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Boring out a b18 and sleeving it for b21 pistons?

Y

yeahoner

Member
Joined
Aug 28, 2019
I’ve searched a bunch. And maybe nobody is as dumb as me. Lots of people asking if they can bore their b18 out for 92mm pistons. Consensus is the walls will be too thin.

What if you bored it out further and sleeved it? Anybody done it? Probably cost more than just getting a b20 block I guess, but I already have the b18 that needs redone. Might get the walls checked for thickness once I pull it apart just to see what we’re working with.
 
yeahoner said:
I’ve searched a bunch. And maybe nobody is as dumb as me. Lots of people asking if they can bore their b18 out for 92mm pistons. Consensus is the walls will be too thin.

What if you bored it out further and sleeved it? Anybody done it? Probably cost more than just getting a b20 block I guess, but I already have the b18 that needs redone. Might get the walls checked for thickness once I pull it apart just to see what we’re working with.
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Your conclusion on the consensus is wrong

Most of the time you’ll be fine is the consensus - some people experience excessive heat builds up


Also your search fu sucks

boring out a b18?

I know this has been covered many times. long story short my b20 sounds like a bag of rocks, I had to drive it like that for many miles to get home... oil cooked off too. I think just about everything inside is no good I dont have any spare B20s blocks, just a bunch of heads. I do have many...
turbobricks.com turbobricks.com
 
Jack said:
Your conclusion on the consensus is wrong

Most of the time you’ll be fine is the consensus - some people experience excessive heat builds up


Also your search fu sucks

boring out a b18?

I know this has been covered many times. long story short my b20 sounds like a bag of rocks, I had to drive it like that for many miles to get home... oil cooked off too. I think just about everything inside is no good I dont have any spare B20s blocks, just a bunch of heads. I do have many...
turbobricks.com turbobricks.com
Click to expand...
I’ve read that thread. I’m talking boring the b18 to b21 piston size. That’s all b18 to b20. Or b20 to b21.
 
yeahoner said:
I’ve read that thread. I’m talking boring the b18 to b21 piston size. That’s all b18 to b20. Or b20 to b21.
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My bad then I thought it had more info b18 to 21 in here

1966 Volvo B18 Max Bore?

Hello All, I'm currently working on rebuilding a B18 for my 122s and I was wondering if someone knew how far it can be bored out to? I've heard you can make a B20 a 2.5L but I don't know if it applies the same for the B18. Thanks for reading all comments welcome.
turbobricks.com turbobricks.com


Seems like it’s a hit/miss
 
Jack said:
My bad then I thought it had more info b18 to 21 in here

1966 Volvo B18 Max Bore?

Hello All, I'm currently working on rebuilding a B18 for my 122s and I was wondering if someone knew how far it can be bored out to? I've heard you can make a B20 a 2.5L but I don't know if it applies the same for the B18. Thanks for reading all comments welcome.
turbobricks.com turbobricks.com


Seems like it’s a hit/miss
Click to expand...
Yeah. I think some sonic testing is in my future. I know the smart move is bore to b20 size or start with a b20 block, but my brain just wants to push the limit all the time. I don’t know enough about how the inside of these castings are structured to know if wet sleeves are an option either. Done right the sleeves could be swappable and extend the life of the engine indefinitely. I’m a medium speed diesel mechanic though, so that’s just how I’m used to thinking.
 
yeahoner said:
Yeah. I think some sonic testing is in my future. I know the smart move is bore to b20 size or start with a b20 block, but my brain just wants to push the limit all the time. I don’t know enough about how the inside of these castings are structured to know if wet sleeves are an option either. Done right the sleeves could be swappable and extend the life of the engine indefinitely. I’m a medium speed diesel mechanic though, so that’s just how I’m used to thinking.
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As far as I know if you want wet sleeves (like many 50-80s Italian gas engines) you will need to design the block with that in mind from the start.

The folks at Swedish Relics who seem to do a lot of this kind of work sonic test the blocks to see which ones can be safely bored. Back when you could pick up these things for free folks seem to have just tried boring them until they get one that works.

Keep in mind that you'll also have to source a B20 head. Phil Singher wrote a good Vclassics article about how not to build a motor that describes what happens when you slap a B18 head on a B20 bore.
 
I’m going to be down in portland in a few weeks. Might bring some things for Swedish Relics to take a look at.

I probably just need to do some horse trading and get a b20 core to build. My conundrum is that I have a good b20 on my stand and a worn out b18 in my car, I want to put the b20 in the car so I can drive it now, but I want to build a race engine and the b18 isn’t the right one to build. I want to pretend it is, but it’s not.

