Questions...Help!
Thread Starter
Safety Car
Joined: Apr 2012
Posts: 4,077
Likes: 239
From: Houston TX
Questions...Help!
So I hang out in the C6 section, I have a ZO6 with the LS7 so I don't get over here much. I recently bought a BBC out of a C3 1968 Corvette. Took it halfway apart last night.
So my questions are....
1. The heads appear to be mismatched, One is stamped 3917215 and the other is 3872702. Is it OK to use these on the same engine?
2. It has an aluminum intake manifold, the casting number is 3919849. What do I have here?
3. It also came with a Delco distributor that has a mechanical drive for the RPM gauge. Also curious about what I have here? No use for this as I'll be going with electronic ignition.
4. I also have a Muncie 4 speed transmission with the angled gears. It has an aluminum case but that's all I really know about it aside from the guy I got it from said it shifted great. How do I figure out what it is?
OK, enough for this one, don't want to wear you guys out. Any info on this stuff is really appreciated. The last old Corvette I had was a C2, 1966 427, wish I still had it.
I have some pics of the transmission I'll attach later today. Thanks!
So my questions are....
1. The heads appear to be mismatched, One is stamped 3917215 and the other is 3872702. Is it OK to use these on the same engine?
2. It has an aluminum intake manifold, the casting number is 3919849. What do I have here?
3. It also came with a Delco distributor that has a mechanical drive for the RPM gauge. Also curious about what I have here? No use for this as I'll be going with electronic ignition.
4. I also have a Muncie 4 speed transmission with the angled gears. It has an aluminum case but that's all I really know about it aside from the guy I got it from said it shifted great. How do I figure out what it is?
OK, enough for this one, don't want to wear you guys out. Any info on this stuff is really appreciated. The last old Corvette I had was a C2, 1966 427, wish I still had it.
I have some pics of the transmission I'll attach later today. Thanks!
Popular Reply
Nov 23, 2020, 02:08 PM
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Thread Starter
Safety Car
Joined: Apr 2012
Posts: 4,077
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From: Houston TX
Team Owner
Joined: Jun 2000
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From: Southbound
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Dr. Detroit
Joined: Mar 2012
Posts: 10,095
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From: New Braunfels Texas
The heads are the same, one is older than the other. Oval Port Closed chamber stuff......very common back then. The intake was Corvette only as it will clear a Corvette hood.
The distributor has a gear to turn the tach as all these old Vettes had mechanical tach drives.
Transmission is most likely an M20 Wide Ratio but no real way to tell Close Ratio from Wide without looking at the gears......I believe you need to count the teeth on the first gear to be sure.
Jebby
The distributor has a gear to turn the tach as all these old Vettes had mechanical tach drives.
Transmission is most likely an M20 Wide Ratio but no real way to tell Close Ratio from Wide without looking at the gears......I believe you need to count the teeth on the first gear to be sure.
Jebby
Pro
Joined: Dec 2003
Posts: 676
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From: Usa
In regard to the transmission there is a lot of good information on this website: https://www.hotrod.com/articles/guid...transmissions/
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Just another Corvette guy
Joined: Feb 1999
Posts: 8,518
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From: Palm Springs, CA.
Hi Joe,
Welcome to C3.
Yes, good info here from most of the guys.
Here's a quick break down:
3872702 head, oval port, 1966 used from 396 325 hp up to 427 390 hp. Valves 2.06/1.72, 98 cc combustion chamber.
3917215 head, oval port, late 1967 through 1968 used from 396 325 hp up to 427 390 hp. Valves 2.06/1.72, 100.9 cc combustion chamber.
3919849 intake manifold, early 1968 single 4bbl (Rochester) used on 427 390 hp.
Does the distributor still have the aluminum band wrapped around it's neck? If yes, then post that number here please and I can give you more exact info on that part as well.
If you can post a pic of the transmission input shaft I can tell you the probability of it being an M20 (wide ratio) or an M21 (close ratio).
All in all these are good parts. Not "rare break the bank" kind of parts by any means, but decent stuff that is certainly saleable to some of your Corvette brothers out there.
Just curious, what are your plans for the engine? Are you building some type of street rod?
Cheers, Greg
Welcome to C3.
Yes, good info here from most of the guys.
Here's a quick break down:
3872702 head, oval port, 1966 used from 396 325 hp up to 427 390 hp. Valves 2.06/1.72, 98 cc combustion chamber.
3917215 head, oval port, late 1967 through 1968 used from 396 325 hp up to 427 390 hp. Valves 2.06/1.72, 100.9 cc combustion chamber.
3919849 intake manifold, early 1968 single 4bbl (Rochester) used on 427 390 hp.
