Confused about the DOHC

[remarque]

I know this has been discussed a million times, but I keep getting different information the more I research. I dont have a 7G but I'm swapping a 4g64 into my 4G Mirage and later down the road I want to swap the SOHC to DOHC.

Heres my problem I read on DSMtuner that you cant swap any DOHC onto the 4g64 block because the pistons are different. now I see DOHCStunr selling his DOHC head and he is saying that its a direct swap. If the 94 GS head is the same as the 1G head how how come the guys at DSMtuner are saying the head want fit? Are the 94 GS piston different than the regular 4g64 pistion?

[mko]

Its a direct bolt on and pistons dont matter, but the 1g or 2g pistons will not fit 4g64 block - these are 85mm, ans ours are 86.5mm bore. There are some minor modifications to 4 of the block passages - need to be plugged, and youll need coil setup instead of distributor. Youll also have little higher compression than the SOHC head.

[remarque]

I knew about the compression and the passages. I just wanted to make sure that it would. Thanks

[bmore303]

Mko said it pretty well. Only thing to add is that 6 bolt 4G64 (G4CS) block won't have any drain holes that need to be filled. Our 7 bolt 4g64 has the 5 holes that need to be filled.

[XXL4G64]

I know this has been discussed a million times, but I keep getting different information the more I research. I dont have a 7G but I'm swapping a 4g64 into my 4G Mirage and later down the road I want to swap the SOHC to DOHC.

Heres my problem I read on DSMtuner that you cant swap any DOHC onto the 4g64 block because the pistons are different. now I see DOHCStunr selling his DOHC head and he is saying that its a direct swap. If the 94 GS head is the same as the 1G head how how come the guys at DSMtuner are saying the head want fit? Are the 94 GS piston different than the regular 4g64 pistion?

are you going turbo or N/T for now

[DOHCstunr]

lets see your mirage

[mysticj]

Heres my problem I read on DSMtuner that you cant swap any DOHC onto the 4g64 block because the pistons are different. now I see DOHCStunr selling his DOHC head and he is saying that its a direct swap. If the 94 GS head is the same as the 1G head how how come the guys at DSMtuner are saying the head want fit? Are the 94 GS piston different than the regular 4g64 pistion?

Mko said it pretty well. Only thing to add is that 6 bolt 4G64 (G4CS) block won't have any drain holes that need to be filled. Our 7 bolt 4g64 has the 5 holes that need to be filled.

The number one reason you can't swap to DOHC on a Hyundai G4CS because the compression will be slightly over 11:1 for a turbo applicaton. For Mitsu 4G64, the compression is the same when swapping from SOHC to DOHC expect for the second generation 4G64 found in the 8G Galant/3G Eclipse. For those engines[4G64], the Evo head will raise compression by a half point while the Sonata/Optima will lower compression by a full point.


BTW, The 92-95 Elantra heads raise compression as well and only bolt to our 4G64.

[kolio]

it's not that the compression is bad. just your margine for error is tiny. you better have a spot on tune otherwise you will blow it up.

slowboy has built motors(DOHC 4G64's) with like 11:1

[remarque]

Wow, you guys revived my old thread. For now I want to stay NA and make a 64/63 hybrid here are some pics of the swap progression. I'm using a 4g64 from an Expo and an 1.8 tranny from a Mirage, I'm going to have to remove the tranny because my 1.8 tranny only can with the front mount. I had to go back to junkyard and get the other two. But right know I have my 1.5 mounts in there and they don't line up.

The first is me taking the 4g15 out and second is the 4g64 in the car.

[mysticj]

Get rid of that exhaust manifold if you can, and go with one from the 96-99 Spyder GS; It's shape and design more like a true 4-2-1 header.

[remarque]

Thanks I was looking for some good headers.

[DOHCstunr]

header.
not headers.