New here, Entertaining idea of building 12v 3.0 3000gt

[Vigo]

Good buy, wish I had your luck

Well, i had to drive a ways and pull it myself, but he gave me the exhaust with it, so i sold the cat to get back down to that $30 number. He was planning to do an electric conversion on his stealth, so i took his running motor and neglected to tell him how bad/complicated of an idea that was... haha. And this coming from someone who's electrifying a minivan.

[Ondonti]

1st Generation junkyard (or buy new OEM 1st gen) DSM headbolts are what I used in the mains. Don't use 2nd gen, they are junk.
I have not tested them hard but I know they will perform better. Avoiding huge knock would help too.

Sticking with a basic stockish engine (with a turbo setup) for the short term is a great idea to get the project rolling. Once you have your AWD you can always swap to a DOHC etc. If you end up breaking an open ring gap 12 valve then maybe upgrade the pistons. I know forged 12 valve pistons are great. At that point you might as well get cheap 3sx rod upgrades for long term health. You MUST balance the motor if you upgrade anything or you have wasted your money. Those didn't exist back when I built my forged motor. I went too low on the compression ratio so I was never happy.

Stock shortblock with big ring gaps and maybe upgrading the mains bolts will be fairly reliable. I might suggest upgrading the rings if you want to put a lot of mileage on it. I went chrome on my Daily and Ed had done that long ago over fears of the stock rings losing their tension against the cylinders. I don't know if my setup will ever get hot enough to really matter and I don't know the makeup of OEM turbo rings.
Also, if you are not smart about using the right temperature spark plugs, you may end things prematurely. I dinged up my forged pistons with a broken stock spark plug that saw way too much boost. Never hurt the forged pistons with detonation and I am lucky I didn't hurt the crankshaft or rods on that motor. Probably helped that I had that motor balanced which keeps the crankshaft from bending and whipping as much as it wants to.

I would say 350-400whp on the tweaked shortblock would be reliable with a good tuning tool. I am not pushing my Spirit's motor because I have no registered backup car that actually belongs to me.

Your biggest culprit might be sealing the cylinder head but you will find out that as time passes and you prove your ignition timing is safe. Head bolts are the same as TT so it won't help. The head flexes. You can always O ring. I only head head sealing problems with detonation anyways :P

[Sundance 6g72]

we had a debate so to speak on the head sealing issues you had. I was trying to point out that the head DOES flex between headbolts.. the question was, did it only happen when detonation occurred or what it just because of high hp?

i think you just answered that though :P

[Ondonti]

Well I would just say that is an issue that I have not gotten back too. I have never had a leak that did not occur during detonation so it is unknown how far you can go. I plan on partial filling my fun cylinder heads (which have been decked quite a bit thanks to various issues) and redrilling the passages if I have sealing issues in the future. I have tried quite a few tricks and they all seem to work well to seal, its the detonation that I did not have under control. The copper wire on mls gasket blew out when detonated but the mains had already flexed from the block (from detonation).

There are many sealing options out there including headlift fixes (posts in the stantions of the head that flex) or copper gaskets with an O ring and Hylomar sealant to prevent leaks that almost always happen with poorly done copper gasket setups. There is also the Steel wire in OEM gasket, copper wire on MLS. Also there is Copper O ring (with real grooves in the block) against MLS gasket or even steel O ring against mls (smaller clearance levels are needed with steel on mls).

I am still happy with stock Felpro but I have not pushed it or used it in my weaker big valve heads.

There are many options to help seal the head but the most important thing would be a safe tune. Every time my head seal failed it potentially saved something else so its not like its the end of the world.

There was a recent group buy for Tool Steel headstuds for people wanting reliable 1000whp over long periods. OEM seems to slowly give up at those levels if you are pushing hard for a lot of runs. Most people that fast don't get many runs to worry about it. They are unobtainium without group buys (2k or more for a set until you get 5 or 10 sold then the price drops 75% or more). Apparently there are some upgraded ARP available out there made of the higher quality steel which Nelson has shown to be reliable over 1000whp but they are 380 dollars a set. The cheap ones are a waste of time.

