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Thread: Guide: How to build a K series motor

  1. #1
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Guide: How to build a K series motor

    Because this topic comes up again and again, typically for people who are just starting to get into car modifying.. 'cos lets face it, corollas are the bottom of the pile

    so you want to build a K motor??

    the different blocks are K, 3K, 4K, 5K and 7K.

    I will focus on 3K/4K with a little on 5K's


    ---3K and 4K have same size pistons (75mm) !! if you have the original Repco/Toyota pistons, ditch them for ACL brand or better. cheap in 20, 40 or 60 thou oversize.
    some 4K pistons are dished. all 5K pistons are dished. 5K has bore of 80.5mm.

    ---4K has longer stroke (73mm) than 3K (67mm?). 4K also has taller deck height than 3K by about 10mm.

    --- 4K crank is IDENTICAL to 5K crank. 5K block is same deck height as 4K, but bigger bores. Apparently 3K and 4K blocks can be bored by 3-4mm, but you may be taking your chances due to core movement during casting.

    So lets start with a 4K block.... we bore it out 40thou for new ACL pistons, then what...
    starting from the bottom.

    in a budget build, chances are you won't want to do anything to the sump... a crank scraper or a windage tray would be a good idea tho.

    oil pumps. there are 2 or 3 different types. early type had a bolt on pickup, later types have the pickup as part of the lower housing (the bit that keeps the gears in).

    K series oil pump gears are SAME diameter as T and R series pumps!!! most T series have the SAME HEIGHT as K series, so they are no improvement. R series (and possibly 3TGTE) pumps have taller gears, and are possibilities for making a high flow pump for a K series..

    you can increase oil pressure a bit by putting a 2 or 3mm spacer behind the pressure relief valve spring )that hangs off the side of the PUMP.. not the oil filter )

    Cranks are fairly well balanced from factory, but if you are going to high rpm often, you may want to have it checked.

    Rods are not too bad. DEFINITELY have them checked for balance, they may be a long way out. Replace rod bolts with either new toyota ones, or something a bit more heavy duty. check balance end to end, and also total weight.

    pistons, as before.. check balance of pistons plus pins.

    Cylinder heads.
    from K to 4K (non-dished) the difference is mainly in the combustion chamber sizes and intake ports. exhaust ports seem to be pretty much the same across the board.. all too small. for intake ports, there are some tiny 25mm diameter ones... normal size is 27mm diameter and the bigports are 30mm diameter. i honestly don't think there is much benefit to going to a bigport head on a street driven motor...

    but anyway, bigports are available from K engines (22010) or from early 3K engines (24010). they can both be identified by the welch plug at the back of the head instead of a bolted on plate. it's a good idea to have this hole covered with an alloy plate and TIG'd so it will never leak.

    if you are building a 4K, then you will want a 3K head. simple reason is it has a 3ml smaller combustion chamber so you get a free increase in compression!!

    regardless of which head you get, port the walls and roof of the exhaust port, and clean up the bowl and short radius area. you can chamfer the new valve guides while you are there and shape the bosses in the port.
    intake ports just need a clean up and blending of the bowl and short radius.

    combustion chamber. remove all sharp edges and DESHROUD THE VALVES. aim for maximum deshrouding at mid valve lift. stock is about 2mm gap... i like about 5mm gap all the way around the valve.

    camshaft. this all depends on what rpmrange you want your power band, and if you are using EFI or a carby. EFI will lower the rpm at which the cam comes on and broaden the effective rpm power band. 230/235@50 thou lift with 435thou lift is a Camtech 609 (adv 275/284)... a good cam that comes on around 3500-4000 and keeps going to about 8000,
    most people will want a little less.. sayyy, 220/225@50thou, but high lift is always good 430-450thou lift is abotu as far as you want to go perhaps.

    over about 400-420 thou lift will require new valve springs (CB4/CB4A from performancesprings in QLD, or FJ20 springs also fit). valve retainers will typically need to be slightly modified to widen the seat area for the inner spring if using dual springs.

    cam towers. early ones are alloy and are taller, whilst later (most of them) are cast iron/steel and they are a few mm shorter. the rocker shaft position is the same for both, but toyota changed to the cast iron to reduce changes in valve clearance with temp.
    just use the later ones...

