should I get a 2.2 or 2.5 common block

[GLHNSLHT2]

Here's what I've come up with when deciding motor size on these cars. If the car weighs 2750 and under go 2.2. if it weighs more then go 2.5. 13's on street tires is a cake walk with the right parts. Here's my setup for a 31201b (funny that's the same weight as the guys AA body) race weight 87 SHelbyZ daytona. This setup got me a 13.907@99.82. I've gone faster since by changing some stuff but you just want 13's 2.5 shortblock (bone stock no balance shafts), stock 87 T2 head and intake, stock intercooler, ported exhaust manifold stock t2 turbo, stock downpipe, cat removed, exhaust routed out the side with a section of 2.25" pipe. With this setup the car went 14.059@99.96. 60fts were 2.2x. Now you don't think ricer mods work? Well here's one that does. I installed a 89 GTC Lebaron short throw shifter in the car. Went to the track and ran a 13.907@99.84. 60fts were almost identical. and the MPH is actually a tad lower Anyway since them I've gone 13.882 but at 101.80 on a 2.360ft with 3" exhaust but still a 2.5" donut. I might make a run or two with the new 3" donut to see if what I I'm seeing in an increase in vacuum at cruise with it will translate into more hp at the track. Turbo sure does come on a lot sooner with less throttle input.

Later

[glhsken]

No Where do you state your Boost... What level...

For the most part, I agree regarding 2.2/2.5 Decision... I stuck with the 2.2 in my T-top 'Tona just for the top end and to be differnet.

Swapping the S70 and going ported ex manifold/3" all the way (with cat), the car feels stronger now at 12 psi boost and auto than it did as a 5 sp at 14 psi.

[GLHNSLHT2]

oops forgot the boost level. Due to a weak wastegate can at 4000rpms I'd have 15psi by 5000rpms I'd have 11psi and it would stay there until I shifted at 5700-5800. The 2.5 liked that shift point.
Last year I installed an MP plus turbo with a big can and the boost is set to 13.5psi which is what I ran my 13.882 run on.
Another thing I learned last year helped a ton with consistency. All my cars would have about a second gap between it's worst and best runs each time at the track. I usually get anywhere from 7-12 runs at the track each time. It was over 100 one day at the track and nothing was cooling off with the hood open in the staging lanes. They have a hose after the timing shack where all the v8 guys pull off to soak their rads each run. So the next run I pulled in and soaked the i/c with the fan running on the rad and let the fan spray some water over the motor. I also splashed some on the intake. After the I/C was good and cold (our water here is very very cold all year due to the aquafer) I pulled back into the staging lanes and shut it off. The I/C stayed cold until I shut the hood and fired it up to due my burnout. I continued to do this process after each run. The car ran with a consistency of less than .1 second. I was estactic about it! No more wondering if I was gonna run slow or if I was gonna have a good run. I can now be somewhat competetive in brackets.
As for your statement about the 2.2 having more top end than a 2.5 I haven't found that in my experience. With the 2.2 it ran quickest shifting at 5200. I had started shifting at 6grand and worked my way down to that. So when I went to the 2.5 I started at 5000rpms (you always hear 2.5's don't rev) and didn't like the times I thought I should be getting. So I started going higher each time at the track. The 2.5 with the same head, manifolds, turbo, exhaust as the 2.2 had liked 5700-5800rpm shift points. Why? Who knows. I just know it does.

Later

[glhsken]

That may be the case for your car. However.. That is not the norm. 99% of the 2.5's are done at 5200 rpm. Dyno plots show this as well.

[GLHNSLHT2]

Quote:

Originally posted by glhsken That may be the case for your car. However.. That is not the norm. 99% of the 2.5's are done at 5200 rpm. Dyno plots show this as well.

I realize that, that's why if you see the 1st time at the track I started with 5000 rpm shift points. About the only thing I can think of is that I'm one of the very few running a 2 piece intake on a 2.5. But that's a whole other can of worms.

Later

[navyboy65]

For any one who cares, my oppinon's:

The common block is just that its the same used in 2.2/2.5's turbo or non-turbo.
As for the block handleing HP, I would say that common and pre common T2 should atlead (stock wise) handle 300HP as thats what the S60 kit does. I would think if you were to go higher you might think about main cap mods, rod mods, and bolt/studs mods???

Well thats what comes to mind???

[glhsken]

A safer limit to the pre-commonblock is about 250 hp with a heavy car. A Lighter "L" body people have gotten away with more but not much. This is just a rule of thumb. A true TII block with a forged crank could go higher...

