Got a spare engine from a member here, so decided to have a crack at a head job..:shock:

After a heap of research, and keeping the basic principles in mind, such as

1. Don't remove too much material
2. Polish exhaust ports
3. Keep intake ports rough
4. Port match intake, leave exhaust as a step between exhaust manifold and head..

and other such advice, here is the result.

Basically, for intake, put the gasket against head and mark how much material to remove.

For exhaust, you can see the difference between the gasket and the head.

Showed the machine shop, and they seemed impressed, but obviously they are trying to wind me up to spend money. These are the same guys who urged me to rebuild the short block and go all out. :P

Got Ralliart Cams and Valve Springs to install, the plan is to keep put these heads on a stock engine, with a Greddy and Extractors, etc. so hoping for a mild increase, keeping in mind reliability is a key factor. :D

May i ask why you keep the intake ports rough?
And from what i understand this has been going on for a few months yeah?

nice work buddy. may be interesting to set up ur greddy and cams on standard heads too for a comparison, because the computer will make you more power anyway.

']May i ask why you keep the intake ports rough?

From what Ive learned, by having a rough surface (240 grit) at lower rpm a boundary layer of air (stationary air adhering to the sidewall of the runner) is created in the runners and this has the effect of reducing the diameter of the runner to the air. The diameter of the runner has a direct influence on the air velocity, in this case it increases. Runner shapes and diameter effects on flow velocities is a topic all of its own, the second gen magnas have a dual length runner system that varies the length of the runner,long for low RPM and short High RPM. A fixed length runner will not flow the same across the entire rev range.

As for a high polish on the exhaust side this helps to keep as much heat as possible in the exhaust gas. The more heat kept in the exhaust the greater expansion as it exits the motor, which creates greater negative pressure pulses which help to increase the scavenge effect.
This is also why ceramic coating Extractors is a 2 way improvement 1, it keeps the heat in the gas by not allowing the heat to escape through the metal of the extractors and 2, stops this heat radiating out into the engine bay.
The high polish also helps stop carbonisation of the exhaust ports which helps maintains free flowing gas.

What Phil said is pretty much what I've tried to do.

Being an absolute amateur, it might work, or it might not. But I'll share the results and we'll see what happens.

Tried to unshroud the exhaust valves a bit i.e. when the valves are open, you need a decent amount of clearance between the Combustion Chamber walls and the edge of the valve, to promote good airflow.

The recommended distance is about 3/16" at .300 to .400 valve lift. I measured about 2/16" (1/8"), but was reluctant to remove any more material. 3 angle valve job may sort that out.

Heads have been with the flow bench guy for about 2 weeks. Dropped in on Thursday to see what was going on, but they've been flat out with other work. Magnas go to the back of the queue.:badgrin:

Yeah, it's been going on for a while. In fact I'm almost over it. :D

Bought a 40th Anniversary Stratocaster this week, so it's keeping me occupied in the meantime.:cool:

get the head guys to relieve around the intake valve next to the squish band, you will pick up some flow there. Usea suitable lubricant and your rolls will last a lot longer and not fill up with alloy. Pay particular attention to the short turn radius. Grit finish is dependant on pressure and local conditions. For NA 240 in a 6G will be too fine, go for a 80 finish from a lubricated roll.
Boundary layer conditions are mostly subjective when placed in print or on the net. The bounday layer would most likely be at most .2-3mm and will thin at higher flows, so its effect on making the port flow faster is minimal. Keeping the boundary layer attached is critical, boundary layer seperation is very bad.
The heat/pressure/ex speed argument WRT header coatings is vexed. The more heat in the exhaust the more back pressure. Whilst this is not a problem per se you need to take into account the design of the engine and headers etc. For a street driven 6G there would likely be no pressure issues as it will need to be very mildly cammed. It does work wonderfully well in controlling heat in the engine bay.

get the head guys to relieve around the intake valve next to the squish band, you will pick up some flow there. Usea suitable lubricant and your rolls will last a lot longer and not fill up with alloy. Pay particular attention to the short turn radius. Grit finish is dependant on pressure and local conditions. For NA 240 in a 6G will be too fine, go for a 80 finish from a lubricated roll.
Boundary layer conditions are mostly subjective when placed in print or on the net. The bounday layer would most likely be at most .2-3mm and will thin at higher flows, so its effect on making the port flow faster is minimal. Keeping the boundary layer attached is critical, boundary layer seperation is very bad.
The heat/pressure/ex speed argument WRT header coatings is vexed. The more heat in the exhaust the more back pressure. Whilst this is not a problem per se you need to take into account the design of the engine and headers etc. For a street driven 6G there would likely be no pressure issues as it will need to be very mildly cammed. It does work wonderfully well in controlling heat in the engine bay.

