MiradaMegacab
Well-Known Member
Aussie Max Wedge intake manifold and a 8-71 blower....
how much power can a 8 1/4 take?
- Thread starter Ed Dorey
- Start date
MiradaMegacab
Well-Known Member
MaMopar didn't use an 8 3/4 rear end for their serious factory cars. They used a Dana for obvious reasons. The OP stated a pumpkin style rear for easy gear changes.
Hard ass Purist? Lol, I'd say you're a hard ass.
Am I cheap? Not at all, using a blower and an 8 1/4 rear isn't economical .
The 9"has an additional bearing for pinion support which helps in a stick shift application with hi shock loads. Period.
I didn't chose the wrong car line, I do however don't think that a factory stock Mirada performs upto my expectations. So I'm wrong to customize my ride with aftermarket parts. Back in the day you could buy a B&M blower kit from any Mopar dealer, that's not the case now. So based on your theory and idiotic outburst I'm supposed to switch to brand X, chevy or a mustang..... smart people choose smart parts that are economically priced. I'm running a K1 3.79 stroke crank with 2.1 rod journals. K1 6.125 rods with a .927 pin. Notice those dimensions are for a an chevy? You're good. I picked up a couple of extra cubes, 387ci , saved money on the pistons, yep, you guessed it. I used an off the shelf forged 2618 alloy piston for a chevy 383......... so by me doing careful deck height measurements and selecting a slightly longer connection rod, I was able to find a piston in a 4.030 bore with the correct compression height. Saving me over $400 for a custom Mopar piston. As soon as you custom order Mopar pistons , your wallet becomes UNJUSTIFIABLY light. The aftermarket companies rape the Mopar enthusiast. A true hot rodder will take the parts necessary to make the build work.
Hard ass Purist? Lol, I'd say you're a hard ass.
Am I cheap? Not at all, using a blower and an 8 1/4 rear isn't economical .
The 9"has an additional bearing for pinion support which helps in a stick shift application with hi shock loads. Period.
I didn't chose the wrong car line, I do however don't think that a factory stock Mirada performs upto my expectations. So I'm wrong to customize my ride with aftermarket parts. Back in the day you could buy a B&M blower kit from any Mopar dealer, that's not the case now. So based on your theory and idiotic outburst I'm supposed to switch to brand X, chevy or a mustang..... smart people choose smart parts that are economically priced. I'm running a K1 3.79 stroke crank with 2.1 rod journals. K1 6.125 rods with a .927 pin. Notice those dimensions are for a an chevy? You're good. I picked up a couple of extra cubes, 387ci , saved money on the pistons, yep, you guessed it. I used an off the shelf forged 2618 alloy piston for a chevy 383......... so by me doing careful deck height measurements and selecting a slightly longer connection rod, I was able to find a piston in a 4.030 bore with the correct compression height. Saving me over $400 for a custom Mopar piston. As soon as you custom order Mopar pistons , your wallet becomes UNJUSTIFIABLY light. The aftermarket companies rape the Mopar enthusiast. A true hot rodder will take the parts necessary to make the build work.
kkritsilas
Well-Known Member
The only cars that got the Dana 60 in any volume were the manual 440s and the Hemis. Automatic 440 Six Packs, and some Hemis actually got 8 3/4" rears. Although the autmatic cars don't shock the rear end like the manual transmission cars, I would describe them as quite serious nonetheless. You may not, that is your opinion. I do, and think that most people do.
Never said using a blower and an 8 1/4" is economical. Did say using an 8 3/4" and a blower would work. Probably more expensive than a Ford 9". But I do believe just as strong as a Ford 9". I also believe that just throwing in a lowest common denominator solution is not really always the best choice. How does the aftermarket for the 8 3/4" stay healthy if everybody jumps to the Ford 9" anytime they want a stronger rear end? Or everytime somebody wants a hotter engine, they get a small block Chevy? The only reason that a small block Chevy has the aftermarket that it does is due to the >50 Million Chevy small blocks that there are out there. Using Chevy parts in a Mopar is a big no-no for me. They will work, but when the Mopar equivalent is just as good, at a non-major cost increase, pretty much puts me with the Mopar parts.
