I have never ported heads before. I have a set of 882 heads that are laying around. I was going to try to gasket match the intake ports and then grind and smooth out the intake runners. Does this even really matter? Is it a waste of time to do this or is it a good first time porting project? thanks for any info.

 

Waste of time? If you have an emergency apendectomy to perform, house fire to extinguish, marriage to save, or some other more pressing matter, it may be a waste of time. However, if you have some time, the equipment, and a will to learn a little about porting iron heads, it may be an excellent opportunity.

You have a spare pair of heads that probably aren't worth anything more than 4½¢/pound in scrap value.

Start with an intake port, since there is more room to work and they are easier to inspect. The port work on the intakes will also generally provide more gain than on the exhaust side, but doing both is best. Make sure your equipment includes at least safety glasses (a face shield is better) and a dust mask or some means of dust collection. If you are using an air operated die grinder, you may also want to have plenty of air tool oil and a pair of gloves, since the expanding exhaust air will create a refrigeration effect and chill the tool (and your hands).

Lay out the ports to match your selected gasket. Try the gasket matching on one runner, then blend the enlarged port at the flange back through the runner. Remove a valve, then clean up the bowl area and blend the runner into the valve bowl. Trim the excess material around the valve guide protrusion into the bowl area while leaving the guide intact. Try removing the obstruction at the short side radius where the flow has to almost reverse to get around the valve face. Removing that excess material reduces or prevents the reversion.

If memory serves me, the '882 castings have siwrl ports - a small ramp that steers the inlet charge and induces a swirl of gasses as the charge enters the cylinder. That's great for low RPM, high torque, amd fuel efficiency at low speeds, but can kill power right at about 3,000 RPM. Removing the "ramp" and creating a more direct route for inlet flow around the entire valve perimeter would also be excellent practice.

That should give you a good feel for the conventions of porting. You should also learn what cutters and mounted wheels work best in what situation, and how to use the sanding rolls and flap wheels to trim and polish the final work. Once you have a satisfactory intake port/runner/bowl, try an exhaust. Watch the short side radius again, the valve guide area, and overall port size just above the valve. Blend it all into a gasket matched port opening at the flange.

Then again, it might all be a waste of time if you don't intend to put your skills to good use on some better head castings.

 

thank you for all of you knowledge. I will try it on these 882's and I am planning to get a set of better heads. are there any stock type heads I should look for. I know the double hump heads and someone told me that vortec heads are a really good start. Are there any other castings that I should look for? It is about time for the local swap meets where I can look for a decent set of heads. But I have found a set of vortecs new for about $425. thansk again for all of your help.

 

882's would be perfect practice heads for a first time porter!

The castings you should look for include (but are not limited to) 416, and 082.

The double hump heads are old school technology. You'd be much better off with a pair of 416's to work with.

As for Vortecs, if you dont know exactly what you are doing (the details havent been posted on how to increase flow in these heads yet I dont think?) then you will just hurt flow.

Most people "boast" their unported vortecs that make just as much, and some times, more CFM/lift than some aftermarket heads (the cheap ones atleast).


The only "problem" with vortec heads is that they require special intake manifolds since their bolt pattern is so different.


You should look up "Sitting Bull" 's post on porting heads. There is definetly gains to be made. I'm working on some 416 heads right now... If I can find a shop around here that has a flow bench I'll get numbers for people to see what can be gotten from them.... though I think that F-Bird88 ( sorry if I have that s/n wrong) has posted some numbers he's gotten... I think he ports heads professionally as well.

 

I would definately put saving the marriage before porting 882's in the priority list.

However, I do agree it would be time well spent. Not for the benefits to be realized, but for the experience.

882's aren's swirls, but they are large chamber and poor flowing. It takes some very careful and flow-emperical porting to improve them. They are thin castings, prone to cracking, and easy to break through walls when hogging them out. However, just doing the basic gasket matching, pocket porting, short-side radius, and blending work won't put you in any particular danger.

sellmanb, I think you mean 081 castings. Basically the same as 416's but with '87-later intake bolt/cover pattern.

Standard Abrasives (do a Google) has a great do-it-yourself guide you can download/print. I studied it for months before tackling mine. You might be okay just studying it for weeks, however...

 

Gasket matching and smoothing the ports is largely a complete waste of time on stock heads. There are few gains to be had there.

Where you REALLY pick up flow, is by smoothing out the bowls, right behind the valve; if you look at the throat right there, you'll see that the factory cast this butt-ugly thing, and then just took a mill bit and jammed it in there; there's sharp edges, casting flash, and all sorts of other airflow-defeating features back there. Also, around the guides is a good place to turn attention to; the best thing to do with them is to streamline them, with a flat side on the side facing the head bolt, and an airfoil on the side facing the push rod, to promote "port bias" and "swirl" into the chamber without creating a restriction. The highest flow areas in a port are the runner beside the guides, and right immediately behind the valve. The area in the throat of the valve is particularly important for low-lift flow numbers. And since the valve spends most of its time at some much lower lift than the "spec" on the cam card, it pays off BIG TIME to pay more attention to low-lift flow than trying to squeeze out the max raw high-lift flow numbers.

Gasket-matching is what some of the people around here who know what they're doing, like to call "monkey-spank", where it makes great eye candy but is worthless for performance. It's actually even harmful in some cases because it has no effect on increasing flow, and instead only decreases port velocity which promotes poor fuel mixture.

 

Five7, you're right. I dont know what I was thinking... dont even think I've seen 082 castings anywhere?


Sofakingdom is 100% correct. On most chevy heads, gasket matching is grossly overrated. But for someone who is wanting to learn how to port heads, gasket matching is a good visual of how the bits grind down the metal since you dont have to do as much feeling.

Your best tool to find how smooth the port work is, is your fingers, and some water.


Something else Sofakingdom said is something you need to pay close attention to. Focus on low lift flow numbers. The high lift numbers will come on their own.

The valve sees it's max lift once, whereas it see's lower lifts twice.


And watch out for the monkey spank... it's everywhere now days

 

I am going to start with the 882's and then see how I do. thanks again for all of the info. I want to learn so I should be good at it.

 

Be sure to post back with your results, i have a set of 882's i would like to chop away at.

 

About gasket matching: Depends upon your intake manifold ports. If they fit within the head intake ports, then I'd agree with what has been said, not much gain. But, if the intake manifold ports are larger than the head intake ports, you've got a shelf that will create a bunch of turbulence and reduce flow significantly, even if it doesn't show up on a flow bench with the head alone. If you gasket match only the heads, you'll actually create an "anti-reversion" effect that will improve low RPM manners with larger cams - a small effect, perhaps, but much better than the head ports being smaller than the manifold ports.