Overbore to .040

[anokabball24]

Want some quick feedback on my project. I talked to my machinist and my block (reman'd unit from an '88 2.2 T2 Daytona) was in fairly rough shape and he's recommending a .040 overbore.

Not wanting to risk anything, I want some feedback on this. What's your opinion on this much of an overbore? My car will be running around 16–18 psi on the stock turbo, will have all forged internals, and should hopefully make around 230 whp.

Just want some peace of mind before I dump money into this block.

[turbovanman²]

Go for it, the only downside is if you blow it up, you can't rebore again.

[RoadWarrior222]

I think your compression goes up a bit though.

[anokabball24]

Go for it, the only downside is if you blow it up, you can't rebore again.

I don't plan on this happening. :thumb:

[135sohc]

Go for it, the only downside is if you blow it up, you can't rebore again.

This^^^

personally I would try to find a standard bore block and go the first oversize (.020 for these engines for standard available O/S pistons) so if something happend your not totally up the creek. Otoh if you were going to keep it a very mild 'safe' build and not play with things a .040 oversized should last as long as your needing it to.

[shackwrrr]

Pop out the freeze plugs and look at the casting lines, mine cracked after .020. The casting lines on mine weren't lines, they were casting crevices.

[anokabball24]

All,

I've just let the machine shop know that I want this ----er sonic checked before I waste any money machining it.

[RoadWarrior222]

Sweet, then you'll know if you can go to .060 :thumb:

[turbovanman²]

I think your compression goes up a bit though.

I would think it goes down, larger bore, same head CC equals less compression.


I don't plan on this happening. :thumb:

We never do, :p

[RoadWarrior222]

I would think it goes down, larger bore, same head CC equals less compression.Simon, Simon Simon, more swept volume for same head CC equals MOAR compression ...

[anokabball24]

Block was sonic checked and is fine for a .040 over bore, min thickness was .205 and there was very little coreshift according to shop.

[shackwrrr]

Block was sonic checked and is fine for a .040 over bore, min thickness was .205 and there was very little coreshift.

Eh, I wouldn't, minimum recommended is .200. After bore you'd be be at .165, pretty damn thin.

[anokabball24]

Eh, I wouldn't, minimum recommended is .200. After bore you'd be be at .165, pretty damn thin.

Oh really? Good to know. This shop has done at least a dozen of these engines. Interesting that they advise .205 being workable. I'd hate to risk it and be out a lot of money.

[shackwrrr]

Oh really? Good to know. This shop has done at least a dozen of these engines. Interesting that they advise .205 being workable. I'd hate to risk it and be out a lot of money.

I've always been told up to 500hp you need at least .200, over 500 you need .250. Some input from others would be nice as these engines might be different.

[shackwrrr]

Well I did some research and for a street engine (n/a) minimum on the thrust side is .170, .125 on the non thrust side. Since its Turbo an you plan to up the boost a bit .190 is recommended on the thrust side and .170 on the non thrust side.

The thrust side is the rear of the block. Its close but if your thinnest spot is not on the thrust side it might be good.

[anokabball24]

Well I did some research and for a street engine (n/a) minimum on the thrust side is .170, .125 on the non thrust side. Since its Turbo an you plan to up the boost a bit .190 is recommended on the thrust side and .170 on the non thrust side.

The thrust side is the rear of the block. Its close but if your thinnest spot is not on the thrust side it might be good.

If I were to move forward with this block I would be investing $1100 into machining and assembly, and another $600 in rebuild parts. That aint worth risking. No way in hell am I going to let all my money ride on where the thinnest spot is.

[shackwrrr]

I agree with you there, Virgin blocks are always the best way to go. The route Im taking with my van is using a TBI block. Lots of those around that have never been rebuilt or molested. They usually didn't have as many components replaced as the turbo blocks so head bolt and transmission holes shouldn't have much wear. The only problem is the oil drain, the boss is there you just have to have it drilled out for the turbo drain.

---------- Post added at 08:00 PM ---------- Previous post was at 07:55 PM ----------

Look at this picture here:

40796

Look on the right side of the cylinder, see how the casting seam created a v notch. This is right where my block cracked at, Since you are so thin this v notch could make your cylinders even thinner. That imperfection is so narrow I dont think the sonic tester would pick it up.

I got that picture from here:
http://www.turbo-mopar.com/forums/knowledge.php?title=Engines:2-2-2-5-Block-Differences

I (http://www.turbo-mopar.com/forums/knowledge.php?title=Engines:2-2-2-5-Block-Differences) attached my cracked block picture

[Gaboon]

Personally I wouldn't worry about it. My block is .040 over, I run upwards of 30 psi (on race gas)with a big turbo and have no issues what so ever. I might also add that I run a fairly decent shot of NOS on top of that. I do however run forged pistons and H beam rods along with a forged crank and ARP fasteners. This is a non lightened 87 SC (2640 lbs) and will run 129 mph through the traps so its making some decent power. but here's the the thing,this is an early T1 block....(actually the original block) you know the ones that everyone said could only take a max of about 250 hp:nod:

[Force Fed Mopar]

The 2.5 in the Lebaron is bored .040 over, no problems, spiking over 20psi on a stock turbo.

