200 Exhaust Manifold choice

[Flade99]

Hi,

I need to replace the exhaust manifold on my 66 Mustang. Its the original 66 block, with a 79 large log head and 83 Carb. What year exhaust manifold will work best with this combination? I was going to replace it with a stock 66 manifold, but I suspect the later manifolds breathe better to match the large log heads.

 

[bubba22349]

Yes some later model exhaust manifolds will flow a little better then the early style manifolds. The 80's Fox body manifold has the biggest outlet and flow but you would need to mod your exhaust system at the head pipe hookup. Otherwise the late 60's through the late 70's manifolds is closer fit to the 66 you had. You could also port your stock manifold some. Good luck.

 

[Soldmy66]

It is a shame that Extrude Honing is SO BLASTED EXPENSIVE.

 

[Flade99]

There is a guy selling a no almost new 68 Manifold. Is that new enough or should I look for a 70s one?

 

[bubba22349]

It might be a good one I am thinking they were about that time frame 68 or 69, Got any pictures?

 

[autoX65]

I have heard some of the earlier 144 -170 exhaust manifolds flow great and I :nono: know for sure they are bigger then 65-66 early model 200 ports so just a little cleaner casting from ones I have compared but the late model output from the 1980-1981 fox has a huge outlet so I think it would be worth it to modify the exhaust pipe to exhaust manifold and how's your entire exhaust system condition wise?

 

[Econoline]

'68 is going to have the smaller exhaust manifold afaik. I have a nice manifold from a '70 250 I won't be needing. If you'd like it PM me and we'll work out a deal, not sure what it's worth.

 

[autoX65]

that looks as good as they get.

 

[CZLN6]

Howdy All:

FYI- there are only two different exhaust manifolds for our sixes; From 1960-1962 manifolds had a flat gasket and had a 1 3/4" outlet. '63 and later manifolds have a donut gasket and have a 2" outlet. Interior volume is greater on the later manifolds also, but I don't remember the exact spec. There is also an eighties emissions manifold for mounting a cataletic converter. For the '63 and later manifolds, there were several changes in the castings to help control cracking, and later to add bungs and taps for EPA control stuff. I prefer the C8 casting as a good compromise between more crack resistant over earlier and fewer bulges and taps of later manifolds.

Prep the new manifold by port matching the ports and opening the outlet to a full 2".

Myths-
*there is no difference between a 250 manifold and a 200 manifold.
*a C8 casting can be found on a 170, a 200 and a 250.

Hope that helps you. Go with the C8 you already have.

Adios, David

 

[Flade99]

Thanks Dave, that is exactly what I needed to know.


My 66 manifold has a hairline crack at the choke tube hole so I'll see if I can get the C8 manifold at a good price.

Flade

 

[CZLN6]

Howdy Back Flade and all:

Take a good look at the photo Econoline posted. Take note of the mis-alignment of the head ports to the manifold ports. The blackened right edges indicate a barrier. Aligning and port matching will be the critical part on getting the most performance out of a stock type exhaust manifold.

Too bad we can't see the top of that '70 casting. That would be where the castings take on irregular shapes due to casting in bungs and taps to accommodate EPA necessities. Taps can be plugged, but the irregular shapes created inside the manifold is what disrupts exhaust flow.

Also note the extra metal and gussets on the '70 casting as compared to earlier manifolds. That's why they are stronger and less prone to cracking and/or breaking.

Glad to help.

adios, David

 

[Flade99]

Thanks for the thoughts. At what level of performance will port matching become noticeable? The engine is currently stock except for the large log head and Fairmont carb. Eventually I'll rebuild the head, look at a mild cam etc. at that time I may consider headers. For now I am looking for reliability, decent drivability and decent throttle response.

 

[CZLN6]

Howdy Back:

My best guess is that starting at rpm ranges above 2,500, it would begin to have a negative effect of maybe limiting flow by 10%, and increase as rpms go up. It is possible that a blockage could cause some reversion effect also.

FoMoCo did not use a gasket between the exhaust manifold and head. IF you're going to do the head later, consider buying a valve job gasket set now. It will include an exhaust manifold gasket. It is considerably more cost effective to buy the whole set rather than just the gasket. Hold the gasket to the manifold to assess alignment, then hold it to the head for the same reason. Using that information you can do a better job of aligning the manifold to the head.

Again, this is not critical. Exhaust is forced out of the chamber and ports at extreme temperatures and under pressure, so if it is not perfectly aligned it is not critical, but it is not as efficient as it could be.

Check your new manifold for flatness across the mating surface. They are almost never perfectly flat, but the gasket can compensate for irregularities of say, .010". Any more than that consider having the mating surface trued prior to installation.

HOpe that helps.

Adios, David