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Discussion Starter #1
I blew my NA-T engine and am planing a rebuild/ strengthen of my engine. (GE VVTi engine) 1998 GS300. Going bonkers trying to figure out cc's of various components. I want to get away from the stock 10.5:1 ratio so I can run more than 8psi. I want to run 9.0:1 compression ideally. Is there anyone on here that's good with the calculations for how to achieve this on the GE engine?

What I have found out is that both the GE and GTE have a .005 piston to deck clearance. I know the GE has less combustion chamber volume, and the head gasket it much thinner. But I don't know if I should go with both dished pistons and a thicker HG, or just one or the other.. Any help would be appreciated.
 

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what gas will you be using with which engine management ?

my “low” boost setting on 91 octane is 14psi on stock 10:1 compression on aem v2. timing has to be tuned carefully of course.

I’m NA-T non-vvti

edit: sorry I didn’t realize my response didn’t directly answer your question
 

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Discussion Starter #3
91 also because it's a California car and the best we have for pump gas. I'm running an AEM Infinity ECU, so full stand alone tuning ability. The non VVTi GE can handle what you're throwing at it because it's slightly lower compression and has way better pistons and rods like a GTE. THE VVTi has super weak stamped steel rods and crap pistons. I'll be going to forged pistons/rods and down to 9.0:1 or around that and be able to run 20+psi for 700-800whp as the goal. Just have to get my specs right for the compression ratio.

The car is set up right, just had too weak of internals. Blew either the rings out or a hole in the piston on cyl#1 on the dyno, but was still making consistent 405whp runs on 5 cyls. Not sure what it would have made on all 6 cyls. But that was only at waste-gate spring 8 psi. Imagine being able to turn up the boost! Until I tear the engine down, I don't know if it's rings or the piston, but I just know the cyl leak-down test is blowing straight into the crank case. Funny thing is the car runs fine, just hard to start and blows a ton of oil smoke out under boost. But will be tearing down here shortly.

Looking for piston dish recommendations and HG thickness etc. Want to set it up right with proper quench area etc.
 

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You are going to have to change the pistons on the vvti block to handle above 400ish, thats just how it goes with that setup.

I would find a set of GTE rods and pistons and drop those in. that with a gte headgasket should get you close to 9:1 with the vvti ge head.
Since those pistons and rods are getting harder to find, if you can find a set from a GE non vvti, you could run those with a gte headgasket and probably end up more around 9.5:1 with the vvti ge head.

If you go custom pistons, just get something in that stock gte range cc wise, and use the gte headgasket. I wouldn't dip below 9:1 compression, but for 91 I would say you should be under 9.5:1 which is why it probably popped something, or cracked a ring/ringland is common on the vvti ge pistons.
 

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91 is basically piss fuel. We have 93 here in the Midwest (Indiana), although I hardly ever, in fact almost never, run it as E85 is readily available in my area (10 stations in a city of 300K people), I did a 10/1 build back in 2014.

If you plan to run 91 I'd go 9.5/1 for extra margin. No way would I attempt 10.5 or even 10.0 if you are going to run 91. It's just not worth it.

Steve
 

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Discussion Starter #6
Yes my goal is to get down to 9.0:1 or in that close area. I will be putting in JE pistons and Manley H-beam rods along with a full engine bearing refresh/hone etc. I have my fuel system setup and engine build being made to "handle" 1000whp safely and the "goal" power level to be around 800whp so I'm not stressing things out. I'll be around 80% injector duty cycle at the 800ish level.

My big question is if a set of GTE spec dished pistons and an OEM GE "thin" HG will get me to 9ish to 1 or if I need to run a thicker gasket. I don't want to do both if it's going to take me down to under 9.0:1. Money isn't a concern and I can get a cosmetic gasket at whatever thickness is needed. Just unsure how to calculate it. Plus there is conflicting information about GE VVTi head CC's etc.
 

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Discussion Starter #7
So Ali, you say GTE dish pistons and GTE HG to get to 9:1? I heard the CC's of the GE head is greater than the GTE, so wouldn't that take me down to less than 8.5:1? Totally not arguing, just what I heard and really don't want to make a mistake.
 

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The best advice I can give you is to search for the EPIC post that member "superstock" made on here, that has every single CC measurements for the GE and GTE pistons and cylinder heads that you will ever need, and all the photos too. All of your answers are in that thread :)
 

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Not trying to go off topic. But Im wondering what would be my CR on a built bottom 2JZ-GE with 1jz gte pistons/rods 2jz gte stock HeadGasket, 2jz-ge crank, 2Jz-ge Vvti head. Been searching every where im afraid to start the project because the rod of the 1jz is shorter.
 

