higher compression ratio.

[FP3065TSI]

Currently I am building a new engine with a Ross/manley combo with a 8.5:1 CR. My question is this: . Would I be able to use a thinner HG to accomplish this? Or would I have to deck the block? I would like to make my compression ratio a little higher(9:1).

 

[cruisintalonawd]

to raise it that much i would think you'd have to get the right pistons

 

[TOONAH]

Yes, you can increase your CR by reducing the HG thickness or by taking a few thous off the head and/or block deck. But you run the risk of valve to piston contact. These are 'Interference' motors. I agree with cruisintalonawd, Get the right pistons. If you do increase the compression ratio to 9:1 you will need to use an MLS/Cometic HG. You will also have to use 97 octane or better gasoline. You will want to do some tuning to the AFR to avoid excessive knock. But its all do-able!

 

[talon187]

get 9.1 pistions. you can run 93 octane and be ok. the only thing is you will have to run less boost and watch for knock like stated above. you will need a good tunning device with the high compression. what are your goals and what turbo do you plan on using ?

 

[thilaksharma]

another way tht we use over here in asia would be
to fit in a 4g67 big port head , the ports are same as the 1G , but the
combustion chamber is smaller thus increasing ## compression,
## compression would be bout 8.9~:1

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

 

[talon187]

so your telling me the 1.8l head has the same port size and would bolt up to a turbo block? hrmm this is instresting. maybe ill try that.. im thinking of build a 6 bolt 2.4 motor from an older hyndia with 9.1cr pistons

 

[cruisintalonawd]

I pretty sure all the 1.8 are SOHC though, but I may be wrong

 

[thilaksharma]

4g67 Dohc

 

[jrohner]

There are 1.8 and 1.6's in hyundai elantras that look exactly like the 4g63. I used a 1.8 Hyundai head on my 1g to gain a little compression and it worked great.

 

[talon187]

maybe ill use the 1.8 head i have that way im still dohc because i want to run 272s only thing is it needs new guides and some intake and exhaust valuves