    if you are using a cam with higher lift than stock (about 8.5mm) GET THE ROCKER TOWERS MACHINED DOWN BY THE INCREASE IN LIFT.
    ie, 11mm lift cam = 2.5mm off the rocker towers.
    this maintains original rocker geometry when they are loaded the most, and reduces both noise and wear... i can't recommend this enough.

    choose a rocker shaft that is not too worn. you can flip them over and use them upside down (make sure the oil holes line up) but if they are too worn, you will lose oil pressure from between the rockers and the shaft.. not good.
    there are slight differences in rockers between engines, but not enough to worry.

    valves, rockers, rocker shafts and rocke towers will change between the different heads.

    of special note is that early heads have a different retainer, as the valves have 2 grooves, one of which is for an oil control o-ring above the valve lock. these retainers severly limit potential valve lift increases, so if you want to run high lift, swap to single groove valves and retainers (and change guides to ones with a groove to accept valve stem seals.

    rocker cover. very early have no PCV fitting...

    head gasket. i use ONLY ACL monotorque BD950MT.. no point stuffing around with any cheapers ones

    timing chain. all early models have twin row chain. later 4K's have a single row. going to higher lift cam/heavier springs? use the twin row. you can buy new sprockets, chains and guides... it is a good idea to swap them all over at the same time.

    hmmm.. early engines use a different width ran belt, so check you have the right pulleys.

    there are a few different water pumps depending which heater hose routing was used.. get whichever suits your needs. they have different lengths of shaft ont he front, and also different bolt spacing for the fan, so be careful.

    early alternators are denso, 25amp... then later 30amp or so...
    get KE70 BOSCH alternator (need top and bottom brackets also). they are better, higher amperage, and you can swap the guts of ford falcon 60A alternators into them (with longer bolts and altered rear bracket). they are also internally regulated, so you justneed 3 wires instead of the original 7.

    fuel pump.. block it off and get a cheap elec pump..

    dizzy. early denso have "octane selector" good for modifying base timign easily. also adjustable for vac start and stop...
    later are not so adjustable and Bosch dizzies also have larger cap.

    sparkplugs. NGK BP5EY or BP5ES. for modded motor, BP6EY is a good start. you couldn't need to go colder.

    ummm.. exhaust manifolds. 4-2-1 pipe sizes about 37-43-50, lengths 45-45-90cm before first resonator. 2" pipe, biggest chamber reverse flow muffler at the back in 2" will be plenty and still quiet.. cannons suck

    intake... early straight runner and later curved runner manifolds both suck as they go down to maybe 25mm internally. they can both be used, and require an adaptor to bolt up to weber carbs.

    the 32/26 ford weber is a BAD choice. the chokes are too big.
    go for something like a euro weber (Fiat etc) with a primary choke around 22-24mm and secondary choke around 27mm. a 34DMS is a good start, but maybe a little big (24mm choke)

    if possible, go EFI using a 4KE or 7KE manifold they are MUCH better than the downdraught manifolds, and control it with a cheap Megasquirt. Thats another story.

    what else...
    early motors have tiny clutch. later models have bigger clutch.. use that... all the flywheels are pretty similar and heavy.. resist the temptation to lighten the stocker and go for an aftermarket alloy or steel one.

    so endeth part 1 of the K lesson ;

    Cya, Stewart
    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

    AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!

  2. #2
    Forum Member Grease Monkey bbaacchhyy's Avatar
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    Default Re: Guide: How to build a K series motor

    keh ?






    I didn't read it all, but seems very informative
    '84 MA61 with 7M-GTE
    Now 5sp, 5 stud,17x8" Ray's, big assed brakes and decent IC
    Better turbo in the wings as well as MAFT !!!!

  3. #3
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Guide: How to build a K series motor

    regarding the difference between early (K and 3K bigport) and late (everything else) Valves and Valve Retainers.

    The 3K BP has a taller retainer, so can't have as much lift, can't run dual springs, and has an O-ring seal. Consequently, the 3K valve has TWO GROOVES, and can't be used with the 4K retainer (well it can, but it doesn't help you.. it just reduces spring bind height). there is no valve stem seal, instead the top valve groove has an O-ring that seals between the retainer and the valve stem. The valve guide has no groove to locate a seal even if you put it on there.

