Hi guys, ive got a nice SPFI EJ18 in my car at the moment. It has the SOHC 16 valve heads on it. I also have whats left of an EJ20TT in the garage taking up space.

 

Now i was wondering.....what exactly would happen if i shoved my EJ18 heads onto the EJ20 block? Would i get a high compression n/a monster, or a valve bending pos?

Can anyone give me some compression ratios from their FSM's?

 

I want to keep it SPFI for now so i would swap over the intake too, i like how simple things are when you havnt got 4 injectors to worry about. And the new sedan is fwd - so theres no point in adding turbos to the equation.

 

Finally in case nobody knows or can figure out if this is do-able, is the EJ18 an interference motor? Mine is an 89' motor and as said has the weird heads on it.

Edit: Just wanted to add, both motors are JDM spec

i don't know what you guys got over there, but in the US no EJ's were interference before 1996. no EJ18's that i've heard of were interference, so i'd expect yours to be non-interference.

 

there are threads about swapping heads on turbo motors and NASIOC may be a good place to search too.

We don't get the same engines you guys do here in the US. You get both genuine Kiwi imports and JDM products, some specs are hard to come by for us.

I am convinced the average Kiwi shop can make anything fit anything.

We don't get the same engines you guys do here in the US. You get both genuine Kiwi imports and JDM products, some specs are hard to come by for us.

I am convinced the average Kiwi shop can make anything fit anything.

Sheep and wellies come to mind....

Hmm might just go get another EJ18 for cheap and bolt this thing together and see what happens. If it goes i'll be a hero - and if it blows up it should be fun anyways.

The piston crowns will be different between the two engines. I also doubt that the EJ18 combustion chambers are small enough to add adequate compression for NA use. But the only way to know for sure is to measure the cc's of the chambers and piston dishes for both engines.

Ok i want to modify my last statement a bit, instead of just doing it - i think i'll take the heads off my EJ20 and compare them to some EJ18 heads.

 

From what i remember the compression ratio on a EJ20TT is about 9.2, so even running that as n/a shouldnt be too bad. If i can get the heads milled to bump that number up - all the better! But first is to take things apart and see what an engine thats suffered total cambelt failure looks like on the inside.