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So Ali, you say GTE dish pistons and GTE HG to get to 9:1? I heard the CC's of the GE head is greater than the GTE, so wouldn't that take me down to less than 8.5:1? Totally not arguing, just what I heard and really don't want to make a mistake.
You should spend some time reading in that combustion chamber difference thread in this section, its good stuff.

lets use a regular GE for reference:
So regular stock GE non vvti engine is 10:1.
-Same regular GE with a GTE headgasket you are around 9.1
-Same regular GE with GTE pistons you get around 9.0
If you were to do both GTE pistons and a GTE headgasket, you would drop below 8.5 and be closer to 8 something.

VVTi is 10.5:1, and its debatable where that comes from but I have heard more that its from the cylinder head and not the pistons, your view may vary.
So if you were to just do GTE pistons or a GTE headgasket, you would end up in what I would guess slightly above 9.5:1, which might be too much for your setup.
If you do both, you would probably end up in the 8.6-9.0:1 range, which might be a hair too low but is on the safer side of things for 91 fuel, and is a little better than a stock gte which make good power safely which isn't so bad.

Since you are choosing custom pistons, I would personally go ahead and use a gte headgasket as it is a proven multi-layer vs the GE single layer gasket (which I think makes it a little easier to blow out). Then, I would choose pistons that are in-between that of the stock GTE and the stock GE, that should land you in that low 9 range.

Here in Colorado at our elevation 91 is like 93, but at sea level 91 is like 91 which is not very great.. so I would say go safer on the compression ratio and up the boost in that case.
You will likely be limited by how much power you can make with this fuel before its not a good idea to push it further, but you could also add methanol and then you would be just fine.

Not trying to go off topic. But Im wondering what would be my CR on a built bottom 2JZ-GE with 1jz gte pistons/rods 2jz gte stock HeadGasket, 2jz-ge crank, 2Jz-ge Vvti head. Been searching every where im afraid to start the project because the rod of the 1jz is shorter.
Honestly I have no idea what happens when you use 1jz rods and a 2jz crank.
I imagine your pistons wouldn't come all the way up to the deck height?? Your compression ratio would be crazy low then if that is the case.
I wouldn't even want to guess what the compression ratio is on that, without more research I would have to turn that engine over without the head on and do alot of measuring.
I am not 100%, but I really think you need to put some 2j rods in that thing, edit*1jz crank prob wont work in that block*

If you had 2jz rods then its this:
A GE block with gte pistons and a gte headgasket is essentially like a gte bottom end setup, which is stock 8.5:1.
Add in a little from the vvti head (Assuming that is where all the .5 comes from), and you will be just below 9:1 most likely.
 

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Honestly I have no idea what happens when you use 1jz rods and a 2jz crank.
I imagine your pistons wouldn't come all the way up to the deck height?? Your compression ratio would be crazy low then if that is the case.
I wouldn't even want to guess what the compression ratio is on that, without more research I would have to turn that engine over without the head on and do alot of measuring.
I am not 100%, but I really think you need to put some 2j rods in that thing, or put a 1jz crank in it.

If you had 2jz rods then its this:
A GE block with gte pistons and a gte headgasket is essentially like a gte bottom end setup, which is stock 8.5:1.
Add in a little from the vvti head (Assuming that is where all the .5 comes from), and you will be just below 9:1 most likely.
Got it might just have to go Eagle Rods, one last question would be how would a 1jz crank help?
 

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I guess it wouldn't actually help in a 2j block cause it wouldn't be the right height for the block then as the 2jz deck is taller.
how did you end up with that combo even? did you have a vvti GE and try and make it stronger with rods/pistons?? cause you should have used 2jzge or gte rods/pistons.

I have never heard of anyone actually trying to mix 1jz and 2jz bottom end parts like that.
Usually you just use the whole bottom end from one or the other, and if you have a 1jz bottom and want more displacement you swap the whole block for a 2jz one.
 

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I guess it wouldn't actually help in a 2j block cause it wouldn't be the right height for the block then as the 2jz deck is taller.
how did you end up with that combo even? did you have a vvti GE and try and make it stronger with rods/pistons?? cause you should have used 2jzge or gte rods/pistons.

I have never heard of anyone actually trying to mix 1jz and 2jz bottom end parts like that.
Usually you just use the whole bottom end from one or the other, and if you have a 1jz bottom and want more displacement you swap the whole block for a 2jz one.
Spare parts
 

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Not trying to go off topic. But Im wondering what would be my CR on a built bottom 2JZ-GE with 1jz gte pistons/rods 2jz gte stock HeadGasket, 2jz-ge crank, 2Jz-ge Vvti head. Been searching every where im afraid to start the project because the rod of the 1jz is shorter.
Do your homework, then check your homework, then re-check your homework. I failed to do my homework properly, ordered 2jz 10:1 pistons for my 1jz, and... ended up with a CR of around 9:1 due to a combination of factors, but the pistons were a big part of that if I recall. Shame too, because I really like throttle response more than peak power.

