Rebuild a '74 F Engine using 3F Pistons

[garykaifong]

Need advices from you all here. I'm not a car expert, so let me try to put up my questions as clear as I can.

I've got a '74 FJ40. The F engine combination ratio is not right. Basically it lacks of power. The max speed I can get it to run is about 80 km/h on a level ground. Not to mention about going uphill. So this is definitely not right.

I took it to my mechanics, who dissembled the engine and told me that (something like this) the cam or cylinders have been grounded to its limit, that it cannot be overhauled with F engine's stock pistons and other parts anymore. Of course, I can consider to replace it with a 2nd hand F or 2F engine, but this is illegal here in Hong Kong, as each engine had its engine number registered. I can do it but I will need to pay heavy tax, which I don't want to. If I do it without re-registration, in the event of any accident, I lose insurance coverage and I will probably go to jail.

So, my mechanics suggested to replace to default pistons and other parts with 3F's. He said it's not worth it to use 2F's as it won't leave much room for future overhaul. He said 3F's may or may not fit 100%, that he will need to buy 1 piece of stock 3F piston from Toyota, and then do the precise measurement before confirming if this approach will work or not.

So, what's you folks' view on this? What should I do?

Many thanks in advance.

Gary

 

[garykaifong]

Help, please!

 

[rugerberetta]

Why not sleeve the cylinders and go back to stock pistons if the block has been bored out to the point it cannot be bored any larger?

 

[Cruiserdrew]

Can't you just quietly replace the motor with a 2F and avoid all the red tape? To the casual observer, they look the same.

I can't imagine that 3FE pistons would work as the design was completely different-shorter skirt, no dome, don't know if the diameter is even the same.

Good luck.

 

[RockDoc]

....don't know if the diameter is even the same.

Good luck.

Original bore for an F is 90mm, for a 3F its 94mm. If I'm not mistaken, Toyota went to a floating wrist pin for the 3F as well.

This diagram shows a 3F rod and piston vs. a 2F rod and piston. I would assume the the F is pretty much the same in basic design and dimension, aside from diameter/bore.

View attachment 324926

 

[garykaifong]

Why not sleeve the cylinders and go back to stock pistons if the block has been bored out to the point it cannot be bored any larger?

My mechanics did say a reason why it can't be sleeved, but I either forgot or didn't quite understand at all. Let me check with them again and revert. Thanks for reminding.

 

[garykaifong]

Can't you just quietly replace the motor with a 2F and avoid all the red tape? To the casual observer, they look the same.

I can't imagine that 3FE pistons would work as the design was completely different-shorter skirt, no dome, don't know if the diameter is even the same.

Good luck.

In Hong Kong, all vehicles are imprinted with a unique chassis number on both the chassis and the engine. Of course, no one will spot it. But touch wood in the event of any accident, the car will be towed for detailed inspection. That's an illegal act and if get caught, one can go to jail.

 

[garykaifong]

Original bore for an F is 90mm, for a 3F its 94mm. If I'm not mistaken, Toyota went to a floating wrist pin for the 3F as well.

This diagram shows a 3F rod and piston vs. a 2F rod and piston. I would assume the the F is pretty much the same in basic design and dimension, aside from diameter/bore.

The diagram is good. Do you think you can also find one with F vs. 3F or F vs. 2F, for comparison? Thanks.