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Question: Torque Converter Install and Expectations

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
It has been a while since I have posted and updated everyone here on my progress with my '79. Over the past wo weeks we removed the original Torque Converter and replaced it with a Precision Industries 2800 Stall Vigilante Torque Converter with new aluminum pan, gaskets and filter. We also replaced the rear 6'' tailshaft which had new bearing and seal. The disassemble and reassmeble of the components went fine. No problems which in itself I find unusual as there is always something else along the way that is either broke or needs replacing. Now, the vette started fine and we added fluid accordingly. The first two test runs were disappointing. Yes, I do feel a difference by being in the powerband quicker but the lack of initial torque and not spinning the wheels from a stop position is something we were expecting. The only other work we did was removing the AC compressor, new spark plugs, and header gaskets. All relatively simple. So, what should be our expectations with this converter upgrade and/or maybe we installed it incorrectly, which I think is difficult to do. The engine is a SB 355 with 180cc AFR Heads, TH350 Auto, and original rearend. Headers, dual exhaust, 1.6 full roller rockers. I'm running a XE 218\224 CompCam. Some technical experience and insight would be appreciated. :thumb
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,457
Location
CenCoast CA
Corvette
71 04 12 19
My knee-jerk reaction is that the high-stall converter was either the wrong selection or just a waste of money.

But...what axle ratio do you have?

Also, would the car spin the tires before?

Has the engine been on a dynamometer? If so, what'd it do in the mid range?

Was the carb re-calibrated after the converter swap?
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
My knee-jerk reaction is that the high-stall converter was either the wrong selection or just a waste of money.

But...what axle ratio do you have?

Also, would the car spin the tires before?

Has the engine been on a dynamometer? If so, what'd it do in the mid range?

Was the carb re-calibrated after the converter swap?

Would not spin the tires before, never Dyno'd prior, and the carb needs to be re-calibrated? Explain please.
 
B

BankOfHell

Guest
I think your stall is a bit high. I have almost the exact same motor/trans you have in my '77 and I put in a 2400. Power on demand all the time.
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
I think your stall is a bit high. I have almost the exact same motor/trans you have in my '77 and I put in a 2400. Power on demand all the time.

PI recommended this stall so it is not a matter of it being to high or the wrong one. They were given all the details prior to making a recommendation. I will be checking my rearend ratio. That may be the problem.
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,457
Location
CenCoast CA
Corvette
71 04 12 19
Considering the 3.55 axle ratio and the mods to your engine, you should have been able to spin the tires easily even before you installed the high-stall converter.

While it's possible the converter was not a wise choice, it's also possible there is something wrong with the engine---spark timing, carburetor calibration, cam timing, etc---that is responsible for a lack of low-end torque.

I'd not worry about the converter for now. I'd start looking for where that low-end torque went.
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
Considering the 3.55 axle ratio and the mods to your engine, you should have been able to spin the tires easily even before you installed the high-stall converter.

While it's possible the converter was not a wise choice, it's also possible there is something wrong with the engine---spark timing, carburetor calibration, cam timing, etc---that is responsible for a lack of low-end torque.

I'd not worry about the converter for now. I'd start looking for where that low-end torque went.

The converter choice is niether here nor there. It was recommended by the manufacturer and it was installed correctly. I definitely have more torque, both initial and midrange so there has been an improvement. Just not the radical torque we were expecting. Prior to the converter upgrade, I have never been able to smoke the tires and still can't. The Holley carburetor is dialed in correctly. The cam might be a bit small NOW but an upgrade over stock. Vacuum is fine. I had the same exact feeling after my topend rebuild with the questions and wondering. Don't get me wrong, I have a nice ride that does move. Just not moving as fast as I think she should be moving. But I'm no expert. Still learning! Maybe the timing needs to be advanced? What do you think it should be at? Also, I when I installed the holley 9895 I replaced the secondary spring with the lightest spring they offered in their spring kit. I'm wondering if the secondaries are opening to soon. Maybe go with a stiffer spring? :thumb
 

Crimson Thunder

Well-known member
Joined
Dec 16, 2001
Messages
814
Location
Orange Park FL USA
Corvette
1970 Marboro Maroon Convertible
IM Lars and ask him to send you his timing papers. I thought I knew almost everything and I learned a lot from reading it.
 

krscholz

Well-known member
Joined
Oct 11, 2008
Messages
129
Location
Caldwell, ID
Corvette
75 Corvette Coupe, 383 Stroker
Kill the Cat

Why bother with a Cat - go dual exhaust with big pipes. Check with your smog laws in your state.
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
Considering the 3.55 axle ratio and the mods to your engine, you should have been able to spin the tires easily even before you installed the high-stall converter.

While it's possible the converter was not a wise choice, it's also possible there is something wrong with the engine---spark timing, carburetor calibration, cam timing, etc---that is responsible for a lack of low-end torque.

I'd not worry about the converter for now. I'd start looking for where that low-end torque went.

Just want to keep you all informed. Made some real progress today. Did a compression check on all cylinders. They all were between 201 and 205. 12* BTDC base timing and 36* BTDC at WOT at 2500 RPM. WOT vacuum is almost at 0 and we are at 11.1 - 11.5 at WOT Air Fuel Ratio so we are running rich at WOT a bit. We had an air flow problem which was solved by installing a 3'' air cleaner element and removing the 2''. So, overall we made some changes with timing and airflow and we do have some wheel spin from a stop position. We did use an Innovative wide band oxygen sensor for air/fuel ratio numbers.
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
Thanks for the update. I'm glad to hear you're making progress and it sounds like your moving in the right direction.
 

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