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Old 11-18-2016, 09:07 PM   #1
SGT StudMuffiin
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2.8L M20 Turbo Build Question

Howdy fellow r3vers,

I had a few questions about building a 2.8L M20 stroker. I've done my research, but all the info out there is so different from each other, that I decided to start a new thread in hopes of finding a more simple answer, specifically for application.

First of all, a little run though of my car. So in June of this year, I decided my slushbox and stock m20 did not cut it anymore, so I decided on going 5 speed and a turbo. While searching for parts for the build, I came across a local guy selling a 2.7i turbo M20 with the G260, MS2 and most of the other parts that I would have to buy either way. I bit the bullet and bought the whole shebang. I gave the whole thing to my mechanic to install and a few weeks later, I got the car back and 4 days after driving it, the head blew on the way to the E30 picnic (about a 2-hour drive for me). The head blew because I had to drive the car 2 days on the base tune and it detonated like motherf****r, so the damage was already done, yet I didn't realize this until I brought my car back home. So basically, I dropped the car off again for a head rebuild and I did some other bits and bobs too (Podi gauge, wideband, electric fan, 75* thermostat, Mishimoto rad, IE HD rockers, Walboro 255lph, etc).

4 months passed and I finally got the car back, and now it was time for another dyno session. I dropped it off as soon as I got the car back from my mechanic (towed it instead of driving it, to be safe). My tuner phones me later that day saying my wastegate was screwed up, but other than the boost leak, the car was running good and drivable. So I ordered a new wastegate (Tial 38mm) and booked the car in for dyno a week later. So, I drop off the car off along with a new wastegate, ready for the final tune (and btw I was only at 11psi on an oringed block, ARPs, and low compression OEM gasket when the head blew and same for the new tune) but on the day I was supposed to get the car back, my tuner phones me saying that as he was finishing up the tune, some loud knock starting happening. I towed the car back to my mechanic, where we discovered a wrist pin let go.

I now need a block rebuild and I really just want to be done with this thing once and for all. While researching on the rebuild, I decided I might as well go 2.8L. Here are the parts I think I want to use:

-M52B28 Forged Crank (84mm stroke)
-Eagle 135mm Rods
-JE Forged Pistons (84.5mm or 85mm bore?)
-Some nice coated main and rod bearings
-Crank spacer thing (necessary?)

Now for my questions:

-With this combo, what compression pistons do I need to buy for an overall CR of 8.5:1?

-Will 135mm rods even work? People say they do, but I always hear of people running 130mm.
-I am going for a reliable yet powerful build. Will these parts cut it and is going stroker even a good idea? I plan to run about 12 psi as a daily driver map, but up to 22psi once in the blue moon when I want some extra fun.

-I talked to Mourad at VAC, he says a cutting ring gasket is the way to go, but my block is oringed. Will it work or do I need a new block?

-Should I go with 84.5mm or 85mm bore? Will 85mm be pushing it a little bit if I want to go for longevity?

-What's the deal with the crank spacer thing?

-What would be a safe rev limit for this stroker?

I hope you guys can help and give me some good advice. My head is spinning right now trying to plan this whole thing, and in the back of my head something keeps telling me this won't be reliable despite the quality parts. Any input is valued, and for sure, go ahead and add any extra comments or observations!

Thanks,
Marcus
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Old 11-18-2016, 09:11 PM   #2
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Go with a running stock unopened block, they're cheap and plentiful. it seems like when people mess with these cars and "build" the blocks it Just causes other problems.


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Old 11-18-2016, 09:38 PM   #3
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Go with a running stock unopened block, they're cheap and plentiful. it seems like when people mess with these cars and "build" the blocks it Just causes other problems.


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But it is just another 25 year old engine. If I decide to triple the power on that, aren't I just asking for problems? A built engine is at least new.


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Old 11-18-2016, 09:52 PM   #4
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You need the spacer for the oil seal.

If you use cutring check what bore can be used with. 85 should be fine though

Use 135mm rods with forged custom Pistons , people use 130mm rods with oem Pistons as longer rods push piston too high out of the block

And find a new tuner
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Old 11-18-2016, 10:10 PM   #5
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You need the spacer for the oil seal.

