All extractors are designed to scavenge. The 421 system helps with low and midrange torque. 

All out larger capacity, high rpm race cars prefer 4 into 1s cause its all about removing restrictions and flow dynamics

There is a company in finland ive learned about this week that seem to cost about $700 aud delviered.

https://www.mcnsport.com/collections/kp60-exhaust/products/martelius-kp60-exhaust-manifold

might require modifications as made for lhd cars

4 minutes ago, 7000rpm said:

All extractors are designed to scavenge. The 421 system helps with low and midrange torque. 

All out larger capacity, high rpm race cars prefer 4 into 1s cause its all about removing restrictions and flow dynamics

There is a company in finland ive learned about this week that seem to cost about $700 aud delviered.

https://www.mcnsport.com/collections/kp60-exhaust/products/martelius-kp60-exhaust-manifold

might require modifications as made for lhd cars

Damn, $700 I'm thinking getting some made locally may be cheaper for your situation (considering mine set me back $210 including courier delivery) I can see why the extra low and mid-range torque would be good for your 4k, this actually was why I looked for a 5k and build it up, try get some better torque in the mid-range, plus more potential for max torque.

Yes the 5ks are much better for that.

Even still though, I know a couple of guys overseas that have developed the 5k engine to extremes for circuit racing, and still use 421s on their race cars.

At the end of the day, a small capacity engine is a small capacity engine.

If you really want torque, should go for a 7k

1 hour ago, 7000rpm said:

If you really want torque, should go for a 7k

true but I still want to rev the balls out of it come motorkhana and club events

I chose 5k because it was a good compromise of my favourite attributes of 4-7k's

good torque, but can take some good revs and top-end

Hello all

Sorry I have not been able to make progress on the motor as I'm currently going through mid-year exams at uni...F**K

anyways, I'm trying to find a slightly bigger valves for the motor, I've spoken to head2head in clayton and We've figured out a plan for the head (porting etc.) and now i'm on the lookout for some valve
Sizes I'm looking for:
- Intake: 37 or 37.5x100x8mm (stock size is 36x100x8mm)
- Exhaust 30 or 30.5x100x8mm (Stock size is 29x100x8mm)

I'm not wanting any bigger as the motor is not being raced full time or that often...otherwise I'd go up by 3mm each side...I'd prefer 1mm bigger both side since the motor will be street driven...plus no need to fit new valve seats, both sides can go up by 1.5mm max without new seats

So If anyone knows where to get valves of these sizes made new or what car they come from, I'd love to know

also headwork involves, porting intake to about 10-15% bigger than 3-KB head, enlarging exhaust ports (also polish for flow), valves will be skimmed so greater and smoother flow, deshroud the valves again aid flow, remove sharp edges on head in combustion chamber (Improve swirl for better burn), 3 or 4 angle valve cut so again aid flow, head will be shaved to increase compression, aiming for static 10:1 c/r, but looking at the cam specs (duration) and since I want it to run on 98 octane fuel, we might be able to get away with and stay safe with 10.3:1 compression (I'm aware some v8 (400cui smallblock chev from blueprint engines) guys seem to run 10.3:1 compression fine on 98 so I'm hoping we can be fine with that.

Edited June 6, 20179 yr by KaboomJohn111

Also looking for some new hydraulic lifters as well

Guys at Camtech doing the cam grind recommended some new ones, so again if anyone knows where to get some, let me know

I run over 11:1 comp on 98 octane and detonation hasn't been an issues. Running twin webers and dyno graphed timing was set though.

Datsun A series are 1mm over. They have longer stems though, so speak to your machinist about work arounds.

 

22 hours ago, 7000rpm said:

I run over 11:1 comp on 98 octane and detonation hasn't been an issues. Running twin webers and dyno graphed timing was set though.

Datsun A series are 1mm over. They have longer stems though, so speak to your machinist about work arounds.

 

What are your cam specs, I know generally the more duration the higher c/r you can run also anything else you did to avoid detonation, mainly because I'm using hypereutectic pistons and detonation is bad for them...really bad

Auckland cam 873 grind (noted on their website )

The critical thing is getting the right timing curve set and right air fuel ratios. Whilst there are general guides, the tuner needs to find what each engine likes on a case by case scenario.

9 hours ago, 7000rpm said:

Auckland cam 873 grind (noted on their website )

The critical thing is getting the right timing curve set and right air fuel ratios. Whilst there are general guides, the tuner needs to find what each engine likes on a case by case scenario.

That cam is much hotter than the one I plan to run, Camtech CT003-517(a), 274/274 adv, 218@50, 442 valve lift, main reason is that I wanted the nice LSA of 110 degrees (because good for street ability...and less inlet reversion and relatively smooth...not very lumpy) I'm doing a ridiculous amount of headwork so (at least the thought process) that the limiting factor of power is the camshaft choice not the head like most k-motors (biggest problem in 5k's and 7k's imo) plus a good head can help carry power of a cam further than expected.

I do need to find a good tuner for Weber carbs, unfortunately there are not many in my area of victoria or they are hard to find also of course dizzy will be re-curved but I forgot the place where someone recommended me to go near where I am so that sucks

Edited June 10, 20179 yr by KaboomJohn111

Sounds like a well thought out design from what i know so far. That cam still maintains a decent amount of lift.

Perhaps ask the guys at weber performance in vic as to which workshops they sell to the most?

4 minutes ago, 7000rpm said:

Perhaps ask the guys at weber performance in vic as to which workshops they sell to the most?

Well, I honestly wouldn't though of that, I feel like a moron now, Thanks for the suggestion

Comes with experience.

This is my 5th project car

Also has anyone had any luck finding a toyota genuine 5k head gasket, as I asked previously

also I've had no luck with headbolts for the motor so...as I'm out of options, time to get some ARP stuff, I know the part numbers for head studs, Thanks RainWarriorDregs

But anyone know if they would have bolts which fit, Later I'll post up all the specs of the bolt, length, thread, taper, diameter etc. 

Cheers all