Upping compression on a 16v 4age

[blackmk3]

A mate of mine has a 4age in a ee90 corolla, which has since spun a big end bearing so hes going to rebuild the motor

however he is wondering if pistons from a 20v would fit in the 16V and connect to the 16V rods just to give it a bit more compression?

(puts on search flame suit) i couldnt find any posts giving me a direct answer

Thanks
Nick

[ChaosAD]

if its a bluetop then no. Just plane a bit off the head and use a trd head gasket.

[rollaholic]

the 20v pistons also have recesses for 5 valves, and they'll be in the wrong position for 16 valve heads

not sure if this will cause valves to strike pistons, but remember smallports are 10.3 compression ratio anyway - probably easier to use a TRD head gasket and / or plane the head a touch.

how high was he wanting to go?

[blackmk3]

Yeah it is a bluetop tvis

Sweet thanks for that info guys

He wasnt looking for a certain compression ratio just purely wanted a bit more wack to it since the motors going to be apart anyway

Looks like a TRD gasket will be the go

Thanks heaps
Nick

[MacrosSiR]

he might need adjustable cam gears if he goes for a thinner gasket

[rollaholic]

if its a bluetop then i reckon a smallport swap would be the way to go probably cheaper than a rebuild too

[Caveman]

he might need adjustable cam gears if he goes for a thinner gasket

Yep you will need adjustable cam gears with a skim or tinner gasket (or both). Timing goes out quite a bit, dont have numbers but it was significant. The adjustable cam gears are about $150 each.

[ee904age]

I had silvertop pistons and rods in a bigport redtop I rebuilt. They fit, the engine turns over with head etc on but hits if cam timing is out. So it becomes an interference engine.

[rollaholic]

i believe the gudegeon pins and big end bearing sizes changed from 18 / 40mm to 20 / 42mm respectively on the smallport onwards, so fitting 20v pistons to an older engine would mean using complete silvertop internals

[ChaosAD]

bigport redtop

Its just the bluetop thats different.Redtop rods are heavier/stronger than silvertop but cranks the same

[matt dunn]

i believe the gudegeon pins and big end bearing sizes changed from 18 / 40mm to 20 / 42mm respectively on the smallport onwards, so fitting 20v pistons to an older engine would mean using complete silvertop internals

Much earlier than that.

The early bluetop had the 18mm pin and 40mm crank,
and everything else from then on has the 20mm pin and 42mm crank.

[3T-Rona]

all i did was get a 20v(silvertop) from a wrecker mate, whip off the head, and crap (water pump, alt) and clean it all up and slap on my 16v head (all new gaskets and shit) so it still has 20v pistons and rods, goes fine, maybe even 'mean' loses traction often enough to get me in trouble although i do have nana bickey wheels....