Hot 4K Engine Rebuild

[shiryo]

Hey guys,

 

don't know if I should put this in here or Regional section, but I felt more fitting to here.

I'm looking at getting my 4k rebuilt soon, not only for reliability but for a bit more zip.

 

I have a basic understanding of what I would like done to it, however I was wondering if anyone can point me in the right direction with regards engine builders that have had experience doing a hot little 4k, or who perhaps specialise in them within the Melbourne metro region.

 

If those could share experiences / recommendations that'd be great.

Thanks in advance.

[kickn5k]

How much coin are you wanting to spend?

I'll send a pm with my contact deets when I get home, and we can have a chat.

 

Stu.

Edited August 29, 2013 by kickn5k

[altezzaclub]

What carb setup are you planning?? Single DCOE, twins, 32/36 d'draught, Mukini quads?? Get that sorted and build the motor around that.

 

Cams are easy to find, extractors also, so just bore it as big as you can and skim the head for some higher compression. Get used to the cost of 98octane going up and up if you raise it very much!

 

kickn5K should have the engineering for you, but let us know what you do and how it goes.

[shiryo]

Yeh awesome, cheers.

 

I'd like to run a mild cam, something that has a nice lumpy idle that won't be annoying for a daily drive, along with either bikecarbs or twin sidedraft webers, extractors and exhaust. Aside from that, I guess just a standard rebuild/freshen up.

 

I'm able to get a 4k ACL complete engine rebuild kit for $260 so that's not bad, it's just the rest that adds up quick...

[altezzaclub]

If you drive around town a lot, get a cam under 275deg and bike carbs or SUs, they will give you better zip low down. Webers with small chokes would do that too.

 

If you are out in the 100kph and want top end take the cam up to 280deg or so and run a DCOE Weber or two to make it work at the 6000rpm end.

 

I've got inch and 1/4 SUs, smaller than most guys who use inch & 1/2, and a Crow 606 cam that's 270deg. This makes it go from 2000rpm and I only take it up to 5000, but I wanted the better mid-range rather than the top end. It cruises at 100kph and overtakes fine with the extractors and head job, & a lightened flywheel. The build thread is here-

 

http://www.rollaclub.com/board/topic/42407-the-girls-ke70/

 

Next time I'll bore it out as much as I can and go for bike carbs to see what the difference is. I'd like to lighten the crank too.

 

The cam will cost $150-$200, get the followers ground too.

Extractors are $215, a new exhaust to finish it will be several hundred. Mine is 2" then inch & 3/4.

Carbs & manifold a few hundrd to a thousand dollars. One guy on here is keen to make mo'bike manifolds for us.

Lighten the flywheel $100. Lightening the crank probably more.

Then balance the whole bottom end for about $150.

Get the valves cleaned up, port the head to match the manifold & skim it 20thou

 

Go have fun...

Edited September 3, 2013 by altezzaclub

[Warehouse_XIII]

Mate, I just got a bunch of work done on my 4k, I will post more details soon but a quick run down is as follows.

 

- Over bored 40thou, new ACL pistons and rings to suit

- Crow 606 cam (lifters faced as well)

- Block decked

- Head skimmed

- Lightened fly

- Crank linished

- New main bearing set

- New cam bearings (only thing the engine builder installed for me)

- Full balance

- Holley 180, the webber licensed 32/36 replica, completely stripped and built up as new (yeah I know side draft is better, this one feel into my lap at a good price and is still a massive upgrade from stock)

- Everything chemi cleaned

- Reseated valves myself

 

I am sure I have missed a few things, obviously there are a bunch of small things like gasket sets, welch plugs etc that all got replaced as well.

I haven't keep a proper total of everything (easier to hide it from the wife that way) but so far I'd say it has cost me around the $1500 mark for all work and parts. That even includes a few new tools cause either I didn't have them (ring compressor) or my old ones broke during rebuild (torque wrench).

 

To save cash I stripped down and rebuilt everything myself, I have done it before as well on several other engines so was confident doing it. Even if it's your first engine build I suggest you have a go, they are easy engines to work on and the feeling you get driving it is so much better knowing you've done it all yourself.

 

Next week I will be taking it up to the exhaust shop around the corner to get a new set of extractors and exhaust put on, no idea on price yet but I know extractors are around the 300-350 mark.

Also I haven't done any major head work other than cleaning and re-seating the valves, I have ported the carb end of the intake mani though. I have a spare head and once I have time I am going to have a crack at porting it myslelf.

