I'm after a little advice on porting and polishing, here's my latestest effort porting.
Q1, whats the quickest way to check porting balance and flow.
Q2, What are some past errors or mistakes people have made porting and polishing.
I'm trying to go a little more techo with my porting and polishing, compared to past years.
Any suggestions on how to improve my heads would be appreciated.
kevo ·
looks like a good job to me tho mate!
i just did a day job die grinding my heads on the v8 to port them out a bit larger,
in the drag racing forum there is a while log post about this subject by the way
good stuff bone boy
tassupervee ·
Possibly one of the most numerous, (and fundamental) mistakes with porting is going too large and ending up with too large port volumes.
This results/can result in weird gas velocity changes and often somewhat sluggish performance until the very highest RPM's in some cases.
Bigger is NOT always better and does NOT guarantee higher gasflow!
Ported my 125 trail bike following this concept, makes sense and works
dangerous ·
Biggest mistakes I have made were:
Making the port too big at the gasket,
Not unshrouding the chamber,
Not getting a nice valve job to blend the port to the chamber,
and lastly creating a hollow in the port under the seat
(on the large curve between the seat and guide)
Your port does look large, but I dont know what engine size or application yours is.
It should work well.
The most critical areas to work on are 1/2" either side of the seat(port and chamber).
Craig at crankshaft Engineering did some stock port opening, large valve heads that
flowed better than any or the as-cast SE/044/041s out there,
and maintained good air speed.
The best tools to use to match your port sizes and volumes,
is a pair of inside calipers, to compare distances from the port wall to various fixed locations
(like the guide or bore locations etc),
And a CC measuring impiment like a syringe or burette, for port volumes.
koolkarmakombi ·
Thats a fantastic site, a bit loud and he is pretty shy about blowing his own trumpet... not
I will definately look at some of those principles for doing my heads
I'm with dangerous on the need for a well decent valve seat job too.
68AutoBug ·
I read an interesting article on a website a long time ago about "Free Horsepower"
and although its not really about porting the heads, it was about "Matching" everything...
and polishing.....
I'm with dangerous on the need for a well decent valve seat job too. [/quote]
hellbugged ·
last thing for me was seat job
a nice three/four angle seat and valve job
keeping the seats not to proud of the chamber will reduce turbulence......
too low will represent wasted lift.
seats...
"first moving the 45 degree seating surface of the seat out to the outer edge of the diameter of the valve yields maximum usage of the valve size. On the intake use an extremely narrow 45 degree cut of about 0.010 to 0.020" and about 2.5 times that on the exhaust.narrow out with a 60 degree cutter/stone and down with 30 deg. finish by narrowing the 60 cut by half with a 70 degree cutter. on both intake and exhaust"
valves...
"the intake valve recieves a 44 degree cut and an undercut of 30 deg that makes the two the same width. The exhaust gets only the 44 degree cut. the reason for this difference from 44 to 45 degrees (valve/seat)is to make an absoloutly sharp edge for the valve to seat on and to pound into ever so slightly when breaking in"
bit of reguritation there, but hey, i don't have countless heads to experiment on and a flow bench to test the results.....i was lucky and had a set of finished berg heads to sit and contemplate over for hours and many "others" to compare and even laugh at too, before setting off on my job.... I can tell you i have picked up and checked out every set of heads at swap meets etc that have crossed my path ever sice....and picked the brains of Jeff, Shimo, Ben, Stan, Pete, Wayne, Richard and even Clyde along the way.
i have no problem admiting i spent 60 hours porting/polishing/matching my heads and manifolds, imagine that at shop rates! (quotes for the job reflected the need for that many hours)
when you sit down and REALLY look at the seating area and realize that this is the narrowest part of the "atomised" fuels short journey, then it's easy to see how important this area is. there are some good examples of the flow around the back of valves(intake)in the "how to hot rod VW engines" book...picture that as a flame from a candle and think about the importance of straightening the air behind the seats to aim at the back of the valve for as far as possible. there's more to consider on the exhaust with their tight turn after the seat. using the acceleration of the long side to help the shorter tighter side needs consideratioin there:blah
heres some recomendations
berg tech articles, and catalouge
bill fishers "how to hot rod..."
the dellorto "superformance" book has great stuff too.
also "hot VW's" ultimate engine guide
[ Edited on 4-1-07 by dumone ]
koolkarmakombi ·
thanks mate, hotrod book on way!
VWFREAK ·
Thanks guys, some good info and some very interesting comments.
We'll see how things develop
jason1957 ·
Shit dumone I wish I had half of your knowledge!
Thanks for the info, now I just have to get my head around it...:duh