Hey, I've got a 4 door KE55 getting painted at the moment, it's pretty stock but i've just found a 2 door sedan with a 5K motor. the shell needs some work so i thought i'd chuck the 5K in the 4 Door for the time being.

 

Anyway, my question is will a 4K head fit on a 5K bottom end or a 5K head on a 4K bottom end? or is there a way to make it fit, e.g. drilling out oil/water ports ect.?

 

Might be a stupid idea but i thought the 4K head on the 5K bottom end would bump up the compression and go a bit harder and that putting the 5K head on the 4K bottom end would de-compress the motor ready for a turbo.

 

Any advice will be appreciated.

 

Cheers, Tom

the theory is sound all but for one fundamental; wrong way around.

 

5k bottom + 4K head = Low comp

 

4K bottom + 5K head = Avgas only man.

the theory is sound all but for one fundamental; wrong way around.

 

5k bottom + 4K head = Low comp

 

4K bottom + 5K head = Avgas only man.

 

it makes sense! ive always wondered why taz_rx runs a 3kbp head on his 5k turbo

 

at the end of the day it all comes down to combustion camber CC

Depends if it's a flat top 5k, if yes, a 4k head would up CR.

true TRD but they seem that uncommon I figured the generalisation will be fine.

true TRD but they seem that uncommon I figured the generalisation will be fine.

 

Yeah you are right, they are really uncommon.

Seems to be that a lot of these guys don't know what type of 5k's they have, so some of the questions can gave two answers.

 

I did find out a couple of years ago that there is 2 different 5k blocks as well.

Again the other block was uncommon as i haven't seen one again.

Whats the difference in blocks?

 

I've seen a few flat top 5K's around the place.

Depends if it's a flat top 5k, if yes, a 4k head would up CR.

 

Is that the right way round TRD??

also depends on how flat a 5k flat top piston is.

Whats the difference in blocks?

Good question - i second it.

Any way to tell them apart without taking them apart ?

I know the 5K block that i have (dished piston) has no welsh plugs along the cam journals as well as the displacement (1486cc) cast just below the deck height.

 

Also have a flat-ish psiton 5K (concave across top, about 3mm at the deepest) Will check what that has that's different.

also depends on how flat a 5k flat top piston is.

 

 

:blinks: Flat top pistons have flat tops...... end of story.

 

There's 2x different "dished" piston 5k's:

 

"O-dish" - around 6-8cc

"D-dish" - around 22cc of dish.

The D-dish 5K had the lugs on the head and slightly bigger ports.

 

The O-dish 5K had no lugs. Virtually identical to a 4K head, smaller ports.

/sep

:blinks: Flat top pistons have flat tops...... end of story.

 

There's 2x different "dished" piston 5k's:

 

"O-dish" - around 6-8cc

"D-dish" - around 22cc of dish.

 

your sense of humour is dead man, DEAD!

the 4k onto a flat top piston 5k will lift the CR cause the 4k has a smaller combustion camber in the head.

Remember I'm talking about a 5k with flat top pistons, they have a thicker head compared to a dished piston head.

 

the difference in blocks is, one hasn't got welsh plugs down the camshaft side(most common) the other has welsh plugs and a small welsh plug under the thermostat housing from what i remember.