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I always thought the close ratio M-22 keeps your engine within its maximum power band (not letting the RPM's drop too far) between shifts maintaining maximum acceleration.


Here's a quote from a Corvette forum I just found...

The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.

The M-21 and M-22 were both a 2.54:1 low.

The M-22, AKA "Rockcrusher" had straighter cut gears and was the stronger of the Muncie gearboxes. Made more noise too.

I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.




http://forums.corvetteforum.com/c3-...ear-ratio-difference-between-m20-m21-m22.html
!!! THE ABOVE INFORMATION IS NOT CORRECT !!!

Here is my post from the CRG regarding trans choices.
http://www.camaros.org/forum/index.php?topic=8594.msg59716#msg59716

SUMMARY


Not knowing your rear end ratio assuming a 3.73 or a 4.10...consider a M20.

A M20 has a steeper first 2.52 vs a 2.20, which with the 302 is extremely helpful in getting the motor spinning and thus making power.

If you have:
3.73's with a M21 or M22 the effective first ratio is 8.206
4.10's with M21 or M22 effective is 9.020

3.73's with a M20 effective ratio is 9.396 ~ steeper than a 21 with 4.10's... interesting isn't it?
4.10's with M20 effective ratio is 10.332 ~ IMHO this is the COMBO... it will LAUNCH the car in first... also makes it very very difficult to stall the car in first EVER.


Close ratio refers to the first gear ratio being closer to the direct through ratio of 1:1.
2.20:1 is closer to 1:1 than 2.52:1... isn't it?

JAMES
 

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Thanks James that is very helpfull information. For the first time I am starting to understand transmission gear ratios. It sounds like a 410 is the way to go, but of course I would be really winding out on the hiway. I have found a correct BV diff that I can get for a decent price. Motor will probably be a 1970 LT1, which will wind like a 302 for the most part, most of the same parts being used. I guess some might think that is not a wise street combination, but it sounds like fun to me. Car only gets driven on nice days in the summer.

Lets just say for arguments sake I use a 342/350 rear gear, would the M20 still be the way to go?
 

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I have found a correct BV diff that I can get for a decent price.
If it's a genuine BV posi, personally I'd have bought it already, they are worth $$. You can always pull the 4.10's and change the gearing later..... but you'd probably love it as it is :D
 

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If it's a genuine BV posi, personally I'd have bought it already, they are worth $$. You can always pull the 4.10's and change the gearing later..... but you'd probably love it as it is :D
Thanks Tim I am thinking of getting it. The guy who is selling it has the BV and BU is a Super nice guy and has 2 of the nicest Camaros I have seen. 2-SS 396 cars, one is a L89. They are triler queens, but as nice as they come. I am starting to think the BV is the way to go. Good point about swapping gear sets later if required.
 

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Yep - the advertised 425hp and 450ft/lbs or so of torque certainly appealed! When I last looked, they were about $5,200 from Jegs (and around $100 more at Summit), but that may have changed recently. I recall you still need to get an intake manifold (the testing that GM did for the quoted power output used a single plane intake and a 750cfm carb, if you use a dual plane intake you will produce a bit less power, maybe 400-410hp?), water pump, fuel pump etc for the engine, so they are not turn-key at that price.
Hey Tim you are correct I checked out the GM 383 crate motor. Is is $5,289.00 in Canada. Looks like a nice motor.
 

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Close ratio refers to the first gear ratio being closer to the direct through ratio of 1:1.
2.20:1 is closer to 1:1 than 2.52:1... isn't it? JAMES
James,
I thought the term "close ratio" relates to the closer spread of gear ratios through the 'box, i.e. there is a narrower band between gears - therefore changing gears will keep the engine revs higher (and in the power band) than if the ratios are wider apart, then the engine labors and the revs decrease.
M20 ratio spread (1st thru 4th) is 2.52 / 1.88 / 1.46 / 1.00
M21 and M22 ratio spread is 2.20 / 1.64 / 1.28 / 1.00
Hence why the M20 was the generic 4spd trans while the M21 and M22 were only for the more potent RPOs.
 