    The 4K's have a thinner retainer, which can run higher lift and dual springs. The valves also have a single groove (for the lock). The dual groove retainer can't be used with the single groove valves, as the rocker will foul on the retainer. There is a valve stem seal on the valve guide, and the valve guide has grooves to locate the seal.

    AFAIK, the valve locks are identical betweeen models.

    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

    AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!

  4. #4
    Junior Member Backyard Mechanic Hokey's Avatar
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    Default Re: Guide: How to build a K series motor

    So how much power would you get from say a 4K with 3K head and all that head work with a webber? also what fails in these engines when you apply forced induction? as in what is the weak link?
    Cheers

  5. #5
    Emo Slayer Backyard Mechanic rollin_stock's Avatar
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    Default Re: Guide: How to build a K series motor

    Oldcorollas, im using a standard 5k engine, just getting dellortos running on this, have them jetted for quite a heavy cam.
    Ive got a 3k head that im going to use once i have selected a cam, im going to convert to solid lifters using 3k p/rods and 4k rocker gear. What pistons would you use, i want to bore oversize if i can to get more cc's and they need to be flat top so i keep comp ratio up? im looking at running pulp, (98octne)?

    Cheers

    Also has anyone modded a sump for a k? Got some pics?
    I want to baffle around the pickup using hinged doors, also want to incorporate a windage tray somehow?

  6. #6
    Junior Member Grease Monkey ira11y's Avatar
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    Default Re: Guide: How to build a K series motor

    nice little tech.... you desrerve some fully wikid sick rep brotha!
    Cheers Michael
    Opinions are like assholes, everybodys got one.

  7. #7
    Olde ****** Automotive Encyclopaedia ToDa30/4's Avatar
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    Default Re: Guide: How to build a K series motor

    Great thread ! i have a 3K-H motor 102,000 orig KMS. on it.i want to do an old skool type mod to it ,i have a set of extractors for it ,and am thinking of a mild cam and better 2 barrel carby ,also a clutch upgrade . i want to use the healthy 3k for a while and take my time to build up a tougher 4K block with hi comp pistons, balanced bottom end & lighter flywheel & fit the 3K head to it . ..OK

    cam what specs & mods required & where to buy

    the carby's u suggest do u have part #'s ,do i use adapter plate or after markt . manifold, is a single side draft any good

    with the clutch are 3K & 4K the same preasure plate , ie .get a hvy dty 4K p/p with a bigger clutch plate .

    want to keep cable clutch . 4 speed & bw rear end at this stage. cheers for any help.
    Project ST215W 300 AWKW Killerwagg'ss .staring in the garage .soon
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  8. #8
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Guide: How to build a K series motor

    wow, people replied to this thread

    Hokey, with my 4K/3K motor running pig as rich, it made something like 47rwkw at about 7500 or 8000 rpm.
    with the EFI, it made the same power at 6000rpm and made a low more below too... with fixed 20deg ignition (doh!!) i hope to tune it properly and dyno it with the EFI when i get back.. just to see what it makes

    forced induction? at a guess, i would suggest the pistons are the weakest link (after tuning ) the rods and crank are beefy, there is not much else to fail (except the block)... the stock repco pistons suck. the ACL are better, but for serious work, some short skirt, more solid (ie forged) pistons might be the go.

    rollin stock, i'me not sure in 5K pistons. i know some people have had flat tops, but i never found out what they were from.

    for a 3K head, perhaps you could look to using 4AG pistons. heck, even the late model GZE pistons could be quite good. this is one thing i would like to look into later

    as for sumps... find pics of good race wet sumps...and copy


    Toda... ummmm define mild something with maybe 250-260deg adv duration and about 400thou lift would be nice. i'm a fan of more lift, but for ease of use, keep it under about 0.420" and it should be ok. depending on what rpm you want, replacement single springs (CB4/ CB4A) from sponsor www.performancesprings.com.au would be good.
    i used regrinds from camtech. i had no probs with them and would recommend them. they were helpful in choosing cam profile.
    for low lift, no mods required. for high lift, if you have original bigport head, with the yuck retainers as pictured above (and double groove valve stems), you may need to swap to later valves and retainers to get the extra lift. if you want dual valve springs it is required. the early retainers will not work with dual springs.