 

As far as driving it goes, I haven't taken it much above 3k revs, but far out she is toey down low. I have been driving with a gummy old spare 4k in it up to this point so anything is a massive improvement, but I can tell once she's all settled in and exhaust fitted my wife is going to have a hard time getting me out of it :-)

 

Hope that's of some help mate. If you can't afford everything straight up, I'd personally look at getting a decent carb and exhaust followed by a cam. Save the dollars up and then strip her down and get the extras done.

[altezzaclub]

I know extractors are around the 300-350 mark.

 

If they want over $250 for the usual blue Hurricane extractors PM me and I'll see what they are here in Orange.

[Warehouse_XIII]

If they want over $250 for the usual blue Hurricane extractors PM me and I'll see what they are here in Orange.

 

Sweet as mate, that would be awesome.

Should be taking her up to them for a quote on the system early next week. I'll send you a PM after that :thumbsup:

[mjmoo75]

If you drive around town a lot, get a cam under 275deg and bike carbs or SUs, they will give you better zip low down. Webers with small chokes would do that too.

 

If you are out in the 100kph and want top end take the cam up to 280deg or so and run a DCOE Weber or two to make it work at the 6000rpm end.

 

I've got inch and 1/4 SUs, smaller than most guys who use inch & 1/2, and a Crow 606 cam that's 270deg. This makes it go from 2000rpm and I only take it up to 5000, but I wanted the better mid-range rather than the top end. It cruises at 100kph and overtakes fine with the extractors and head job, & a lightened flywheel. The build thread is here-

 

http://www.rollaclub...the-girls-ke70/

 

Next time I'll bore it out as much as I can and go for bike carbs to see what the difference is. I'd like to lighten the crank too.

 

The cam will cost $150-$200, get the followers ground too.

Extractors are $215, a new exhaust to finish it will be several hundred. Mine is 2" then inch & 3/4.

Carbs & manifold a few hundrd to a thousand dollars. One guy on here is keen to make mo'bike manifolds for us.

Lighten the flywheel $100. Lightening the crank probably more.

Then balance the whole bottom end for about $150.

Get the valves cleaned up, port the head to match the manifold & skim it 20thou

 

Go have fun...

 

Hi there, did you get the work done locally?

 

I'm from Bathurst and looking to have some work done on a spare k4 I have.

[Andy43]

We just changed the crow 606 for a 740 in one of our 3k race motors, Seems to pull good to 8000 and is usable to 8500.

Don't forget to time the cam in, if you can run the engine in on a dyno do it, Lighten the flywheel and weigh the clutch, (they vary from 3.0kg to 4.5kg)

Get the dissy recurved and don't run the carby lean as nothing kill's a new motor faster than detonation.

Don't rev it with no load as you will destroy the ring sealing.

Cheers

[Andy43]

Also Keep a eye on eBay, new piston sets less than $100 and gaskit kits less than $100.

Just make sure the gaskit kit is for 4k as sump bolt patten and timing cover gaskit are a little different

[snot35]

Hey Andy, are you finding much difference between the 606 and the 740?

[altezzaclub]

Hi there, did you get the work done locally?

 

I did, but the engineer has since closed down and gone to work for the mine... I'm sure there's some hot builders in Bathurst, I'll ask Rob when I get back to Orange if you PM me in a week to remind me.

[Evan G]

i do have a lightened flywheel and extractors for sale (Y)

[Andy43]

I'd have a look at Evans flywheel, A few kg's of the flywheel makes heaps of difference.

Crow 606 vs 740 in 3k.

 

Don't get me wrong the 606 is a nice cam, On the Race track the 606 is very forgiving and is usable to 7000 rpm.

I am currently using this grind on my Daughters Speedway Car, Basic set up is 60 thou off a bigport head, 3kh carby with 21mm pri venturi and 24mm sec venturi. the exhaust is via a stock 2 outlet manafold and open 2inch exhaust.

 

The crow 740 has more duration in the exhaust than the inlet and I think this may be why this is such a awesome cam.

We gear for 6000rpm on corner exit and anything up to 8500 on entry, the 606 doesn't like the big revs however the 740 loves it.

Set up again is similar 60thou off head and a longer exhaust but this one is 3inch and heat wrapped, Carby is off the late model 3k 21mm pri 25mm mech secondry's

 

I'm also building a 4k for the street car its going to have the 740, downdraft Weber, ported bigport and extractors, I'm getting quite excited it fire it.

I'll give you a report in a few weeks on how street-able the cam is.

 

Other cams of interest.(3k)

Clive 161 the boys running the datsun 12A love this cam, I hate it, just not impressive with our set up.

Wade 446B Nice street cam pulls to 7000 usable to 7300, I do think the 606 or 740 are a better grind.

 

Anyway have a chat to the blokes a CROW they know there stuff and I'd go with there recommendation.