luke70 Posted September 21, 2012 Report Share Posted September 21, 2012 Hey guys, Just looking for your opinion on weather you think I should keep my 4k with the webber carby and exhuast on it and throw a upgraded cam on it or or if it would be better to upgrade to a 5k.? Any ideas or input welcome in just looking for more power and the best way to do it Note: don't want to go down the ae71 1.6l route or any other engine Either a 5k or upgrade the cam in my 4k cheers Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted September 21, 2012 Report Share Posted September 21, 2012 Bore the 4K out to take 5K pistons, get a 1500cc 4K, solid lifters and have the cam cut. Been done, works, writeups here and there on Rollaclub. The 4K is the cheaper option if you don't want to do that, so just fit a cam. It will always be a 1300cc and you will notice that if your're working hard up winding hills. The 5K is better, obviously, but getting rid of the hydraulics is a pain if you went that route. Harder to find 5Ks too. Quote Link to comment Share on other sites More sharing options...
towe001 Posted September 22, 2012 Report Share Posted September 22, 2012 Nothing wrong with hydraulic lifters, nothing right about them either. But there's nothing right or wrong about solid lifters either. It just comes down to how much maintenance you want to do on the motor. Me, i hated the idea of it, so i preferred the hydraulic lifters over the solids. Quote Link to comment Share on other sites More sharing options...
Jono.C Posted September 22, 2012 Report Share Posted September 22, 2012 Bore the 4K out to take 5K pistons, get a 1500cc 4K, solid lifters and have the cam cut. Been done, works, writeups here and there on Rollaclub. Do you know what compression this ends up with? As somewhere i was looking suggested about 13.1 Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted September 22, 2012 Report Share Posted September 22, 2012 My 4K head has a combustion chamber of 31ml. 5K gasket is 7.5ml. 5K piston dish is 6ml. Cyl volume is 362ml (3.14x4x4x7.3) So 362+6+7.5+31 is squished into 6+7.5+31cc That's 406.5 squished into 44.5, or 9.1:1. Using the shallow dish 5K pistons. Not high at all. Quote Link to comment Share on other sites More sharing options...
ATOYOTA Posted September 29, 2012 Report Share Posted September 29, 2012 What are some good ways of making a 4K faster without bumping up compression? Is it just the basic stuff like cams/carbs/exhaust? Quote Link to comment Share on other sites More sharing options...
towe001 Posted September 29, 2012 Report Share Posted September 29, 2012 Is it just the basic stuff like cams/carbs/exhaust? Pretty much. Basically a motor is a pump - when the piston goes down it sucks in air and when it goes up it pushs the air back out. The more air that the piston can suck into the cylinder and then expel as quick as possible. Intake, exhaust and cams (longer duration and more lift). And then match the carbs (for the fuel) to how much air is going into the motor and in theory the motor well make more power. Another thing is the spark side of things - the bigger, stronger the spark the bigger and cleaner the bang. If your thinking of pulling the cam, you may as well also work the head a little as well - clean up the intake ports with something like 180 grit sandpaper suitable for metal. The ports need to be kept a bit rough to keep the fuel in suspension. Quote Link to comment Share on other sites More sharing options...
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