Sorry if my outburst was idiotic in your opinion. Point was, as idiotic as you may think it is, is that the Mopar aftermarket will only continue to exist if we support it. There is nothing superior about a Ford 9" over a Mopar 8 3/4". Yes, it has one additional bearing. The 8 3/4" has a thicker case. Depending on the failure mode, it may be better to have one vs. the other, but there is no clear technical superiority for the Ford 9" over the 8 3/4".
My statements are not theory. We are on an FMJ body message board. We are already out in the cold, not only with the average street machine crowd and the aftermarket, but even with the Mopar crowd in most cases. If you want to save money, if that is the over-riding concern, go with a more popular platform. If you want to stick with the cars on this board, you are going to pay more money, and parts are not going to be easy to come by. And by extension, an 8 3/4" may be more expensive than a Ford 9"; but depending on the deal at the time, maybe it won't be. Ford 9" rears are getting expensive, too. Aftermarket parts are cheaper for the Ford 9", but not night and day different (i.e. Ford 9"parts are not 10X cheaper than 8 3/4" parts).
Never said using a blower and an 8 1/4" is economical. Did say using an 8 3/4" and a blower would work. Probably more expensive than a Ford 9". But I do believe just as strong as a Ford 9". I also believe that just throwing in a lowest common denominator solution is not really always the best choice. How does the aftermarket for the 8 3/4" stay healthy if everybody jumps to the Ford 9" anytime they want a stronger rear end? Or everytime somebody wants a hotter engine, they get a small block Chevy? The only reason that a small block Chevy has the aftermarket that it does is due to the >50 Million Chevy small blocks that there are out there. Using Chevy parts in a Mopar is a big no-no for me. They will work, but when the Mopar equivalent is just as good, at a non-major cost increase, pretty much puts me with the Mopar parts.
Sorry if my outburst was idiotic in your opinion. Point was, as idiotic as you may think it is, is that the Mopar aftermarket will only continue to exist if we support it. There is nothing superior about a Ford 9" over a Mopar 8 3/4". Yes, it has one additional bearing. The 8 3/4" has a thicker case. Depending on the failure mode, it may be better to have one vs. the other, but there is no clear technical superiority for the Ford 9" over the 8 3/4".
My statements are not theory. We are on an FMJ body message board. We are already out in the cold, not only with the average street machine crowd and the aftermarket, but even with the Mopar crowd in most cases. If you want to save money, if that is the over-riding concern, go with a more popular platform. If you want to stick with the cars on this board, you are going to pay more money, and parts are not going to be easy to come by. And by extension, an 8 3/4" may be more expensive than a Ford 9"; but depending on the deal at the time, maybe it won't be. Ford 9" rears are getting expensive, too. Aftermarket parts are cheaper for the Ford 9", but not night and day different (i.e. Ford 9"parts are not 10X cheaper than 8 3/4" parts).
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I may have stirred the hornets’ nest about which is better (the 8¾” vs. 9”) – In which I should have not worded it the way I did.
Mates, I’m sorry.
I read somewhere about 15 years ago that testing showed, using stock parts, the 8¾” tested stronger than the 9” did. Stock parts is the key word or phrase.
The rear pinion shaft support bearing in the Ford 9" may or might not help it out (Honestly, I don’t know).
The Ford 9” failures are from the thinner diameter pinion shaft (1-5/16” or 1.312”) – which is actually thinner than the 8¾” ones are.
741 is 1-3/8” (1.375”)
742 is 1-3/4” (1.75”)
489 is 1-7/8 (1.875”)
Now (I believe) the aftermarket parts address that issue – so this might be a moot point.
I’ve heard from a Mopar club member. He said about 3/5ths (60%) of all Hemi cars came the Dana 60. The rest, as well as all race Hemi’s and Max Wedges came with the 8¾.
One of the reasons I want to install 8¾”s into my vehicles is the ease of changing the chuck/pumpkin/3rd member – or whatever one wants to call it. Well, it is not “easy”, but makes changing gear ratios a lot easier to do on the bench than under a car.
