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Author Topic: Big Block Distributor Hold Down Clamp  (Read 4295 times)
Camarocards
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« on: July 16, 2013, 09:06:19 PM »

Which hold down clamp is correct for a '68 396/325? The wire type or the plate type?

Thanks,

Bob
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Bob
'68 SS L35 01D
Ed Bertrand
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« Reply #1 on: July 17, 2013, 12:52:44 PM »

From the start of V8 production in 1955, all engines used the solid (stamped) steel clamp you show in the top picture. This was P/N 3704912.

Then, in late 1959 (for the 1960 model year), GM went "cheap" on us and used the wire clamp you show in the bottom picture. This was P/N 3772532 and used a "retainer" (P/N 3770598) to keep the legs from spreading.

Then, in early 1968, GM went BACK to the solid (stamped) steel clamp you show in the top picture (P/N 3704912). Apparently the wire clamp couldn't do the job, so in a rare move, GM went back to something that actually worked!

Now, as to which one you should have, it really depends on the build date of your engine. Very early 68 engines could still have the wire clamp. They were phased out, but still intermittantly used in early 1968 because of what they had left in inventory. Toward mid year production, the wire clamp had mostly dissapeared and the solid clamp was now prevalent.

Hope this helps.
Ed

« Last Edit: July 17, 2013, 02:18:40 PM by Ed Bertrand » Logged
Camarocards
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« Reply #2 on: July 17, 2013, 01:18:02 PM »

Ed,

Thank you very much! Very helpful indeed.

I have both the wire clamp and the stamped clamp in my stash of parts, hence my question on which one was correct.

My car is an 01D build so from the info you've provided it looks like it could be a toss up on which one to use. Now, if I go with the wire clamp version what finish would it have gotten? Would it have the overspray from when the engine was painted (assuming of course that the distributor and clamp was installed prior to the engine being paint)?

Thanks,

Bob
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Bob
'68 SS L35 01D
Ed Bertrand
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« Reply #3 on: July 17, 2013, 01:45:00 PM »

I believe the wire clamp was black oxide (as was the bolt) and the retainer was natural steel. The stamped clamp was usually natural, but some examples have been seen with varying amounts of orange paint on them. Supposedly, both Flint and Tonawanda painted the engines before the distributor (and clamp) was installed, so you shouldn't see any orange paint on the clamp, but I'm wondering if maybe some of the clamps were installed loosely before paint. I'll ask John and/or Jerry to comment on this.

As for which one to use, what's the build date of your engine?

Ed
« Last Edit: July 17, 2013, 02:45:40 PM by Ed Bertrand » Logged
Mike S
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« Reply #4 on: July 17, 2013, 02:00:00 PM »

I checked both my '67 L35's and they have the stamped clamp.
They are: original unrestored survivor - T0214MZ - 4B LOS and restored convertable T0308MW - 5B NOR

Mike
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« Reply #5 on: July 17, 2013, 02:09:15 PM »

Thanks Mike.

Ed-The engine is a January '68 build. Don't know the exact date since I'm not in frontbofbit at the moment.

Thanks,

Bob
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Bob
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Ed Bertrand
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« Reply #6 on: July 17, 2013, 02:20:53 PM »

Quote
I checked both my '67 L35's and they have the stamped clamp.

There may be a difference in usage between small blocks and big blocks, so I'll see if John or Jerry can elaborate.

Ed
« Last Edit: July 17, 2013, 02:45:15 PM by Ed Bertrand » Logged
Jerry@CHP
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« Reply #7 on: July 17, 2013, 03:08:29 PM »

What I can add here is the wire style was used on 67 and 68's.  But, I'm not sure on the BB cars.  I'll have to dig though all of my survivor photos and take a look.

In the Nov '68 Super Stock magazine article with Jerry Stahl and the '68 Z28 road test, they talked about how they did not like the wire style hold down as the timing kept moving around while doing their road test.

Jerry
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Steve68
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« Reply #8 on: July 17, 2013, 03:25:25 PM »

My 68 L78 has the wire hold own clamp (original). 06 build.