[Sundance 6g72]

was not aware of there being 2 different sets.

this interest me also (talking about arp studs for 12valve 6g72)

But if I remember correctly and understand what i have read there is a bit of gap between the inside surface of the bolt hole and the surface of the factory bolts themselves, and If i have read correctly on one of the Mitsu forums that space is filled with the ARP Heads Studs. (I will try to find where i read this.) So if this is true then the ARP Head Studs are actually better for the head adding rigidity after the head has been properly torqued, and not only that studs have been proven to hold a torque better than a bolt.

we were talking about head lift and the head flex that you ran into

[Mdoe8]

Thanks for the input Brent.

I will definitely snag the 1g dsm headbolts for inexpensive peace of mind, and stock head bolts for the head. Probably will go with a metal head gasket as well. As for the spark plugs, I planned on going with the 9's I believe it is (did my research but can't remember the full spark plug name off hand...i always go NGK).

I also am planning on sticking with the SOHC, even with the awd setup. I will have 99% of the awd parts by next weekend. It would be very fun to make an AWD turbocharged SOHC 3000gt. I know the transmission will bolt right up, what about the flywheels/clutches?

Good call on the rings. Where would I go to get the better-than-stock rings? IIRC, there are some chrome sets on ebay but I'm not positive on that. I'd really like to hit the 400awhp mark with this setup. I know it CAN do it, the issue becomes reliability. With a solid tune, I'd bet it can make 400awhp all day long without major issues.

Quick question regarding engine rebuild/refresh. If I'm using stock rods/pistons and one of the bearings isn't perfect, do I have to measure and get the appropriate sized bearing or just get a "stock sized" bearing? I've seen piston kits that randomly come with bearings, how can I be assured that these are properly sized? Or is this just a "close enough but not blueprinted" rebuild that is most common? Excuse my ignorance, I'm not extremely familiar with all of this yet.

1st Generation junkyard (or buy new OEM 1st gen) DSM headbolts are what I used in the mains. Don't use 2nd gen, they are junk.
I have not tested them hard but I know they will perform better. Avoiding huge knock would help too.

Sticking with a basic stockish engine (with a turbo setup) for the short term is a great idea to get the project rolling. Once you have your AWD you can always swap to a DOHC etc. If you end up breaking an open ring gap 12 valve then maybe upgrade the pistons. I know forged 12 valve pistons are great. At that point you might as well get cheap 3sx rod upgrades for long term health. You MUST balance the motor if you upgrade anything or you have wasted your money. Those didn't exist back when I built my forged motor. I went too low on the compression ratio so I was never happy.

Stock shortblock with big ring gaps and maybe upgrading the mains bolts will be fairly reliable. I might suggest upgrading the rings if you want to put a lot of mileage on it. I went chrome on my Daily and Ed had done that long ago over fears of the stock rings losing their tension against the cylinders. I don't know if my setup will ever get hot enough to really matter and I don't know the makeup of OEM turbo rings.
Also, if you are not smart about using the right temperature spark plugs, you may end things prematurely. I dinged up my forged pistons with a broken stock spark plug that saw way too much boost. Never hurt the forged pistons with detonation and I am lucky I didn't hurt the crankshaft or rods on that motor. Probably helped that I had that motor balanced which keeps the crankshaft from bending and whipping as much as it wants to.

I would say 350-400whp on the tweaked shortblock would be reliable with a good tuning tool. I am not pushing my Spirit's motor because I have no registered backup car that actually belongs to me.

Your biggest culprit might be sealing the cylinder head but you will find out that as time passes and you prove your ignition timing is safe. Head bolts are the same as TT so it won't help. The head flexes. You can always O ring. I only head head sealing problems with detonation anyways :P

[Sundance 6g72]

just for refference, i was running ngk gr5s (stock type plug for sohc 12v) and i hit 11.5psi with them just fine (as far as i know)

but i did the smart thing and switched to ngk gr7s and gapped them around .035 (they were at .045ish and had blowout problems)

for your goals, i think the gr9 would be a great choice but IIRC brent used gr8? Just keep the gap correct and you should be good. im not sure if there is a problem with going with to cold of a plug, im sure its better than too hot of a plug

[Mdoe8]

Yeah the gap would be low .030's.

Another question: Does megasquirt support the GM boost solenoid for controlling boost? I had bought one for a previous build (aem ecu powered) and never got around to using it.

