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heron heads. porting and the lateral approach.

 
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musicalannette  



Joined: 21 Feb 2012
Posts: 403
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)
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morghen  



Joined: 21 Jan 2005
Posts: 7764
Location: Romania

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

Interesting idea, will do some digging on this.
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gegge  



Joined: 27 Jul 2007
Posts: 1018
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.
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musicalannette  



Joined: 21 Feb 2012
Posts: 403
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.
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