OP, are you able to run a flex fuel setup? If so, you might tune it around the higher octane fuel, if any are available locally. Get the best of driveability with the vvti and higher compression on low boost (and still plenty of power, let's be honest), and turn up the wick when you're running a more appropriate fuel for those special occasions. :)
 

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Discussion Starter #17
Thanks guys, a lot of good info. Too keep it simple, the JE pistons and Manley H-beams are going to be GTE spec. Also keeps the cost down since they are mass produced this way. And I'm thinking of a custom 1mm or right in that area HG so it's not quite as extreme of a change. Probably will just end up doing a GTE gasket. Have to do more math. I also forgot to mention I'm running 264 cams. That's not enough to effect any compression factors right? I've heard "big cams" with huge overlap can have compression effects. But these are very mild..
 

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Discussion Starter #18
The more I read on the topic, it seems people are leaning towards higher compression and good tuning rather than going way low. Like 9.5 being a good CR. For better drivability off boost and more snappy response. I imagine turbo spool time is better too. I'm considering just doing the GTE spec dished pistons and leaving everything else GE spec. as far as CR goes. According to what I've been reading a GTE HG on a GE head is too much quench area. Obviously a GE HG w/ GE head keeps quench correct, but lowers the CR w/ dished pistons. So I just need to see what the CR would be in a GE w/ just GTE pistons being the difference.
 

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Both of you have GE vvti head setups but your tuning and fueling may vary.
I will start by saying depending on your ecu you may want to talk to your tuner, they may have a good recipe already with what they are comfortable with.

If you have good fuel in your area and/or are on a standalone with a good tune, shoot for 9.5:1.
honestly I would just put cheap ge non vvti pistons and rods in it (cause the ge vvti ones are worthless) and use a gte headgasket to bring down the compression and throw some boost at it.
the bottom end even with those stock parts will handle more power than pump gas can support.

If you have bad fuel or are on the stock ecu type stuff piggyback area... go closer to 9:1 so you have a safety factor, so you could do both of them gte pistons and gte HG.
All of those setups would perform well, I have done a few different ways and everyone I talk to has a different recipe so just use it as a guide.

If you had an E85 setup purely, you could get away with 10.5:1.
If you were on a flex fuel setup, shoot for 9.5-10:1

so If I had 93 gas available at sea level, I would not do both of them personally.
if I had a non vvti ge block already, I would lower the compression just using the gasket (the non optimal squish doesn't mean much on these engines at these power levels)
if I had a vvti ge block, then I would be forced to do rods and pistons, but I prefer using the multilayer gte hg vs the single layer ge one and that lowers the compression, so I would use ge non vvti pisons and rods to keep it in that mid 9 range.

If one had a vvti ge block, they could just do gte pistons and that would get a good CR ratio and optimal squish, but you are using a single layer GE gasket which I do not think is as good for boost because the single layer is not as forgiving as several layers which can expand and contrast at different rates (real gte HG has differenet metals on different layers).
I think lots of people who try this pop headgaskets, and usually warp those vvti heads. It actually happens on stock is300s alot the first time they get a little too hot and the higher compression.

someone may make big power on it and be just fine, but to me using the multilayer HG is more important than "optimal" squish, which has never seem to come up cause alot of the guys making big power on GE motors are using gte HG's just fine.

on ge non vvti you already have the right pistons/rods, so HG is an easy choice.
On a vvti block, you might be tempted to just do pistons, but I would also suggest looking into using the gte gasket (the factory one, not a custom one).
I guess that is the end of my multilayer vs single layer rant.

Hope that helps out some of you guys in putting together these custom setups, work the numbers off of the fuel/ecu setup you have and use common sense.
There isn't a wrong way to do it, unless the engine self destructs.. then you probably did it wrong =)

Edit*
I have also a few time taken some of the recess off the bottom of the GE cylinder head, it has like an .025 - .030 recess on there that a gte doesn't have.
if you shave off .01-.02 you can bump up the compression and bring the squish back down.
Truegs300 this might be a better route for you than using a custom gasket.

so you could do gte headgasket and GE head with .02 shaved off for better squish and compression bump.
If you get too far off of the factory squish you are slightly affecting valve timing, but that can be compensated with cam gears etc..

Also, for those wanting perfect everything, a nice setup would be a ge non vvti block, gte headgasket, and gte cylinder head.
You would get optimal squish, be using the multilayer gasket, and have a mid 9 compression ratio.

And a combo you should stay away from is a gte head with a ge headgasket, just don't there is not enough squish and is in interference territory.

Have I thoroughly confused you guys yet?!?? Good cause it is confusing as F!
 
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