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posted on April 5th, 2011 at 01:02 AM
Really good heads....
I figure this is the best place to ask for opinions, since most of the guys who read here would have experienced opinions. (Mods, please move it if
need be)
Many moons ago I took 3/4 sec off my times on a 1641, std TP heads, std inlet but with single stromberg, cheap extractors, by porting my heads using
the "How to Hotrod Your VW" Bible . You beauty! So then I plonked
down for a pair of CB heads, 039's I think (it was about 15years ago, can't remember), did the same thing, added 1.25's to the
std-small-ish-unknown cam, and woo!hoo!, lopped off another 1/2sec! How easy is this?!?! 15.6's from a street steel 1641 with std intake and cam?
I know a bit more now than back then about both AC VW's and also matching components (I reckon I was just lucky!), but with the huge range of
off-the-shelf parts available, cheap-as-dirt CNC-porting, etc, a decision on heads is 10 times as hard as before.
One year, when I get to it, the old crappy block behind the shed will be a 76str x 92bore (thick wall, but might still go thick 88's yet), Web 163
cam (249@.050, 1/2" lift@valve) 6500-7000RPM Oxyboxer, mainly coz I like making stuff, not buying it. I still reckon the ideal set of heads FOR ME
would be ones that I have ported myself (got 20yrs at it now on various motor types, mainly bikes) using a flowbench that I've built myself. I'm
also realistic enough to know that they will NOT be the fastest heads around, coz I'm not that good! So, I would like opinions based on experience of
better VW tuners than me (uhmmm, not hard really!), on which heads they like and why. Things like valve size to bore ratio, CSA's and valve size to
pinch point percentage.
I'm really leaning towards the Aircooled.net L6 heads for the 92 bore, 42x37, with huge airspeed, if I plonk down for the 88 bore, then maybe his L5
heads, 40x35.5 with extreme airspeed. Very similar to DRD heads, in fact they may even be those heads under license, who knows? I'm chasing
hand-finished heads, not CNC. If I buy a set of heads, I'd rather pay twice as much for hand-finished small valves than CNC big valves any day, even
at twice the price.
Any opinions on what seems to work and what doesn't? If I did my own heads I'd probably go for 40Int, with small exhausts like 33's, and monster
velocity for both, but a bit unsure of what AC VW's really like with a mid-range cam with high lift.
Oh yeah, home-made inlet manifolds and carby set-up, home-made tuned exhaust, the usual! Just love making this stuff.........
Have a nice day everyone!
dangerous
A.k.a.: Dave Butler Muffin Man
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posted on April 6th, 2011 at 05:23 AM
Sounds like you have the ability and equipment to do the heads your self.
Get someone local to fit some seats and go for it.
Dont focus too much on high velocity or you will choke the engine.
Velocity IS important, but not the be-all and end-all....especially when you want your power peak to be in the higher rpm ranges.
Get your self a couple of velocity probes,
and do the maths on what minimum cross section you need(usually at the seat throat)
for your desired rpm-peak-power goal.
Quote:
Originally
posted by westi
That's mad Alan.
cnfabo
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posted on April 6th, 2011 at 10:01 AM
email KROC in canada, he is the man, and will port u a set of heads for around $650 us not including buying the heads and manifolds...
modnrod
Fahrvergnugen
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posted on April 7th, 2011 at 12:59 AM
WOO!HOO! I got an answer! HA!HA! I've been waiting for 2 days, it's been driving me nuts, I was beginning to think it might be a secret, and I'd
have to get shot first.....teeheehee!
Thanks cnfabo, a good contact is very handy, I might yet farm them out, so I know they're done properly the 1st time at least. Does KROC have a
website as well for his company, or do you know of some of his work? Would certainly save endless hours of pain, not to mention beer money for my
mate's shop with the bench.........
Onya Dave, that's the spirit! Do it yourself, even if it takes me a few times......and it probably will! First time I made up an inlet manifold for
something it was truly awful, oh well . If you're
interested, with the airspeed I was going to go as fast as I could until it starts to get "fluttery" at 1/2", then smooth it out a bit to slow it
down a touch, speed it up, smooth it out, etc, and it's good. Aiming for maximum speed with choke off at about .550", and keep the lift under that,
and around 88% in the throat. I was going to try the smaller exhaust to boost up the mid-range (but might still need to go to 35.5 to keep the ratio
just above 70%), and use the biggest inlet I could jam in the hole that doesn't become too shrouded. I wanted to use a "high-tulip" exhaust valve,
and a dead-flat intake, usual hotrod Buick/AFR style chambers/valves. For a core head pattern, do you know if the 044's have the same port sizing as
the 040/043's, or are they bigger to begin with? I know they have more meat, but I'm not sure if I need to go that big on port sizing to achieve
what I'm chasing, a smoothed out 040/043 might have enough cc's, and the 044 too big, any advice there too?
Has anyone tried reducing the stem diameter (like down to 5.5mm or 6mm, works well on mega-RPM bikes) significantly with replacing guides, to
drastically cut the weight of the whole deal after it too? Like lighter single springs, thinner pushrods, etc? I realise it isn't a race motor,
probably only spin up to 7-7.5, but it would be nice to change the cam and inlet set-up and spin it past 8 if I ever wanted too. Just curious if the
"diminishing gains" rule applied there.
Thanks again for the replies.
bajachris88
A.k.a.: Chris Leete
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posted on April 7th, 2011 at 08:47 AM
How about dual runners per cylinder and have a butterfly that closes one runner via vacuum armature at low rpm creating a smaller cross section to
have the greater air velocity at low rpm , then using a frequency based
relay kit from jaycar have a VSV vent the vacuum in the armature opening up both butterflys and increasing the cross sectional area for your higher
rpm figures
(probably best to do this in the intake manifold...
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
modnrod
Fahrvergnugen
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posted on April 7th, 2011 at 03:44 PM
That's a bloody good idea actually Chris, but I could go 4 small CV carbs for the airspeed and bottom end, then run a "joiner pipe" between 2
cylinders for high rev to feed it properly.........
Uhmmm, yep, I have a Yamaha Vmax in the shed (one of the old evil ones!). Works good on them.
. You beauty! So then I plonked
down for a pair of CB heads, 039's I think (it was about 15years ago, can't remember), did the same thing, added 1.25's to the
std-small-ish-unknown cam, and woo!hoo!, lopped off another 1/2sec! How easy is this?!?! 15.6's from a street steel 1641 with std intake and cam?
. If you're
interested, with the airspeed I was going to go as fast as I could until it starts to get "fluttery" at 1/2", then smooth it out a bit to slow it
down a touch, speed it up, smooth it out, etc, and it's good. Aiming for maximum speed with choke off at about .550", and keep the lift under that,
and around 88% in the throat. I was going to try the smaller exhaust to boost up the mid-range (but might still need to go to 35.5 to keep the ratio
just above 70%), and use the biggest inlet I could jam in the hole that doesn't become too shrouded. I wanted to use a "high-tulip" exhaust valve,
and a dead-flat intake, usual hotrod Buick/AFR style chambers/valves. For a core head pattern, do you know if the 044's have the same port sizing as
the 040/043's, or are they bigger to begin with? I know they have more meat, but I'm not sure if I need to go that big on port sizing to achieve
what I'm chasing, a smoothed out 040/043 might have enough cc's, and the 044 too big, any advice there too?
, then using a frequency based
relay kit from jaycar have a VSV vent the vacuum in the armature opening up both butterflys and increasing the cross sectional area for your higher
rpm figures 