[leroycash]

I'd call Larry at Wells Speed in Weatherford TX. Theres also 'Kajun' Jon Bergeron in Whitney, TX.

I can send you a measured drawing of both versions of the aftermarket 'Muncie' (10/27 spline and 26/32 spline)

An aftermarket Muncie with the Euroricambi gearset and a 26 spline input is perfectly happy behind a 502/502 ZZ502 BBC. If you are going to get rough with it, I'd go 32 spline output, shifter handle be damned. If you want to try and run with the big dogs, an M23 takes up where the M22-based stuff leaves off. An M22-based, italian gearset, aftermarket 'Muncie', with the roller sidecover, iron midplate, Supercase, Super Tailhousing and 26 spline input and 27 spline output weighs about 85 pounds dry and takes 1-qt of 75w90 non-synth GL4.

Okay I'm back online. Thanks for the historic background and contemporary status of the Muncie system. Gulp. That's a lot to digest but I'm learning a lot from your posts. I believe Muncie=good for this project. I want to meet up with one of your retailers in Texas to see the parts and figure it out in real time. In the meantime your offer to send a measured drawing of the two spline configurations might help me figure out the shifter issues. How can I get that drawing? A pdf would be fine, or whatever you have. I can dump it into CAD one way or another and go to work.
In an earlier post you mentioned what you thought would be a good rear gear and tranny combination. It was a streetable 3.23 rear end and a 2.98 first gear. Is this option part of the modular system you mention? I'm still trying to square the gear combinations with the M22 system. I'm understanding with the M22 (Italian) gears which have a more consistent strength and a shallower pitch I can assemble a 2.98 1st gear and a couple different second gear options to run with a 3.23 rear gear. This could be in a stock case or a super case. If I go with the super case and the cast iron midplate the overall assembled length increases by 0.147" due to the thickness of the case. I'm not sure if the modular gear set (assuming that's what we're talking about here) dictates the 27 or 32 spline output, or if either is still an option. If I go with the 27 spline output the D/S will be longer than if I use a 32 spline output by 0.700". In other words the tranny assembly gets longer by 0.700". No big deal as I have no D/S yet. You also recommend a 27 spline mainshaft. You said this gives me two options for the shifter. This is where it gets confusing to me. I'm sure it will be clearer when I see some parts. I don't understand how this affords me 0.700" more or less dimension for the shifter location. Somehow the 32 spline output is dictating the shifter mounting points even though we're well behind the shifter at this point. I'll figure it out. It's just geometry.
Hey thanks again for all this useful information. I look forward to getting started!

 

[leroycash]

Bought a 389 block

So I finally bought a 389 block for my 1950 Streamliner project. Its a nice 1965 WT casting with standard bore. I just have the block and main caps so far. The block was originally put in a 65 GTO with manual transmission and a 1x4 carb. Not that it matters but my hope of using a muncie 4-speed and similar carb set up seems right. Now I have an opportunity to buy one of two possible heads. Both are cast iron. One is a pair of 73 4X (3H) heads with 98.21 cc chamber volume and screw in studs originally for a 400 block. The other is a pair of 76 6S (9) heads with 93.74 chamber volume originally for a 350 block. The 6S chamber volume works best for my combination if I'm calculating it right. My plan is to increase the stroke from 3.75" to 4.25" using an aftermarket crank and rotating assembly. Using KB pistons that are off the shelf with a 3.5 cc volume, a head gasket that is .038" thick and a deck height of .020" I get a compression ration of 9.35:1. Does this sound right? Are the heads from a 350 problematic for any reason I'm overlooking? Would like to make the next move to get this project underway.

 

[LATECH]

The 1973 4X heads would be the prize.

That old 65 block can prolly be bored to 4.15. Get it sonic checked first.
4.120 with a 4.25 stroke Is a 455 :thumbup:
with this combo and zero decking, you would end up at 9.49 to 1 static
Pretty much what you want for a pump gas job.
The 4x heads have screw in studs, but you want to upgrade to BBC studs to make your valvetrain adjustable.Use poly locks to, not just self locknuts.
Be sure to have your cam choice before the heads go off, so you can get the correct springs and have the heads checkto ensure guide top clearance and spring clearance/bind issues.