Steve
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« Reply #9 on: July 17, 2013, 04:35:52 PM »

My 1968 Z28 07C, 06-19 engine build, has the stamped steel hold down.  The hold down and the bolt were painted silver.  Apparently they were painted with a brush as there was some silver paint on the distributor wire.  It doesn't look like it was sprayed on the wire, it appears that a paint brush left the paint.
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Jerry G.

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« Reply #10 on: July 17, 2013, 05:25:55 PM »

Jerry,

I've been following a similar thread on distributor clamps but it had more to do with small blocks and the correct finish. My question was more aimed more at big blocks and which type clamp was used. The type of finish will then of course need to be answered as well.

Perhaps other members can take a peek at their big block engine and report back what type of clamp is installed and what month the car was built.

Thanks,

Bob
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Bob
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« Reply #11 on: July 17, 2013, 06:03:47 PM »

Bob....Can't think of any reason they would use different ones for different engines.  All the engines, big block or small block, would get the same part as they came down the engine assembly line.
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Jerry G.

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« Reply #12 on: July 17, 2013, 06:29:28 PM »

Jerry,

You would think so, right? It would seem to make sense. I'm just not sure which one to use since I've seen both type clamps advertised.

I just had a friend check his '69 427 Corvette he is restoring and it has the wire type clamp. Go figure? I even asked him to check the NCRS judging manual but unfortunately the manual makes no mention of distributor clamps.
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Bob
'68 SS L35 01D
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« Reply #13 on: July 17, 2013, 07:09:40 PM »

<< Now, if I go with the wire clamp version what finish would it have gotten? >>

Which hold-down version doesn't affect the finish - they were installed (with the distributor) at both engine plants prior to engine painting, and masked with a coffee can, and it's not unusual to see engine orange overspray on the distributor lower housing and on the hold-down.
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« Reply #14 on: July 17, 2013, 07:45:18 PM »

Quote
I just had a friend check his '69 427 Corvette he is restoring and it has the wire type clamp. Go figure?

My 69 427/390 Corvette (VERY late October, 1969 build) has the stamped clamp! And no, the 68/69 (latest - 5th edition) Corvette Technical Information Manual and Judging Guide, doesn't mention the clamps.

Ed
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Camarocards
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« Reply #15 on: July 17, 2013, 07:55:56 PM »

Thanks Ed.

My friends Vette is also a 427/390. Not sure of his build date though. I'll ask him what his build date is.

Thanks,

Bob
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Bob
'68 SS L35 01D
Ed Bertrand
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« Reply #16 on: July 18, 2013, 12:10:41 PM »

Here's an interesting tidbit. On the Corvette side of the world, it's known that the wire clamp was used on ALL engines in 1967. Since both Corvette and Camaro engines (as well as all the rest of the divisions) were assembled at Tonawanda and Flint, I can't see any 1967 engines using the stamped clamp.

Ed
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Mike S
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« Reply #17 on: July 18, 2013, 12:45:45 PM »

I'd be shocked if there are no other members here that have a BB 67 or 68 to reply to.
I'm not that lucky to have two 67 L35 BB's and both have the stamped clamp, especially on the survivor I have had since 1980.
I'll go play Lotto now  Smiley

Mike
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« Reply #18 on: July 18, 2013, 12:57:33 PM »

That's why this is such a mystery Mike. Your two engines should NOT have the stamped clamp and the 69 Corvette Bob referenced above SHOULD!! I can see this is going to be another one of those items that'll drive us all nuts!!

Ed
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Camarocards
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« Reply #19 on: July 18, 2013, 01:01:55 PM »

Ed - Well, here is more more interesting info. I found this picture in the '68 Chassis manual. Unfortunately, the picture is for a 6 cylinder engine but the interesting thing to note is that it clearly shows the wire type clamp.

Mike - What is the build date on your cars?

