info on who have done this before and what problems they ran into !!!! :hmm:

A 5k head has a 16 cc combustion chamber....

 

You do the math and report back with your findings. :hmm:

wow that sounds kinda small....? i don't know what a 3k head is.. but just comparing it to a 4ac/4afe head (they have almost ideantical combustion chamber capacities) that's fairly small.

If u do that u will decrease the compression ratio.... worthwhile coverting if plan to turbocharge or supercharge ur engine.... if not u will end up with low compression and decrease in power...

If u do that u will decrease the compression ratio.... worthwhile coverting if plan to turbocharge or supercharge ur engine.... if not u will end up with low compression and decrease in power...

 

 

Incorrect. 5K head on a 3K block will have a ridiculously high compression ratio as most 5k engines have the combustion chamber in the pistons (eg: Dished pistons). Not sure what the final compression ratio would be, but it would be fairly high.

 

A 3K head on a 5K block DECREASES the compression ratio as the dished pistons and the extra capacity 3K head will create a bigger combustion chamber which is better for Forced induction......

3k bottom end + 5k head = ..........................i want to be there when you fire it up! he he.......!

 

cheers phatke30!

Incorrect. 5K head on a 3K block will have a ridiculously high compression ratio as most 5k engines have the combustion chamber in the pistons (eg: Dished pistons). Not sure what the final compression ratio would be, but it would be fairly high.

 

A 3K head on a 5K block DECREASES the compression ratio as the dished pistons and the extra capacity 3K head will create a bigger combustion chamber which is better for Forced induction......

 

U r rite..4got 5K had dished pistons... Correct me if I m wrong, 3K head on a 4K block will increase the compression ratio...

 

3K head, assuming with compression ratio 9.0

 

CR = (pi/4 * bore² * stroke + V_c) / V_c

 

V_c = (pi/4 * bore² * stroke) / CR - 1

= (pi/4 * (7.5cm)² * 6.6cm) / 9 - 1

= 36.45cm³

 

 

Assuming both 3K and 4K has identical piston head and gasket thickness, the combustion chamber volume of the 3K heads stay the same 36.45cm³

 

4K block matched with 3K head

 

CR = (pi/4 *( 7.5cm²) * 7.3cm + 36.45cm³) / 36.45cm³

= 9.85

 

 

Does this mean that I can swap to a 3K head and fix twin carburettor set up like twin webers or twin Sus

 

Thanks.

You could attach twin carbies to your standard 4k head, keeping in mind that if you put more fuel & oxygen in, it's going to have to escape somewhere. So you should upgrade to extractors and a bigger exhaust....have a look through the FAQ if you need more info.

 

However putting a 3K head on a 4K will increase compression (depends on what 4K engine it is though)...