7M head differences

[TheNewRed]

Well guys, i took both of my heads into class to perform practice valvejobs on, and as i was cutting seats i noticed a significant difference between the two. One head has a radiused seperater that divides the two intake valves on each intake port. As for the other head, the divider is set closer to the valve guides by about 1.25", and instead of being a nice radiused piece, its very blunt and wide. I dont know if this is a year change, an GE-GTE change or what but it seems to be a very significant difference. Lets discuss...

Blunt, and fat. the edge is closer to the guides

another of the same as above

Now with the sharper divider, that starts about 1.25" closer to the intake manifold mounting surface.

and another

 

[Zumtizzle]

Welcome to 2001.

The head has a casting number on the intake side.

Higher the number newer the casting.

And the head difference happened in 89 or 90.

But there have been 15or16 Known Revisions.

 

[NewWestSupras]

There are different casting revisions on the 7M head, I'm not sure if it's pre & post '89 though. You can tell by the number stamped on it, perhaps Ian or another more knowledgeable member could give revision dates...ooops Zumtizzle beat me to it.

 

[IJ.]

no mark all the way through to #16 that were the last of the 7M castings.

 

[TheNewRed]

You guys said a lot but nothing far off from what i already know. Im more directied towards which ones going to yield more power, and what specified years, and variations we can get these heads from.

 

[IJ.]

There are at least 16 revisions...

Most will have been done as production changes at the foundry to make it release easier or to correct inherent defects and the later heads will have been an effort to reduce emmisions.

No one I know or have ever seen has data on year/revision or has even flowed them stock for stock.

I don't know what more you want?

Easy rule of the thumb is bigger number means it's a younger head so has had less time to be damaged by stupid owners overheating it but as always a hardness test is the #1 thing to do before starting any work on a 7M head.

 

[grimreaper]

is there a "proper" way to test hardness or is it something that varies from machine shop to machine shop?

 

[Zumtizzle]

http://www.supramania.com/forums/showthread.php?t=74868

Use this.

 

[NashMan]

umm i found out some thing really neat today and made me think wtf at the same time thous number mean what casting it is

i found another set of numbers for the casting it hard to read but right in the front were the timing cover it some of them are easy to read some are not

 

[NashMan]

so no one has any comments about this and why

 

[grimreaper]

so the "3" is the casting number? I dont see anything else easily.

 

[nuggets]

FWIW, my car has a build date of 02/89 and my head casting number is 9.

 

[NashMan]

bother are the same cast number but there different heads, one has big ports alot more free flowing and the other's ports are very restive ports and a lot smaller too


there is a casting that is hajnd written on every head and that by the timing cover some of them are very hard to read

 

[Keros]

bother are the same cast number but there different heads, one has big ports alot more free flowing and the other's ports are very restive ports and a lot smaller too


there is a casting that is hajnd written on every head and that by the timing cover some of them are very hard to read

Perhaps one head has been worked over in the last 20 years?

 

[NashMan]

Perhaps one head has been worked over in the last 20 years?

no there is no chances there both stock heads




on a side not i herd they changed the ports 3 times but i have only scene 2 different ones ???? i wounder if this is true

 

[Nick M]

For reference material....Here is casting number 2. Exhaust then intake.

 

[NashMan]

ok after may years i am pretty sure they had a an n/a head and trubo head but later on down the road they just ketp one for every thing and usedone type of head


or some one at the founderly put the wrong plugs in the casting mold

 

[Nick M]

That could be the big port casting reason. But, some have pointed out the big port head on early and late 7MGE. Who knows. And it isn't like Toyota will ever say. And by Toyota, I mean Toyota in Japan.

 

[Backlash2032]

Going from the Toyota world to the GM world and back to tinkering with my old car, its nice how well documented all the different heads are for an LS type engine. Known good combos, known bad combos, which heads flow the best, which heads have the biggest/smallest chambers blah blah blah.