[Sundance 6g72]

i think that is what diy actually sells

let me take a look for you

edit:

http://www.diyautotune.com/catalog/b...3bb0300e4cdbe3

[Mdoe8]

bonus, thanks!

I've got the controller and pigtail in my garage!

[Sundance 6g72]

nice! I never looked into the ebc much but from what i could tell, it has a big leanring curve to get it working. Not sure if you ever actually used it or not but be carefull with the first test run

[Mdoe8]

I've never used the GM solenoid itself, but have used probably a dozen electronic controllers in my day. I've been through a lot of cars lol

[Sundance 6g72]

thats good

i undid my wastegate once and kept it stuck shut and it made the turbo super responsive and i hit overboost almost instantly compared to when the wastegate lines are hooked up (mbc) I dont like the idea of it progressvely opening as boost builds but i guess thats what i get for not using an ebc. helps traction :P

speaking of boost control and overboosting, the megasquirt overboost setting has worked well for me so i guess there are no worries there as far as doing the ebc wrong. MS has your back

[Mdoe8]

Good to know!

Back when I had a supra still on stock twins, I would run race gas and plug the wastegate before taking it down the 1/4. Picked up a few mph this way, only hit around 24 psi and tapered down from there.

[Sundance 6g72]

hahahahaha

intake temp = over 9000 :P

[Mdoe8]

Yeah intake temps rose but it still ran great, never missed a beat. Only like that for 12 seconds! Ran a 12.5@119 iirc (kuhmos suck off the line). Took 15 seconds to put the line back on so it was quick and easy.

My turbo ls1 rx7 just ran wastegate pressure at first, worked perfectly.
Evo, supra, vr4, mr2, rotary rx7, and 300zx all had EBC's.

[Ondonti]

I should mention what I forgot...
The twin turbo oem MLS headgasket is the best known gasket that is proven to hold lots of power. People have recently been opening up the bore of the gasket before going with another gasket but most people chamfer their pistons to allow for the oem gasket while using a huge overbore. OEM pistons will never worry about that stuff. Opening up the gasket is unproven btw. Chamfering is well proven.

Ed got a set of 91.1mm chrome rings from Summit Racing and I did the same. I just got the 1.2 1.5 3.0 ringset that matches up with 1992+ motors that are oem 8.9:1. 8.85:1 motors in early years are 1.5 1.5 and 3.0 and are beefier if you want oem pistons because the top ring is located much farther down.
I have stock rings in my Duster because I don't really care what happens to that shortblock over time.

You will be able to use TT clutch setups. I bolted a TT clutch setup to my motor as a test but it is too large for the Chrysler bellhousing. n/a mitsu clutch setup is a smaller diameter.

Mitsu also has +1 bearings (not sure exactly what they are called) but I have never used them. I just stick with good enough for now. SOHC motor bearings will probably be pretty clean but if they are not then just throw in some Clevite 77's in base size. My Duster currently has a crank rod journal out of tolerance and I just measured a bunch of junkyard bearings and put in the thickest set. Thats another reason I don't care about that motor over the long term. Had no problems over a couple hundred miles.
I know when people are pushing hard they get picky about bearing clearances (and I can't quote any numbers) but I would not go to that level with stock rods. Ruins the point of running "cheap" parts.
3Si people say the most important bearing issue is making sure the "crappy" mitsu oil pan has no dents and that the pickup is not clogged. For some reason mitsu oil pans love to oil starve the motor but I think there are just a lot of owners running low on oil. That or the oil is not draining quickly enough (12 valve heads do have poor drains, no idea what dohc heads look like, 12 valve just needs to be drilled out to match the size of the block returns) combined with low oil level. The more rpms, the more oil in the head.

[Mdoe8]

Interesting that the twin turbo head gasket would line up, but the heads don't bolt up. Is some modification needed to get the tt head gasket to fit?


Also, when you say your rod journal is out of tolerance, did you actually measure it with plastigauge or just see that it didn't look good?

[Sundance 6g72]

nono the heads bolt up just fine.. its getting the right timing belt, and getting acc. stuff bolted on and working right

[Mdoe8]

OOOhhhh, gotcha. So if I were to swap 12v suitable pistons to my dohc block...it would do me no good?