What he said.........:eh: :shifty:


lol You sure know ya stuff mate!

I was considering having a go at this a while back when i thought my head gasket was gonna go...

Looks like you've done a top job mate. :D

Thanks for the comment, but I am not an expert at porting. I do have something to do with race cars so I've picked up a bit of info here and there.

']May i ask why you keep the intake ports rough?

Golf ball.

While port matching is a good thing to do, porting modern motors is really a very last ditch effort for every scrap of a HP you can make.

Although the 3rd gen motor is far from cutting edge, the casting quality from what I have seen is quite good. It still allows for improvement but without flow testing it really is just a excersise in porting, and results can not be expected.

It comes from the old days when dirty great chunks of sand were used in conjunction with poor sand cast practices. The old motors had burrs, hot spots and all sorts of casting defects which were not fixed. This just isn't the case any more.

It still can't hurt to do, and it looks like you have done a pretty good job! Kudos to you for your effort and it might sneak an extra 1 or 2 hp for you :)

Golf ball.

I have not a single Clue what that meant:confused:

']I have not a single Clue what that meant:confused:

more air flow due to the dimples?

cos golf balls travel through air they have the dimples to be more aerodynamic or something like that

thats what i think anyway....imperfections increase air flow

Golf Balls have laminar flow and the reynolds numbers are low enough for such a technique to work. Intake ports have neither and such things have been proven not to work for at least the last 20 years...never stops people from trying though.
Having a pair of 24v 6G heads on the bench I would agree that they seem reasonably well cast. The valve seat machining is typical production and thus poor. The short turn radii is also less than good. The intake valve shrouding is as described. I reckon there is around another 10-15% to be gained before more radical work is required.

']I have not a single Clue what that meant:confused:

perhaps it was a reference to who would fish the ball out of the 19th hole- ie your avatar pic- and laminar flow -the speed difference may come into play considering the hole is moving at an unconstant variable, juxtaposed between yesterdays lunch - gravity- internal air pressure and the ensuing retrievers in uniform- hastening an untimely and embarassssing
public exit.

Taking into account Behr's explaination of the situation :bowrofl: , it's hard to put engine airflow concepts and optimum head design into practice. For amateurs.

The flowbench guy (drag racing guru) wants to do more work on the port floor, which would probably be aimed at the short side radius. Reckons there is heaps to be gained, but I'm not sure about handing over $600 to find out.

Air flows in and then hits the valve guide, which is a massive disruption. Some wisdom suggests bevelling or knife edging the valve guide so the air flows better around it. This is what I did at each intake on the heads, where the airflow splits from one intake port into 2 valves.

Maintaining port velocity seems to be the key. Fast laminar airflow along the port floor to fill up the cylinder efficiently on intake, is my simple understanding of it.

Hmmm...could you force air into an engine? Nah, it wouldn't work......:badgrin:

Extrusion Honing.
Has anyone looked at extrusion honing?
This is where an abrasive slurry is pumped through the ports, the idea is that the slurry will remove those areas that restrict the flow.

I know that there is a head shop in Western Sydney that does this, has a flowbench as well.

It would be more than interesting to see :-
a) Standard head'
b) Port and Polish,
c) "Expert" worked head and
d) Extruded head.

Gerry

problem with extrusion is that you cannot control well where it removes material. It is excellent for some old cast iron ex manifolds, rubbish at porting a head, particularly one where porting is uncommon.
Having removed guides totally from another head it was only worth 1cfm. I doubt the 6G7X would be much better in this regard.
Re the porting guy, what are you trying to achieve? If a mild improvement, then a mild job, 3 angle seats and a clean up of the port bowl will be best value for money. To get the most out of more work may require another camshaft etc...and lots more money.

so how much labour would be involved in a mild job ? any rough idea for a 6g?

