Need diagram for early 70 / late 70 ignition shielding?

[Lawrence M.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Terry....

Do you know the size of these screws? I too have the early style box shielding and "Buba" replaced the screws with rivets Thank you.

In a thread about a year ago Joe Lucia reported his original screws were phillips drive, pan head #8-18 X 1/2". If you can find that thread I think he included photos of his original screws.

[Larry M.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Mike,
The items that you marked in red in the second photo are (I'm pretty certain) stylized drawings of the exhaust manifold bolts with their french locks; the locks being drawn as a straight-across piece of metal, not curved, as you'd expect to see.
On my '72, the 90 degree #2 brackets attach to the inner holes of the outer ram's horns; the 45 degree brackets attach to the center ram's horn holes.
Of course, that only takes care of cylinders 5, 6, 7 and 8; my '72 doesn't require them for 1, 2, 3 and 4, as your does.
Larry

[Terry M.]

Re: Need diagram for early 70 / late 70 ignition shielding?

In a thread about a year ago Joe Lucia reported his original screws were phillips drive, pan head #8-18 X 1/2". If you can find that thread I think he included photos of his original screws.

Larry,
I tried finding that thread before my "I don't know" post above, but I couldn't find it. My recollection is the same as yours about the pictures though. Sometimes we get off the original subject of the thread and then when important information is posted future searches don't easily turn it up because it is buried with other subject matter.

For Mike F here is a PDF of the four spark plug shields from the 1969 AIM, and because Kurt asked about the 2-piece distributor shield (and it was on the back side of the spark plug shield page, so scanning it was easy) a PDF of that is here.

[Mike G.]

Re: Need diagram for early 70 / late 70 ignition shielding?

my 70 LT-1 is serial number 12551. i have the later style. i was told my car is a early number to have this style shielding

[R N.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Larry,
I tried finding that thread before my "I don't know" post above, but I couldn't find it. My recollection is the same as yours about the pictures though. Sometimes we get off the original subject of the thread and then when important information is posted future searches don't easily turn it up because it is buried with other subject matter.

For Mike F here is a PDF of the four spark plug shields from the 1969 AIM, and because Kurt asked about the 2-piece distributor shield (and it was on the back side of the spark plug shield page, so scanning it was easy) a PDF of that is here.

Thank you Terry for posting the scans.

[Bill L.]

Re: Need diagram for early 70 / late 70 ignition shielding?

I would really like to hear more on the change over to the later style shielding.

My 70 is serial number 11327 and the only, what appeared to be, original shielding were the rear supports and top shield. Both were late style. The bolts that held the supports were clearly correct and looked like they had not been removed.

The build date is the first week in June. I have been wrestling with what to do come judgment day.


Bill

[Jack H.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Thanks, for chiming in Michael. YES, the 'early/late' distinction applies to running changes one at a time based upon the happenstance of their occurance. And here we've got a great example to conduct 'school' on.

Open up the AIM page that Pat Moresi gave. Now, look at the bottom of the drawing where the ECR block records running changes. You'll see it documents the changes associated with the ignition shielding were approved/authorized in early March of 1970.

That does NOT tell us when the assy line at St. Louis was fully converted, but it establishes the first 'possible' date when the new version of the parts were available. Typically, changes were phased in to use up the on-hand inventory of the earlier parts and for 'some' period of time both early and late parts were used rather randomly until the early parts were exhausted.

So, now you know what 'early' and 'late' mean as far as the ignition shielding goes on a 1970 Corvette... Prior to the ECR release, it'd have to be the early parts on the line. After the ECR release, it could have been either version. MUCH after the ECR release, the line was probably using only the later parts.

[Steve D.]

Re: Need diagram for early 70 / late 70 ignition shielding?

My 70 is 10498. Built the last week of May. I have the early shielding. A word about the french locks. If any of you guys decide to use the repop examples, they come in 2 finishes the correct natural steel and stainless. Be warned the nw natural steel are not the quality of the factory supplied locks. The look is 100 percent fine. The problem is installation. You must grease the manifold bolts. If you do not I can almost guarantee the locks will twist into pretzels when you tighten the bolts.

[Terry M.]

Re: Need diagram for early 70 / late 70 ignition shielding?

I would really like to hear more on the change over to the later style shielding.

