2.4L High Compression Ratio Questions

[needsy]

Ok, this question kinda has two parts.

1) What 2.4L motors will net a high compression ratio when used with the 2.0L head? I'm looking to build a motor like the one in this thread: My low cost high compression daily driver E85. Please no discussion of the merits of this project; I just need sources of shortblock.

2) As another route, will the G4CS pistons work in a 4G64? Using the 4G64 would be nice because I have a 2G, but I don't know if there was ever a 4G64 produced that would net a high compression ratio when combined with the 2.0L head. Am I correct saying that 6 bolt parts are needed on a G4CS, but 7 bolt parts can be used on a 7 bolt 4G64? If 7 bolt parts can be used on the G4CS then this is rather moot.

I know I could get custom parts, but I am trying to keep costs low until I know this setup will perform as I hope it will. This is just a proof of concept.

Thanks in advance

 

[mobythevan]

If they made a 4G64 that was 8 valve SOHC it would yield the same results.

 

[GS ice T]

All I can tell you is the I have a 4G64 block w/ a 4G63 head and last time I did a compressin test I was getting 200-210psi and I just went back and looked at the stock specs of a 4G64 engine and standard compression is 192 with a CR of 9.5:1. I bought the motor like this but apparently this setup can produce pretty high compression numbers. Hope this helps if you decide to go that route.

 

[mobythevan]

All I can tell you is the I have a 4G64 block w/ a 4G63 head and last time I did a compressin test I was getting 200-210psi and I just went back and looked at the stock specs of a 4G64 engine and standard compression is 192 with a CR of 9.5:1. I bought the motor like this but apparently this setup can produce pretty high compression numbers. Hope this helps if you decide to go that route.

You have BC 280 cams according to your profile, that will make a difference on cranking PSI compression measurements. You also list wiseco pistons, what CR are they?

 

[needsy]

Interesting. I measured with volume of the head that came with the 4G64 I have, and it was the same as the 4G63 head. Are there different 4G64 SOHC heads? Mine is SOHC 16 valve.

 

[mobythevan]

I don't know what you have then. good luck

EDIT
It just occurred to me, you need pistons from a 8v SOHC. So an 8 valve 4G64 would work if there was such a thing.

 

[needsy]

Ok, so I guess that makes my question:

a) Are there any 4G64s that came with 8 valve SOHC heads

or

b) Will the G4CS 8 valve pistons fit in a 4G64? They have the same stroke and bore, and both have the extra 6mm depth, right? Anyone know about the crank journals? Would it be possible to use 4G64 rods with G4CS pistons?

Anyone know where I can look up these specs?

 

[jrohner]

Maybe the newer 4g64 stuff would be worth looking into, they may fit by putting them in 'backwards' like people do to put evo8 pistons in DSM's. The newer kia optima's engine is pretty much like an evo 8 engine (except they are 2.4). Some people put the kia head on galants and 3g eclipses to make them DOHC.

 

[mobythevan]

I just went up to the search and entered "8 valve 4g64", looks like they came in trucks and vans, probably other stuff as well.

 

[needsy]

Thanks a lot for the help mobythevan. The list from RRE really helps. I had seen that before, but forgot about it.

 

[m_0ney_pit]

all the nt 96-99 spyders had them. the galants also had them. the compression ratio is determined by the pistons not the head. there are aftermarket pistons made for the 4g64 in 9:1 and 9:5:1 (and lower) ratios.

 

[mobythevan]

Yeah, but the pistons are determined by the head. They don't put 2 valve relief pistons with a 4 valve head and you want the 2 relief pistons for the high compression.

This is the piston you want for this higher compression, notice its for an 8 valve engine and basically a flat top:

You must be logged in to view this image or video.

 

[toofast82]

The newer kia optima's engine is pretty much like an evo 8 engine (except they are 2.4). Some people put the kia head on galants and 3g eclipses to make them DOHC.

That sounds interesting! I personally would "neva eva" put a KIA part on any car i had. Especially in a boosted situation

 

[mysticj]

That sounds interesting! I personally would "neva eva" put a KIA part on any car i had. Especially in a boosted situation

Hyundai/Kia Siruis engines are the same as Mitsu Sirius engines with some noticeable differences.

The pistons from a G4JS is almost flat(~-3cc) with 4 valve reliefs.
G4JS Piston Shot

 

[jrohner]

Hyundai/Kia Siruis engines are the same as Mitsu Sirius engines with some noticeable differences.

The pistons from a G4JS is almost flat(~-3cc) with 4 valve reliefs.
G4JS Piston Shot

And I think they are supposedly 10.5:1 compression. So if their head cc is the same as ours, you could use the 1.8 Elantra head and get over 11:1.

 

[MidShipCivic]

8 valve SOHC 4g64 pistons will bump your compression to about 13:1 and it also lacks 4 valve reliefs.

16v SOHC 4g64 pistons will remain at their 9.6:1 compression, since their head CC's are the same verses the 4g63.

 

[mysticj]

And I think they are supposedly 10.5:1 compression. So if their head cc is the same as ours, you could use the 1.8 Elantra head and get over 11:1.

G4JS head cc's is 56. Elantra 1.8 head will make about 12:1.

 

[mobythevan]

8 valve SOHC 4g64 pistons will bump your compression to about 13:1 and it also lacks 4 valve reliefs.

Theoretically the high end is 13:1, but I think i am seeing more like 12-12.5:1. It starts to depend on a lot of factors like HG thickness, piston to deck clearance, milling, etc. I am not hitting the piston with the valve even though the reliefs are not there, but it is running close.

 

[needsy]

Did you end up using the Fel-Pro gasket you mentioned in the other thread? Anyone know if the valves travel the same distance in a stock 2g head as in a 1g head?

 

[mobythevan]

I did use the standard felpro gasket, it has the larger bore diameter. It is not really a question of how far the valves travel, it really depends on the cams duration and ramps. When the cam starts to open the intake valve and how fast it opens, that is the critical spot that you will hit the piston. If you tak note of how the valve events occurr you will see that the piston is at the top and the intake is just starting to open. As the intake is opening the pistons is starting to move back down. This is the time that a valve gets closest to a piston if the timing is correct.

 

[GS ice T]

You have BC 280 cams according to your profile, that will make a difference on cranking PSI compression measurements. You also list wiseco pistons, what CR are they?

Sorry it took so long to get back to you. I'm not sure how much the 280s affect the compression measurements but yes I do have wiseco's. I went to their site and it shows my particular setup has a CR of 9.7:1

As for 1g and 2g heads, intake cam has the same duration but the exhuast cam is open 8º longer on a 2g. But I recall reading that one or both cams on the 1g have more lift so it kind of evens out.