Datsun Roadster Forum-311s.org

Last magazine appears to be April 2013

https://www.dsrcvic.com/index.php/club-magazine

The biggest problem with the title is the ambiguity of it, and the fact that most people have no idea of what is really involved with 'porting' and why the 'Secret Squirrell' - "you can't port it yourself" BS myth is used to scare people away....

How much do you want to spend?

1) clean up the casting flash
2) smooth the lip of the intake seat insert where it creates a 'lip', impeding smooth flow to the valve at the edges of the 'bowl'.
3) (apparently not universal) 60 - 80 grit sanding roll to 'texture' the intake port. There are other 'textures' used, including dimples like a golf ball.
The 60 - 80 grit is easy for the DIYer. DO NOT MAKE THE PORT ANY LARGER. This is not about flow, it is about keeping the fuel in suspension in the air for a more complete and consistent burn. It makes a difference!
4) smooth the exhaust port. Doesn't have to be a mirror polish, even smooth to the touch is better, once the casting flash is gone.
5) port matching - as long as there are no lips/edges impeding flow into or out of the ports with their respective manifolds, personally, I would not bother with it. A lip in the opposite direction of port flow can help reduce reversion in the opposite direction. As long as the intake runner is big enough for the flow you want and does not overlap the port on the head, and the exhaust port is smaller than the header you are bolting on...no lips to impede flow...good enough for street and not much to be gained..... unless you are racing and need every little bit.

Someone could have only 1 or 2 of the above done and say they have had their head ported....and technically, it would be true....All of the above can be done by a competent DIYer with only a few careful hours spent.

6) Valve Job - Not really porting, but very important performance wise. Get a good, performance, 3 - 5 angle valve job. The valve throat can also be sized to 89-90% of the valve diameter.
This and eliminating the seat insert lip will get you the majority of your increased air flow. Getting a 'back cut' on your valves is also a disputed performance item. Some like it, some don't. For the U20 I don't believe larger valves would ever be required - even for racing, jmo.

With these 6 items you will get a very noticeable gain in performance.

7) Port Shaping - This is where the money REALLY starts to add up, and what the 'Secret Squirrell' porting BS comes from. This is likely best left to professionals or very savvy amateurs and DIYers. For racing or when you want every last bit of performance, leave it to the professionals - preferably someone who has a flowbench and can do the testing and give you before and after flow results (ideally both flow and velocity). Depending on what you want, everything from enlarging the port, if warranted, to cutting away material to both improve overall flow, direct the flow somewhat to improve swirl or tumble, help keep fuel in suspension, and help uniform, consistent combustion - as much as is possible anyway.

8 ) Combustion Chamber - Porting? Not really....but...Personally, I don't like sharp edges in the combustion chamber. I smooth the combustion chamber, the edges of the combustion chamber which get sharp when the head is cut, and cut away and smooth the excess spark plug threads. I don't want any areas for carbon to build up.

Lots of porting videos on Youtube - from beginner to professionel...

Before you ask...I don't have a U20 or Dyno results.....

iloveredmeat wrote: ↑Wed Apr 26, 2023 6:18 pm

Alvin wrote: ↑Wed Apr 26, 2023 11:54 am

spyder wrote: ↑Wed Apr 26, 2023 11:39 am Didn't you originally post it?
It must have had a link because I at some point read it.

No. Unfortunately all I had was a photo someone sent me…can’t recall who. Yes, someone subscribed and posted a link but that’s gone.

@ tjp posted it, has anyone reached out?

I have no clue where this came from. I basically have never owned a U20 and definitely don't know anything about porting heads.

tjp wrote: ↑Sat Apr 29, 2023 10:52 am
I have no clue where this came from. I basically have never owned a U20 and definitely don't know anything about porting heads.

This is where it came from. You scanned and posted the article:

tjp wrote: ↑Sat Sep 06, 2014 8:27 am Best I can do with a small crappy scanner. Hopefully these pages are legible.

http://s1316.photobucket.com/user/tputl ... t=2&page=1" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Alvin wrote: ↑Sat Apr 29, 2023 11:03 am

tjp wrote: ↑Sat Apr 29, 2023 10:52 am
I have no clue where this came from. I basically have never owned a U20 and definitely don't know anything about porting heads.

This is where it came from. You scanned and posted the article:

tjp wrote: ↑Sat Sep 06, 2014 8:27 am Best I can do with a small crappy scanner. Hopefully these pages are legible.

http://s1316.photobucket.com/user/tputl ... t=2&page=1" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

hmmmmmmmmmmmm..... 10 years ago. That explains why I don't remember it.

I probably still have the magazine. I'll take a look for it.

tjp wrote: ↑Sat Apr 29, 2023 11:33 am

Alvin wrote: ↑Sat Apr 29, 2023 11:03 am

tjp wrote: ↑Sat Apr 29, 2023 10:52 am
I have no clue where this came from. I basically have never owned a U20 and definitely don't know anything about porting heads.

This is where it came from. You scanned and posted the article:

tjp wrote: ↑Sat Sep 06, 2014 8:27 am Best I can do with a small crappy scanner. Hopefully these pages are legible.

http://s1316.photobucket.com/user/tputl ... t=2&page=1" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

hmmmmmmmmmmmm..... 10 years ago. That explains why I don't remember it.

I probably still have the magazine. I'll take a look for it.

Yes, same here! A fellow roadster owner revived this, asking if I could help read the article...and I had to remember that I only posted the teaser page that someone else sent me. So thanks for looking!

I have the article scanned but am unable to compress the pages enough so they will post on this site. Anyone have adobe pro and can do this for me?

Hi Tim,
I have Acrobat Pro and some other tools that should work.
I just pm'd and emailed you.
Thanks, PM

Tim scanned the article and I squeezed the pages into postable size.

Thanks Tim.



Here are 3 jpg files:



Here are 3 PDF files:

iloveredmeat wrote: ↑Sat Apr 29, 2023 3:09 pm Hi Tim,
I have Acrobat Pro and some other tools that should work.
I just pm'd and emailed you.
Thanks, PM

Thank you Peter and Tim!
Strong team effort. I hope the roadster owner that requested this chimes in with some love as well.

I'd also like to request a thread title change, so it's easier to find:

"Cylinder Head Porting U20 in Roadster Magazine"

is what I'd like to change it to, if that's ok with everyone let me know and i'll edit

Alvin wrote: ↑Sat Apr 29, 2023 6:46 pm I'd also like to request a thread title change, so it's easier to find:

"Cylinder Head Porting U20 in Roadster Magazine"

is what I'd like to change it to, if that's ok with everyone let me know and i'll edit

I'm just a newby grunt, but that sure makes sense to me

Lou Mondello the author is probably the most knowledgeable and respected U20 engine builder anywhere. I’d tend to believe what he says!

Here is the issue as I see it. If you bolt 50mm Mikuni Kogyo carbs on to a solex manifold with the stock insulators the butterflys will hit the insulators and not open all the way. Therefore you will have to open the insulators so the butterflys will clear. Why would one not match that diameter all the way to the valve? Either the carb works or not!

Yes great job thanks guys, interesting article.
Now on the last page last section Lou mentioned about real dyno figures in the next roadster magazine #104 2014.
Does somebody have that also in their archives?

Thanks again,
Richard