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James,
I thought the term "close ratio" relates to the closer spread of gear ratios through the 'box, i.e. there is a narrower band between gears - therefore changing gears will keep the engine revs higher (and in the power band) than if the ratios are wider apart, then the engine labors and the revs decrease.
M20 ratio spread (1st thru 4th) is 2.52 / 1.88 / 1.46 / 1.00
M21 and M22 ratio spread is 2.20 / 1.64 / 1.28 / 1.00
Hence why the M20 was the generic 4spd trans while the M21 and M22 were only for the more potent RPOs.
Hey Tim/James which ever is the proper term and I am still learning a lot, what combos works best for the set up i am going for.

Which will the M20 work with best the 373, 410 and or 342. At what point is the gearing of the transmission more favorable for the rear end gear selection? I surely want the best matched combination for a street car. Although I am not planning to race the car, I am looking to create a car that would perform like a bad a$$ Z 28 would have performed if you checked all the right options back in the day. Since my car is not a real Z 28 I like the idea of being able to build it to get the optimum performance out of it.

Thanks guys your help is invaluable as always. Who knows, by the time my car is finished I may actually end up knowing what I am talking about! :beers:
 

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My 68 Vette came with 427/390 and M-20 w 3.08s
I upgraded to 3.42, the optional 'sport' gear, Vette has a/c

Plenty of 69 Z came with M-20 WIDE RATIO boxes.
M-21 and M-22 are Close Ratio boxes.

If you are in competition, you want the the close ratio boxes and a lot of gear, comprehend this as NORTH of 4.10s...otherwise the low torque of these engines, especially 302, comes into play.

Multiply the 1st gear 2.20 or 2.52 x your gear ratio to get the drive ratio

For my 68 Ragtop, going with mild 396, 200-4R with 2.74 1st gear and 3.73s. OD of .67 will allow it to cruise like 2.6 gears
 

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My 68 Vette came with 427/390 and M-20 w 3.08s
I upgraded to 3.42, the optional 'sport' gear, Vette has a/c

Plenty of 69 Z came with M-20 WIDE RATIO boxes.
M-21 and M-22 are Close Ratio boxes.

If you are in competition, you want the the close ratio boxes and a lot of gear, comprehend this as NORTH of 4.10s...otherwise the low torque of these engines, especially 302, comes into play.

Multiply the 1st gear 2.20 or 2.52 x your gear ratio to get the drive ratio

For my 68 Ragtop, going with mild 396, 200-4R with 2.74 1st gear and 3.73s. OD of .67 will allow it to cruise like 2.6 gears
Thanks george. I am in search of the best all around set up for my car. I fugure the experts here will know from experience what is the best combo for the parts I have access to. Looking forward to nailing it down and getting her built. Getting a little bit closer everyday. One step at a time... :beers:
 

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If starting from scratch, a 383 isn't much more money than a 355, and probably the cheapest extra power you'll find along the way.

I'd be wary of "ported and polished" 186 heads unless the guy really knows what he's doing. Just as easy/likely to ruin them as improve them unless he has some experience (and a flow bench) And for the money you'd have sunk into a set of 40 y/o castings.....too bad none of the aftermarket heads are offered with camel humps..

Not sure I like the idea of 10.6:1 on a street engine either - just seems unnecessarily high considering the potential downside.
 

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Agree with Al. I think a ZZ383 might be the way to go. That way you have torque at lower RPM and an engine with modern aluminum heads (no older heads will be anywhere as good), roller cam and warranty :). The 3.73 or 4.10 will get old in a hurry on the highway trust me. You could run 3.42 like a friend of mine does with a 69 with a ZZ383 and not suffer as much. I have 3.73s behind my 406 however have GV OD to make it much more highway friendly. I know a few guys with the ZZ383 and it has been a great engine for them with zero issues.
 

