Drilling Your Heads...

[Harry/FDK]

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

[Peter]

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

[richie]

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

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

[Harry/FDK]

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

Only the Fins. And within reason...

[Harry/FDK]

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.

[Neil Davies]

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!

[Jon]

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

[Rick Meredith]

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

oooh... good point!

[Type1/DVK]

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

[Jim Ratto]

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

[John Rayburn]

It's time to call Jeff.

[Bruce]

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

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

[John Rayburn]

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

[Steve D.]

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)

[Jason Young]

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

[richie]

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

[Harry/FDK]

It's time to call Jeff.

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

[Harry/FDK]

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

That's what we want !

[Harry/FDK]

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

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.

[alex d]

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

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

[Harry/FDK]

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.

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

[Type1/DVK]

before messing up some heads

Test on some 1200's?

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

Love to see the scan'ed part!

[Harry/FDK]

Alex, any news ?

[alex d]

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  )

[Type1/DVK]

or make a picture and post it @ hi-res

[Johannes Persson]

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

[Lee.C]

Hmmmmmm VERY VERY VERY Interesting 

[eugene]

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.

[Johannes Persson]

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

[eugene]

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