CALE12 Posted March 28, 2008 Report Share Posted March 28, 2008 info on who have done this before and what problems they ran into !!!! :hmm: Quote Link to comment Share on other sites More sharing options...
Felix Posted March 28, 2008 Report Share Posted March 28, 2008 A 5k head has a 16 cc combustion chamber.... You do the math and report back with your findings. :hmm: Quote Link to comment Share on other sites More sharing options...
tas_ae71 Posted March 29, 2008 Report Share Posted March 29, 2008 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. Quote Link to comment Share on other sites More sharing options...
rsdn Posted March 29, 2008 Report Share Posted March 29, 2008 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... Quote Link to comment Share on other sites More sharing options...
Xany Posted March 29, 2008 Report Share Posted March 29, 2008 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...... Quote Link to comment Share on other sites More sharing options...
Clapped out Posted March 30, 2008 Report Share Posted March 30, 2008 3k bottom end + 5k head = ..........................i want to be there when you fire it up! he he.......! cheers phatke30! Quote Link to comment Share on other sites More sharing options...
rsdn Posted April 1, 2008 Report Share Posted April 1, 2008 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 + Vc) / Vc Vc = (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. Quote Link to comment Share on other sites More sharing options...
Xany Posted April 1, 2008 Report Share Posted April 1, 2008 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)... Quote Link to comment Share on other sites More sharing options...
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