So I was mocking the Hooker LTs up on the car today and was testing gaskets to see which ones matched my heads properly. I discovered that the exhaust port on the ported AFR 210s that came with my engine when I bought it are considerably larger than the ports in the Hooker LTs I have for the car. It seems obvious that a header with a bigger primary tube would be better suited to my application, but it's not in the cards right now, and I just want the car to run and get bugs shaken out before I try and squeeze every last HP out of it.

Now, how much am I hurting myself by having a header tube that doesn't completely cover the exhaust port? Is this just basically a little bit of added backpressure, or does this dramatically screw up the dynamics of the airflow? Actually, the gasket that fits the heads hardly has any material between the bolt hold and the port opening, I'm hoping it all seals up properly, although it should since FelPro sells it this way and I doubt they would make a gasket that doesn't work properly.

FWIW, this is on a 383 with a Vortech YSi blower spun to about 58,650 impeller rpm.

 

Not a good scene, Birdie.

The header inlet needs to be at least as big as the port. I just measured a very well ported AFR LT1 exhaust that has a max corner to corner dimension of 1.68, and an area that is smaller than the inside of 1-3/4 primary pipes.

If you are using Hooker 2231s, these are 1-3/4 primaries and 3 inch collectors with the opening shaped like the port. That shouldn't be smaller than your port. Any smaller header primary will not be very useful for your blown 383.

Did you check the actual header or just the gasket? Maybe the gasket was the wrong one or oversize (bigger than the port). You might try making a paper cutout of the head ports by putting a fairly thick piece of paper over the port, poking in bolt holes then rub the port edge with a wooden stick or something similar to cut out the port shape. Transfer this to the header locating it with the bolt holes and see what you have. If that still shows you that the header is smaller than the port, you can then have a panic attack.

If this engine is going to be much over 650 fwhp, you might be looking for 1-7/8 primaries, but they might be difficult to find.

 

Hedman makes a set that are 1-7/8" and they fit a '93 and '94.

 

This really isn't a "better suited" situation. You REALLY need to have the primary tube be at least as large as the exhaust port.

You ever try to fill a bottle at the kitchen sink; where the stream of water was "fatter" than the bottle opening?

 

That is not a good situation, at all. I think it would be worse than having a smaller port that matched the header. That "lip" is going to cause a lot of turbulence and reverse flow.

Rich

 

How would this affect a naturally aspirated set up? I'm running a set of AFR 210's as well, ported by AFR, and Grotyohann long tube headers. I did notice while mocking things up on the engine stand, that the primary tubes, particularly by the bolt holes, are not larger than the exhaust port. Its not a drastic size change, its ever so slight. I dont remember the exact measurements I took off hand, it was maybe a 32nd of an inch on either side by the bolt holes. I would imagine this has got to be a problem for a few guys out there, considering that we are kinda limited to header choices. If I didnt have these headers when putting the car together, I would have ordered a set of Kooks.


Nick

 

I'm not an expert on fluid dynamics and I don't know what your mismatch looks like, BUT...

It's not just the are of the header tube that sticks out into the airstream. The effect is larger than the physical size of the obstruction.

Again...

Take something to the sink that has a small opening. Intentionally choose something that has a smaller opening than the stream of water coming from the faucet. Then turn the water fully on and stick the container under the stream. What the water does...? That's what your exhaust flow will do.

 

I was in the same boat. I bought some AFR 210's not really realizing the size of the exhaust ports until I really looked at them.

When I measured my opening on my Hooker LT's flange I had 1.65" height X 1.32" width.

When I measured my AFR 210 exhaust port I have 1.70" height X 1.62" width.

I decided that was flat dumb of I to have a set of heads that flowed what they do and not have the supporting parts.

So I sold my Jet Hot coated Hooker LT's to a bud to help offset the cost of some Kook's 1-3/4" stepped to 1-7/8" SS headers.

The exhaust gasket used with the Kook's is really, really close to my AFR 210's and almost perfect to the flange on the header.

A large reasoning behind this purchase was these heads flow well on the exhaust side @.600 - 235.8 @.700 - 251.0 that I bought the headers for my next very powerful supercharged setup.

 

I also had bought the AFR 210's, worried about the port size mismatch and decided on the Kook's stepped header. I am very happy with the fit and impressed as hell with the finish on these headers. Dyno numbers in the next week or two will tell the story.

 

If you absolutely cannot get a new set of headers, you could get out the diegrinder and transition the header flange a little. It would be better than having the "step"

 

I thought of that when I realized my problem. I looked at my Hooker LT's and concluded that if I tried that I would go thru the headers....pretty thin metal.

 

Yeah, I thought of that and reached the same conclusion. There is quite a size difference in the port and header tube, mine's about 1.61 wide like yours.

Getting info on custom headers right now, probably will do that. Have someone local who I trust.

If the Kooks start out as 1 3/4" at the flange, how can it possibly offer that much more width? I'm actually discussing 1 7/8" stepped to 2" with my fabricator.

 

I suppose you could use an adaptor plate solution.

It's kind of cheesy, but it could work.

 

I was going to say try to "port" the header as much as possible like someone else said. You probly couldnt do much witht the thin flanges on the Hookers, you might be able to if they were thicker like 3/8's.

 

I believe kook's sell's a straight 1 7/8 header but i'm not certain... I have these header's that Kurt Tamez setup.. 1 7/8 stepped to 2" only thing is they don't fit w/ the heater/ac box in the car... http://www.streetsleepers.com/images...cs/Headers.jpg