C2 Exhaust Heat Shield Questions???

[Rick B.]

Hello, Was reading a past series of on C2 Under Car Exhaust Heat Shield posts where an informal analysis was conducted on the subject. While the part numbers were clarified it was unclear on 2-1/2" configurations from 63-67. I am interested in the configuration of 65 2-1/2" shields.

Furthermore, I noticed there was a "sequence" of part numbers over the years. My understanding for 2-1/2's they were?

63 3828285/86
64 3851673/74
65-67 3851673/3864180

One of my confusion points is 65 AIM pg L76 sht1 and pg L84/sht2 lists 3851673/3851674 AND pg L75/sheet2 lists 3851673/3864180. I understand 67 AIM also uses 3851673 & 3864180. Which 65 is the correct for 2-1/2s and are 65 and 67s 3851673's the same configuration?

Much appreciation for the help in advance

[William C.]

Re: C2 Exhaust Heat Shield Questions???

Remember that the '66-67 models switched to 2 inch headpipes on all smallblock applications, so actually the only comparable years are 64-65 as I recall. '63 configuration was a little different due to the different hanger at the trans.

[John H.]

Re: C2 Exhaust Heat Shield Questions???

In '66-'67, although the exhaust manifold outlets were 2", the headpipes were swaged down from 2-1/2" to that size just below the manifold outlet; the rest of the headpipe (and the intermediate pipe to the muffler) was 2-1/2" on 4-speed cars. The only headpipe that was 2" all the way back was on the 300hp Powerglide cars, which also used 2" intermediate pipes to the mufflers.

In '65, the base 250hp engine used 2" exhaust manifolds and exhaust system (like the '66-'67 300hp Powerglide car), and used the 3828281/3864178 heat shields; L-75 300hp and up used 2-1/2" exhaust manifolds and exhaust system, and used the 3851673/3864180 heat shields (same shields used on '66-'67 4-speed cars).

[Rick B.]

Re: C2 Exhaust Heat Shield Questions???

John, couple of clarifying questions......what about part numbers 3851673 and 3851674? They are listed in the 65 aim on pg L84/sht2 & L76 (both 2-1/2 engines used 2-1/2's)
The 2-1/2 part numbers you listed above are indeed listed on pg L75/sheet2. (there is where I am confused) Why Different part numbers for these engines?

2nd question. I believe I had read, exhaust heat shields became shorter over the years. So, are the 65, 66, 67 shields exactly the same or are there length and other differences?

[John H.]

Re: C2 Exhaust Heat Shield Questions???

John, couple of clarifying questions......what about part numbers 3851673 and 3851674? They are listed in the 65 aim on pg L84/sht2 & L76 (both 2-1/2 engines used 2-1/2's)
The 2-1/2 part numbers you listed above are indeed listed on pg L75/sheet2. (there is where I am confused) Why Different part numbers for these engines?

2nd question. I believe I had read, exhaust heat shields became shorter over the years. So, are the 65, 66, 67 shields exactly the same or are there length and other differences?

Rick -

I don't know offhand why the L-76 and L-84 usages show the 3851674 RH shield, or how it differs from the 3864180 RH shield used on the L-75 2-1/2" pipe application; the L-75, L-76, and L-84 all used exactly the same front exhaust pipes (3849861-2).

[Rick B.]

Re: C2 Exhaust Heat Shield Questions???

John, thanks for the reply, Hopefully Joe L can weigh-in on these part#'s and why the differences