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  #1  
Old 10-20-2016, 08:12 AM
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HighwayThunder HighwayThunder is offline
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Default Torque Converter

The hydraulic roller lifter cam I installed changed the power range of my 390 from 1800-2000 rpm to 2200-2400 rpm. I purchased a Boss Hog torque converter from Summit to match the higher stall speed. Ever since I received it there's been the lingering suspicion that the new converter is identical to the stock converter.

My trans guy told me that the new converter would have a smaller diameter, so I was surprised that the Boss converter appeared to look the same as the stock item. I called Summit, who referred me to Boss, who assured me that they shipped the correct item. I guessed that the difference must be in the internals. But still.....

In the photo, the Boss converter is on the left, the original stock converter is on the right. Any opinions?
Thanks and Cheers,

Richard
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  #2  
Old 10-20-2016, 11:18 AM
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Default

A smaller housing unit would not be required to achieve the relatively small increase in "stall" value you specify, rather only a modification of the internals. Generally, at this level a modification is made between the relationship of the impeller and turbine unit (as in blade angle and/or clearance) within the existing housing. Therefore, it looks the same on the outside (except paint & any character marks). Scott.
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Old 10-20-2016, 11:40 AM
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I haven't noticed much difference in dimensions in all my stall converters over many engines, either.

Make sure you know that these stall converters are designed to slip until they lock up. Essentially, they act like your clutch would in a manual setup as you compensate for torque that happens later in the rpm range. That means they generate more heat and you should be prepared to cool it.

Racing is a wonderful thing but it also changes the service of your car which is fine as long as you understand it, want it, and it looks like you are preparing for the changes. - Dave
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Old 10-20-2016, 04:10 PM
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As Dave said - more heat.

And more fuel used since the efficiency of the torque-convertor is woeful any time the revs are below the lock-up level, REALLY noticeable with low speed around town driving, more so if your rear gears are 3.5:1, 3.2:1 or higher, i.e. cruising gears.
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Old 10-21-2016, 08:55 AM
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Default Thanks for the help

The reason I questioned the torque converter is that I've had trouble tuning up the car. I get the car tuned to run optimally but then it stalls when I try to drive it. Y'all have convinced me that the converter is unlikely the cause, that it's a poor carb/ignition tune-up.

Have a friend who has a performance engine shop about 17 miles away. I'm going to get the car to him to set it right.

Cheers,
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Old 10-21-2016, 10:05 AM
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Quote:
Originally Posted by HighwayThunder View Post
...I get the car tuned to run optimally but then it stalls when I try to drive it...
Yep, that's typical of an OEM converter on a hot cam.

Your car's drivetrain was engineered as a system. When you change the torque curve, that mis-matches the system. Normally, the cam seller will suggest compatible components with the sale of a hot cam. Otherwise, your engine builder would advise his customer.

Driving an automatic with an OEM converter and a hot cam around town is miserable. I'm surprised you haven't asked about a shift kit. - Dave
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Old 10-21-2016, 07:27 PM
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Quote:
Originally Posted by simplyconnected View Post
Yep, that's typical of an OEM converter on a hot cam.

Your car's drivetrain was engineered as a system. When you change the torque curve, that mis-matches the system. Normally, the cam seller will suggest compatible components with the sale of a hot cam. Otherwise, your engine builder would advise his customer.

Driving an automatic with an OEM converter and a hot cam around town is miserable. I'm surprised you haven't asked about a shift kit. - Dave

What Dave sez!

I had similar issues after I fitted the Isky 270 cam to the 429 in my F100.
I have a stock C6 torque converter and after getting the 780 Holley tuned to work with the cam I realised thet cam was as radical as I could go with a stock converter.
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Old 10-21-2016, 07:57 PM
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Quote:
Originally Posted by scumdog View Post
What Dave sez!

I had similar issues after I fitted the Isky 270 cam to the 429 in my F100...
I have a lot of respect for a 270 duration cam. It has its place in racing but for daily driving I wouldn't go over 260 with proper rocker arm ratios and piston/valve clearances.

But hey, that's my opinion. For a grocery-getter, I need vacuum as well. - Dave
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