My 70 is serial number 11327 and the only, what appeared to be, original shielding were the rear supports and top shield. Both were late style. The bolts that held the supports were clearly correct and looked like they had not been removed.

The build date is the first week in June. I have been wrestling with what to do come judgment day.


Bill

Bill,

Based on your description, I would believe the car

Few of the changes we document are a perfect change situation where one style ended one day and another style began with the next car coming down the line. I would expect there was a period where either style ignition shielding was present. Since it sounds like you have good documented evidence, simply believe what you have found.

[R N.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Hello Everyone,

I'm posting some photos of the screws (#8-18 x 3/4" pan head, Phillips drive) that attached the two halves of the shielding only and do not attach to the supports. My good friend Scott Sims (another 1970 aficionado) sent the photos to me and I want to share with others whom may be interestered.

[Jack H.]

Re: Need diagram for early 70 / late 70 ignition shielding?

BELIEVE what Terry's saying! It took something like a threat to life, limb, property for most manufacturers to 'cleanly' make a transition on a given running change. To do that would normally require the old parts to be gathered up, taken off the assy line, and then either written off as scrap or transferred to another area of the company where they still had value (like service).

Expect to find most savvy judges to be tolerant of cars built either way around the time frame when a running change is known to have occurred. Plus, this change was primarily a cost reduction that 'fell out' of the need for Chevy passenger cars to have RF shielding inside the distributor cap.

So, the Corvette line didn't have much interest in being in a hurry as they'd have wanted to use up all of the on-hand + in-pipeline inventory of the early version of the shielding system. Corvette didn't have a windshield glass embedded radio antenna option to worry about supporting...

[Terry M.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Another consideration Jack would have been how labor intensive it was to install all the "early" style shielding. The "later" style has a lot less pieces and would represent a significant reduction in both material and labor cost. That might hasten the introduction of the newer style.

I think the left front and right rear chrome shield are the same, or close enough to it that the parts are interchangeable. That could also hasten the implementation of the newer style.

I would be interested in seeing the change authorization paperwork for this stuff. It would be real interesting seeing the cost Data.

[D S.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Larry,
I tried finding that thread before my "I don't know" post above, but I couldn't find it. My recollection is the same as yours about the pictures though. Sometimes we get off the original subject of the thread and then when important information is posted future searches don't easily turn it up because it is buried with other subject matter.

For Mike F here is a PDF of the four spark plug shields from the 1969 AIM, and because Kurt asked about the 2-piece distributor shield (and it was on the back side of the spark plug shield page, so scanning it was easy) a PDF of that is here.

Terry, in the attached 1969 distributor shield.pdf that you provided what goes through the hole in the rear of the shielding where item 3 shows 3695126 Grommet (427 engine). Do the coil wires feed through there? Given the four braided wire grounds on that side it sure looks tight without grounding something out. Like the coil.

Thanks,
Scott

[Terry M.]

Re: Need diagram for early 70 / late 70 ignition shielding?

Terry, in the attached 1969 distributor shield.pdf that you provided what goes through the hole in the rear of the shielding where item 3 shows 3695126 Grommet (427 engine). Do the coil wires feed through there? Given the four braided wire grounds on that side it sure looks tight without grounding something out. Like the coil.

Thanks,
Scott

Yes Scott, I believe it is the coil wires that go through there. I am not sure that continued throughout the 1969 model year though. My recollection is the grommet was for only part of the year.

[D S.]

Re: Need diagram for early 70 / late 70 ignition shielding?

The 1970-1972 JG states that the box style shielding continued through at least S/N 16,000 something in 1970 Corvettes. Whether the hole was there on all of them is not known. But can you imagine how much of a pain it already is to remove the shielding every time one needs to get to the distributor or coil or even the tachometer cable? If coil wires were run through that hole it appears that the coil wires would have to be disconnected from the coil to remove the shielding.

What caused me to ask about the hole? From time to time the car would crank but not start. I kept suspecting the points. After checking the points for the correct gap setting or not being burned out and after reinstalling the shielding it still wouldn't start. So, I decided to leave the shielding off. It would start immediately. I knew then something was grounding something out and I saw those three coil wres routed under the shielding and up to the coil. After reinstalling the shielding I re-arranged the three wires where they were not touching anything. The car started. Then I wondered about that hole again.

Thanks,
Scott