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Old 12-25-2015, 06:09 PM
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sjdiesel sjdiesel is offline
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Default School me on manual conversion for my 1967 GTO

I am in the body work stages of restoring my 1967 GTO. Car is a factory 400/th400 car and I am considering swapping out the th400 for a Muncie. Plans for the engine include a 461 stroker, ported 670's, "stump puller" HR cam, etc. I like the "sleeper" look so this car is going to look very factory.

This car will be a street car and probably never go to the track. I love drag racing but think this car will stay on the street. With that said, manual cars are a lot of fun so I am looking into what it will take to convert my car to a manual and if it is cost feasible or if I should just stick with the auto.

I really want to stick with the Muncie manual since it is factory and seems like the most cost effective swap. I have looked into the 5 and 6 speed swap kits from various companies but the trans alone is like $3k.

So who here has done this swap? What is all involved?

Parts needed:
Sheet metal tranny hump
Pedals
Z bar
Clutch fork
Misc bolts and levers
Shifter and boot
Pontiac bell housing
Transmission m20? M21? This is where I am confused.
Flywheel and clutch. Need help here too.



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Old 12-25-2015, 06:20 PM
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Here are a couple links for parts:
Pedals and z bar stuff
http://www.hitechclassics.com/mobile...y.aspx?id=1847

Tunnel hump
https://www.yearone.com/Product/1964-72-gto/a670b

I found an m20 out of a 69 GTO near me for sal for $800. Comes with bell housing, flywheel, pressure plate, and shifter. Is that a fair price? Do I want an m20? I would assume to just buy a new flywheel and pressure plate with my clutch assembly but at least this has the trans and bell housing. Seller says the trans is in good condition. He was going to install it into his fire bird but sold the car.


Also found an m20 wide ratio trans and hurst shifter for $550 local to me as well.


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1967 GTO
Koerner built 468 with Edelbrock RP’s 315cfm by Butler, Luanti Voodoo HR 20510713, 4l80e, Holley Terminator EFI
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Old 12-25-2015, 06:47 PM
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A wide-ratio M20 Muncie (2.52 or 2.56 low gear) would be best if you're using a 3.55 or lower rear numerically.

A close-ratio M21 or M22 (2.20 low gear) would be best used with a 3.70 or higher gear numerically.

A lot of this has to do with starting off in low gear without killing the clutch. Driving on the streets is a real pleasure with a 4-speed if you choose the right combo of low gear and rear gear.

For example, you don't really want to couple a close-ratio M21 with a 3.08 or 3.23 rear gear, but a wide-ratio M20 would work quite nicely.

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Old 12-25-2015, 06:59 PM
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Thanks B-man. I will be running 3.55's but may swap out for 3.23's.

So then are all M20's wide ratio?


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Koerner built 468 with Edelbrock RP’s 315cfm by Butler, Luanti Voodoo HR 20510713, 4l80e, Holley Terminator EFI
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Old 12-25-2015, 07:08 PM
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Quote:
Originally Posted by sjdiesel View Post
Thanks B-man. I will be running 3.55's but may swap out for 3.23's.

So then are all M20's wide ratio?


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Ratios of the M20 , M21 , M22

Year 1963-1965 Type: M20 Rings: None Ratio: 2.56 / 1.91 / 1.48 / 1.00 / 3.16

Year 1966-1974 Type: M20 Rings: Two Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11

Year 1963-1974 Type: M21 Rings: One Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27

Year 1967-1974 Type: M22 Rings: None Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27

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Old 12-25-2015, 07:09 PM
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Quote:
Originally Posted by sjdiesel View Post
Thanks B-man. I will be running 3.55's but may swap out for 3.23's.

So then are all M20's wide ratio?


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Yes.

1963 - 1965 M20 wide-ratio 4-speeds have 2.56, 1.91, 1.48, 1.00 gearing. The 1966 - 1974 M20 trans will have 2.52, 1.88, 1.46, 1.00 gearing.

In contrast to the M21/M22 close-ratio with 2.20, 1.64, 1.28, 1.00 gearing.

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Old 12-25-2015, 07:18 PM
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On first gen GTO,s I think you have to weld in the bracket that holds the Zbar to the frame.
Honestly though. Ive converted a 69 over to manual from automatic. After 2 broken muncies and a 10 bolt rear I put an auto back in it. That was with a 400 motor and street tires on the street. A 455 will make mince meat out of those muncies.

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Old 12-25-2015, 07:39 PM
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[QUOTE=Bruce Meyer;5508808]On first gen GTO,s I think you have to weld in the bracket that holds the Zbar to the frame.
QUOTE]

Yes, and if the inner fender is in place, it will be a b%&ch to weld.

