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4k change pistons to flat

Featured Replies

Hello
I have a 4k with piston dished (with holes).
Can I change to a flat ones from a 3K? Any problem with the valves? Will touch on pistons?
Everything in the engine is stock.

Regards

Edited by joseke
small errors!

Does your cylinder head have two lugs, under number 1 and 4 spark plug?

 

  • Author

Hello
Thank you for your answer! 
Yes have that two lugs on the head on that position. What does that mean?
And If did not have that, what what would be the diference?
Thanks in advance!!
 

It means that your cylinder head has less of a combustion chamber (to suit dished pistons) as opposed to the run of the mill flat top piston heads. You can change over to flat top pistons, you just need to find the relevant cylinder head to match,

 

cheers!

It means you have a 4ku not a 4kc (assuming it's not actually a 5k) which is supposedly more powerful and quite rare in Aus. Converting it to kc pistons and head would be a backwards step. 

Why did you want to do it anyway? 

  • Author
20 hours ago, Clapped out said:

It means that your cylinder head has less of a combustion chamber (to suit dished pistons) as opposed to the run of the mill flat top piston heads. You can change over to flat top pistons, you just need to find the relevant cylinder head to match,

 

cheers!

19 hours ago, Taz_Rx said:

It means you have a 4ku not a 4kc (assuming it's not actually a 5k) which is supposedly more powerful and quite rare in Aus. Converting it to kc pistons and head would be a backwards step. 

Why did you want to do it anyway? 

 

Well
If the head of this engine has less combustion chamber, with flat pistons from a 3K, in this 4k, will have any problems with valves?
I would like to will increase the compression ratio and get a few more HP on this 4K that´s the goal.
I have a big port 3K-B head, and a twin carbs from ke35SR,  and I was considering to put this in this 4K engine, to get even a few more HP. And make little more things, without spending a lot of money.

King regards

 

 

Edited by joseke
some errors

You can use flat top pistons and 3k head.

If you use flat top pistons with your head, which is a twin squish head, the compression will be too high.

You can just deck the 4k head you have and use the original style pistons to increase the compression ratio

It's a common mod in Portugal, 3K pistons in a 4K (twin squish head)

Interesting 

what compression ratio do you end up with?

what octane fuel do you use?

On 6/4/2017 at 5:05 PM, Taz_Rx said:

It means you have a 4ku  which is supposedly more powerful

My ke11 had a 4ku in, was healthy and was absolutely zero difference from a standard 4k.. i had high hoped but nope

12 hours ago, 7000rpm said:

Interesting 

what compression ratio do you end up with?

what octane fuel do you use?

Nevermind what I said, asked a few questions and they change to 3K head when they use flat top pistons

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