20v head on 16v bottom

[hillclimb86]

i have just had my bigport engine rebuilt 40thou oversive pistons by my mate who his a engine builder and he says that the bottom end is sold as i was going to put the 16v head on hiflowed and cams etc but the engineer said i would be wasting my money. can i now put a 20v head on or do i need to change the pistons. the 20v head willl be worked cams, polished, valves etc thanks

[Gilly]

20v pistons have cutouts to accomodate the valves so they can't contact the pistons in the case of a cambelt breaking, which would in turn bend a shite load of valves and hand you a hefty reco bill.

fitting 20v head to 16v block will work and has been done before (e.g speedtech's KE70 in NZ 20v head on a ze bottom end making 270rwkw's!!!!!!! turbo'd obviously) just means trouble if you snap a cam belt. this is basically like all motors, most manufacturers don't have non interference motors like toyota does.

edit changed example due to retarded post i put up earlier!!!!!

[Dxaqta]

josh youngs motor was a 20v block with a 16v head

[Gilly]

yeah it was too!!! god i'm a retard!! not used to staying up that late!!

[mattysshop]

if you have a smallport 16v head you won't be wasting your time.. a big port NA motor in my opinion wouldn't perform as well as a side by side built smallport motor, everything done the same.. i belive the smallport head will come out on top..smallport heads, and even to a degree bigport heads require very little porting.. mostly just some blending, and taking out rough cast spots etc.. polish the flats in the chamber, and do some decent valve springs, and some 280-290 with 8mm lift should give some good results.. especially if your running quads, or dual carbs..

my 2 c

[DRFT - 86]

4AGE, 7 rib block, ported smallport head, linished/rebalanced rods, Adaptronic ECU, raised compression, 20Valve quads, 110rwhp@6400rpm

Is that not the truth or what.................?

Mattysshop has the results to back his view up...........

[mattysshop]

i can can vouch for the smallport.. 110rwhp is awsome out of stock cams..

(made an extra few ponies with the sealed air box off.. ) with consistant mid 15's with slight room for improvment..

raised compression is only decking the head 20thou.. stocko gasket.. haven't bothered with the TRD metal one i have.. not untill the stocko one blows through..

[DRFT - 86]

yeh pretty damn good I would say.............. no question...

[biggo]

question for matty - was it worth it?

my stock 20v pulled 121hp @ 8000rpm and it was still making power!!

[mattysshop]

considering i out run 20V's in ae92/ae82 (haven't tried an AE86 20V yet..).... yes... very worth it....

also.. mine is a completly fresh motor.. rings bearings etc etc.. if i went down the 20v path i would have rebuilt it befor putting that in.. and with the (not so big now.. but once were) dramas of the dizzy, and water outlets.. made more sense to keep the best 16v incarnation..

my motor cost me $200 to buy..

then about $400 on the bottom end with me doing most of the work, or my mate Craig at extreme custom engineering..

the head was the expensive part.. it had to be straightened, then i ported it, then sent back to be shaved, new guides, stem seals etc (Barclays engineering trade) $580..

ACL VRS gasket kit ($88 trade)..

so thats the motor with no manifolds..

stock 20V, or full recoed 16V with some bits 'n' peices done to it along the way..

[biggo]

lol i neglected to mention quads, cos i root em everytime i turn the key!!

oh well, you would probably out run me anyway, i have an overly active autometer shitlight ( http://www.ae86drivingclub.com.au/forums/emoticons/tongue.gif ) and a poopy 3.7 locked center

[mattysshop]

run yours on the quater.. i wanna take mine down again in a few weeks.. see what she does..

[Gilly]

question for matty - was it worth it?

my stock 20v pulled 121hp @ 8000rpm and it was still making power!![/b]

Wezzo's Blacktop was a freak engine Biggo, it shat all over my silvertop!!! was an extremely low klms and auto, never saw a hard day in it's life until Matty put it in the KE70.

[biggo]

so it was, still gotta give that auto ecu a big F off and repair the damage seen elsewhere on the forums.

Come to think of it, i was extremely unprepared for the dyno run, as i mentioned the 8000rpm limit is my daily one, spare rims in boot, 15x8s on it and that crappy 3.7 ratio. there maybe another bee's dick of hp in it yet!

[biggo]

run yours on the quater.. i wanna take mine down again in a few weeks.. see what she does..[/b]

it will be done, ill let you know when im ready for a shot. Might be awhile tho http://www.ae86drivingclub.com.au/forums/emoticons/sad.gif

[hillclimb86]

thanks for imput ill take the risk with the cam belt snapping got silver top to day heads off going to get worked on monday