Honestly, I don’t care which differential he goes with. All I was doing was stating facts that might help him make his decision.
BudW
Mates, I’m sorry.
I read somewhere about 15 years ago that testing showed, using stock parts, the 8¾” tested stronger than the 9” did. Stock parts is the key word or phrase.
The rear pinion shaft support bearing in the Ford 9" may or might not help it out (Honestly, I don’t know).
The Ford 9” failures are from the thinner diameter pinion shaft (1-5/16” or 1.312”) – which is actually thinner than the 8¾” ones are.
741 is 1-3/8” (1.375”)
742 is 1-3/4” (1.75”)
489 is 1-7/8 (1.875”)
Now (I believe) the aftermarket parts address that issue – so this might be a moot point.
I’ve heard from a Mopar club member. He said about 3/5ths (60%) of all Hemi cars came the Dana 60. The rest, as well as all race Hemi’s and Max Wedges came with the 8¾.
One of the reasons I want to install 8¾”s into my vehicles is the ease of changing the chuck/pumpkin/3rd member – or whatever one wants to call it. Well, it is not “easy”, but makes changing gear ratios a lot easier to do on the bench than under a car.
Honestly, I don’t care which differential he goes with. All I was doing was stating facts that might help him make his decision.
BudW
I have seen some 383’s B-bodies (at least 3) come from factory with a Dana 60. I “think” (no facts to back this up) it was part of a drag pak option, or something to that nature.
Also, I’ve seen a Dana 60 in a ’69 (not 100% sure of the year) 383 4bbl automatic Fury (C-body), while I was working in a dealership decades ago. The parts department did verify it was correct for that car.
BudW
Edit: about 30 years ago, I’ve also seen a big guy carrying a mangled propeller shaft with the broken back half of a Hemi 4-speed and broken snout of a Dana 60 (both still attached to propeller shaft), saying he broke it and wants parts to fix it.
Being he was a good 3 times bigger guy than I was and what he broke – I didn’t want to ask him how he broke it (but wondering about it to this day, I still do).
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MiradaMegacab
Well-Known Member
You do realize the 6-71 Blowers are a GMC design.. yet again your idiotic comments come out.... And it's a well known fact that Mopar cone style sure grips for the 8 3/4 are lacking in a quality design.... The spider gears seize to the differential pin, spinning the cones to an instant death, as you know, the roll pin that retains the pin also shears, so with your vast knowledge, what holds the differential pin in then? The seized spider gear. And when that bond frees up? Instant rear end locks up, due to the pin getting wedged between the diff and the case..... That's a real safe setup to have at the track.... lol locking up the rear tires, a wonderful design........
MiradaMegacab
Well-Known Member
Ed, I'm curious as to the engine build. What fuel will you be running? Stoker pistons are in the-15 to -20 cc dish. That's gonna put you at a high CR of 10 to 11:1.
I'm running a -30cc dish with 64cc heads and that nets a 8.5CR....and a 3.79 stroke.
With the 408 you're gonna need a -40cc piston.......
I'm running a -30cc dish with 64cc heads and that nets a 8.5CR....and a 3.79 stroke.
With the 408 you're gonna need a -40cc piston.......
kkritsilas
Well-Known Member
Being a little free with the term "idiotic" aren't we? Note how often I have called you idiotic.
Yes, 8 3/4" rears fail. Ford 9" rears fail. Dana 60 Rear end fail. GM 12 bolt rears fail. Neat thing is, just like the Ford 9", you don't have to stay with a factory cone style locking differential (see Eaton for a worm gear type True Trac, as one example). So if you are concerned about a roll pin failure, you can get away from it. Your point would be?