 

[leroycash]

On the subject of later model cylinder heads for my 389 build I was told the 6S (9) High Performance (AIR) heads were designed to reduce smog. How they did this I'm not sure. Should these heads be avoided? They have the right chamber size for my app (93.74cc), they have the large valves, and they use screw-in rocker studs. Sounds pretty good to me. Matches the specs for a pair of 6X-4 heads, no?

 

[MouseFink]

On the subject of later model cylinder heads for my 389 build I was told the 6S (9) High Performance (AIR) heads were designed to reduce smog. How they did this I'm not sure. Should these heads be avoided? They have the right chamber size for my app (93.74cc), they have the large valves, and they use screw-in rocker studs. Sounds pretty good to me. Matches the specs for a pair of 6X-4 heads, no?

All 1955-1966 Pontiac heads have 68 CC combustion chambers, pressed in rocker studs, small valves and the valve seats cannot be enlarged to accept large Pontiac valves. The 1955-1964 intake manifolds will not fit the bolt pattern on 1965-1979 heads.

 

[leroycash]

Hey thanks Mousefink ans LATech. I understand about the manifold, cylinder head and chamber size issues in earlier-to-late Pontiac parts combos. I think I'm good there. What's confusing me is the "S" designation on the 6S HP AIR heads. What did Pontiac do to these heads to make them smog reducing? I'm wondering, is it something that will effect their performance? Everything else including chamber size, large valves, screw-in studs, etc makes them identical to the 6X-4 heads. Just wondering if anyone knows if they are to be avoided. Many thanks.

 

[MouseFink]

There is not a dimes worth of difference in any pair of Pontiac heads made after 1971.

 

[leroycash]

389, 400 or 455

Ok, so another pair of heads came up available locally in good condition for a good price. Their #62's with big valves and a 72cc chamber size. My question has to do with the specific issues I'll need to address when swapping out 1965 #76 heads (small valves) for 1969 #62 heads (big valves). You've all probably encountered these issues before buts it's all new stuff for me. To pull it off I'm pretty sure the pistons will have to be custom because no one makes a 389 bore (4.0625+0.030") piston with 14 degree valve reliefs. My machine shop can do this since the pistons will need to be dished to achieve my desired static compression ratio of 9.5:1. They'll mill the standard size flat tops down to an 11cc/14 degree/big valve dish. What I'm wondering now is whether the cam lobes will align properly with the push rods at the valve train. Since the valves are larger on the new heads and spaced differently than the smaller valves front to back, how will this effect cam choices? Or will the 65 cam lobes be wide enough to line up with the spacing required for the new 69 push rods? How does this geometry work?

 

[Mr. P-Body]

Put that WT block on the auction block. GTO guys will PAY for them. Use a portion of the proceeds to get a 400 (017 or 988 casting) block. These are the strongest production blocks after '59. The pistons available for the 4.250 stroke "key" on the standard 400 bore (4.120). A 389 block is "used up"
by then.

Your 16s, if properly done, are very good. A "dished" piston is required to add chamber volume. We've learned, a dish and a small chamber can make more power than a deep chamber and a flat-top. I suspect it's due to the "longer" short-turn in the shallow heads. I KNOW the 72 CC E-heads flow a little better due to that.

Icon now offers a stepped-dish piston that provides 9.5:1 with 72 CCs. It uses the Eagle 6.635" "BBC" rod. They (Icon) also have one for the 6.8" rod, but the dish must be enlarged (it's for the aluminum heads).

FWIW

Jim

 

[leroycash]

Hey, Thanks Jim. I agree the block would auction well. I'm getting excited about the 389 though. It's in great shape and I'm considering keeping the 3.75" stroke instead of bumping it up to 4" or 4.25". I don't think I want to make a lot of changes to it. Never planned to take it to the track anyway. Still, I would like to get it to breath better which is why I'm looking at the #62 heads. If the 389 and 400 heads are interchangeable, as everyone seems to think, that upgrade along with a better exhaust and maybe a hotter spark would be enough. So I'm still unclear about the alignments at the valve train and whether that's a show stopper. The push rod spacing is set by the block and for a 389 the valves are spaced one way. The rocker and valve spacing is set by the #62 head (originally used on a big valve 400) which is spaced another way. I'm beginning to think this can't work. Am I wrong about something here? Thanks again for your comments.