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If starting from scratch, a 383 isn't much more money than a 355, and probably the cheapest extra power you'll find along the way.

I'd be wary of "ported and polished" 186 heads unless the guy really knows what he's doing. Just as easy/likely to ruin them as improve them unless he has some experience (and a flow bench) And for the money you'd have sunk into a set of 40 y/o castings.....too bad none of the aftermarket heads are offered with camel humps..

Not sure I like the idea of 10.6:1 on a street engine either - just seems unnecessarily high considering the potential downside.
Agree with Al. I think a ZZ383 might be the way to go. That way you have torque at lower RPM and an engine with modern aluminum heads (no older heads will be anywhere as good), roller cam and warranty :). The 3.73 or 4.10 will get old in a hurry on the highway trust me. You could run 3.42 like a friend of mine does with a 69 with a ZZ383 and not suffer as much. I have 3.73s behind my 406 however have GV OD to make it much more highway friendly. I know a few guys with the ZZ383 and it has been a great engine for them with zero issues.
Well guys, way to throw a wrench into my master plan. I have a 342 10 bolt already, but I was hoping to go old school all the way with a 12 bolt. The concept was Pretending my car is the real deal. Well almost, kind of sort of. I have to admitt I will have to take a closer look at the stroker set up. I checked the website and the ZZ383 will cost 5.5 K, then I need a carb, Intake, Distributor etc. Now my headers and chambered exhaust would not fit so add more parts and $$$$. Can I even set the ZZ383 up to look old school? Can I can get all of my accesories and pulleys etc in the right place to look stock. The point of this build is to make a nice clone. I am concerned that with this motor I may loose the old school appeal. However if the motor will just plain chew up and spit out the LT1, it might be worth a second look. By the time it is all said and done it may cost twice as much for the stroker upgrade. I could also turn the 350 LT1 into a stroker. It Would not cost all that much more, then I would have the best of both worlds. I am just not familair with the newer motors. I'm Just an old dog that has a hard time learning new tricks! Woof Woof! One Step forward, two steps back!

:stirpot: :clonk: :confused:
 

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I wasn't thinking ZZ383 for you - I was just saying that if you're starting with a bare 010 block you might as well build a 383. I haven't priced recip assemblies recently, but I'm not certain that if a 383 kit is any more than a 355 kit. 383s are so commonplace anymore that most manufactures make and stock the parts. I think you can build a nice 383 to suit your needs for quite a bit less than $5500 if you don't get hung up on date codes, casting #'s and part # stamps for the peripherals. My opinion is that a clone is fine - but lets face it, your VIN kinda gives the whole thing away from the start. 28 cubic inches is worthwhile, esp if it essentially costs you nothing extra. Plus, with your 383 dressed to look like a 302 and built appropriately you could run circles around a legit factory Z/28, and you wouldn't need 4.xx gears to do it. Have you ever driven around in a car with 4.10's? It pretty much sucks w/o OD.
 

