6G74 -Stroker/4.0L Information
This information has been floating on Club3g since 2008. Not sure if much, if any of it has been posted over here. I think this community has started picking up on the 6G74 swap a little more lately, and some may not be aware of the performance possibilities just yet.
For those of you who have done the 74 swap already, feel free to get in on the discussion, help others looking into it, and keep looking ahead as we are not limited to just the 6g74 swap anymore.
You can use a 6G74/75 block for this build. The 6G74s are easy to find, and they are inexpensive. THose currently with a 74 swap can swap in parts also. The "ultimate" choice, though more expensive is finding a complete 6G75;
6G75 Deck height 228
6G74 Deck height 228
6G75 Bore 95
6G74 Bore 93
6G75 Stroke 90
6G74 Stroke 86
Crank
The crank out of the 3.8L 6G75 is a direct drop in replacement for the 3.5L block.
6G75 Main journals 64
http://i228.photobucket.com/albums/e...h_03110809.jpg
6G74 Main journals 64
http://i228.photobucket.com/albums/e...h_03110810.jpg
Rods
6G75 Rod Journals 55
http://i228.photobucket.com/albums/e...h_03110811.jpg
6G74 Rod journals 55
http://i228.photobucket.com/albums/e...h_03110812.jpg
Though similar rods are used in both the 6G74 and 6G75, there is one vital difference. The rods you will want to use for this build are the rods from a 6G74 as they are much thicker than those being used in the 6G75 engines.
6G74 Rods
http://i228.photobucket.com/albums/e...32008035-1.jpg
6G75 Rods
http://i228.photobucket.com/albums/e.../032008034.jpg
Pistons
The bore needs to be taken from 93mm to 97mm. That's a 4mm overbore.The pin downset will need to be changed from 31.75 to 29.75 in order to achieve the full stroke movement of the 6G75 crank and rod/piston combination.
6G75 Wrist Pin downset is 29.75
6G74 Wrist Pin downset is 31.75
Heads
6G75 Head (both Mivec and non-Mivec) are a direct bolt on. The Mivec and non-Mivec heads have their pro's and con's, as the Mivec heads have an intake port similar to the 1G 4g63 heads while the non mivec have ports similiar to the 2G 4g63 heads. The Mivec heads will require an external switching system/controller to operate the MIVEC system.
MIVEC Head Shown;
http://i228.photobucket.com/albums/e...s/IMG_0661.jpg
Non-MIVEC Head Shown;
http://i228.photobucket.com/albums/e...ds/pics286.jpg
The 6G75 head has a 65cc combustion chamber, compared to 43cc of the 6g72/4 heads. Doing just a 6G75 head swap will lower compression alot, so you will need to account for this with aftermarket pistons to get your desired compression ratio.
The best heads to use on any 6G74 swap are the 6G75 heads because they have larger valves, and unmodified 75 heads will outflow a set of PnP'd 74 heads by nearly 18%;
http://i228.photobucket.com/albums/e...alant/Flow.jpg
Cams
Aftermarket cams for the MIVEC heads are still waiting for production, but at this time the best choice is the non-Mivec heads. You can swap in a set of RPW cams for a 6G72/4 into the non-Mivec heads. You can still use the aftermarket cam gears from a 72/74.
A build such as this, paired with other items is easily bringing the reality of 300+WHP numbers to us now...