4k Cams. Any Cuts Better Than Others?

[Felix]

altezzaclub, I reckon those 1 1/4" SU's will go great with a cam making max power around 6 grand.

 

Smaller carbs have higher airspeed, hence more torque lower in the rev range. It all comes down to matching components to get the best from your intended application. Keep the cam duration below 260 degs and you will have a low-mid torque monster for a 4k. You are on the right track.

 

Lower duration cams increase cylinder pressures at lower revs, and obviously run out of puff sooner. Higher duration cams are the opposite, plus really need closer matched gearing to keep them on song.

 

At one stage with my 5k ke15, the old DCD died so I fitted a stock 3k carb (19mm primary venturi) with some minor rejetting. Coupled with the 4.5 diff I had in the car at the time the motor made ridiculous torque in the low end. Could do 3rd gear hillstarts with ease on my 30 degree driveway. 2nd gear corners were 3rd gear corners with mass throttle response and squirt away from them. Really killed off the power over 4.5 grand though compared to a DCD, but still just had the edge over a new VU commodore at the time.

 

28/36 DCD's are a great carb, with their replaceable venturis (like with sidies) they can be tuned for whatever power range (or capacity motor) you want. I ran 25/25mm chokes on a 4k and now 26/27mm chokes with a 5k. The carbs aren't exactly easy to come by, but you will not get a better allround totally tunable, set and forget carb for a street motor. My old 4k with a dcd, 270 deg cam and ported head, was quicker than my mates twin 1 3/4" SU'd 5k with a 280 degree cam (unported head) in a ke20 club car. Twin 1 3/4" SU's outflow twin 40mm DCOEs if you didn't know.

 

I don't build for max power (leave that to the uninformed kids obsessed with kw figures), but more for trying to achieve the best allround performance/economy compromise with the widest possible powerband. To me throttle response and a motor that just goes in any gear from any revs is the way to go.

 

Oh yea, I've met Ivan Tighe, he was a real nice hands on old guy. Did work experience at Tighes many years (12-13) ago. I kinda doubt he has much to do with the business these days as Dean his son was taking over the reigns back then.

Edited November 3, 2009 by Felix

[SLO-030]

Any spare DCD's Felix :)

[Felix]

SLO-030, no sorry have got two decent ones, but none I could part with.

 

Watch ebay UK if you don't mind bringing in parts from overseas. New ones come up from time to time. UK is a good source for tuning parts like venturis.

 

That crow 606 is pretty much identicle to the Tighe 113. Good cam, and will make power to much higher than rated with a modded motor made to breath.

 

The Wade 609 is more a top end cam suited to a 5k. 291 degs duration.

It is easy to work out duration from timing figures for a cam:

opening degrees + closing degrees + 180 = advertised duration

 

do it for both inlet and exhaust. :)

[altezzaclub]

Thanks Slo-030, I'll ph Crows for a price on that-

 

Look at the 50thou figures, it opens really quickly! So although the duration & lift is the same as the Tighe 113, its getting valves open faster.

 

I assume that means it might shut later and faster too, which leads to bounce at high revs, but I don't expect to use 7000 or 8000 so that's not a worry.

[KE55PIG]

Ok awesome info comeing up in this thread

1 quick q

Am i going to be running out of air ? with my 286 deg cam with me twin 3k carbs or should i be ok ?

[rob83ke70]

you are going to have a lot of fun, and I mean that in a perverted sense of the word, setting your engine up to idle and be drivable with that camshaft :) but hey, its all a learning experience. It took me years to get the 4k in the ke55 with that cam to the stage where I'm happy with it.

 

Robert.

[snot35]

Just a quick point. I'm wondering if the whole smaller carb better airspeed argument applies in the same way to SU's. After all, we have a piston to regulate airspeed. Of course it's ideal if the piston is completely open at the same time as maximum air flow of the whole system, but if this doesn't happen I doubt that it going to matter quite so much, as long as you have the right needles.

 

Indeed Datsun A12's had a sport model in Japan that used 1.5 SU's.

Edited November 4, 2009 by snot35

[KE55PIG]

yea i have a feeling it may well take me awile to get it running wel i may pass it to a dyno tuner to play around with it or me see if they can get me moving better then what ill be able to setup

[altezzaclub]

KE55 are you going to smooth out the corners in the downdraught manifold for the twin 3K carbs??

 

When I rallied the old Datsun 1600 I had I started with stock twin-coke and worked the horrible manifold as much as I could. That 90deg bend from carb to manifold was terrible from the factory.

[KE55PIG]

the casting marks are goren need to open up were the base of the carby sits a bit and angle them so they can can flow straight on a \ angle in to the runner ins stead of L

What i have heard also is that there not that bad as they have a long straight wich pic the airspeed back up and all that.

Edited November 4, 2009 by KE55PIG

[rob83ke70]

I have twin aisans off a 3k-b and they are going to go on my ke11, so it should be interesting to see how they go. I'm not putting *that* crazy of a camshaft in it :)

 

Robert.

[KE55PIG]

my cam aint crazy what u talkin about hahahah hehehe can't wait to get it all runing

Edited November 4, 2009 by KE55PIG

[rob83ke70]

just for the record, with the crow 740 camshaft, it was much much much more streetable with the twin su's than it ever was with any of the downdraught webers that I've tried (dgv, dhsa2, and adm) or with the standard carburettor.

 

when you're done, come up here and compare with kylie's ke55 or alternatively we will visit you...

 

Robert.

[KE55PIG]

yea hopefully this will be done buy febuary running ok

[SLO-030]

Speak to Chris Hastings at Wade cams. Got quoted $87 + $15 post to regrind one of my cams to a 1489c profile. I dare say it would be the same for a 606 grind.