Audi A4 BTCC / STW engine specs - 305 bhp from an N/A valver.

Yes, so tilted backwards?

 

Yup, if of course its in a golf(easier picture) it would also improve combustion chamber shape, and also lower cr a tad too.
If anyone is doing this its pretty simple, just make sure you re-counter bore head bolt perches so the spot where the headbolt head sits will be parallel to block face, its often overlooked if the head face is angle milled and youll never get correct torque on the bolts.

 

Could it be CR related, the combustion chamber is quite large and the amount of material that can be removed from the head is limited by the lift/duration of the inlet valves vs pockets in the piston, tilting the head back will allow more parent material to be removed from the head without the inlets becoming too close.

I take it the angle of the pockets in the pistons are different??

Probably a million miles off but just a thought off the top of my head, and without reading the rest of the thread

 

Ya, cr has a lot to do with it, but angle mill over parellel mill has the advantage of tilting exhaust and also raising intake port angle, its all a pretty package really!
Correct on the intake valve info, eye brows need not be deepened further with this method of skimming

 

Any idea on the amount of angle from 90 degrees the heads are? Would be nice to compare angles on the pistons.

Has anyone seen any VW heads with rollers bearings fitted for the cams? I’ve seen one Cosworth turbo engine and one Vauxhall head with them, both from rally cars, but never any others. With the valves removed you could spin the cams by finger tip and they’d spin for ages

 

approx 2.5-3 degrees from what I can see you'd get away with off my drawings, but thats a small bit of a guess.
Ive read about roller carriers but I think when you really really get down to it there not worth the hassle unless your really trying to shave the max amount out of the engine. But every bit counts I guess, i think they fit them when they have other problems to get around too, room, oiling, and more stuff ive forgot.
I remember reading though that they hinder the movement off heat from the camshaft to the head(soaks up along valve and follower)compared to the normal style line bored/caps setup.
Ill dig it out, ive it saved somewhere as ''untitled'' along with the rest of the ''untitled'' files so it might take a while.

 

I just thought of something else there the angle milling would do, by milling it so the head is tilted back, and the exhaust valve no longer sitting at 90 degrees, the curtain area between exhaust valve and bore wall is increased, small amount we're talking, but it would make a difference, hmmmmmm....

 

And it's a 84.5mm bore...

 

Found this, angle milling piece>http://www.circletrack.com/enginetech/ctrp_0312_angle_milling_cylinder_heads/index.html

 

on the 16V head its 1.5 / 2.0 degrees

 

I see alot of "popular" guys in here
Probably 1 of the best threads I have read in a very long time

 

BUMP

 

Just to add to comparions...


Firenza 2279cc

97mm Bore x 76mm Stroke

 

One of Blydenstein's articles covered it - one of the 2.3 8v head castings had a "hump" in the inlet port floor.

One head he just reshaped it slightly, one he removed it. Second head flowed noticeably better on a rig, first head made the power (and the midrange torque). He said it was all a matter of swirl and mixing inlet charge properly

 

just came across my notitions i made then.

Crank 9.8 kg
rods H ca 500gr
ABF head but 058 number
inlet port 50 x 34.5
exhaust flange 37x 41/42
head skimmed under 2 degree angle
( kc 1.5 degr)
Head gasket replaced after 2000 km
Cams get flat spots after about 8000 km
lobes drilled trough with 8 mm hole
powergasket ( heat barrier) between head and inlet manifold ( ca 5mm )
crank sensor on top were distributor is and measuring on flywheel

 

Re made, as in angle of fixture of flange faces?

Wow, just weighed the standard 2.0L forged crank, 13.5kg(approx)

 

yes - just to add that comment back into the mix - 2.5mm more off the exhaust side - if the head is 190cm wide, I make that about 3/4 degree

 

Ya I was thinking, when you said it necessitates water passages to be remade I was getting worried

 

thats what the guy said, and he knows his stuff - I guess its a slight reposition but I dont know enough of the consequences of taking 2.5mm of material off to add more info

 

I dont see how internal waterways could be re-positioned in a head but I guess he knows more than I do, Interesting stuff Rob.