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2g head on 6 bolt block in 98 gsx

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something i just found while still researching:

October 29th, 2009, 07:29 AM
As some of you may already know, I blew my FP3052 a few months ago. The reason was unknown, and I did a lot of research and had no luck finding a likely cause, though I was pretty sure it was from oil starvation. I accidentally stumbled onto a few threads on DSMTuners just a few minutes ago, and I think they explain why the GT30r CHRA most likely failed.

When installing a 2g head on a 6bolt block, you have to enlarge the holes on the head to accept the larger, 12mm 1g head studs. Something I was unaware of is; The main oil feed for the head is through one of the head stud holes. (see picture 3b)

I believe that I did not enlarge them enough, even though the head only needed a little attention to make it "fit". In the thread I linked above, it explains that the larger 1g/ARP studs interfere with the head oil passage creating higher oil pressure and sometimes oil starvation. Since the 3g lifter swap I have only had lifter tap once or twice. I assumed that there wasn't an insufficient oil condition at the head. That is, until my newly 'fed-from-the-head' turbo failed after only a few months of hard driving.



This head has had oil port mod 1 done.
The head boltholes have been reamed for the 1g head studs. To prevent any issues with oiling issues in the head,
I have reamed the bolt hole that is in the path of oil flow to .500 the bolt hole was .470 the ARP head stud being used is .465
Leaving only appox. .005 total or .0025 clearance on either side around the head stud. I feel the addition .030 will alleviates any problem with oil into the head.

is this still concerning the simple oil port mod, or is this something different all together.?
 
This is one viewpoint explaining an oil pressure problem that arose after that person installed a 7 bolt head on a 6 bolt block. All 7 bolt engines used 11mm head bolts while 6 bolt engines used 12mm head bolts. It's believed by some that when you do this, you restrict the oil delivery passage to the head.

The head feed passage is through the head-bolt bore in the head (traveling around the bolt) on the corner nearest the exhaust and trans sides of the head. You supposedly see less oil delivery to the head, however using BogusSVO's 2nd head oil port mod and slightly overboring the bolt bore, IMO you should be fine. Oil Port Mod #2

The oil feed hole in the head is the only one to be concerned with. The feed hole is beside the bolt hole in the block, but travels around the bolt in the head. If you slightly overbore out the hole in the head, the oil flow through it should be acceptable. Here's a picture of the oil feed passage in the head:
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Also, a note about the 1G CAS swap, some have reported a misfire problem that arises due to the poor accuracy of the 1G CAS in producing an acceptable crank position signal for the more picky 98+ 2G ECUs. Plenty of people have used the swap without any problems, but using a proper 2G crank sensor would eliminate any chance of this problem occurring.
 
I believe the difference is in the torque converters. The 2g torque converter is a bit thicker than the 1g so you need the thicker adapter plate to put a 6 bolt in a 2g auto.
 
As far as I know, another option (& what I'm probably going to do), instead of running a 1g cam sensor is to pick up a Kiggly crank sensor. This should allow you to run the 2g cam sensor with the Kiggly crank sensor. This should plug right in & not have to worry about the random missfire issue with the not as accurate 1g CAS. In turn you also see a more accurate crank signal.
 
Good luck. They are expensive and Kevin quoted me about 2 weeks from order to get it done. Give yourself some padding in time for it.

d
 
i did that rebuild 2g head 1g block and the list of mods are a few only.

machine the hole of your head to 11 mm to 12mm

use your motor mount the only mount I modify is the mount by the side of the timebelt

Oil pump 1g, water pump 1g, CAs 1g, head 2 g, pistons 1g rods 1g, manifuld 2g turbo big16 td05h
crankshaft 1g and 6 bolt flywheel
 
okay lets say i were to decide to leave the 1g head with the swap.... will my 2g coil packs work? and why?
I've already ordered my kiggley transmission adapter kit and have a complete 1g semi built engine. and now i've been thrown for a loop telling me i need the 1g coil pack.
 
i did that combo and all things everybody say is correct, please take note about te holes from the head and you need use the 2g motor mount making a little cut in the mount by the side of time belt.
 
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