5MGE experienced??

[oldeskewltoy]

As many of you know... much of my porting work has been on 4AG heads.... I was asked to port a 5MGE head.

It was delivered to me cleaned and pressure checked. This is not the first head I've found this type of crack in. I've experienced this twice before... on one head (Volvo "530" head) it was terminal....




on the second head (Mazda/Fords 2.2) it was checked and found to be tight, and it was ported, I've not heard back that there is any problems with it....





So back to the 5MGE... the above cracks (top photo) are quite tiny, do not lead beyond the seat, and when it was pressure tested, it checked out ok.... So does anyone have any experience with this on a 5MG head.....???????



On a side note... I believe I know why 7MG heads have gasket issues where 5MG heads dont....... the aluminum is harder in the 5MG casting then the aluminum in either the 4AG, or the 7MG

[dnegative]

On a side note... I believe I know why 7MG heads have gasket issues where 5MG heads dont....... the aluminum is harder in the 5MG casting then the aluminum in either the 4AG, or the 7MG

Finding a 7MG head that hasnt been on a motor that's had the gasket fail is quite a task, nearly all 7MG heads are soft because at some stage they got hot
If you put a good hard head on a decked block, drill the extra coolant galley hole and pull it down properly on a MLS gasket they dont fail.


How much work is in the head now?
If its not a lot ($$$) I would be looking for a good core to use, cracks normally get worse lol
Depends how much the customer intends to use it too I guess.

[oldeskewltoy]

Finding a 7MG head that hasnt been on a motor that's had the gasket fail is quite a task, nearly all 7MG heads are soft because at some stage they got hot
If you put a good hard head on a decked block, drill the extra coolant galley hole and pull it down properly on a MLS gasket they dont fail.


How much work is in the head now?
If its not a lot ($$$) I would be looking for a good core to use, cracks normally get worse lol
Depends how much the customer intends to use it too I guess.

concerning the hardness... what I'm talking about specifically is the 5MGE head is MUCH harder to remove material from. The 4AG and 7MG are easier to remove material from.... THAT is all I'm basing my opinion on.... I know the 7MG head gasket fails... my opinion was part of that failure might be related to the specific aluminum alloys they chose to pour the 7M heads from.


As to how much I've done....... its half finished...

[MA61 Turbo A]

Hi,

The 7m head i just had built was hard as fk.

When i ported my 5mge head, i cleaned up the bowl area's, re-tapered the exhaust port but i left the inlet. Are you planning on removing the reversion on the inlet port ?

Cheers

Brad

[oldeskewltoy]

Hi,

The 7m head i just had built was hard as fk.

When i ported my 5mge head, i cleaned up the bowl area's, re-tapered the exhaust port but i left the inlet.

Are you planning on removing the reversion on the inlet port ?

Cheers

Brad

Would you go a bit further in what you are describing???

Here is what I've done to the inlets so far....

[oldeskewltoy]

as far as exhaust....



seat and bowl work....



to see what changes(gif).... http://ost.ebeans.ch/displayimage.php?pid=162

short radius...



note the absence of a top angle cut on the valve seat - this NEEDS a third angle, and it'll get one





port and bowl work......


top view shows right side "hogged out", left side untouched - center shows both sides "hogged out", and finally.....



the bottom view, mostly finished port/bowl


From....



To....

[MA61 Turbo A]

Hi,

On the inlet port what you have highlighted in green, 3, the chamfer/reversion is what I left in place. Some of these have cutouts for the injectors, some dont. I have seen the port opened out to this but have know idea of the advantage it would give.

On the exhaust I opened it out to the diameter of the gasket, a little bigger than what you have done. I used the primary's of the extractors that I made to give a small reversion for scavenging.

My inlet is not stock 5mge but I did use the lower half of the inlet. The 'd' shaped runner manifold is the one to use.

Cheers

Brad

[oldeskewltoy]

Hi,

On the inlet port what you have highlighted in green, 3, the chamfer/reversion is what I left in place. Some of these have cutouts for the injectors, some dont. I have seen the port opened out to this but have know idea of the advantage it would give.

On the exhaust I opened it out to the diameter of the gasket, a little bigger than what you have done. I used the primary's of the extractors that I made to give a small reversion for scavenging.

My inlet is not stock 5mge but I did use the lower half of the inlet. The 'd' shaped runner manifold is the one to use.

Cheers

Brad

I assume you mean most often the entire chamfered edge is blended away??? Note #3 is only in one area.... directly opposite the port work on #2, and no where else....

[MA61 Turbo A]

Hi,

Correct, they blend the chamfered edge away. I haven't seen any real world results from doing this, some argue against doing it, so I left mine.

Brad

[oldeskewltoy]

Hi,

Correct, they blend the chamfered edge away. I haven't seen any real world results from doing this, some argue against doing it, so I left mine.

Brad

The reason I did only the area I did has more to do with straightening the air flow - making it easier for the air/fuel charge - to get to the valve, then it has to do with opening the port.

[oldeskewltoy]

exhaust port #4.......

[Art Racing]

I understand from you posts on another site that the engine is to be turboed? In which case I think that there is far more to be gained with cam work and sorting out the valve lash adjuster/rocker/valve geometry than on the combustion chamber itself, as that is where the issue occur. Our class rules don't allow the addition of material so the advice I have inherited from the original race team, and from our own work, is that the rounding of the sharp ridges within the chamber, as you have already started to do, is about all you can achieve in the chamber itself. We then get the pistons custom made to increase the C/R and make the squish area more efficient; again you can't do that if it is to be turboed. We run around 11:1 C/R on Avgas.

As far as the inlet/exhaust goes, we leave the reversion on the exhaust side, but increase the dia of the inlet. The dia of the D shaped runner is 39 whereas the inlet tract is only 35 chamfered to 37 at the manifold face, and the Group A homologation papers state the tolerance as +4% and -2% according to the factory, so we take the inlet to 36.5mm and the chamfer to 38.5 'legally'; the race engines are either at 100% or less than 10% throttle for the majority of the time so you can do better things with the resonator box to make up for not having the reversion on the inlet side; obviously with a street engine that isn't possible and I would not open the inlet as far as we do for the race motors.

But with that head - I wouldn't use one with cracks like that; especially if it is for a performance build.

Regards,

John

Group A MA61, ex Win Percy TTGB and Peter Williamson

[MorGo]

First:those cracks are nothing;very many heads have them.
Second:without removing quides you can do a little real porting;just cosmetic fettling..
The port is just bit small and it NEEDS to have proper 3-angle valvejob.Backcutting the valve and just smoothing out the chamber.Not increasing size,just rolling those edges. Late 3T-GTE heads are same looking.
No,no dynodata;customers tend to be that they take the head and never afterwards hear about them.

[oldeskewltoy]

First:those cracks are nothing;very many heads have them.
Second:without removing quides you can do a little real porting;just cosmetic fettling..
The port is just bit small and it NEEDS to have proper 3-angle valvejob.Backcutting the valve and just smoothing out the chamber.Not increasing size,just rolling those edges. Late 3T-GTE heads are same looking.
No,no dynodata;customers tend to be that they take the head and never afterwards hear about them.

Not sure what tool size you use, I use 1/8" and 3/32". I don't want to take TOO much from either intake, or exhaust port roofs because the valve springs are an issue

intake
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exhaust

[MorGo]

Don't worry,there is no need to remove much material from the ports.But the quides need to be removed,ports modified,quides contoured in lathe and after re-installing quides the seats need to be cut again.On the intake think how to "straighten" the port (widen the floor) and exhaust just some clean-up since it's pretty good as is.