It's still a mystery to me why some cars have stamped clamps and others have wire clamps, particularly in light of what Ed reported in an earlier post. It also doesn't look like there is a rhyme or reason as to which size engine got which clamp since the Chassis manual shows a wire clamp on a 6 cylinder engine.
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Ed Bertrand
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« Reply #20 on: July 18, 2013, 01:22:34 PM »

Bob, 6 cylinder cars got the wire clamps from the beginning of time! Even way into the 70's. I don't think 6 bangers ever got a stamped clamp, but of course, in light of what we're seeing, who knows!

You can't go by images in the service manuals. Most of the time they just found a picture that was good enough to show what was being referenced. It may be from a prior (or even several years before) and may not even be a Chevrolet part! HERE'S another example of what I mean.

Ed
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« Reply #21 on: July 18, 2013, 01:36:50 PM »

Thanks Ed. Looks like mystery continues!
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Bob
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« Reply #22 on: July 18, 2013, 01:46:07 PM »

My '67 10B LOS L-30 has the wire clamp. FWIW
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68camaroz28
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« Reply #23 on: July 18, 2013, 06:27:06 PM »

Our 12/21/67 built 302 had the wire holder where our 69 Nova 396 had the clamp. I as others have seen the wired clamp style on 68's.
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Chick
68 Z/28 NOR 01B Orig motor/trans/rear
69 Z/28 NOR 07A Orig Block & GM Cross-ram/carbs
69 L34 Rest. Nova Father/Son Car
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67 L89 Corv Tribute
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« Reply #24 on: July 18, 2013, 07:13:41 PM »

 The more accurate way to gauge this is when the motor was assembled being the distributor was installed then.
My 67 L35 block assembly date codes are:
T0214MZ and T0308MW - both have the stamped clamp.

Chick, I assume the 302 date is what is stamped on the pad?

This is certainly an interesting topic.
Mike
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« Reply #25 on: July 18, 2013, 07:59:00 PM »

Well, I didn't think I'd cause such an in depth discussion when I posted my original question! I figured surely someone must have run into this during their restoration, I'd get my answer and continue on with my project. Boy was I wrong!!

Anyway, I thought I would start to tabulate what we know so far from all of the previous posts:

Year    Engine    Build Date     Clamp Type

67         L30          610B               Wire
67         L35          704B               Stamped
67         L35          705B               Stamped

68         Z28          801B              Wire
68         L78          806?               Wire
68         Z28          807C              Stamped
« Last Edit: July 18, 2013, 08:06:08 PM by Ed Bertrand » Logged

Bob
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Ed Bertrand
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« Reply #26 on: July 18, 2013, 08:07:21 PM »

Bob, I put them in monthly order for you and added a year digit at the begining of each date code. i.e. , 610B would be the second week of October, 1966.

Let's keep it going folks.

Ed
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Mike S
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« Reply #27 on: July 18, 2013, 08:24:47 PM »

Hi Ed,
   Good compliation. As a suggestion, I think it would be more granular if the engine assembly date was recorded too being some units sat on the rack from days to months before being placed in the chassis. Maybe something like below?

Year    Engine    Engine Date   Body Date     Clamp Type

67         L30                          610B               Wire
67         L35         0214          704B               Stamped
67         L35         0308          705B               Stamped

68         Z28                          801B              Wire
68         L78                          806?               Wire
68         Z28                          807C              Stamped


Mike
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« Reply #28 on: July 18, 2013, 08:46:23 PM »

Thanks Ed!

Mike - Good suggestion!
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« Reply #29 on: July 18, 2013, 10:30:07 PM »

Guys,

   68   L35    0321    805C    Stamped
     VT
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« Reply #30 on: July 18, 2013, 11:59:07 PM »

My 1968 07C Z28 has a engine build date of 0619.  It is already on the list....just need to add build date if you do decide to do so.
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Jerry G.

