Mr D.

Need help with cracking the code on BB Exhaust Manifolds for 66-74 cars. If you seen my post yesterday I decided to go with the $149 manifolds from 1A Auto. I called them today and they list the following part numbers.

66-69 RH w/ A.I.R. holes P/N PLP1390113
70-74 RH w/ A.I.R. holes P/N PLP1390113

70-74 LH w/ A.I.R. holes P/N PLP1390112

All 3 have A.I.R. holes and there tech dept say that the 66-69 LH (which they do not carry) is different from the 70-74 LH manifold. I thought this was strange and was thinking they were all the same from 66-74 with the just GM part numbers changes for minor upgrades. So, I picked my ZIP catalog and they list the following numbers.

66-67 RH w/ A.I.R. holes P/N EX-381
68-74 RH w/ A.I.R. holes P/N EX-381

66-67 LH w/ A.I.R. holes P/N EX-382
68-69 LH w/ A.I.R. holes P/N EX-382

70-74 LH w/ A.I.R. holes P/N EX-383

Well its starting to look like the 66-69 LH manifold is different from the 70-74 so I grabbed my Chevrolet by the Numbers and this is what they have to say.

66-69 RH w/ A.I.R. holes P/N 3880828
70-74 RH w/ A.I.R. holes P/N 3880828

66-69 LH w/ A.I.R. holes P/N 3880827
70-74 LH w/ A.I.R. holes P/N 3969869

Well it does look like the LH manifolds are different between 66-69 and 70-74. What is the difference????? Will a set of 70-74 manifolds work on my 69??? Are the exhaust pipes different??? Sorry this is so long but I got stumped today on this.

72ls5fla

Here is what I know ...

All 70-74 B cars with AIR have fours holes in each manifold.

I am nearly 99% sure that the 68-69 manifolds are the same. The casting numbers are the same for one side of the car between 68-74, and different on the otherside.

What I can not say for is the 66-67 manifolds and the AIR configuration for them. I personally have never seen a BB Vette with AIR not have 4 holes in each.

I was always under the assumption that the bolt pattern, and casting configuration was exactly the same for 66 - 74.

Maybe 65' is the odd year ????


My car has AIR and I had to buy a passenger side manifold from them, it works just fine and my AIR tubes screwed in without any problems.

I hope this helps some.

Bill

BBShark

I considered buying the 1A auto manifolds for my 68 BB but your right, they don't list them as fitting earlier BB. I eventually bought original GM manifolds but I did seriously consider the 1A auto manifolds. I even photographed a set of early 68 427 manifolds (...27 and ...28) in the same orientation as the 1A auto picture. After laying the image of the 68 manifolds over the 1A auto picures I can see absolutely no difference. Even the cast fixturing pads are there. I paid as much for 1 original GM manifold as you could buy these brand new. If I were to do it over, I would probably go for the 1A's.

Mr D.

I have always thought that ALL Corvette BB manifolds were the same. Unless someone says otherwise I will get the 70-74 set from 1A Auto. I sure they will work just fine with a stock 69 exhaust system. Very strange

wombvette

Let me Splain this as best I Kin. The 67-69 LH manifold is the same except that some have smog and some dont. This manifold goes down very near the block and the outlet turns out. The 70-74 LH manifold goes more straight down. Both styles will fit all of the big block engines but the exhaust hookups will be different. Which means a LH 69 front exaust pipe will not fit, you will need a 70. The RH manifold is the same throughout except some have smog.


[Modified by wombvette, 10:36 PM 3/18/2004]


[Modified by wombvette, 10:38 PM 3/18/2004]

Mr D.

Wombvette, thanks for the info. That clears up everything. I just need to get a 70 set of pipes to go with the 1A Auto Manifolds.