na 4g63 head same as turbo?

92_civic · Post by **92_civic** » Fri Jan 04, 2008 2:38 pm

sorry for what I am sure is another noob question, but I just came across a couple of NA 4g63 heads, and was wondering if they were the same as the turbo head? also I remember reading something about 1g and 2g heads, is one better than the other? and what was the year break for the 1g and 2g if the 2g really is better?

thanks in advance for the answers guys, I really appreciate it

Post by **DJpowerHaus** » Fri Jan 04, 2008 4:21 pm

There are a few heads out there.

The DOHC heads had a few variations. We call them "16" / "18" / "20" based on a casting mark on the back of the head not necessarily what you'll find them on (The 2.4 DOHC had a 18 head).

The 16 is a high compression small port head.
The 18 is a high compression large port head.
The 20 from a 1G (pre 93.5) is a low compression large port head.
The 20 from a 2G (post 93.5) is a low compression small port head.

To answer your question, the 2.0L head turbo or non turbo should be the same. The best way to check is to check the casting mark on the back of the head though.

If anybody has any more information on the heads feel free to add it or correct me. I need pictures too and displacements of the heads so that I can add this info to the site (which I'm updating this month)

92_civic · Post by **92_civic** » Fri Jan 04, 2008 10:45 pm

thanks for the reply DJ, are any of these heads better or preferred? I could have sworn the newer heads had some type of valvetrain improvement, but I can't find where I read that now

Post by **DJpowerHaus** » Sat Jan 05, 2008 1:12 pm

Depends on what you are doing. Non-turbo you'd probably want a 16 high comp head. I can't imagine non-turbo ever needing anything more than a ported small port head. High horsepower and turbo you'd probably want a 20 low compression large port head although there are some with the opinion that a smartly ported small port head can flow better (more material to work with). Not sure what the best application would be for an 18 head.

I don't think the valvetrain changed at least between the 1G and 2G heads other than a little bit better hydraulic lifters.

The later Evo style heads probably have some nice improvements, but I'm not sure about all the details. They have lighter forged rockers which we can use in our heads. There is the MIVEC too, but I dont know shit about it. The old Starion FSM had pages of theory and explanations. I'd hope the newer manuals carry on this tradition. If anybody has any technical documentation I'd love to read it.

slowquest · Post by **slowquest** » Sat Jan 05, 2008 2:35 pm

Got an address? I'll send you copies of everything Mitsu gave us techs.

Post by **DJpowerHaus** » Sat Jan 05, 2008 8:01 pm

Thanks for the info. I'll read up on this stuff.

Edit. Okay. That was neat. The SOHC MIVEC stuff is so weird. Can't wait to see the DOHC MIVEC manuals.