73-74 Big block air cleaner ring

[Mike E.]

How do I differentiate between a small block and big block air cleaner ring. Spell out as many variables as you can, please. Pics would be helpful, too, if possible. I want to make sure I know.
Thanks!

[Jimmy P.]

Re: 73-74 Big block air cleaner ring

How do I differentiate between a small block and big block air cleaner ring. Spell out as many variables as you can, please. Pics would be helpful, too, if possible. I want to make sure I know.
Thanks!

Hi Mike,
The air cleaner ring on the big block 73-74's has an off center inner lip. Could say more elliptical in shape. While the small block ring is circular and the same inner lip size all the way around. Both have only three cut outs to fit down on the base. UNLIKE THE '75 RING WHICH HAS FIVE CUT OUTS in the ring. I think the photos will help show the differences. The first photo is from the big blocks. The second I used arrows to show where the lip gets smaller. The last photo is from a small block. The outside diameter is exactly the same for both.
Hope this helps.

[Mike E.]

Re: 73-74 Big block air cleaner ring

Thanks, Jimmy. Is there also a difference in height of the first "step" in the ring from the bottom of the base? Have I heard 1/2 vs. 7/8"? Or am I dreaming that up?
Thanks again for your input!

[Jimmy P.]

Re: 73-74 Big block air cleaner ring

Mike
I just went back and looked at my revision notes and looked over our team discussions on this. Yes, there is also a height difference between the two rings. Here is the sentence we put in the latest revision.

"The LS4 metal flange is shorter than the flanges for 350s to accommodate an LS4 carb that is closer to the hood. The measured height difference is 3/8” or 0.375 between the two flange heights and as a result, an LS4 with a 350 flange will result in an obviously compressed rubber hood seal."