'70 LT1 spark plug heat shield

[Donn M.]

I've reviewed the many past threads in the archives on this subject and still need help.
Car is #407065, mid March, left/front spark plug heat shield and chrome cover.
AIM page #187 on oil filter, dip stick, etc. shows this heat shield horizontally flat.
page #192 shows the heat shield in an upside down V shape and part #3919807. Date of drawing is not clear.
page near rear of book is a redraw design dated 3-6-70 w/the heat shield flat and the chrome covers only on the back.
A previous owner had the car restored and it had the chrome cover under the #3919807 heat shield while the other 3 have the chrome cover on top. There has been no discussion about this in past NCRS judging events. #3919807 is the heat shield with the hole on the top for the temp connection and past archives state that it is impossible to put the chrome cover over this type of heat shield and after many, many hours, I agree. It seems GM #3919807 is always referred to as "early 1970 Left/Front heat shield" in all references. I think it's meant for 350's without chrome covers on front.
I know Judging manual states the change to only back plugs have chrome covers after about Ser # 14,000 and I have the box type dist/coil cover. I'm thinking the Restorer purchased a kit that had the wrong heat cover for this application and I should install a flat heat shield.
Can some of you with original early '70 small blocks give me advice as to your car's heat shield?
Thanks, Donn

[Terry M.]

Re: '70 LT1 spark plug heat shield

I've reviewed the many past threads in the archives on this subject and still need help.
Car is #407065, mid March, left/front spark plug heat shield and chrome cover.
AIM page #187 on oil filter, dip stick, etc. shows this heat shield horizontally flat.
page #192 shows the heat shield in an upside down V shape and part #3919807. Date of drawing is not clear.
page near rear of book is a redraw design dated 3-6-70 w/the heat shield flat and the chrome covers only on the back.
A previous owner had the car restored and it had the chrome cover under the #3919807 heat shield while the other 3 have the chrome cover on top. There has been no discussion about this in past NCRS judging events. #3919807 is the heat shield with the hole on the top for the temp connection and past archives state that it is impossible to put the chrome cover over this type of heat shield and after many, many hours, I agree. It seems GM #3919807 is always referred to as "early 1970 Left/Front heat shield" in all references. I think it's meant for 350's without chrome covers on front.
I know Judging manual states the change to only back plugs have chrome covers after about Ser # 14,000 and I have the box type dist/coil cover. I'm thinking the Restorer purchased a kit that had the wrong heat cover for this application and I should install a flat heat shield.
Can some of you with original early '70 small blocks give me advice as to your car's heat shield?
Thanks, Donn

Donn

This is late at night, and I probably should do this early in the day when I am less fatigued. With that disclaimer, I'll try anyway.

Let's try to clarify things a bit.

1) Trust the TIM&JG for the style of RFI (Radio Frequency Interference) items you should have. Your car should have the box around the distributor and the four-flash chrome plated RFI shields. These RFI shields attach by brackets to the exhaust manifold bolts. Of those the Left front and Right rear are somewhat of a V shape. You should, of course, also have the larger V-shape (sometimes called "boomerangs") between the front two and rear two RFI shields on each side. These "Boomerangs" touch the engine mounts at their lowest point. On each side of the engine, at the rear, are vertical channels to shield the spark plug wires as they are trained from the distributor box to the horizontal shields. Please note that NONE of these parts are heat shields. They are found in the AIM under the U69 option pages. It is these horizontal pieces that are reduced to two pieces (one om each side of the engine, at the rear) later in 1970 production.

The heat shields are made from galvanized or tin-plated material, The ends are curved to wrap around the spark plugs at each end of each shield. These four pieces are present all through 1968 to 1972 (and I suspect beyond). They attach to the cylinder case with one bolt each and are designed to protect the spark plug and wire boot from the heat of the exhaust manifold.

I hope. while lengthily, that this explanation of nomenclature helps to clarify the discussion. I am fairly sure Chevrolet/GM has different nomenclature for these parts, but it is too late for me to retrieve my AIM from the garage. Let's work with this nomenclature for the moment, and perhaps someone (you??) with the AIM at hand can dig up the proper names for these parts. That may or may not be less confusing.