If you use cutring check what bore can be used with. 85 should be fine though

Use 135mm rods with forged custom Pistons , people use 130mm rods with oem Pistons as longer rods push piston too high out of the block

And find a new tuner


Thanks that definitely clarified a few confusions? Why a new tuner though? I wasn't too surprised to see it go I mean the internals are stock and old after all.


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Old 11-19-2016, 07:59 AM   #6
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The seal spacer is mandatory. A 135mm rod works fine if you use pistons that have a lower compression height to compensate for it, such as the ones in the IE 2.9 stroker kit. The rod ratio (rod/stroke) is higher this way too, it's not a big difference but it's closer to stock geometry. Rev limit depends mostly on your top end, and you won't likely gain much from revving to 7,000rpm+ vs 6,500 without a cam that suits it. Got any pictures of the wrist pin failure?
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Old 11-19-2016, 09:33 AM   #7
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The seal spacer is mandatory. A 135mm rod works fine if you use pistons that have a lower compression height to compensate for it, such as the ones in the IE 2.9 stroker kit. The rod ratio (rod/stroke) is higher this way too, it's not a big difference but it's closer to stock geometry. Rev limit depends mostly on your top end, and you won't likely gain much from revving to 7,000rpm+ vs 6,500 without a cam that suits it. Got any pictures of the wrist pin failure?


Unfortunately I have no pictures and my car is still sitting at my mechanic. On the other hand, I have 284* Camshaft so I don't plan to rev to over 7000, I just wanted to make sure that because of the longer stroke it won't be limited in revs. Also, if I went ahead and bought some JE 8.5:1, would my compression be higher than that?


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Old 11-19-2016, 10:13 AM   #8
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I'm not familiar with the compression height of the 8.5:1 JE pistons, and whether it's appropriate for the 84mm stroke and 135mm rod combo, but I don't think it is. I think you'll need a custom piston with a lower compression height.
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Old 11-19-2016, 01:32 PM   #9
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Originally Posted by SGT StudMuffiin View Post
But it is just another 25 year old engine. If I decide to triple the power on that, aren't I just asking for problems? A built engine is at least new.


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What are your goals? Seems like 400 whp is safe and that's about triple when you convert that to crank hp


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Old 11-19-2016, 01:40 PM   #10
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Unfortunately I have no pictures and my car is still sitting at my mechanic. On the other hand, I have 284* Camshaft so I don't plan to rev to over 7000, I just wanted to make sure that because of the longer stroke it won't be limited in revs. Also, if I went ahead and bought some JE 8.5:1, would my compression be higher than that?


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Je do either off the shelf Pistons of custom. Custom will get you what you want. Off the shelf there might be some places that sell them but you need to tell us what Pistons you mean. What specific JE Pistons are you talking about ? Who sells them ?
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Old 11-19-2016, 03:21 PM   #11
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Je do either off the shelf Pistons of custom. Custom will get you what you want. Off the shelf there might be some places that sell them but you need to tell us what Pistons you mean. What specific JE Pistons are you talking about ? Who sells them ?


VAC has them. I should also mention I'm not specifically looking at just JE, if they work better, I could go for CP, Wiseco, etc.


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Old 11-19-2016, 03:22 PM   #12
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What are your goals? Seems like 400 whp is safe and that's about triple when you convert that to crank hp


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Yea I'd like about 350 whp or so and then up to like 450 once in a while.


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Old 11-19-2016, 03:22 PM   #13
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Does anyone know what pistons are compatible with the 84mm crank and do the 135mm eagle rods even work with the crank?


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Old 11-22-2016, 08:01 AM   #14
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this has all been done before. Do some research, the information is out there...

http://www.e30zone.net/e30zonewiki/i...0_Stroker_Info
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Old 11-22-2016, 01:32 PM   #15
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VAC has them. I should also mention I'm not specifically looking at just JE, if they work better, I could go for CP, Wiseco, etc.


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doesnt look like they have a JE piston for you without getting them to do it custom, but you should call them its a straight forward request. there are others that can do it to. topend etc
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