Okay so yesterday I was collecting an complete interior from R spec for a Dutch MK3 forum member to take over there from the UK at the end of the month. Talking to the guy, he had two motors, the 2.5R (rotted body) and a MK3 3Ltr with a twin turbo from the MK4 in it, very nice but during our talk he said that the MA61 5gte engine was a better block and bottom end than the MA70, but the head from the MA70 would swap right over. This would produce a better revving motor as it was a bit stroked? The theory behind this would result if Turbo'd would be a bit of a monster. Any informed opinions please. Ian :biglaugh:
Engine swap for the better or worse?
- Thread starter ianstaley
- Start date
Eh, I can see where he's thinking that. First, a little information:
5m - Was found in the MA61 (Mk2 Supra), it displaces 2.8L. Two valve per cylinder head design
7m - Was found in the MA70 (Mk3 Supra), it displaces 3.0L. Four valve per cylinder head design.
Now, the reason the 7m displaces more, is because it has a longer stroke. Shorter stroke engines (5m, 1jz, etc) tend to have higher revving capacity. However, they usually make less low end torque as a result. A question you have to ask yourself then, is what is your driving style like? I've had cars of both types (good low end, or good high end), I tend to prefer good low end for "normal" cars, but good high end on my sporty cars.
Now, what he is suggesting (a 7m head on a 5m bottom end) is basically the inverse of what the 6m (5m head on a 7m bottom end) was. To clarify, a 5m bottom end and 7m head will bolt together, but that's about it. Far as I remember, there are a few other differences that need to be accounted for, so it isn't quite that easy. However, if one were to swap out the pistons in the 5m bottom end... perhaps. I promise you that the guys over on celicasupra.com have done a LOT of research into this very subject.
All in all, you could de-stroke the 7m you have with a different crank and rods to produce a lower displacement, higher revving engine. Lot of work, but if it's your preference, it can be done.
5m - Was found in the MA61 (Mk2 Supra), it displaces 2.8L. Two valve per cylinder head design
7m - Was found in the MA70 (Mk3 Supra), it displaces 3.0L. Four valve per cylinder head design.
Now, the reason the 7m displaces more, is because it has a longer stroke. Shorter stroke engines (5m, 1jz, etc) tend to have higher revving capacity. However, they usually make less low end torque as a result. A question you have to ask yourself then, is what is your driving style like? I've had cars of both types (good low end, or good high end), I tend to prefer good low end for "normal" cars, but good high end on my sporty cars.
Now, what he is suggesting (a 7m head on a 5m bottom end) is basically the inverse of what the 6m (5m head on a 7m bottom end) was. To clarify, a 5m bottom end and 7m head will bolt together, but that's about it. Far as I remember, there are a few other differences that need to be accounted for, so it isn't quite that easy. However, if one were to swap out the pistons in the 5m bottom end... perhaps. I promise you that the guys over on celicasupra.com have done a LOT of research into this very subject.
All in all, you could de-stroke the 7m you have with a different crank and rods to produce a lower displacement, higher revving engine. Lot of work, but if it's your preference, it can be done.
