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To address the question you had in another thread, the powerglide you have behind your 6 cylinder will NOT be capable of containing any stout small block or big block. No. You will have to have a transmission built that will stand up to a large amount of torque without grenading. A TH400 at least, better yet a 4L80E with the overdrive to make the car drivable on the street.
Mark

Originally Posted by astroracer

To address the question you had in another thread, the powerglide you have behind your 6 cylinder will NOT be capable of containing any stout small block or big block. No. You will have to have a transmission built that will stand up to a large amount of torque without grenading. A TH400 at least, better yet a 4L80E with the overdrive to make the car drivable on the street.
Mark

I'm not saying that it's the right choice for a build, but the old powerglide can indeed be built to handle the horsepower and torque. Here's just one of many articles pointing out the specifics of building one for rugged service - Powerglide Transmission Build - Building a Two-Speed Trans for Our '95 Camaro Drag Car - GM High-Tech Performance Magazine A quote from the article tagged here,

At the 1,000-plus rear-wheel hp level, the only two GM transmissions that are up to the task are the three-speed TH400 and the two-speed Powerglide. "Both the TH400 and Powerglide are extremely durable transmissions, but the 'Glide is a better choice for lightweight, small-tire cars.

Originally Posted by rspears

I'm not saying that it's the right choice for a build, but the old powerglide can indeed be built to handle the horsepower and torque. Here's just one of many articles pointing out the specifics of building one for rugged service - Powerglide Transmission Build - Building a Two-Speed Trans for Our '95 Camaro Drag Car - GM High-Tech Performance Magazine A quote from the article tagged here,

Yup, agree with that 100%. BUT! The OP is under the assumption he can just bolt a 600 HP BBC in front of that stock 6 cyl. PG and go racing... THAT is not going to happen. AND if he wants something that is "drivable on the street" he needs to go OD for livable RPM's...
Mark

Originally Posted by astroracer

Yup, agree with that 100%. BUT! The OP is under the assumption he can just bolt a 600 HP BBC in front of that stock 6 cyl. PG and go racing... THAT is not going to happen. AND if he wants something that is "drivable on the street" he needs to go OD for livable RPM's...
Mark

Yup, and I agree with that 100%. I think the key here is that Ken (OP) said in Post #9 that,

Originally Posted by Ken1960

I guess I want my cake and eat it too.

Ken, Mark's advice in Post #10 is 100% on target. To change from your anemic 6 to any V8 you need to start from scratch and build a platform, knowing what engine you're going to use. New brakes, new suspension (minimum new springs, bushings, ball joints), new drive shaft for starters, then also consider that your wiring is going to be 50 years old in another year. Bringing your Chevelle to a modern day, reliable cruiser pulled around by 600+HP is not going to be a cheap project, especially if you start taking it to a shop for someone else to do the work. Thing is, a '67 Chevelle is one sweet ride, when done right. You need to sit back, make a realistic plan, budget the plan, and then go for it focused on the end.

Originally Posted by astroracer

AND if he wants something that is "drivable on the street" he needs to go OD for livable RPM's...
Mark

And if he goes OD, he'll need to go easy on the cam. All grinds have a "cruise rpm range" where the motor gets "up on the cam" and begins to be efficient. The motor will be inefficient under that range and you will have wasted money on an OD trans. Again, it's the combination of parts that you have to pay attention to.

Bottom line: Overdrive trans needs stock or very close to stock cam for the motor to be efficient in the cruise rpm range dictated by the OD trans. I got into an argument with a know-it-all on another forum who was convinced that his 300 degree cam (255 @0.050") was well-suited for use with his 700R4.

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Originally Posted by techinspector1

Bottom line: Overdrive trans needs stock or very close to stock cam for the motor to be efficient in the cruise rpm range dictated by the OD trans. I got into an argument with a know-it-all on another forum who was convinced that his 300 degree cam (255 @0.050") was well-suited for use with his 700R4. .

Tech, I have been over this many times and you have nailed it, any performance cam will raise your powerband ( ideal rpm range) over a stock cam, and will be totally ineffecient at 1800-2000 rpms at highway speeds that a OD can add unless you throw in a gear change. I actually saw a guy put a 700r4 behind a mildly built motor and loose fuel mileage! He dropped his rpms down around 1800 and had to step on the gas anytime he went up a slight hill since his powerband had been raised with the performance grind. This is the same reason my blown duel carb'd 32 actually gets pretty decent fuel mileage (I have achieved 16 mpg) turning 2900-3000 rpms at 70 mph with my foot out of it but all bets are off when both carbs are wide open.