i was wondering what the difference in heads were between the 7mgte and the 7mge. My GTE has bad valve seals so im not driving it but we got an 86.5 non turbo car and i was wondering if i could swap out the heads without any problems. the 86.5 NA has a distributor and my 87 turbo has the coil pac anyway any help would be greatly appreciated.
differences in heads
- Thread starter SBM713
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What about a cressida head to a supra head? any differences?
and what about a 87 compread to a 91 head? any better?
and what about a 87 compread to a 91 head? any better?
Other than minor casting differences, there are 2 major 7M head variants.
And that is in the intake port.
Some have a long divider coming up from the valves,
and the other has no divider.
I think if you look on some of the other Supra forums like possibly supracelica,
you will maybe find the year break-downs on where they appeared over the years.
From what I read, the 'no divider' head is best for peak power & turbo applications,
and the head with the divider makes for better low & midrange power & NA engines.
Then, of course there is the Group-A head (very rare) that had less valve shrouding in the combustion chamber.
This is something people seem to forget about when they are trying to build a killer 7M.
The 7M has a shrouding problem around the intake valve.
By installing big valves this problem gets worse,
since the head of the valve is now closer wall of the combustion chamber.
When I put larger valves in my head, I cut the wall back by 1.5mm.
Then there is the little 'finger' that sticks down between each pair of valves that also interferes with flow into the cylinder.
On the Gr.A head, this has been eliminated, as it was in the later 1J/2J heads.
And that is in the intake port.
Some have a long divider coming up from the valves,
and the other has no divider.
I think if you look on some of the other Supra forums like possibly supracelica,
you will maybe find the year break-downs on where they appeared over the years.
From what I read, the 'no divider' head is best for peak power & turbo applications,
and the head with the divider makes for better low & midrange power & NA engines.
Then, of course there is the Group-A head (very rare) that had less valve shrouding in the combustion chamber.
This is something people seem to forget about when they are trying to build a killer 7M.
The 7M has a shrouding problem around the intake valve.
By installing big valves this problem gets worse,
since the head of the valve is now closer wall of the combustion chamber.
When I put larger valves in my head, I cut the wall back by 1.5mm.
Then there is the little 'finger' that sticks down between each pair of valves that also interferes with flow into the cylinder.
On the Gr.A head, this has been eliminated, as it was in the later 1J/2J heads.
16 different casting variations that I know of 17 if you include the Group A heads but George is correct the differences are minor in most.
Agreed 100% on unshrouding larger valves if it isn't done it's a total waste of time and would more than likely flow worse than stock they're that close to the CC wall.
Agreed 100% on unshrouding larger valves if it isn't done it's a total waste of time and would more than likely flow worse than stock they're that close to the CC wall.
From what I've seen, the GE cams shift the power band to the left. You get more low end, but lose on the high end.
That's probably a better way to put it...haven't seen an increase in peak that much though (15-20 HP here). Those numbers are close to Dyno variation from day-to-day and the increase in peak is going to depend on the tune (as it would with any cam). I'm not 100% convinced the increase in peak is solely due to the switch to NA cams since the cases I've seen also involved tuning on the Dyno (and other changes). Not saying it's not true, but it's a definite "grey area" as to the benefit. IMO, if you're going to change cams you need to have done a few other things to the motor to justify the swap.
Precisely my point...some folks seem to think you can install a 3' downpipe, install a new intake, shim the CT26 and then put on a NA intake cam. Doesn't work that way 
Cams are one of the last things you want to do with a head to get that remaining flow through the motor...and a NA cam is not exactly what I would call the 1st choice to do that.
Cams are one of the last things you want to do with a head to get that remaining flow through the motor...and a NA cam is not exactly what I would call the 1st choice to do that.
N/A cams have more duration. More duration will make more power. Where the peak happens can be changed by changing the cam timing.
So instead of changing the cams can you just swap the Turbo Head with an NA Head? Then you could just do some of the other mods that are listed above, like remove the shrouding...