[shackwrrr]

Personally I wouldn't worry about it. My block is .040 over, I run upwards of 30 psi (on race gas)with a big turbo and have no issues what so ever. I might also add that I run a fairly decent shot of NOS on top of that. I do however run forged pistons and H beam rods along with a forged crank and ARP fasteners. This is a non lightened 87 SC (2640 lbs) and will run 129 mph through the traps so its making some decent power. but here's the the thing,this is an early T1 block....(actually the original block) you know the ones that everyone said could only take a max of about 250 hp:nod:

And to correct another post, the thrust side is towards the front.

Its not that .040 isn't recommended, the block is just thin, yours might be thicker. Crank spins clockwise looking at pullies, as the rods push the crank forward and pistons back therefore thrust is on the rear.

[RoadWarrior222]

Well now you have a purpose in life, to find the "perfect" block... now if you were a factory race team they'd probably let you have the pick of 50, but it's gonna be work pulling even half a dozen and hoping you find one better.

[Gaboon]

Its not that .040 isn't recommended, the block is just thin, yours might be thicker. Crank spins clockwise looking at pullies, as the rods push the crank forward and pistons back therefore thrust is on the rear.

Edited my post after thinking for a second... Thrust side is always to the right when looking from the flywheel end (crank spinning counter clockwise)

[anokabball24]

Thanks for the feedback everyone. I guess my biggest concern is that I'd be spending close to $2000 rebuilding a very worn block and am stuck with .040 slugs should something happen. Just seems like a large investment for something that could inevitably be replaced by something in better shape (i.e. a fresher block that doesn't require the max overbore)

Not to mention the crank needs to be cut .030/.030.

Just doesn't seem like a cost effective build.

The hunt for a decent CB ensues.

[turbovanman²]

Personally I wouldn't worry about it. My block is .040 over, I run upwards of 30 psi (on race gas)with a big turbo and have no issues what so ever. I might also add that I run a fairly decent shot of NOS on top of that. I do however run forged pistons and H beam rods along with a forged crank and ARP fasteners. This is a non lightened 87 SC (2640 lbs) and will run 129 mph through the traps so its making some decent power. but here's the the thing,this is an early T1 block....(actually the original block) you know the ones that everyone said could only take a max of about 250 hp:nod:

Shadow is making over 500 whp on his early T1 block too, :p

[Force Fed Mopar]

The crank in my T2 was cut .030/.030 :)

[anokabball24]

Can you guys help me verify what block this is. Dude said it's from a '90 Lebaron Turbo (GTC?)

http://i563.photobucket.com/albums/ss72/durangort59/026-1.jpg

http://i563.photobucket.com/albums/ss72/durangort59/025.jpg

http://i563.photobucket.com/albums/ss72/durangort59/027.jpg

It looks like a CB, but I can't tell for sure. Thoughts?

[Force Fed Mopar]

Looks like it has the fuel pump hole in the side still and the block date is 8/29/88, makes it a late '88 non-common block.

[turbovanman²]

Square or round tooth timing belt? Round tooth is CB, square tooth is 98% non CB.

[anokabball24]

Keep it coming fellas. I asked the guy if it's round or square tooth.

[shackwrrr]

Looks like it has the fuel pump hole in the side still and the block date is 8/29/88, makes it a late '88 non-common block.

That's the water pump hole. Rear pan rail is strait and no fuel pump hole makes it early common block.

If the crank is good, I would build up the 2.5

[RJ138]

Don't the balance shafts automatically make this a common block?

[Force Fed Mopar]

That's the water pump hole. Rear pan rail is strait and no fuel pump hole makes it early common block.

If the crank is good, I would build up the 2.5

Ahh yeah I see that now. Also has the large front seal housing.

[anokabball24]

Appreciate the feedback guys. Looks like I may have found the ticket.

[turbovanman²]

Don't the balance shafts automatically make this a common block?

No, 2.5 tall decks had balance shafts, but the late casting, bs's AND if the crank gear is round tooth, its a CB.
Pictures didn't show up for me yesterday.

L

[bakes]

I got my lancer 40 over now was 30 plus im running 30psi and getting ready to drop 75 shot on her

[anokabball24]

I got my lancer 40 over now was 30 plus im running 30psi and getting ready to drop 75 shot on her

Bitchin. WHP/TQ?