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Old 12-25-2015, 07:50 PM
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If your going with the 670 heads you might want to consider a 4" stroke crank. It will be easier to set the comp ratio for pump gas with a slight dish to the pistons. A 433 cid motor will be a great combo with an M20 trans and a 3.55 rear as 4" stroke motor works great with a manual trans.

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Old 12-25-2015, 08:03 PM
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Make sure your crankshaft is drilled for a pilot shaft bearing/bushing.

Make sure your flywheel is balanced appropriate for your engine.

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Old 12-25-2015, 08:12 PM
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Quote:
Originally Posted by Bruce Meyer View Post
On first gen GTO,s I think you have to weld in the bracket that holds the Zbar to the frame.

Honestly though. Ive converted a 69 over to manual from automatic. After 2 broken muncies and a 10 bolt rear I put an auto back in it. That was with a 400 motor and street tires on the street. A 455 will make mince meat out of those muncies.

This is what I worry about. This makes me want to leave it an auto......

Has anyone out there had similar luck? Is the Muncie a reliable setup?


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Koerner built 468 with Edelbrock RP’s 315cfm by Butler, Luanti Voodoo HR 20510713, 4l80e, Holley Terminator EFI
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Old 12-25-2015, 09:01 PM
TedRamAirII TedRamAirII is offline
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I think the choice is a M-22 or a TH400. If you want to race I would choose the TH400. If you want to flush these young punks' street cars down the drain, get a M-22W. Its a M22 Wide Ratio so it will be good with the gear you are running. Ck out 5speeds.com

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Last edited by TedRamAirII; 12-25-2015 at 09:14 PM.
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Old 12-25-2015, 09:10 PM
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sjdiesel sjdiesel is offline
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Default School me on manual conversion for my 1967 GTO

Autogear's are like $2k for just the tranny!!! I'm not Rockefeller . That's serious money.

I figure about $2k + my time to modify the car to do the manual swap if I get savvy. Or rebuild my th400, roughly $800(assumption) to rebuild + a continental 10" "jim hand" converter $800 = $1600 and no modifications to the car.

Thoughts?


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1967 GTO
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Old 12-25-2015, 09:21 PM
TedRamAirII TedRamAirII is offline
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If it was me.......I would build the 400, with a good converter. I would also keep 150HP N20for back up HP. You don't want to get spanked by some kid in a Mustang. Its like a little insurance policy.

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Old 12-25-2015, 09:50 PM
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Quote:
Originally Posted by TedRamAirII View Post
If it was me.......I would build the 400, with a good converter. I would also keep 150HP N20for back up HP. You don't want to get spanked by some kid in a Mustang. Its like a little insurance policy.

See now this I like


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1967 GTO
Koerner built 468 with Edelbrock RP’s 315cfm by Butler, Luanti Voodoo HR 20510713, 4l80e, Holley Terminator EFI
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Old 12-25-2015, 10:49 PM
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As this is the street section and real muscle cars have 3 pedals,continue with your swap!If this is going to be a"race" car then go with the auto.If your going to end up with a 461 I would go with a M20 and something like a 3.31 and avoid big sticky race tires.Tom

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Old 12-26-2015, 02:01 AM
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Quote:
Originally Posted by tom s View Post
As this is the street section and real muscle cars have 3 pedals,continue with your swap!If this is going to be a"race" car then go with the auto.
I like the sound of that!

I've put 7,000 miles on my M21 (who knows what was on it before I bought it). It's never given me an issue, and I've never heard people complain about the Muncie - here or anywhere else.

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Old 12-26-2015, 10:57 AM
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Could you not drill, tap and bolt on the Z bar bracket like second gen F bodies do if no welder around?

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Old 12-26-2015, 02:29 PM
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I've done this swap (most recently on a '65 GTO s couple years back). Other than welding the z-bar on the frame, just about everything is a bolt-in. Chances are that your crank is already drilled for a pilot bearing (is it an original '67 crank?). In the end, it all depends what you want to do with car. If it will see a lot of passes and you want to build a bracket car, then just beef up the TH400. If it's just a boulevard bruiser, then the 4-speed will just be more fun (IMHO).


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Old 12-26-2015, 08:27 PM
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What is the rear gear currently? If it is in the 2.93 - 3.23 range I would look at the M22Z (2.98 1st, 1:1 4th). I have one behind my 440 w/2.93 gears - works quite well. Swapping over to 4 speed will run you about $3k if done correctly.

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