martygalindo

Hello All,
Somewhat new to this forum but have a question I am looking for 3/4 or full length headers for my 67 Olds cutlass that has a later year olds 350 not the 330 not finding a lot of choices so far.
concern is a lot of headers are for 400CI and for 68 and up will they fit in a 67 engine compartment and at what engine displacement does block size change? just dont want to
do multiple returns do to improper fitment. Thanks for you help. Marty

Brosmobile67

Does it need headers? My exhaust guy says that there are little to any gains unless you have an extreme intake/carb and matching cams etc. But I'm just into stock cruising anyhow and the occasional tire chirp.

oldcutlass

Your exhaust guy is wrong, there is a significant gain to long tubes. Try American Racing headers, they are very expensive but fit.
https://americanracingheaders.com/co...ons/oldsmobile

Kennybill

ARH are nice and they fit (talking BB). I saw a pair 65-67 on a car @the Miller meet. The owner said his car was the "test mule" for fitment. I checked out the site and there's and ad for making monthly payments. Yikes!

martygalindo

Hey thanks for the replies, I talked to a tech at summit today they assure me they have headers that will fit from a few of their vendors, they also were adamant in saying all olds V8 engine blocks are the same size
I said what about big blocks vs small block they say no difference in footprint with Olds, So I'm gonna order a set of the silver ceramic coated pipes and see what happens. Thanks for the input.

olds 307 and 403

The flange pattern is the same, the deck difference causes the fitment issues

OLDSter Ralph

1. Did you see his "tech" certificate ? If not, he is just a "telephone order taker".
2. What kind of cars does he drive ? I'll bet it was never an Oldsmobile.
3. The blocks interchange as far as engine mounts. But the deck height is higher (taller) where the heads bolt on the block (400-425-455).
4. Get the telephone order taker's name and write it down when you order the headers.

cjsdad

Sooo, basically they are all the same footprint until you get to the top of the deck of the small block. Then things get different. The "big block" Olds is actually a "tall block" Olds. The outer dimensions are the same except for the height of the block. The heads all have the same external dimensions as well, more or less, and the exhaust ports are all in the same position. So if you put a "small block" Olds "SBO" next to a "big block" Olds "BBO" the only difference externally is the BBO will be taller. Headers made to fit a BBO will then hang down lower on the vehicle if they are mounted to a SBO. They will fit! But they will drag the ground every chance they get. I am in the exact same position as you are right now though so I have been formulating a plan. I read it here on a different thread about buying a set of headers made for a BBO and cutting a short section out of the upright tubes and welding them back together. This will raise the collectors up to the correct height on the vehicle so they will not drag. I plan to do this with a cheap set of ebay headers first to see if it will work well enough. If it does, I will then do it with a better set if necessary. At least that is the plan...

OLDSter Ralph

Keep in mind that this "taller block" (big block) is also moving the exhaust manifold face outboard a corresponding amount. This means wider because the cylinders are at 45 degrees from vertical thats why the BBO intake manifolds are wider than SBO. On a "small incher", the BBO headers will be moved inward and lower. Just food for thought.

oldcutlass

The main issue with the 64- 67 Cutlass is the frame rails are narrower so the 68 and up may have some interferences that cannot be compensated for.. The difference between the BBO and SBO as stated is deck height. Using BBO headers a on an SBO while they can bolt up, they will hit the cross member and lower control arm brackets.

lemoldsnut

The other question you asked was about what displacement is small block and big block, So it is like this: 260. 307.330,350,403 all small blocks (short deck height), 400,425, 455 all big blocks. (tall deck height) The valve covers, oil pans, timing covers, water pumps, brackets, and pulleys, distributors, all will bolt on betwee67 n them, and they have the same exhaust bolt up flange on the heads. However, due to the deck height differences clearance to a frame and even in some cases to the engine it self can be effected with headers made for one or the other.

64-67 as already mentioned is the worst for putting headers on a small block.

Hope this helps some.
Larry

1967Supreeeme

I actually bought the cheap stainless ebay headers for my 67 for this exact reason. To butcher up up and practice doing stainless with my new TIG.