Exhaugst manifold question

[pedal2themetal45]

HI
I'm getting ready to put a 200 in my comet and I have kind of (maybe) decided to use a stock exhaugst manifold.. (for stock apperance all though I have a Duraspark for it) Is their one that flows better than another. Or should I just bite the bullet and get a header? I'm not realy looking for performance, Its going to be my econo car.
Thanks
tim

 

[66Sprint6]

Ide say bite the bullet!! But if not, go with the 69+ 250 manifold (which may be the same as the 200 in those years). When mine cracked I read somewhere that the 69 250 manifold flowed better than the 66 I had so I went with it.
Matt

 

[CZLN6]

Howdy Tim:

I prefer a '68 to about '75 casting with no thermactic air pump bungs. earlier were lighter cast and prone to cracking. Later are likely to have extra bungs and taps that disrupt air flow. The '68 to '75 have extra gussets in weak areas.

All '63 and later manifolds will have a 2" outlet and a donut gasket attachment to the head pipe.

I've heard that Econoline engines came with a larger exhaust manifold. I have never seen one so can say nothing about that either way. We can identify no difference in exhaust manifolds between 170/200/250 of these years.

To get the most out of a cast manifold- *make sure the outlet is a full 2" *be sure to leave the lip where the head pipe seats *gasket match the manifold portholes and slightly more *contour the manifold port into the manifold to smooth the sharp, right angle turn, *finish up by smoothing both the interior and exterior and coating the exterior with barbeque grill paint, or better yet, Eastwood's paint on high temp exhaust coatings. A smoother inside will reflect heat and help to maintain velocity. Add a 2" system to the back for a slightly improved, stock appearing exhaust system.

Clearly, a header is better for performance, economy, less weight and under hood heat, but it takes alot of miles to make it pay in mpg.

FYI- the first generation of the DuraSpark ignition is stock appearing. They first appeared in '74, and were replaced by the DuraSpark II beginning in 1976.

Adios, David

 

[Anonymous]

David,

Is there anyway to improve the exhaust flow with the stock manifold - other than what you just posted (thinking radical porting)? Is it because of the long runs for cylinders 1-2 & 5-6? Or is it primarily where they transission together to form the single 2" dia outlet?

Just looking at it tells me it's quit restrictive.

 

[kirkallen143]

Just an addition, when I bought the new exhaust manifold for my bronco the casting was a "C6.." and it only came with a 1 3/4" exit. I am going to try and bore it to a 2", hopefully with success, cross your fingers.

Kirk Allen ' 73 bronco

 

[Anlushac11]

8)

I dont have the money for a header right now but anything has to be better than the late model Mustang with the coffee can sized light off converter attached to the manifold.

I was going to go to a old cars junkyard near here and see if I can get a reagular exhaust manifold and do the porting and port matching mentioned.

You said not to mess with the donut gasket seat but Im wondering if its possible to open this up from 2" to 2 1/4" so I can run 2 1/4" pipe all the way back.

Good info on what years to avoid. Thanks!

 

[CZLN6]

Howdy All:

The following is only my opinions, based on some experience and horse sense.

Stang 200- Beyond what I've already described you're really wasting your time. ( and I've done that too) If you need more performance. A header is the only real answer. The problem is all of the issues you raised and more. The Port in the head is elbow shaped then transitions into a log wall. Hard right angles and tight turns destroy flow even when being pushed out. It is interesting to put a cast log manifold on a head on a flow bench and then replace it with a header-like pipe. The manifold pulls CFM down. The pipe picks it up. The higher the flow the greater the effect.

Anlushac11- I doubt that you will be able to bore the outlet to 2.25" and still maintain a fire wall ridge to seal against. I'd also worry about the structural integrity of the casting at that location. Additionally, while the area of a 2.25" circle is significantly larger than a 2" circle the difference in performance will be slight if at all. The difference in the exhaust system would also be slight Unless you're planning to go to a header in the future. If that's the case I'd do a 2" outlet for now, adapted to a 2.25" system ready for later.

Smoothing the inside and bending or softening the sharp turns will be most useful.

Hope that helps. Are you enjoying the journey?

Adios, David

 

[Anonymous]

Thanks David!

As always, I value and trust your experience. It's just a shame a factory exhaust manifold is so restrictive. Sure, many where (and still are) but I guess that's what keeps the aftermarket in business.

 

[pedal2themetal45]

Yes.... By all means THANKS DAVID I also trust in your experience and knowlage..
tim