hi just chasing the difference between 3,4 and 5k carbies as I'm chasing a new unit to put on a junior sedan and as far I I can tell are all the same in fitment but am unsure wether the jets are any bigger on the 5k ones?? and at around $250 delivered to my door may be a good place to start seeing as all is brand new any help would be appreciated thanks Darren

I don't have any throat/jet measurements, but the carbs differed greatly from 3K to 4K in their emissions gear.

 

The late model 4K KE70 carbs have a spaghetti of hoses on them to apparently be more environmentally friendly and probably suck all the power out.

 

Also keep in mind a 5K carb is from a van, they were probably intended for all low-down power, I'd be surprised if they breathe well up high.

 

I know 3K carbs have manual secondaries, I'm not sure if any come with vacuum secondaries. Others probably know.

 

As you're running off the street and you're probably building a lot yourself, my recommendation would be to get the cheapest carb you can, tear off all the emissions crap and plug up any holes, rebuild it with a $50 kit off eBay, and see how it goes. If you need more air, lathe out the throats a tiny bit at a time, and drill the jets if required.

 

I have a 3K carb I did this to and managed to get it almost perfect, very responsive at all throttle positions. It'd run out of air at 8500rpm on a worked 060 over 4K. The only emissions gear I ran was a hot idle valve but you probably don't even need that.

Edited December 27, 201411 yr by Super Jamie

thanks Jamie wasn't sure wether it would work so i'll grab either a new 4k or 3k one pollution gear will go straight away as will choke butterfly I think I read a post here earlier saying 4k carb was better on a 3k so I might do a bit more research an forget the 5k

Yeah I take the choke butterflies out too, just run rich idle.