As for the 6-71 (all of the X-71 series really) blower, it isn't is a GMC design, originally. It was basically designed by the Roots brothers before the turn of the century (that's why this type of supercharger is often called a Roots). GMC just standardized it to a 71 cubic inch cylinder size (the 71 part of the model), and varied the number of cylinders (3,4,(don't think there was a 5 cylinder, but could be wrong), 6,8,and I think there was a 12, which makes up the first number of the supercharger, so a 6-71 is for a six cylinder engine, each cylinder being 71 cubic inches) for different power levels. If you put a GMC made blower on a Mopar, I may even have a problem with it. But seeing as nobody mentioned anything about using a 6-71 blower, I again, fail to see your point. Over and above that, GMC hasn't made a blower in over 50 years, and even if you got an original GMC 6-71, you wouldn't be able to use it, as the purpose of the entire X-71 series was for use as pumps on two stroke diesel engines. Anything that even remotely resembles an X-71 series today bears very little resemblance internally to a a genuine GMC pump anyway. Unless you are buying a historical piece, you will be buying an aftermarket supercharger, no GMC involvement, even in what looks like X-71 supercharger case. As well, the X-71 supercharger family is not very efficient; so in supercharged applications, you far more likely to see a centrifugal (Paxton) or twin screw type (Vortech VTS or Whipple) of supercharger.
Yes, 8 3/4" rears fail. Ford 9" rears fail. Dana 60 Rear end fail. GM 12 bolt rears fail. Neat thing is, just like the Ford 9", you don't have to stay with a factory cone style locking differential (see Eaton for a worm gear type True Trac, as one example). So if you are concerned about a roll pin failure, you can get away from it. Your point would be?
As for the 6-71 (all of the X-71 series really) blower, it isn't is a GMC design, originally. It was basically designed by the Roots brothers before the turn of the century (that's why this type of supercharger is often called a Roots). GMC just standardized it to a 71 cubic inch cylinder size (the 71 part of the model), and varied the number of cylinders (3,4,(don't think there was a 5 cylinder, but could be wrong), 6,8,and I think there was a 12, which makes up the first number of the supercharger, so a 6-71 is for a six cylinder engine, each cylinder being 71 cubic inches) for different power levels. If you put a GMC made blower on a Mopar, I may even have a problem with it. But seeing as nobody mentioned anything about using a 6-71 blower, I again, fail to see your point. Over and above that, GMC hasn't made a blower in over 50 years, and even if you got an original GMC 6-71, you wouldn't be able to use it, as the purpose of the entire X-71 series was for use as pumps on two stroke diesel engines. Anything that even remotely resembles an X-71 series today bears very little resemblance internally to a a genuine GMC pump anyway. Unless you are buying a historical piece, you will be buying an aftermarket supercharger, no GMC involvement, even in what looks like X-71 supercharger case. As well, the X-71 supercharger family is not very efficient; so in supercharged applications, you far more likely to see a centrifugal (Paxton) or twin screw type (Vortech VTS or Whipple) of supercharger.
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MiradaMegacab
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Ed Dorey
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Not quite sure as I haven't gotten that far yet. I do know that Scat Industries makes the stroker kit. Other than that I need to figure in how much boost I'm going to push and then decide on pistons.
slant6billy
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Good luck! Small block mopars are fully capable of making power and numbers that shatter records the ford and chevy can't shatter. Build it strong then build it stronger!
MiradaMegacab
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MiradaMegacab
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jasperjacko
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I agree with the idea of making it strong to start with. You do not want rearends, axles and drive shaft parts flying in all directions, for your sake, and by-standers.
Second, a supercharged stroker motor will far out stress these parts than any hemi of the 60's.
Second, a supercharged stroker motor will far out stress these parts than any hemi of the 60's.
Don’t forget the stress the engine takes going from full load to no-load, in an instant (if/when breakage occurs).
There is not a rev-limiter made that can slow down an engine, before RPM’s hit double red-line – which often creates even more “breakage”.
MiradaMegacab
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MiradaMegacab
Well-Known Member
408 going in
Interesting reading.....
Interesting reading.....
MiradaMegacab
Well-Known Member
Yeah baby
brotherGood
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I'm too lazy to read all this, but I've got a buddy selling his 8.75 out of his Volare. 3.23 gears, 35 spline spool. if this is going to be a track car..this'll be a good investment.
Ed Dorey
Well-Known Member
where is the 8.75 located at? I may be interested if it's close enough.
