H75 vs H89 heads

all your DIY needs
Post Reply
Posts: 72
Joined: Tue Jun 30, 2009 8:00 pm
Location: Oamaru

H75 vs H89 heads

Post by agallagher » Mon Sep 05, 2011 6:35 pm

Im building up a new engine for the wagon,a14 with f12 cam and sidedrafts etc all off my old wagon
Its got a h75 head thats been ported but i was wondering if it would be beter fitting a h89 head to it instead since ive heard theyre
better performance wise,im not sure so your opinions and veiws whould be great!

Committee Members
Posts: 7303
Joined: Sat Jul 19, 2008 9:04 am
Location: Datsun City
Location: Christchurch New Zealand!!!!

Re: H75 vs H89 heads

Post by Bartman » Mon Sep 05, 2011 7:53 pm

The H75 head has an open chamber. The H89 is more closed. (Although not as closed as an A12 head, it has a deeper roof)
Depending how ported your H75 is, you'd be better off with the H89. It May be able to have the H75 skimmed down to make it closed chamber. (I once heard someone say it could be done) but this may lead to the compression being bumped up too high, or (Given that you're going to run a big cam) cause some valve to piston clearance issues.
They don't call me the man with the rubber arm for nothing you know.............

User avatar
Financial Member
Posts: 404
Joined: Fri Jan 13, 2012 6:58 pm
Location: Blenheim

Re: H75 vs H89 heads

Post by Tony_Whenua » Sun Feb 16, 2020 4:10 pm

I’ve got two engines in the shed I am working on. These are the plans for each.

1) A14 with H75 head. Original cam and dellortos.

2) A12 with H89, street cam, head planed & running dellortos.

I have a 3rd A12 with G25 head (stock one originally in Ute). Will likely sell on.

Have I done this right or should I switch heads over?
"Dude you're like 30 degrees retarded" - Chris_g1 & 2 Doors

Post Reply