Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

heron heads. porting and the lateral approach.

 
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions
View previous topic :: View next topic  
Author Message
musicalannette  



Joined: 21 Feb 2012
Posts: 413
Location: UK

PostPosted: Sun Apr 15, 2018 11:34 pm    Post subject: heron heads. porting and the lateral approach. Reply with quote

As far as I am aware, the 924 is a heron type head.

Someone posted a reply about porting and high lift cams for increased power.

It is not uncommon as a tuning method (especially for racing) that approaching porting from a different angle can yield quicker cheaper results.

If they skim the head at anywhere between 10 deg and 20 deg to allow a change in angle of both the inlet tract and the valve (assuming that the valves will not hit the piston/cylinder wall) it can have an effect of moving the inlet port angle and the valve out of the way of the airflow (for N/A induction).

You will have to dowel the head the cylinder, make spacers to make sure the head bolts ate torqued correctly and make the holes for the headbolts the correct angle.

All of this is dependent of the castings and the max angle is best found by having a few cylinder heads to try and work out the casting thicknesses.

But in competition with that sort of mod it is very tricky to see and could yield a good percentage benefit the inlet tract (perhaps more than porting) with just a skim, drill and a few spacers. Sure somebody has tried it and I am not the only one to know of this. Perhaps porting on-top will add increased gains again? The type of head LIKES pressure charging really.
Perhaps someone has done this and will share the angle with each other? Or then again perhaps someone wants to go faster down the straight and doesn't want to get beaten in a one make race.........or maybe its been tried and it doesn't work well on this engine......really a flow bench is needed to optimise the angle along with spare heads to trial on.....but I remember it working to great effect on Coventry Climax engines. Should work on the 2.0 N/A. I think it is a well made engine and probably the best choice of engine without having to buy specialist service tools and cost you a fortune in parts. Heron designs are by there nature a cost/easy machining design, giving the head a slant is the OPPOSITE of why it was all squared up for machining. (PS I am not sure if copper and silver are a cure for arthritis/rhumetism)
_________________
I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....
Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
morghen  



Joined: 21 Jan 2005
Posts: 7904
Location: Romania

PostPosted: Mon Apr 16, 2018 7:28 pm    Post subject: Reply with quote

Interesting idea, will do some digging on this.
_________________
red 924 and not red 924
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
gegge  



Joined: 27 Jul 2007
Posts: 1029
Location: Sweden

PostPosted: Tue Apr 17, 2018 7:02 am    Post subject: Reply with quote

You are right, but there are gains that doesn´t require that much work. Keeping the CR without swaping to flat-tops and miling the deck could be a problem though.
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
Back to top
View user's profile Send private message
musicalannette  



Joined: 21 Feb 2012
Posts: 413
Location: UK

PostPosted: Tue Apr 17, 2018 8:14 am    Post subject: Reply with quote

I think milling the deck kind of defeats the object of it tbh and along with it makes the CR problem even worse.
But you are right a bit of increase in CR and plug positioning may result in having to swap the type of plug aswell. At worst you might have to go to the local airport for AVGAS and change the type of plug to start with!
My thought was it MUST have been done by one or other guy here on here even if they may not want to tell you perhaps one would share the angle! Especially for a N/A guys. The forced induction stuff less likely to worry about it as a bit lower compression and bit more boost is always an option.
_________________
I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....
Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
musicalannette  



Joined: 21 Feb 2012
Posts: 413
Location: UK

PostPosted: Tue Apr 24, 2018 9:46 am    Post subject: Reply with quote

sorry.

having thought a bit more, yes.

you could mill the block to get a better angle.

you would probably loose some cubic capacity.

At that point changing the pistons to allow this to happen (smaller height) from the little end to the top of the piston, then you could gain quite a bit of benefit with valve obstruction, lighter pistons too would help with the max rpm.

the problem then becomes the head gasket holes for the pistons, they would need to be oval when this is done, it might make you have to think about that before you even start.

so a making a special copper head gasket might be your first thought.

but I am sure moving the valve to a more "pent" head will give better flow results for n/a (it might well improve the forced induction aswell). but it could be ou are having to replace more parts need than is first anticipated.
_________________
I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....
Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
morghen  



Joined: 21 Jan 2005
Posts: 7904
Location: Romania

PostPosted: Tue Apr 24, 2018 7:52 pm    Post subject: Reply with quote

just speaking out of my ass, but wouldn't then be easier to make custom slanted top pistons to get the same effect?
_________________
red 924 and not red 924
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
gegge  



Joined: 27 Jul 2007
Posts: 1029
Location: Sweden

PostPosted: Tue Apr 24, 2018 8:30 pm    Post subject: Reply with quote

morghen wrote:
just speaking out of my ass, but wouldn't then be easier to make custom slanted top pistons to get the same effect?


At TDC in theory, yes. But at max piston speed and max flow some 90° later, not so much. At BDC when the important ramming occur, not the remotest.

The idea behind an inclined inlet, AND more important valve seat, is a better transition into the cylinder. As it is now, the flow is hitting the cylinder wall head on. The effect is more obvious in order to create more tumble. The 924 relies on swirl instead.
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
Back to top
View user's profile Send private message
musicalannette  



Joined: 21 Feb 2012
Posts: 413
Location: UK

PostPosted: Wed Apr 25, 2018 6:15 am    Post subject: Reply with quote

let me show you the cov climax head that it worked well on.

you have probably seen it before.

under COVENTRY CLIMAX CYLINDER HEAD.

about 4/5 down the page.
http://caterham.nl/parts-for-sale/

iirc it was moving the whole tract plus some of the valve head out of the way on the inlet that made the difference. I think is was something quite large 20 to 30 deg now I remember.

there is the jag v12 H.E. head that ran 12.5 :1 that combustion chamber might be applicable too f you dont move the head.

but I think the flow increases would help more.

just an odd thought, no one will ever try but that has been done with these little engines where a few h.p. in a car that weights 400-500kg makes a big difference....along with 2 eggs for breakfast!

it is fitted to fork lift trucks and lots of other things where a very light engine was needed, and normally was at an angle. the aluminium castings were of a very high quality for the time probably better than most vehicle stuff (reliant etc) because the money was in industry and the process was sorted out.

the bmw m10 in the brabham t55 F1 was a copy of this, but I am sure the Coventry climax was a copy of something else.

it was fitted in the hillman imp.the rival to the mini in the 1960.s

sadly the mini came out just before it and the mini was successful. really the hilman imp was the better car.(more room, more go, better handling and an opening rear hatch! )
the mini had the limelight and fashion and the imp didnt sell as well.
the engines though were used fir racing due to lightness.
_________________
I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....
Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions All times are GMT + 11 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group