Performance 7K Quad Carbs

[pol090_ke11]

Hello everyone I'm very curious about building my 7k engine into a tough street engine in my 1970 ke11.

I have currently been reading a discussion about using quad motorbike carbs on a 4k engine and I would like to use the same setup on my 7k.

I'm also going to try and get this engine to rev a bit harder as I know they aren't as rev happy. I have a basic understanding with engines but I would also like to talk with other people to find out more on how to do so.

I will also be getting a regrind on the cam, tracking down a light weight flywheel, porting and polishing the head, double valve springs, larger valves, quad carb setup, electronic dizzy, performance headers and exhaust system.

The only thing I'm really not sure on is the internal side of things pistons, push rods, conrods, ect so if someone has any info on this please let me know.

[altezzaclub]

Basically, if you have it apart get it all balanced, from the crank pulley to the clutch, inclusive.

 

If you're really keen you can knife-edge the crank and polish it, so it weighs less and has fewer issues going through the oil, but I don't think its worth it unless you're racing. The same goes for forged pistons and rods, stock will do unless you're going racing, and I don't think 7Ks race!

 

That lovely Tasmanian topic on building a V8 KE70 drifter includes the bit where he replaced the almost-stock intake system with twin quad throttles and lost power is interesting- Your bike quads might be wasted on a 7K!

 

http://www.nissansilvia.com/forums/index.php?showtopic=431244

[pol090_ke11]

Ok so if I went away from using quad carbs and went to a itb's setup this would be worth doing?

I have also been reading the early nissan A series engines (A14-A15) quad carb setups and it seems to work for them.

and yes i think i will be pulling the whole engine down so balancing and polishing will be happening.

[Taz_Rx]

FYI - 7k and 7afe rods have the same toyota part number..... and spool make 7afe rods. :wink:

[snot35]

I'd say the main problems that you're going to have is that this is a long stroke, narrow bore motor. If you want it to rev, you need it to breathe. To do that you need big valves, or really long duration cams, which is going to make it quite a cranky street motor. Given it's the same bore as a 5K I'd be guessing there isn't the room for big enough valves in there to make it a really revvy motor. Properly tuned ITB's will help the torque aspect of the motor, which is something I'd emphasize more than revving.

[altezzaclub]

Ah, the Nissan A series... easily capable of 7000rpm, they have a low-friction 3bearing crank and probably Nissan themselves were surprised at how strong they were! My A15 had a better response than my L16 with twin Webers, just not the pulling power.

 

I don't know the 7K well enough to predict, but I thought they were more of a slugging workhorse than the smaller 5 and 4K. Hopefully someone on here has tried hard to make them into a high-revving quick response fun motor, otherwise you might be disappointed at the end of 4 or 5 thousand bucks spent.

 

Any system that feeds one throttle body straight into one cylinder has to be the best, so bike carbs or twin Webers or ITBs, whichever is cheapest and easiest. I like the bike carb idea myself...

[pol090_ke11]

I have thought about changing rods and what not but I think the only internal change will be pistons and try and get the comp up.

 

I was almost contemplating doing a completely worked A15 engine but then again I also want to keep the 7k and do something different.

All I can ask is if someone has done a worked 7k with itb or quad carbs, cam, port and polishing, etc etc to drop a line in this thread

 

thanks to everyone with there opinions ;)

[philbey]

Gavclassic built a mean 7K on carbies for his KE15/17?

[Crostek]

The thing with ITB on a small engine is not to go to big in the butterflys,

I have 2004 ZX6RR throttle bodies on a custom manifold made for my 5k and the butterflys are only 38mm,

The intake ports on my head are 33mm (Ported 3k head as per trd manual see FAQ) and the the inlet valves are 38mm this gives me around the 160hp on the flow bench, have not yet dyno'ed the motor to find the real Hp.

 

I have not look at a 7k head but are the ports quite big?

 

The main flow stopper in the 3k head is the hump where the valve guide sticks in, a quick port each side of this really opens up how the head flows. In my head the guide is cut down and tapered down in size too.

[tojo2]

If you're really keen you can knife-edge the crank and polish it, so it weighs less and has fewer issues going through the oil,

 

Just for weight loss. Oil level is well below crank.

 

Eaisier / cheaper done by lightening flywheel if nesesary

 

Better to spend $ on conrods like Taz Rx said. Belived to be weakest link

[Taz_Rx]

I have not look at a 7k head but are the ports quite big?

 

Depends which motor.

7KC has exactly the same sized ports (in & ex) as a 4k or 5k.

7KE has oval inlet ports, port and round out the ovals and you then have 3kbp sized inlets. Exhaust ports on the other hand are quite a bit larger than 4/5k. The 7ke also has fatter manifold bolts/studs too.

 

http://www.rollaclub.com/board/topic/23452-exhaust-port-size-differences/page__p__273324__hl__port__fromsearch__1

Edited December 1, 2010 by Taz_Rx

[Hiro Protagonist]

Just for weight loss. Oil level is well below crank.

 

You can still get windage though, especially at high rpm...

[Jonty111]

Anyone have any recommendations on where to get yours hands on stronger conrods. I hear you can use the ones out of a 5k but i have no idea where to start looking for such a particular part

Edited October 9, 2012 by Jonty111

[Jonty111]

then i checked ebay lol my bad

[Gavclassic]

My 7k in my KE17 is used for motorsport, standard pistons, rods, crank etc. All balanced and lightened, bigger valves and a port job and fed by twin 40mm Webers, dynoed at 105hp ATW. I only rev it to about 6500 but thats plenty because its all torque in just 800kgs of car. You wont find any off the shelf set of extractors to suit, the pipe diameter is to small for 1800cc, my extractors and system was about $2000, engine build not including accessories $3500 and all running through a K50 5 speed with standard clutch and original KE17 diff with LSD. Apart from cracking the extension housing twice the car has been bullet proof since it was buit 4 years ago. This was a fairly mild rebuid according to my engine builder because i still like to use the car for Motokhanas and car runs with the club. My next 7k will be more aggressive and will also run twin 45mm Webers but will be in a Toyota 700 which is about 120kgs lighter than my KE17 Sprinter.