R 16 Head Porting

[Daryl Smith]

My next Project.....After much reading, conversation with a couple of head porters, and comparison of other intake and exhaust ports, I have decided to give it a go. Careful, steady hands, and a predolection to remove tiny bits at a time should get me there.
Not much on the web about these particular heads, but, Volvo B20, and Triumph TR are quite similar. A search through threads for those should give you an idea what I will attempt to put in here. Possibly a bit of oddball stuff....
I will attemtp to post a bunch of pics as it goes....

[Daryl Smith]

Port walls are only about 1/4" thick, so not a lot of material to remove there, But, I am sure significant gains can be seen on the exhaust. The exhaust which I see as the biggest choke point preventing decent power from this engine. Not the best shape for flow....

[Daryl Smith]

If anyone knows of a reliable company which can do a base and completed flowtest (in a reasonable amount of time) for me in the Vancouver area, I am all ears....Send a PM or post on here.

Thks

[JT68]

As you said, there is not a ton that can be removed on the exhaust side. On racing heads we have removed most of the bump in the exhaust ports, but it won't do much for you if you leave the tree trunk of a guide and big valve stems in place. If you cut away the guide, that is a serious valve&guide longevity compromise - doesn't matter much on a race head to be rebuilt after one season - terrible idea on a street head - (The exhaust guides are 1/3 longer for good reason.)

[greydog]

Thinking is rebuilding the h20.
I'm toying with the R16 rod, vg30 piston u20su combo, probably upgrade the cam too.
Would a port match be worthwhile?
Dan

[Daryl Smith]

As the walls are about 1/4" thick, I'm planning on taking no more than 1/8" off at any point. More than enough, in my opinion, to significantly reshape the port.
The Valve guide does not have to be removed, it can be re-shaped slightly more aerodynamically.
As far as the valve stem, yes, I believe a smaller stem will help flow here, especially since it's such a small port and the stem/guide looks to be where the choke point is, however they are not the big problem, the port shape is.
About an inch past the area around the guide I believe the port is too big, if I can figure out how, I would like to try to decrease the size of the port in that area by filling the floor .100" - .150" - this would also (hopefully) have the benefit of increasing the short side radius for increased flow...

I welcome any and all opinions, ideas, and experience in this thread. This is new to me, but something I've been studying and thinking about for quite a while. I will say that the 'science'/results involved in porting has changed dramatically since these cars were built/raced, so, 30, 20, or even 10 years ago in some instances, what was done then is now proven to be unhelpful or harmful to increasing airflow.

[Daryl Smith]

Dan,
My opinion on port matching the exhaust is that it's a total waste. Ports are too big anyway.
Intake - you want smooth flow as much as possible. If the port on the intake manifold is smaller than the port on the head, and there are no ridges blocking flow in, it's not a totally bad thing. That would leave ridges on side exiting the head, which 'may' help reduce reversion into the intake.

The carbon in the intake port in the cutaway of the intake port (somewhat cleaned) above is a sign of reversion, which you want to try to eliminate or minimise.

[greydog]

Thanks Daryl. Sounds like if I do anything I'll leave the exhaust ports alon
Dane

[Gregs672000]

I would have you talk to Steve, but I know he's completely buried.

[redroadster]

On carb ...enginez the quick carbon build up on the intake valve head negates the benefits of smooth ports after a ...month . Careful matching of the intake to head likely the best benefit.

[Daryl Smith]

Some Pictures of the stock ports and combustion chamber....

My reading on the topic suggests a LARGE percentage of 'porting' airflow increase can be had simply with a good performance 3 angle valve grind and cleaning up the ridge of the valve seat in the bowl area (2nd intake port picture).
If you are having your head rebuilt, the 3 angle grind should be pretty much standard, getting that ridge smoothed shouldn't cost much....

[Daryl Smith]

The head has now gone to the machine shop to get new valve guides for 7mm stem valves and get a rough cut to accomodate approx. 45 mm intake valves and 35 mm exhaust valves.
When it comes back (hopefully approx. 2 weeks) I will begin the porting process - this will include removing all casting flash inside the ports, a rough 60 - 80 grit finish in the intake port, a smooth finish in the exhaust port along with some reshaping of the exhaust port around the valve guide, some minor modifications to the combustion chamber, and finally the head will be shaved approximately .030" - .040" to get the compression needed for my dished pistons.
I am still looking at options to reduce the size of the exhaust port once past the guide area, and a shop nearby to flow the head....

[Daryl Smith]

Anyone try reducing the size of the exhaust port before??

[fj20spl311]

If you need to reduce the exhaust port size, maybe using the larger valve stem with a titanium valve to reduce the weight?

[greydog]

How would you do that? Exhaust port so gonna be hot. Add weld metal? you'll be limited by ability to reach and if you just pile it up at the outlet for instance, won't that cause turbulence and defeat what you're trying to do?
This is really interesting to me and something I've not seen. My porting experience has been to increase port size but, even then, just port mat so to reduce turbulence. I apologize if I'm asking dumb questions....
Dan