Any motor running big #'s should be main studded and think about ARP rod bolts (wave loc are their best) Plenty of cars out there running 400ft lbs and mid to high 300hp with the caps they came with.

[ForceFed Wraith]

The more I read on the board, the more it makes me want to convert my 90 2.5 to a 2.2.

What should I do in place of the balance shafts? Can I just leave them in and not put the chain on since I dont need them spinning ... or is there a better alternative?

[GLHNSLHT2]

Quote:

Originally posted by ForceFed Wraith The more I read on the board, the more it makes me want to convert my 90 2.5 to a 2.2.

Why???

[ForceFed Wraith]

with a shorter throw on the crank, it seems it will be more revv happy as opposed to being wound out at 5000. Plus I dont need those balance shafts and would like to have a forged crank (not sure if the 2.5s had a forged).

[GLHNSLHT2]

Quote:

Originally posted by ForceFed Wraith with a shorter throw on the crank, it seems it will be more revv happy as opposed to being wound out at 5000. Plus I dont need those balance shafts and would like to have a forged crank (not sure if the 2.5s had a forged).

go back through my posts. You'll see my 2.5 likes 5700rpm shift points. I seem to be the only one that can do it but heck all the parts are stock. I took out the balance shafts and dropped it under an 87 T2 top end with a ported exhaust manifold and 2.25 and 2.5" straight pipe out the side exhaust. The combo has upgraded slightly since then, but the 2.5 instantly liked 5700rpm shift points with the 2.2 top end being all the same as I had ran it the year before with a 2.2 shortblock under it. The 2.2 liked 5200rpm shift points at the track. Don't ask me why, no one can explain it. I have my theories but it'd start a holy war. But just because everyone else can't get revs outta the 2.5 doesn't mean it can't be done.

[turbovanman]

Quote:

Originally posted by ForceFed Wraith with a shorter throw on the crank, it seems it will be more revv happy as opposed to being wound out at 5000. Plus I dont need those balance shafts and would like to have a forged crank (not sure if the 2.5s had a forged).

2.2's rev higher and make less bottom end torque, 2.5's rev lower and make more bottom end torque-take your pick! My 2.5 is running 26 lbs of boost on stock crank, pistons and rods, nuff said! As for balance shafts, some 2.2's even had them, if you don't want them, take them out, simple as that!

[ForceFed Wraith]

How do you guys run all this with stock internals?

I ran 14 psi on my 2.5...freshly rebuilt and melted a piston top. I've taken the head off and can still see cross hatch marks on the cylinder walls from the honing (around 8000 miles on motor). 14 psi isn't really a whole lot but it is comming from the mitsu turbo ... probably much warmer air charge than the Garrett, even with the intercooler.

I also melted the piston exactly on the opposite sides of the spark plug ... clearly thats detonation and not a hot plug. Is this a common place to melt the piston ( right under the squish area)?

My plan was to get the copper head gasket and hopefully eliminate detonation and replace the mitsu turbo with a proper S60 or hybrid.

While its all off what else can I do to make this thing robust? Obviously the 2.5 crank can handle it and there is no need for a heavier forged crank.

[turbovanman]

Quote:

Originally posted by ForceFed Wraith How do you guys run all this with stock internals? I ran 14 psi on my 2.5...freshly rebuilt and melted a piston top. I've taken the head off and can still see cross hatch marks on the cylinder walls from the honing (around 8000 miles on motor). 14 psi isn't really a whole lot but it is comming from the mitsu turbo ... probably much warmer air charge than the Garrett, even with the intercooler. I also melted the piston exactly on the opposite sides of the spark plug ... clearly thats detonation and not a hot plug. Is this a common place to melt the piston ( right under the squish area)? My plan was to get the copper head gasket and hopefully eliminate detonation and replace the mitsu turbo with a proper S60 or hybrid. While its all off what else can I do to make this thing robust? Obviously the 2.5 crank can handle it and there is no need for a heavier forged crank.

Carefull preperation, and lots of fuel. A air/fuel guage and Egt are your best friend. I don't have an egt but run a safe fuel ratio. I deburred my crank and rods, had the rods rebuilt with ARP bolts, and balanced it.
Again, make sure you have enough fuel and watch your timing. 14 psi with no intercooler and no extra fueling is playing with fire. Sounds like you went lean, thats why it melted, you would have heard detonation but If I remember, preignition melts pistons, not detonation-that just shatters them.

[GLHNSLHT2]

Having the right timing curve on a 2.5 is imperitive because of the increased dwell time.