives now and what it has for a converter now. So if you knew what it was doing that you didn't like we could make recommendation.
As for stall speed choice there's plenty of good reading online. But basically, very basically, the greater the torque your engine makes (stroker/bigger motor) the higher the stall speed you need. And the steeper the final gear ratio (includes the trans first gear) the less you need a higher stall speed.
So with your trans and rear gearing it shouldn't need much higher stall than stock though it might be more fun to drive with a 2200 something RPM stall speed. And pretty the same goes for your engine improvements. But both combined I would go for 2200 RPM to 2400 RPM range, maybe 2600. And I agree a trans cooler should be installed.
Good luck.
As for stall speed choice there's plenty of good reading online. But basically, very basically, the greater the torque your engine makes (stroker/bigger motor) the higher the stall speed you need. And the steeper the final gear ratio (includes the trans first gear) the less you need a higher stall speed.
So with your trans and rear gearing it shouldn't need much higher stall than stock though it might be more fun to drive with a 2200 something RPM stall speed. And pretty the same goes for your engine improvements. But both combined I would go for 2200 RPM to 2400 RPM range, maybe 2600. And I agree a trans cooler should be installed.
Good luck.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Why are you blaming the converter ? Is it expectations it should be more powerful ? Is it bogging down ? Is it hesitating ? are you expecting big tire spin ? And how does it compare to the stock motor with all your changes
Melting Slicks
Joined: Jun 2002
Posts: 2,844
Likes: 99
From: Orrtanna Pa.
Your cam isn't really that big, so a converter not much more than 2500 could help. But before I'd pull the trans to do a converter, I'd try full length headers, then sort out your ignition curve and carb tune. You would be amazed...……..
Le Mans Master
Joined: Nov 2016
Posts: 9,256
Likes: 947
From: Lake Tahoe, CA
So let me get started I have a 77 Corvette with stock engine bore. I have a comp cam 270H
Operating Range:1800-5800 RPM
Duration Advertised:270° Intake / 270° Exhaust
Duration @ .050'' Lift:224° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers:.470'' Intake / .470'' Exhaust
Lobe Separation Angle:110°
L98 aluminum heads reworked with stronger springs was told will take. 510 lift. With steel head gasket. Figure my compression is around 10.1 I have 1.6 rockers do I'm around .501 lift now. A Edelbrock intake with 750 Holley dual feed double pumper mech carb. It has aTH350 and stock converter I'm running a 3.73 gear. I needed some advice on a converter don't really want a expensive one just a street car I take it to cruise ins. It runs really well now just not coming out of the hole like it should with out braking it. I hope for your in put.
Thanks
Operating Range:1800-5800 RPM
Duration Advertised:270° Intake / 270° Exhaust
Duration @ .050'' Lift:224° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers:.470'' Intake / .470'' Exhaust
Lobe Separation Angle:110°
L98 aluminum heads reworked with stronger springs was told will take. 510 lift. With steel head gasket. Figure my compression is around 10.1 I have 1.6 rockers do I'm around .501 lift now. A Edelbrock intake with 750 Holley dual feed double pumper mech carb. It has aTH350 and stock converter I'm running a 3.73 gear. I needed some advice on a converter don't really want a expensive one just a street car I take it to cruise ins. It runs really well now just not coming out of the hole like it should with out braking it. I hope for your in put.
Thanks
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
Following because my wife's 79 has a similar problem. I saw a tremendous improvement by following the @lars timing method, so be sure to do that first (his email is all over the Forum, PM me if you can't find it, or disregard this advice if you've already done this step). The 79 had been maintained according to stock spec's at great expense by the PO, and I changed nearly every part related to the ignition. Still looks stock.
That said, I agree completely that a different TC could help a lot, so I'm hoping to learn something.
Le Mans Master
Joined: Oct 2010
Posts: 6,936
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
I agree tuning will help a bunch. I have a 2800 stall 9" FTI convertor that they built to. Not slip a bunch and it's very good. I have a bigger cam going in after this week I think it will be really nice.
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Melting Slicks
Joined: Aug 2003
Posts: 3,416
Likes: 291
From: dayton oh
The general rule i follow with TC's is this: TC stall should be 2-300 RPM AFTER the cams powerband (so that the motor gets the full workload [stall] when its making power)
Based on your specs, the stock TC is loading your motor 200 RPM BEFORE it hits its powerband (1800).
i experienced this in my first build when i had the same TC mismatch as yours: the car wouldnt launch hard, but when it hit 1800RPM it felt like WARP 9! I should've gone with the CC262 to gain this 2-300RPM powerband/TC overlap.
Based on your specs, the stock TC is loading your motor 200 RPM BEFORE it hits its powerband (1800).
i experienced this in my first build when i had the same TC mismatch as yours: the car wouldnt launch hard, but when it hit 1800RPM it felt like WARP 9! I should've gone with the CC262 to gain this 2-300RPM powerband/TC overlap.