Is there any (good) reason for having the inner two exhaust ports on each head slightly narrower than the outer two? No variance in height, just in width, and the 4 "inside" ports are almost exactly the same size, and the 4 "outside" ports are almost exactly the same size.

Any thoughts?

 

Why do you ask? Do you have some ported heads like this? How do the inner and outer exhaust port flows compare?

Perhaps if the exhaust ports have been enlarged, the inners were kept narrower because of header bolt hole spacing. That's the reason for spread-port heads. If inner/outer flows vary a bunch that's not a very wise porting job.

There are other possibilities. Tell us more.

 

Yes, unfortunately I do.

Don't know the flows, thinking about pulling them and getting this checked out. I as well figured that it was due to the bolt holes. But why not keep the outer ports the smaller size as well for consistancy? I'd think it would affect the tune in some cylinders being leaner than others. I have a sequential FAST system but no individual cylinder control.

These are AFR 210 heads that were cnc'd and touched up by hand. Heads were on the engine when I bought it. Previous owner claims that AFR touched them up by hand themselves, however I contacted AFR and Tony said he hasn't hand ported anything themselves in like 7 years and have no records of anything they would have. This is long before I realized the size differences. They're said to be 223cc on the intake side now.

As for the porting itself, it looks great. The person who did this definately knew how to use a grinder. This is for a blower car, and the exhaust port is actually wider than it is tall, and a rounded rectangle shape vs. D-port. They almost look square, but they are a fair amount wider upon measuring. Is it possible that the inner ports actually flow the same as the outer ones despite being slightly narrower while being no taller? It baffles me that someone who could have such good (cosmetically speaking) porting ability would purposely do this if it was flawed in actual performance. Aside from the two different size ports, they seem quite consistant in outlet size when comparing the two groups of like-sized ports.

Should I be having a panic-attack about this, or is it possible this is intentional and in some twisted way beneficial? BTW I will be running a custom header with these heads, Hooker LT's don't cover this port by quite a stretch.

 

Not to be rude but, did you buy this motor off a crack head? Maybe they started porting the exhaust side then realized they messed up and figured the heads were worth more than the car then they got rid of it... Those are some nice heads to go and port the exhaust on... or not. I would get them flow tested but IMO I think it will do you no good on a supercharged car, turbo - yeah to a point.

 

Any other thoughts? OldSStroker?

 

1. Have a head flowed. If there is considerable difference in the exhausts, and you want the max out of the engine, you might either have the other ports reported to flow the same or have very custom cam made with the lobes different for the inner cylinders from the outer cylinders. I'd only do this if there was considerable difference. How much? Don't know, but a good simulator could tell you if you gave it (or your cam design guy) actual flows (with a pipe on the exhausts).

2. Trace the ports and bolt holes and send that to your header guy. I'd do this even if I didn't do 1. above.

I don't think this is all that big a deal if you get headers at least as big as the ports. Don't have that panic attack.

 

Thank you OldSStroker, sounds like a good plan. Flowing the heads was gonna be my first course of action. Headers won't be a problem, they'll be built on the car and will be at least as big as all the ports. Got a good plan worked out on the headers.

I'm relieved to know this can be dealt with.

BTW, car already has a fairly small cam in it supposedly designed for these heads. 225/233 .522/.542 114lsa with 1.5 rockers, and I put on 1.6 rockers to up the lift to .557/.579. Seems small for these heads on a 383, especially with the 1.5 rockers although maybe not with a blower. Granted it was designed for a street setup and I'm running more of a race setup. Should I try running this first provided the flow sheets don't show something really weird, or should I just plan on getting a new one? 90% race/10% street car.

Also, I'd probably end up fixing the heads vs. a frankenstein cam. I figure that would be better if I ever needed to sell these or use them for something else.