The Cal-look Lounge

I just cleaned up my heads to have the valves/seats and springs checked. I also carefully grinded out all the casting flash. If one would drill small holes in the cooling fins, would it aid in heat dissapation ? Anyone experimented in the past?
Thanks,
Harry

do you mean drilling the casting flash near the exhaust ports?
or drill through the fins?

Yep,its supposed too,more surface area equals more heat disapation :)  I have never actually tried it though\
cheers richie,uk

Only the Fins. And within reason...

I just would like to get more cool air through the holes of the fins. I'm sure there are some early racers that experimented with that. I bet Ugly Duckling did. ;)

You'd need to measure how thick the fin is, then work out the diameter of hole that would give you more exposed surface area!

You have to consider how much surface you remove by drilling, against the amount of surface you get in the circumference.

oooh... good point!

and maybe it will slightly mess up the airflow.. more circulation around the holes? i was wondering about drilling also, why nobody did it.

if you go into one of the old VW service books from the 60's, there is a bulletin in there for 1200cc engines, if they experience "pinking" (pinging) under load, VW said to drill holes through fins. I don't have book at hand, it's buried at home, so i don't know size, how many, etc. And no I have never tried it.


Take care,
JIm

It's time to call Jeff.

You also have to consider the reduction in mass.  Less mass means less heat sink.

I think I'd rather just paint the fins flat black.

Paint 'em 80's pink- it doesn't make a fokken difference unless its in sunlight.

As for drilling holes, you would have to do some math to make sure that by drilling holes you would actually be INcreasing surface area instead of DEcreasing.  TMFWIMOTPNMAD

(Too Much F'ing Work In My Opinion To Probably Not Make Any Difference)

sounds like something vw would have thought of through the years and years of R&D if it was actually a good idea.

Except the costs would outplace the gains,and money talks,i would think it would be too time consueming for a major manufacturer to do,but the inventive home hobbiest or small shop could spend the time,particularly on heads with minimal fin area[Comp Elims,Super Flos,Angle flows,910s etc]and see some gains,well maybe ;)

cheers richie,uk

Yes, i bet he has experimented in the past doing this.

That's what we want !

Hi Jim, i just talked to the father of a german colleque of mine who is digging out that manual and actually did it himself for VW. Tomorrow i'm getting the paperwork and then we'll see.
Take care Figment.

I think I have that book, I'll try to scan that part

I did some homework today and foud out that you actually can create More surface area by calculating what you posted.
Thanks Neil/JHU
One more thing that got me thinking is the angle to drill. (More surface/direction of airflow?) I wish there was a way to simulate all this before messing up some heads.

Alex if you can. please do,
Thanks,
Harry

Test on some 1200's?

You probably can test it on your workbench.. sort of like mythbusters :)

Love to see the scan'ed part!

Alex, any news ?

yeah, I found the book! I'll scan it this evening (which can be tricky as I don't own a scanner  ;D )

or make a picture and post it @ hi-res :)

Interesting question FDK/Hurry,

In the seventies it was very popular to do this modification on moto-cross bikes, they were all aircooled at that time.
I did some calculation and found that the ratio is:D=4s, s=thickness of fin, D=diameter of drilled hole.

Ex:if you drill a hole that is four times the thickness of the fin you have the same cooling area, but if you drill a hole that is two times the thickness of the fin you have 50% more cooling(exposed) area.

The thickness of a cooling fin on an original type one head is aprox 2.5mm, with the ratio D=4s, shows us going bigger than 10mm hole decreases the cooling area, I think that 5mm hole could be a good starting point.

I think it is worth a try.

Regards
Johannes

Hmmmmmm VERY VERY VERY Interesting  ;) :)

I'm afraid the holes (R) should be smaller than 2D to gain any cooling area. Wit a hole you get rid surface on both side of the fin. So holes of 2-3 mm should  have some worthy gains. Other thing to consider is the effect of the reduced conductive area trough the aluminum for the heath to  quickly migrate from the hot areas around the chamber further trough the fins. It will be maybe better to increase the number of holes towards the end of the fins. In theory the concept seems valid. Now we need some real word testing. So who will be the first. Imagine a wild 36hp cased engine with some reworked, drilled okrasa heads running down the strip. ;D

Eugene,
You are absolutely right, there are cooling surfaces on both sides of the fin, my misstake.
The new ratio should be like this: D should be less than 2s.

Regards
Johannes

If testing on an working engine looks complicated, someone could run some tests on a bare head with an electrical heater of some sorts attached to the combustion chamber and a blower or fan  providing some air steam trough the fins. Taking temperature readings for a drilled and stock head. Doing so the effect of the  turbulence, produced by the holes, has  on the  heath dissipation could be studied. This could be very interesting.

Regards
Iztok

I looked this up in the old VW service book....for 40HP motors with old round boss 1200 heads....VW suggested drilling 10mm holes (6) in the ribs that extended from above rocker cover rail (upper) to outward most fin. It was done to lower head temperature and reduce pinging on heavily loaded motors.

Johannes, Eugene and Jim, thanks for the input. As Jim knows i'm currently rebuilding my 2165 engine. It's getting VERY tempting to do some calculations and have the Heads under the drillpress.

Thanks,
Harry


And Jim, be carefull with that axe as well ;)

Now i know which manual you mean. I have made a scan of the page:
(http://i242.photobucket.com/albums/ff310/vatovec/headholes.jpg)

But i think those holes were drilled to allow more air to pass to the exhaust port. Biger- 10mm, holes because of this.

I'm just a hobby wrencher, but when i started this topic, i had the feeling that it makes sense to drill through the fins around  the bottom of the head (combustion chamber side), all the way through the 7th fin. (I have 044's).  And with your input the holes should be at 2-3 mm. What do you think?

Thanks/Regards,
Harry

And thinking about drilling the upper cylinder fin (s) as well.
Regards,
Harry

Get an old head , put it on an electric owen with the cyl. side down, cover it with the tin and use a cold source of air to blow air trough the slot the shroud is blowing it. Take temp readings when the temp have stabilized. Then drill the head and repeat the procedure as close as possible. If the temps are cooler the procedure of drilling holes shall be known as the Hurry mod. ;D

Regards
iztok

probably to cool the mixture better, like a intercooler.. but this time with drilled holes  :D

Iztok,

 ;)

Very interesting topic, I wish I had time to experiment myself.  I do know Porsche heads cool way better then a VW, thanks to a lot more fins= surface area. As far as drilling holes straight through, I don't believe that will work. Possibly at an angle though, that would give you an ellipsed hole, which would be more surface area than straight, and also more work.

i think these holes are not designed to increase surface area merely to allow more air over the exhaust port, as the fins blocking this now have a gap to let the air through

Whoops, I guess next time I should look at the pictures ;)

Couldn't Resist The Temptation..

wow, those heads look pretty perforated!!

There is one thing that people seem to have over looked in this thread - That is that its not just surface area that diserpates heat its the amount of material itself - so if you start removing "material" then there is less of it to diserpate that heat.

I wont be drilling mine thats for sure - just my 2 cents  :)

Cool Hurry! At least I hope so  ;)

 ;)

wow dude, that's nice! hope it will work! but how are you going to know íf it will work??

There's something called a cyl.head temp gauge. ::)

i know ;) but do you have refrence to old vs. new? with exactly the same ambient temps/humidity and so? to make it a good comparison..

Lets say i have a lot of references from the past. (did my homework).

With some Revestreker Decalls it will run cooler...

an interesting test would be to watch a running engine with one of those IR cams, I'm sure we would see the hot spots that need help

PS: I've been without internet all last week, I see someone posted that picture for me  ;D