    carby, i had a weber 34DMS from a 1973?74? Fiat 124 sports. i think that it was only available for 1 or 2 years but any of the webers with a primary around 22-24mm should be ok if jetted correctly. 26mm primary is a bit big for a small motor. good for 2L but not for 1.2 or 1.3.
    adaptor is a redline part. i think it is the same as a gemeni adaptor?? i can't recall the part number atm, but it should still be available.
    there is early and late clutch. early is smaller and differetn design. most later 3K and 4k are same design. i like the RPM clutches for weight and use, but the if there is an EXEDY available, i think i will try that next, as some of them seem to be better made.... and i had a PBR friction plate fail on me ..
    larger clutch goes with different flywheel. i think the early small one was restricted to the KE10 and KE20 models.
    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

    AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!

  9. #9
    Olde ****** Automotive Encyclopaedia ToDa30/4's Avatar
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    Default Re: Guide: How to build a K series motor

    Cheers Doc. very helpfull ,an address for redline & camtech perhaps?,any opinion on extreme clutches as their local to me .im going to do this build with my son the KE30 will be his 1st. car,reckon the 250/260 cam would be the go, just want a street car that he can try and drift ,and zap around mallala on occasion. i will be back to pick ur brains again ,I'll rep u up for ur help as if u need it thanks again
    Project ST215W 300 AWKW Killerwagg'ss .staring in the garage .soon
    ST185R 385 AWKW now SOLD ..Daily '89 Eunos Roadster.
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  10. #10
    Junior Member Domestic Engineer myne's Avatar
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    Default Re: Guide: How to build a K series motor

    If anyone in SA wants spare motors, I know of atleast 4 laying around behind my mechanic's shed. Dont think he'd want much for em.

  11. #11
    Olde ****** Automotive Encyclopaedia ToDa30/4's Avatar
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    Default Re: Guide: How to build a K series motor

    mmmm! which series K motor? 4K be nice,where is he located in adelaide
    Project ST215W 300 AWKW Killerwagg'ss .staring in the garage .soon
    ST185R 385 AWKW now SOLD ..Daily '89 Eunos Roadster.
    Project '75 KE30 37.4 RwKw PIMPster. doing it for Angela RIP 1964 - 2011

  12. #12
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Guide: How to build a K series motor

    250-260 would be good for street motor. mine was 275/284 435thou (609 regrind), with the EFI it would come on strong at 3500, but a bit lower would have been nice. there was enough top end.
    http://www.camtechcams.com.au/
    http://www.camtechcams.com.au/Page0065.htm
    the 621 looks good.

    nope, no idea on extreme clutches.. sorry.
    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

    AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!

  13. #13
    Olde ****** Automotive Encyclopaedia ToDa30/4's Avatar
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    Default Re: Guide: How to build a K series motor

    WOW cheers for that # 261 2500 to 6500 range .i reckon is the go.thanks again
    Project ST215W 300 AWKW Killerwagg'ss .staring in the garage .soon
    ST185R 385 AWKW now SOLD ..Daily '89 Eunos Roadster.
    Project '75 KE30 37.4 RwKw PIMPster. doing it for Angela RIP 1964 - 2011

  14. #14
    Junior Member Domestic Engineer myne's Avatar
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    Default Re: Guide: How to build a K series motor

    Quote Originally Posted by ToDa30/4
    mmmm! which series K motor? 4K be nice,where is he located in adelaide
    Personal messaged

  15. #15
    Olde ****** Automotive Encyclopaedia ToDa30/4's Avatar
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    Default Re: Guide: How to build a K series motor

    where can i get ACL parts ,cheers dave
    Project ST215W 300 AWKW Killerwagg'ss .staring in the garage .soon
    ST185R 385 AWKW now SOLD ..Daily '89 Eunos Roadster.
    Project '75 KE30 37.4 RwKw PIMPster. doing it for Angela RIP 1964 - 2011

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