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« Reply #31 on: July 19, 2013, 09:07:54 AM »

Update:

Year    Engine    Engine Date   Body Date     Clamp Type

67         L30                          610B               Wire
67         L35         0214          704B               Stamped
67         L35         0308          705B               Stamped

68         Z28                          801B              Wire
68         L35         0321          805C              Stamped
68         L78                          806?               Wire
68         Z28         0619          807C              Stamped

Ed
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« Reply #32 on: July 19, 2013, 12:15:41 PM »

Update:

Year    Engine    Engine Date   Body Date     Clamp Type

67         L30                          610B               Wire
67         L35         0214          704B               Stamped
67         L35         0308          705B               Stamped

68         Z28                          801B              Wire
68         L35         0321          805C              Stamped
68         L78                          806?               Wire
68         Z28         0619          807C              Stamped

Ed


Ed, per my earlier post our 01B built 68Z engine was assembled 12/21/67.
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Chick
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69 Z/28 NOR 07A Orig Block & GM Cross-ram/carbs
69 L34 Rest. Nova Father/Son Car
69 L78 Surv Nova Purch 4/69 31K miles
67 L89 Corv Tribute
68 Corv 427/400 Orig motor
07 Corv Z06
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« Reply #33 on: July 19, 2013, 12:33:07 PM »

Update:

Year    Engine    Engine Date   Body Date     Clamp Type

67         L30                          610B               Wire
67         L35         0214          704B               Stamped
67         L35         0308          705B               Stamped

68         Z28         1221          801B              Wire
68         L35         0321          805C              Stamped
68         L78                          806?               Wire
68         Z28         0619          807C              Stamped

Ed
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rare396bronze
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« Reply #34 on: July 24, 2013, 11:18:24 PM »

06a L35 & 06b 327/210 hp stamped brackets
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« Reply #35 on: July 25, 2013, 06:06:30 AM »

06a L35 & 06b 327/210 hp stamped brackets
What years and motor assembly dates?

Mike
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« Reply #36 on: July 25, 2013, 01:05:27 PM »

My 67 L-30 (610B, with wire) has an engine assy date of 0812 if you would like to update.
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Ed Bertrand
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« Reply #37 on: July 25, 2013, 01:35:31 PM »

Update (07-25-13):

Year    Engine    Engine Date   Body Date     Clamp Type

67         L30         0812          610B               Wire
67         L35         0214          704B               Stamped
67         L35         0308          705B               Stamped

68         Z28         1221          801B              Wire
68         L35         0321          805C              Stamped
68         L35                          806A              Stamped
68         LF7                          806B               Stamped
68         L78                          806?               Wire
68         Z28         0619          807C              Stamped

Ed
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« Reply #38 on: July 31, 2013, 08:59:49 PM »

68         L35         1215          812E              Wire


Jim
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« Reply #39 on: August 01, 2013, 12:41:47 PM »

I researched this some.  My parts history book shows the 3772532 wire clamp was to be substituted with 3704912 starting November 1969.  The October 1, 1967 P&A 34 shows 1964-1968 all (8 cyl) clamp unit 3772532.  The October 1, 1970 P&A shows 67-70 3704912 for all 8 cyl.

Steve
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« Reply #40 on: August 01, 2013, 01:34:31 PM »

My July 1969 Camaro Master Parts Catalog shows this:

     2.363  Clamp Unit, Ignition Timer Distributor
     -----------------------------------------------------------

               1     3772532     1967/8  CYL
               1     3704912     1968-69/8  CYL

A 2-15-69 P&A 34 shows:

               1     3772532     64-67 All 8 CYL
               1     3704912     68     All 8 CYL
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Jerry G.

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« Reply #41 on: August 06, 2013, 09:38:09 PM »

12A 1968 build date  L89. Stamped hold down, no finish.
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monaroman
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« Reply #42 on: August 23, 2013, 05:52:55 PM »


Hi there,

Looking to purchase a GM stamped style distributor bracket.

Does anyone have a accurate photo front and back of the stamped style bracket?

What was the bolt marking?

Thank you.
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1968 Z28
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« Reply #43 on: August 24, 2013, 12:10:19 AM »

This one is from my 1968 Z28....There is a possibility that different years might have different bolt heads.

Bolt Head



Bolt Lengthwise - 1 1/8" by 3/8"



Clamp - up side



Clamp - Down side

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Jerry G.

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