Anyone know what comp a 1.8 hyundai head will put a 4g64 at?

carguyf545 · Post by **carguyf545** » Thu Jul 05, 2007 11:44 pm

they should be the same. i have a 1.8 head and i have looked at the two side by side. they look the same.
my n/a had 240 p.s.i of compression. it was a chore to turn it over with the spark plugs in.

89coltgt · Post by **89coltgt** » Fri Jul 06, 2007 2:48 am

The 1.8 head has a slightly smaller combustion chamber volume, so it will raise the compression.

carguyf545 · Post by **carguyf545** » Tue Jul 10, 2007 12:01 am

im pretty sure the ports are the same.

i all most threw out my elbow tring to turn it over with the plugs in.

89coltgt · Post by **89coltgt** » Tue Jul 10, 2007 3:57 am

The port sizes are the same between the 4g67 and 4g63, but the '67 has a slightly smaller combustion chamber, in fact it's the same size as the 4g61 head. The head is a popular upgrade for the 4g61t guys, they keep the same comp ratio but have larger ports.

jeffball610 · Post by **jeffball610** » Tue Jul 10, 2007 4:41 pm

I hope the ports aren't the same size as 1G 4G63 heads. The 1G ports are huge. That's why a lot of people put 1G heads on their 2G motors, so they can pick up some power on the top end where big ports are better. In a NA motor, you want smaller ports to keep air velocity high. If the 1.6L head has smaller ports, but the same size combustion chamber, then I'd go with the 1.6L for an NA motor. If you're going turbo, there's no reason to use any head other than a 1G 4G63 or a well ported 2G head. Since the subject of this thread was compression for the head change, then we need to measure combustion chamber size and port size. If I get a chance, I'll see if I can get a 1.6L and 1.8L heads. I get them for about $40 a piece, so it's not a huge investment for research purposes. Unless someone has these already and can measure them.

Post by **DJpowerHaus** » Tue Jul 10, 2007 9:26 pm

I'd love to see someone make a 11,000rpm high compression NA 2.1L engine. Sure would save the hassle of all this turbo crap.

89coltgt · Post by **89coltgt** » Wed Jul 11, 2007 3:56 am

The combustion chamber volumes were discussed on 4g61t.org in the past, lemme see if I can dig that info up.

89coltgt · Post by **89coltgt** » Wed Jul 11, 2007 4:36 am

Here we go:

http://forum.4g61t.org/viewtopic.php?hi ... 67&t=14041

Post by **DJpowerHaus** » Wed Jul 11, 2007 6:12 pm

From that thread:

casting marking "16" head:
- came stock on the 4G61 (1.6L)
- has a 43 ccm combustion chamber
- uses smaller ports (in comparison to a "20" head)

casting marking "18" head:
- came stock on the 4G67 (1.8L) and some JDM 4G61
- has a 43 ccm combustion chamber
- uses lagerer ports (like the "20" head)

casting marking "20" head:
- came stock on the 4G63 (2.0L)
- has a 47 ccm combustion chamber
- uses large ports

The "4" or "5" below the casting marking is some sort of revision. It's function is unknown.

Edit: volumes are approximations.