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Dirty D
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1,386 Posts
Discussion Starter · #1 ·
has anyone done this? or is it even possible?

ive always wondered why the 3000gt with a smaller engine has dohc but the 4g doesnt, even though its in the same family of engine.
 

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Elitist Prick
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2,632 Posts
1. Heads, not head.
2. No, sorry.
 

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Elitist Prick
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2,632 Posts
Again, not it. Them. 2 heads. No. Completely different bolt pattern.
 

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chucknasty
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558 Posts
sure you could. but why? the only two that would work are 3kgt and hyundai xg350. also, both of those suck ass compared to the NONMIVEC 6g75 heads much less the MIVEC 6g75 heads. hell that is why 3kgt guys don't bother with their heads when they swap 6g75's in. the 6g75 MIVEC heads are the best heads designed for a 6g series engine. i mean they are even better than the 6g74 GDI heads. the only heads that i would say can compete would be 6b31 and those are not swappable.
 

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chucknasty
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558 Posts
more cams only means that you can run higher profile cams without having too much lope. too much lope and oyu have to raise the idle. you can run 272 on the sohc heads while maintaining a 800 rpm idle so why?

now people always say "but hondas..."

well honda makes their dohc heads specifically better, larger chambers, ports, they often come with higher profile cams. that is why they have a gain. also, both the hyundai and 3kgt heads would require a spacer made or custom head gasket since your compression ratio would be ridiculous and you would risk smashing valves (i know this because people were going to swap 6g75 nonmivec heads onto a 6g74 but oyu can't without using a 6g75 crank or you have very little compression ro shave the heads).
 

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chucknasty
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558 Posts
think of it this way, OHV engines lope like mother fucker with a high profile cam. that makes the sound everyone hears that makes them turn their heads. well when it gets too high the engine stalls. that is why racing ohv engines start their engine only right before the race and idle around 1500 to 2k then cut it right after.
 

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chucknasty
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558 Posts
SOHC vs DOHC Valvetrains: A Comparison

that explains a bit of it. since our sohc engines have the spark plug in the middle of the combustion chamber and we run 4 valves per cylinder with each intake valve has it's own rocker and 2 exhaust valves share a rocker it's not much difference. if you take apart a 6g74 dohc head and the 6g75 head (mivec or not they are both much better) you can see the difference.
 

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chucknasty
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558 Posts
i run evo 8 brembos, not stock.
 

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chucknasty
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558 Posts
PM me for details though. don't want to clutter this thread.


also edit:

mivec's apperently use one rocker per valve pretty cool
 

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resident crossplatformer
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1,427 Posts
Again, not it. Them. 2 heads. No. Completely different bolt pattern.
actually no, bolt pattern never changed in the engine family
sure you could. but why? the only two that would work are 3kgt and hyundai xg350. also, both of those suck ass compared to the NONMIVEC 6g75 heads much less the MIVEC 6g75 heads. hell that is why 3kgt guys don't bother with their heads when they swap 6g75's in. the 6g75 MIVEC heads are the best heads designed for a 6g series engine. i mean they are even better than the 6g74 GDI heads. the only heads that i would say can compete would be 6b31 and those are not swappable.
exactly, and this is why a buddy of mine is building my 6g75 in exchange for a set of NON-MIVEC heads, it has been noted from Ray Pampena (the guy you can send your 6g75 in with 10 grand and get it back displacing at least 4.2 liters) that the 6g75 intake ports are some of the best designed out there

to settle this, why would you want the 6g7 DOHC heads? Outside the fact they flow poorer (or nearly the same) in race spec performance porting with bigger valves compared to the stock 6g75 none MIVEC heads, as is brought up, there is the issue of how to control the engine with them (well, if you don't have to worry about smog, a 1999 3000gt ECU reflashed or a standalone will do), and also using these heads alone for performance just parts wise due to, well, there are 4 cams, 4 cam gears, will be twice as expensive
one thing I should point out, a timing belt or tensioner pats won't be too difficult if they are used in the tall deck 6g7 engines (6g74's and 6g75's), you can order these parts from Rock Auto if you dig a little
 

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chucknasty
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558 Posts
actually no, bolt pattern never changed in the engine family

exactly, and this is why a buddy of mine is building my 6g75 in exchange for a set of NON-MIVEC heads, it has been noted from Ray Pampena (the guy you can send your 6g75 in with 10 grand and get it back displacing at least 4.2 liters) that the 6g75 intake ports are some of the best designed out there

to settle this, why would you want the 6g7 DOHC heads? Outside the fact they flow poorer (or nearly the same) in race spec performance porting with bigger valves compared to the stock 6g75 none MIVEC heads, as is brought up, there is the issue of how to control the engine with them (well, if you don't have to worry about smog, a 1999 3000gt ECU reflashed or a standalone will do), and also using these heads alone for performance just parts wise due to, well, there are 4 cams, 4 cam gears, will be twice as expensive
one thing I should point out, a timing belt or tensioner pats won't be too difficult if they are used in the tall deck 6g7 engines (6g74's and 6g75's), you can order these parts from Rock Auto if you dig a little
i agree with everything except about ecu. with our cruddy 4g64's we swap dohc heads all the time. they use a camshaft sensor on one cam you just splice that and you are good to go. ecu needs to only read postion of one cam for timing as they run in unison (one timing belt)
 

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illusionperformance
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6,935 Posts
I was just repeating what other people have said on here before about doing this swap

Sent from my BlackBerry 8530 using Tapatalk
 

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chucknasty
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558 Posts
I was just repeating what other people have said on here before about doing this swap

Sent from my BlackBerry 8530 using Tapatalk
it's all good. maybe the v6 is different but i doubt it. these are mitsubishi's not ferrari's so it's probably just one camshaft sensor on the rear bank. too bad i am on a good ol' distributor so i can't go out check lol. but i am 80% sure there is only one sensor on the rear bank. the ecu assumes if one camshaft is in the right place they all should be which makes good sense.

if oyu want more power than what bolt ons can get you i recommend you buy another set of heads or if you have a project car just take yours off and send them to cosworth. they have experience with our heads and make some fantastic progress. non-mivec heads with a light p-n-p flowed around 400 cfm at .500 lift if i remember correctly. although some aggressive cams would really help. that and some 11:1 pistons. combine all that and you would have a very nice engine. the major component is there already high flowing heads. just have to compensate the rest.
 

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illusionperformance
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6,935 Posts
it's all good. maybe the v6 is different but i doubt it. these are mitsubishi's not ferrari's so it's probably just one camshaft sensor on the rear bank. too bad i am on a good ol' distributor so i can't go out check lol. but i am 80% sure there is only one sensor on the rear bank. the ecu assumes if one camshaft is in the right place they all should be which makes good sense.

if oyu want more power than what bolt ons can get you i recommend you buy another set of heads or if you have a project car just take yours off and send them to cosworth. they have experience with our heads and make some fantastic progress. non-mivec heads with a light p-n-p flowed around 400 cfm at .500 lift if i remember correctly. although some aggressive cams would really help. that and some 11:1 pistons. combine all that and you would have a very nice engine. the major component is there already high flowing heads. just have to compensate the rest.
im thinking about picking up a 272 cam from rpw, when i rebuild the engine.
 
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