Does the distributor still have the aluminum band wrapped around it's neck? If yes, then post that number here please and I can give you more exact info on that part as well.
If you can post a pic of the transmission input shaft I can tell you the probability of it being an M20 (wide ratio) or an M21 (close ratio).
All in all these are good parts. Not "rare break the bank" kind of parts by any means, but decent stuff that is certainly saleable to some of your Corvette brothers out there.
Just curious, what are your plans for the engine? Are you building some type of street rod?
Cheers, Greg
Last edited by Greg; Nov 23, 2020 at 02:34 PM.
Melting Slicks
Joined: Mar 2010
Posts: 2,268
Likes: 374
From: Randolph nj
So what are your intentions with this fine specimen of a motor ,, I love big blocks and I must ask why you took it apart in the first place ,, was it blown up ,, knocking ,, did you hear it run before you bought it .. If you have some pictures post them up or have someone post them for you ,you know the old saying a thousand words,,,WELCOME
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Sorry. I have trouble assisting those who have NO knowledge about these cars, go out and buy one, then ask for help -- without doing the first thing to help themselves.
As most of the folks on this Forum know, I've gone out of my way to help folks who are doing their best to work on their C3, but find a 'snag' or get a bit 'confused' (as we all do). But THEY are doing something on their own to begin with...not just expecting others to prop them up at the 'git-go'. If that makes be the Christmas Grinch --- so be it.
As most of the folks on this Forum know, I've gone out of my way to help folks who are doing their best to work on their C3, but find a 'snag' or get a bit 'confused' (as we all do). But THEY are doing something on their own to begin with...not just expecting others to prop them up at the 'git-go'. If that makes be the Christmas Grinch --- so be it.
its called Help for a reason
Just another Corvette guy
Joined: Feb 1999
Posts: 8,518
Likes: 3,865
From: Palm Springs, CA.
Yeah..... it doesn't sound like you've "gone out of my way to help folks who are doing their best to work on their C3".
If you read Joe's post and actually understood it, you'll see that he already owns a C6. He DID NOT say he bought a C3, only that he bought an engine from a '68 Corvette, he is tearing it down and looking for info on specific parts. Sounds like he has enough experience to do that kind of work so it appears nobody is holding his hand from the "git-go" as you suggested.
Like theandies said "That is EXACTLY what this forum is here for.
So put on your big boy pants and apologize for stinking up his thread with your bad cyber manners.
If you read Joe's post and actually understood it, you'll see that he already owns a C6. He DID NOT say he bought a C3, only that he bought an engine from a '68 Corvette, he is tearing it down and looking for info on specific parts. Sounds like he has enough experience to do that kind of work so it appears nobody is holding his hand from the "git-go" as you suggested.
Like theandies said "That is EXACTLY what this forum is here for.
So put on your big boy pants and apologize for stinking up his thread with your bad cyber manners.
Team Owner
Joined: Jun 2001
Posts: 23,363
Likes: 1,059
From: Virginia USA
Sorry. I have trouble assisting those who have NO knowledge about these cars, go out and buy one, then ask for help -- without doing the first thing to help themselves.
As most of the folks on this Forum know, I've gone out of my way to help folks who are doing their best to work on their C3, but find a 'snag' or get a bit 'confused' (as we all do). But THEY are doing something on their own to begin with...not just expecting others to prop them up at the 'git-go'. If that makes be the Christmas Grinch --- so be it.
As most of the folks on this Forum know, I've gone out of my way to help folks who are doing their best to work on their C3, but find a 'snag' or get a bit 'confused' (as we all do). But THEY are doing something on their own to begin with...not just expecting others to prop them up at the 'git-go'. If that makes be the Christmas Grinch --- so be it.
So if I go out and buy a Corvette (or even just an engine) without ever ridden in one, touched one or have no knowledge of one you'd not help out. WOW, that's a good way to introduce someone to the Corvette world. To each is own I guess........
Burning Brakes
Joined: Oct 2012
Posts: 1,152
Likes: 252
google results "how to identify muncie transmission":
https://www.chevydiy.com/muncie-4-sp...ication-guide/
http://www.superchevy.com/how-to/tra...d-input-shaft/
https://www.ecklers.com/pit-stop-blo...dentification/
r
Last edited by Dynra Rockets; Nov 24, 2020 at 09:07 AM.
Thread Starter
Safety Car
Joined: Apr 2012
Posts: 4,077
Likes: 239
From: Houston TX
So I took off the side cover and counted the teeth on the first gear. There are 26 of them. No groove on the input shaft either. Also, no drain plug on the bottom. I think Sully called it as there's no letter on the case.
Last edited by meanjoe; Nov 24, 2020 at 10:06 AM.