3k-3kc

[bmews]

After studying WiKi I see that the 3KC is somewhat detuned from the original 3K. I can't see much in the way of external stuff on the engine or carb so I presume the cause is entirely internal to the carb. Can anyone enlighten me please.

Barry

[Felix]

the original 3k engines had the big port welschplug head, and no pollution gear.

 

as they had to lug around increasingly heavier vehicles, the engines became more torque orientated (smaller ports). yea, also emmisions........

[Super Jamie]

emissions moreso i think. a smallport 3k-h with just a fast idle valve and pcv made 73bhp. a smallport 4k-c with all the emissions spaghetti and exhaust gas recirculation made 60bhp on the same scale. realistically, you'd probably be lucky to coax 40hp at the treads out of either of them

 

if you take off all the emissions crap and vac secondary, the 4k-c carb actually has larger secondaries than the 3k carb, and hence more potential for flow and power

 

either way, it's just comparing crappy engines with a 40 yearold design. i've driven a car with a stock 3k, stock 4k, mild 4k and now my fairly decent 4k. they're all nothing to write home about in stock form, but are quite alot of fun in the lighter shells, if you have the suspension and traction to go with it

[blown 5k]

Get about 130hp out of one then theyre fun :)

[Super Jamie]

agreed :) even two thirds of that is lots of fun

[bmews]

Thaks guys. Yes I presume it is the "emission stuff" that is the culprit but where is this emission stuff? All I can see is a PCV and an idle cut off. Must be hidden somewhere or is it just a very small carb?

[Super Jamie]

pcv and fast idle help your car. 3k-h emissions system is good

 

feeding exhaust back into the inlet manifold, and making air pass thru a thousand throttle hoses and valves so it can actuate the secondary throat doesn't help. 4k-c is bad, and trust me, you can't miss it

 

teddy or justin or xany, post a photo of your engine bay when it was stock

[Teddy]

jebus, that could be hard to find *scratches head*

 

hang on..

[mikeys toy[RL]]

3KC's here were u.s. emissions....they had an a.s.s. valve and air injection consisting of an air pump going into a rail with a tube protruding into each exhaust port.

they had slightly lower compression and a little more valve overlap to compensate for n.o.x. emissions.

later 4KC's had no airpump, but had an e.g.r. valve and a charcoal canister along with a catylitic converter.

i don't know how much of this compares with your stuff.....

[bmews]

Ahhhhhh, I see the photo's. A real can of worms. The 3KC in my car is really clean, only PCV and one other pipe from rocker cover to aircleaner or carb.

I guess the power reduction must be due to a smaller carb or a reduced compression ratio because there is no obvious visible difference from a 3K.

Case closed, you've satisfied my curiosity.

Barry