']May i ask why you keep the intake ports rough?
And from what i understand this has been going on for a few months yeah?

as i knew it or was told when i was doing my rana it helps mix fuel and air because i always thought it was better smooth.

Big fella!!

can you measure the inlet seat ID's, and the id and od of the valve itself, a simple 30deg back cut should be very benificial .. . . .understand it abt 85% of the OD, 90 - 92% should prove benificial . .. . .

appologies post last sandown. . . .

i try to use 60 grit and 80 grit flap wheels . .. . as nero said - dont waste time polishing - try to get the shape right.... re short side, some bumps around the guides, splitter takes up a lot of area. . . .overall, for a production casting, its more than reasonable . . .. .

rgds

sdo

simon it will be interesting to see what comes back from canberra when the 3lt heads go up there. The ports are awful flat!

Funny how I've got a set of heads sitting around waiting to be snapped up but everyone sits on the fence until someone gets the courage to have a crack at it.

Well done. Nothing like getting your hands dirty. There are some ugly casting marks in the exhaust ports, short side inlet needs attention, deshrouding, 3 cut is fine for road, tidy up the sharp edges in the combustion chamber.

This last item should be high on the priority list of anyone that has a force fed or is about to force feed their Magna. Sharp ridges storing heat will cause premature detonation and/or cause you to run less boost and ineffiecient timing to counter this.

Anyone know how well these heads WELD? I'd like to reshape mine all Honda-style clover leaf.

with regard to welding chambers

the late model honda's (and late 20v toyota's and the 4v v8 ford actually use the chamber walls aroiund the valves to improve the discharge coeff by reducing the rate of change of x-sectional area past the seat .. . . .. some of the old david vizard books shouw this technique in some detail and it does work. . . . just be aware that you will need to replace the inserts which can get expensive......

have a look at endyn's website for some excellent approach to port design, and exceptional flow results . .. . .

neil - in some cases - changes the port finish locally changes velocity, and can help (in some situations) for getting air to go around a corner. . . .. have a look at race tech engine series mag for cnc ported heads and then have a close look at the finishes applied to both the ssr and long side. . . . i thought it twas interesting . .. .

hope that is useful

rgds

simon

with regard to welding chambers

the late model honda's (and late 20v toyota's and the 4v v8 ford actually use the chamber walls aroiund the valves to improve the discharge coeff by reducing the rate of change of x-sectional area past the seat .. . . .. some of the old david vizard books shouw this technique in some detail and it does work. . . . just be aware that you will need to replace the inserts which can get expensive......

have a look at endyn's website for some excellent approach to port design, and exceptional flow results . .. . .

neil - in some cases - changes the port finish locally changes velocity, and can help (in some situations) for getting air to go around a corner. . . .. have a look at race tech engine series mag for cnc ported heads and then have a close look at the finishes applied to both the ssr and long side. . . . i thought it was interesting . .. .

hope that is useful

rgds

simon

Helpful in spades. I see Endyns gets varying press across the industry but it's always welcome to see and hear a fresh, educated approach esp when the status-quo was established in the days of "need more power = bigger carby and another 100cubes".

Can we twist your arm for some scans of the David Vizard literature or some web links :D :pray:

this guy is exceptional if into 4 stroke (and two) theory . . .. . .

http://www.profblairandassociates.com/GPB_Updates.html


old DV stuff

http://www.geocities.com/motorcity/track/6992/vizard.html


ahve a read of the DSR (sports racer) forum . .. . .

speadtalk forum exceptional re engines .. . . .sometime spent reading all posts is worthwhile

http://speedtalk.com/forum/viewforum.php?f=1&topicdays=0&start=1200


also - read (and understand) the flow data on the honda 4v heads from endynes site - exceptional when you work out dicharge coeff's. . .. .i understand the bloke is circa 55-60 yrs old - and it shows that experiance (and continous testing) is where the hard work (and gain) are

rgds

simon