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I wasn't thinking ZZ383 for you - I was just saying that if you're starting with a bare 010 block you might as well build a 383. I haven't priced recip assemblies recently, but I'm not certain that if a 383 kit is any more than a 355 kit. 383s are so commonplace anymore that most manufactures make and stock the parts. I think you can build a nice 383 to suit your needs for quite a bit less than $5500 if you don't get hung up on date codes, casting #'s and part # stamps for the peripherals. My opinion is that a clone is fine - but lets face it, your VIN kinda gives the whole thing away from the start. 28 cubic inches is worthwhile, esp if it essentially costs you nothing extra. Plus, with your 383 dressed to look like a 302 and built appropriately you could run circles around a legit factory Z/28, and you wouldn't need 4.xx gears to do it. Have you ever driven around in a car with 4.10's? It pretty much sucks w/o OD.
Hey Al, sorry my bad, I thought you were referring to the ZZ383 that Tim was talking about as well. I talked to a few engine builders and you are correct, it costs about a thousand dollars more give or take to build a stroker over a 350, depending on who you talk to of course. The guy who can build me the LT1 has all these stock vintage parts kicking around in boxes from back in the day. No one has been looking to build an LT1 in quite some time so I can get the parts pretty cheap. The guy (Jack) has a nice shop and has been building motors since 1972. Super nice guy. He built a LT1 for his 1970 Yenko Nova, a really nice clean car. Looks like it just drove off the Yenko lot brand new. We talked about building a stroker but there is some metal work required to make clearance for the rods and I would need new rods, crank and pistions. Other than that he can use all of the same parts as he would use for the LT1. As far as the porting and polishing goes, it would be minimal. He said he would clean up the ridges and make the heads flow better. He comes with high recomendations from some serious Camaro builders I know. They won't let anyone else build their motors. He really knows his vintage Chevy stuff.

I will digest all the suggestions and decide which way to go. Actually my original plan was to build a stroker way back when, but then I got a crazy idea to build a 302, which morphed into the LT1.

You are right though, no matter what motor I build, it will look like a 302 once it is dressed up with all the right parts.

As far as fooling anyone goes, this is an up front 6 banger dressed as a Z 28, no disputing that. The build is not to impress anyone but me. Its going to be a very origninal 6 with as many 69 Z28 parts that I can find to bolt onto it. That VIN will be displayed proudly and loudly. Some day when I can afford the real deal, I will put the 6 back in Grandma and use it and use it as my daily driver. Gives a whole new meaning to numbers matching...
 

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The extra cubes will make all the difference no matter what u do. Honestly I wouldnt even think about putting old school heads on a small block. New heads are much better and way cheaper than trying to get old heads to perform. ZZ383 has some nice pieces like roller cam as well however like everything has a price. I went 406 instead and the parts add up quicker than one might think. That said it has torque that really is very nice especially compared to a typical small block. U wont like 4.10s or 3.73s with a 4 speed if u plan on driving any distances....
 

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Thanks Lorne. If I had the money a nice tremac and a ZZ383 would be no problem. However I only have so much set aside for this project, so I need to find options that fit my budget, until I win the lottery that is. (Checked my tickets tonight, no such luck!)The above combo might end up costing 12 K and that would not include exhaust, accessories ect. Perhaps up to 15K for the full swap. I am trying to get mine done for half of that if possible. So far I have most of the parts already except the motor. I guess the one option for torque and cubes would be to make the 350 a stoker. I had no idea that a stroker would destroy a 350 that bad. I thought the little small block winding out at 8K would be a force to rekoned with. I am so out of the loop with the modern gear. I haven't got out much since 1980! Great suggestions. I appreciate it.
 

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NO, not selling. His car is just out of the paintshop and back together (mostly).
This was intended to be "sample the wine and cheese" before you decide.

Low buck 350 w, vortec heads, 'little' solid cam, 480-500 lift on less duration then the factory cams for better driving, more low and midrange power
or a late 1pc seal, 4-bolt main, zz4 cam with heads of your choice....
I may be in Arlington N of Seattle next FRI or SAT. Mebbe u meet up with my criminal Chevelle-Elky guys (several own a Camaro or two) for technology transfer
 

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NO, not selling. His car is just out of the paintshop and back together (mostly).
This was intended to be "sample the wine and cheese" before you decide.

Low buck 350 w, vortec heads, 'little' solid cam, 480-500 lift on less duration then the factory cams for better driving, more low and midrange power
or a late 1pc seal, 4-bolt main, zz4 cam with heads of your choice....
I may be in Arlington N of Seattle next FRI or SAT. Mebbe u meet up with my criminal Chevelle-Elky guys (several own a Camaro or two) for technology transfer
Hey George how much to build his engine
 
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