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On Probation
Location:
North East NSW
Registered:
December 2002
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3k / 4k block strength
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Sat, 04 January 2003 09:09
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hi there,
i'm building a tough and reliable street 4K to go in my KE35 hardtop. twin dellorto 40s, bigport head, 3core and thermo fan, electronic ignition, 60 thou pistons, balanced everything, 5 speed, ae86 front struts, ae86 rear shocks, borg warner 6" diff & custom leaf pack, still need to research the cam i'll be using, aiming for low rev torque and a sub-7000rpm power peak
i'd like to go 160 thou tosco pistons but for street lastability i'd want to wet sleeve it and run dry sump but i am on a budget
anyway, in my garage i have two 4k blocks (one good, one not so) and a saveable 3k. i know you can fit a 4k crank and rods in a 3k if you try, and they are the same bore and deck height so it all fits
i've heard rumors that the 3k block is stronger than the 4k, and was wondering if anyone could confirm or deny this? i suspect bill sherwood would know.
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Location:
Vic
Registered:
May 2002
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Re: 3k / 4k block strength
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Sat, 04 January 2003 12:19
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Of all the k blocks ive gone through only 1 has cracked. It was a 4k and it cracked between the 1st 2 welsch plugs under the manifolds. This 4k had no ribbing between the plugs.
All 3k's ive seen have the ribbing between the plugs but only some of the 4k's do.
I'll check my ke70 tomorrow to find out if the standard 4k has the ribs or not.
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On Probation
Location:
North East NSW
Registered:
December 2002
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Re: 3k / 4k block strength
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Sat, 04 January 2003 12:38
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wow, well spotted!
one of my 4Ks (engine number beginning 00, i assume its an early one) has no ribs, this has previously been 40 thou with a bigport. it came to me with a blown head gasket tho i think from heat (dark chocolate colored bores)
the other 4k (engine number beginning 903, i have access to the vehicle its orignally from, i will check date) has the sydney harbor bridge between the casting plugs like my 3k does
thanks heaps for the tip man!!!
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: 3k / 4k block strength
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Sat, 04 January 2003 17:03
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I was going to say the 3K is a much stronger block than the 4K, but I didn't know that there was a 4K block with the extra ribbing - It may well be as strong as a 3K.
Everyone that's tried a 4K block in the Sports 1300 class has had them crack in the place Bmak wrote.
I guess you could make a rough check to see if an extra-ribbed 4K block is about as strong as a 3K by measuring the weight of the two.
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I supported Toymods
Location:
Perth, Western Australia
Registered:
December 2002
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Re: 3k / 4k block strength
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Sat, 04 January 2003 17:27
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So I have competition hey?! Yep, I'm about to start pulling motors down to source parts. I plan on using a 4K crank and rods in a 3K block (more for CAMS hmologation than block selection). The build will also include a decent oil pump and "winged sump", big port head, current cam that has been used to good effect, twin 40mm Webers, headers, and electronic ignition regraphed to suit. My bore will be 120" over to give me the "as close to 1400cc as possible", at 1397cc.
At this stage we are going to start cutting costs, one because we can't afford the right procedures at the moment, and two: we don't really know where the standard reconditioned motor needs reinforcment (ie, at what stage does shotpeening become effective insurance?). So if anyone has real experience in 3/4/5K motors and their week and strong points, don't be shy! Also looking for a piston with a bore width to suit the recond block at 78.048mm, either in standard form or that requires minor modification?
Jamie, keep in touch and we'll info share!
Clint!
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Location:
1st street on the right
Registered:
November 2002
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Re: 3k / 4k block strength
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Sat, 04 January 2003 22:11
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I used to run a ke20. started out with 3 the 4k. neither had any probs but migrated onto 5k. This didnt last long after we got 112 hp out of it, but since it only weighed 650 kg boy did it go. I think we used a fiat piston that had a recess for valve clearance. this was needed as the cam posts were shaved to open the valves further as well as the larger cam.
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Location:
Vic
Registered:
May 2002
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Re: 3k / 4k block strength
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Sat, 04 January 2003 22:43
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Clint: check out the oldcorollas club on yahoo http://groups.yahoo.com/group/oldcorollas
You will find that k motors can take a fair bit in standard form without throwing anything out the side.
My race car currently has a back up motor in it while my good motor gets a rebuild. This motor is a standard 3K apart from the cam & induction etc. I constantly rev this motor to 8000 without any problems & have done so for 4 races so far & plan another 2.
I have done this many times over the years and only found the main problem to be the standard piston skirts cracking but the motors never blew up.
When i supercharged a 5K i also had no problems & that bottom end was standard. this motor ran 15psi up to 8000rpm without problems. This 5K also had the ribbing between welsch plugs.(it was imported, dont know if aussie 5K's have the ribs)
I dont think you will have any problems with a K motor if the revs are kept under 8000, maybe 7500 to be real safe.
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On Probation
Location:
North East NSW
Registered:
December 2002
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Re: 3k / 4k block strength
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Sun, 05 January 2003 00:08
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oh this is excellent!
bill, i dont think the ribbed 4k has extra ribbing, just that there is a 4k with no ribbing, and then one that looks identical to 3k ribbing (there are slight differences, mostly around the crank area because its wider). i'll get some bellhousing bolts and get the 3k on the engine stand, strip it down and weigh them both as bare crankcases. thanks for the tip 
clint, we will definately stay in touch! check out the yahoo group as brad suggested. if you have dyno2000, i just uploaded a heap of cams to the Files/Dyno secion (it might not be accurate but its a better indication than guessing). where are you getting 120 thous from? (ps: did you get the money for that manifold yet?)
adding to brad's post, i've heard that any K motor, doesnt matter what its had done to it, joins the big engine bay in the sky pretty quickly if you rev it over 9000 on a regular basis. the original rods seem pretty tough, i've heard 350 chev rods drop straight in, dont know if this is 3k or 4k length tho
thanks for the help guys
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Location:
Vic
Registered:
May 2002
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Re: 3k / 4k block strength
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Sun, 05 January 2003 10:21
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I checked out my KE70 today & it has a ribbed block. This is the very last of the KE70's (84 model) so it must be the early 4k's that didnt have the ribbing.
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