Or I just keep driving the car with 85psi compression on cylinder 4 while I build the b20. It runs shockingly well considering.
 
yeahoner said:
I’m going to be down in portland in a few weeks. Might bring some things for Swedish Relics to take a look at.

I probably just need to do some horse trading and get a b20 core to build. My conundrum is that I have a good b20 on my stand and a worn out b18 in my car, I want to put the b20 in the car so I can drive it now, but I want to build a race engine and the b18 isn’t the right one to build. I want to pretend it is, but it’s not.

Or I just keep driving the car with 85psi compression on cylinder 4 while I build the b20. It runs shockingly well considering.
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You can make a fun B18, according to some they rev a bit more freely. With a B18 you can either take it to B20 bore or just rebuild it and sink some cash into a better valve setup, a good cam, tight squish at 10:1 compression, and some port work.
 
Boring out the cast in sleeves didn't work out well when my brother did it to a B20. He had all 4 bores sleeved to run 3.66" pistons and it broke into the water jackets when it was machined. The machine shop brazed the deck to stabilize the sleeves but the motor eventually leaked coolant into the crankcase. The crank was stroked 1/4" to make it a 2350cc engine and it ran like a scalded ape but didn't last.

I think we saved a standard bore B20 block when we closed up shop. I wish you had made this post earlier because we scrapped 2 pick up truck loads of blocks, most of which were over sized and would need custom pistons, not to mention at least 40 cylinder heads.

That said, we have a set of Arias forged 3.6" (91.44mm) pistons that will bring a 6 bolt crank B20 up to 2101cc's. Let me know if you're interested.
 
I’ve got a b18 that’s currently 0.040” over and needs a rework if you want a free one to try some silly stuff with. Also have a couple b20 heads that I’m done pulling measurements from. Huge thanks to hiperf on that.

Here in the next bit of free time I have, I plan on running some CNC port profiles on a couple of different heads to see what they look like.
 
hiperfauto said:
Boring out the cast in sleeves didn't work out well when my brother did it to a B20. He had all 4 bores sleeved to run 3.66" pistons and it broke into the water jackets when it was machined. The machine shop brazed the deck to stabilize the sleeves but the motor eventually leaked coolant into the crankcase. The crank was stroked 1/4" to make it a 2350cc engine and it ran like a scalded ape but didn't last.

I think we saved a standard bore B20 block when we closed up shop. I wish you had made this post earlier because we scrapped 2 pick up truck loads of blocks, most of which were over sized and would need custom pistons, not to mention at least 40 cylinder heads.

That said, we have a set of Arias forged 3.6" (91.44mm) pistons that will bring a 6 bolt crank B20 up to 2101cc's. Let me know if you're interested.
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Thanks. This is the exact type of story I was hoping to hear when I posted. I knew I couldn’t be the only person with the idea.

I’ll keep your offer in mind once I get this engine torn down and see what I’m dealing with. Two little kids means I’m moving slow, but the older one is getting to the age where he likes to help.
 
cwdodson88 said:
I’ve got a b18 that’s currently 0.040” over and needs a rework if you want a free one to try some silly stuff with. Also have a couple b20 heads that I’m done pulling measurements from. Huge thanks to hiperf on that.

Here in the next bit of free time I have, I plan on running some CNC port profiles on a couple of different heads to see what they look like.
Click to expand...
The generosity here is mind blowing. I’m up north of seattle so I’m not sure how realistic that motor is. A b20 head might be worth shipping if I end up boring the b18 I have out to b20 size. I also have a friend in Oregon who might be real interested in cad files for head porting. I know he’s got a couple b20 projects going including a stroker build and has all the equipment to do that right.
 
Yeah, if you’re ever east of pdx, let me know. It’s just a mock up block that’s been taking up space.

I’ve got a couple b18-20 things in the works. Soon to be on the mills is a fuel injector holder/fuel rail. Then my intake manifold. Also going to be doing some little bits like alternator relocation brackets, breather boxes, maybe even a couple billet valve covers.

My shop has been booked to almost full capacity with local aerospace prototypes, so finding time has been tough. But the schedule really opens up late May/early June and I can get some more of my stuff going.
 
cwdodson88 said:
Yeah, if you’re ever east of pdx, let me know. It’s just a mock up block that’s been taking up space.

I’ve got a couple b18-20 things in the works. Soon to be on the mills is a fuel injector holder/fuel rail. Then my intake manifold. Also going to be doing some little bits like alternator relocation brackets, breather boxes, maybe even a couple billet valve covers.

My shop has been booked to almost full capacity with local aerospace prototypes, so finding time has been tough. But the schedule really opens up late May/early June and I can get some more of my stuff going.
Click to expand...
I'd certainly be interested in the fuel rail work. Been looking at modern EFI for my 144.
 
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