I see you are having trouble getting the LF and RR RFI shield to fit over the heat shields in those locations. A suggestion: Loosen the exhaust manifold bolts and the wing bolts and try to slip the RFI shield in place. There is some play in the opening for the bolt holding the heat shield in place as well. Leave that bolt lose a small amount as well. Some minor bending of the RFI shield may be necessary, but they will fit with the heat shield under the RFI shield. I remember it being a struggle.

As I remember the original RFI shields for my 1970 (#2161) were the same for the LF and RR. The RR needs the hole for the temperature sender for the TCS system,
Edit add: The LF has the hole for the trmp gauge sensor wire. Here is the best shot I have in my files.
1100884 alternator 009.jpg

[Donn M.]

Re: '70 LT1 spark plug heat shield

Terry, Thanks for the response and the detailed explanation of all the various ignition shielding. I think I may have confused the issue with too much information in the original thread. I really just want clarification on which type of heat shield I should have on the left/front which goes under the RFI chrome cover.
I currently have what is often referred to as "early '70 front LH" and shown as GM part#3919807 on page K192 in AIM. This part is currently on the car and can only be installed with the RFI chrome cover under the heat shield.
20240204_102917.jpg
20240204_102704.jpg

Page 187 of the AIM shows the LF heat shield being flat.
20240204_103136.jpg

U69 is a redraw dated 3-6-70 and shows the LF heat shield flat but, no part #. In various places I hear the RR and the LF heat shields are interchangeable, so I took my RFI cover off the RR this a.m. and it also is flat.
20240204_102457.jpg

It's now pretty clear to me that the part #3919807 is not the right heat shield for this car. The picture of yours's is pretty confirming.

Terry, thanks again for the response. I've had the RFI brackets off, exhaust manifold bolts out, front french locks off, the LF heat shield off at least 6 times, Etc., Etc. I've got a flat LF shield on order.

THANKS AGAIN ! Donn

[Terry M.]

Re: '70 LT1 spark plug heat shield

Donn
I don't think my LF & RR heat shields are flat, but it has been at least several decades since I had them off. Unfortunately, my car is 80+ miles from where I am, so verification is not possible anytime soon. I do recall that those two heat shields are interchangeable as are the RFI shields.

I suppose we shouldn't rule out the chance that the reproduction parts are sufficiently different from originals to create these issues. As I said last night, I do remember those shields were difficult to install, but not impossible.

[Donn M.]

Re: '70 LT1 spark plug heat shield

Terrry, I agree that the RR & LF heat shields are interchangeable as during my search some GM boxes were marked both RR & LF.

On the RFI chrome covers mine are most likely GM service replacements and I don't think they could be interchangeable;
RR = about one inch longer than LF, RR both ends are open so spark plug wires can go out rear into vertical shield
and there is a hole at the back/bottom of the RR for a wing screw to attach RR to the vertical shield.
Again, these are probably not originals.

Thanks again, Donn

[Terry M.]

Re: '70 LT1 spark plug heat shield

Terrry, I agree that the RR & LF heat shields are interchangeable as during my search some GM boxes were marked both RR & LF.

On the RFI chrome covers mine are most likely GM service replacements and I don't think they could be interchangeable;
RR = about one inch longer than LF, RR both ends are open so spark plug wires can go out rear into vertical shield
and there is a hole at the back/bottom of the RR for a wing screw to attach RR to the vertical shield.
Again, these are probably not originals.

Thanks again, Donn

Donn
What I hope is a better picture of the LF on my early 1970. I am not inclined toward disassembly since the car is in unheated, unlighted storage. Sorry the pic is upside down. It will take someone with more computer skills than I have to change that.

L F RFI Shield.jpg

[Donn M.]

Re: '70 LT1 spark plug heat shield

Terry, Thanks for the pic.. It's pretty obvious that you don't have the Gm # 03919807 that I enclosed in the previous thread/picture that is advertised as "for early 70 left/front". I'll let you know when I get the new part and installed.
Thanks again

Donn