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One way to build a strong 2.6 liter Red Block

Q

qwkswede

Old and Slow
300+ Club
Joined
Mar 19, 2003
Location
Denver, CO
This is pretty old news to alot of people. But I spent some time cleaning up and completing the information. Its somewhat obsolete these days since you can just buy stuff from John V or R-Sport International. But, if you are determined and really like the way i rolled my own then you can do it too.

The engine has been together and running since 2006, and has about 15k miles on it at the time of this writing. Its seen a bit of track time on the road course, and half a dozen drag days. Its not babied, and usually runs about 20psi boost. Its pretty strong and surviving so far. I had a similar stroker motor before this one, and it mysteriously threw a rod. So, I'm batting about .500 on the whole DIY stroker motor thing.

I'm not the only one who has done this. TerribleOne has/had a similar project thread too. So search around.

There are pictures in the text. If you don't see them, then my server must be down. Send me a PM and I'll fix it. Or maybe later I'll attach them to the post here. But my server is usually pretty reliable. Just ask if you don't see images. I?m re-posting it here for so people can find it easier and search for it on google or turbobricks.com website.
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Shortblock details

This is how you build a strong long stroke Volvo Red Motor
Block

I started with a 1984 B23 block. At the time of assembly, this was considered the strongest foundation to start with. The block is a little heavier than the late blocks due to more iron in some spots, and it also has a forged steel crankshaft that doesn?t come in the later motors. Since then people have proven that the later blocks and cranks are strong enough for just about anything you can throw at them. But I started with the best at the time:
Block Specs:
1984 Volvo B23FT
Bore: 3.800″ (.030″ over)
Deck Height from crank center to top: 9.125″
Crankshaft


The backbone of a strong motor is the crankshaft. I started with a B23 forged crank. My machine shop did an offset grind on the rod journals to use Mitsubishi 4G63 connecting rods. The rod journals now hold the mitsu rods with about .010″ side clearance. Much nicer than the Volvo setup which guides the rods from the piston. The crank was heat treated after grinding. In metric measures, I started with an 80mm stroke Volvo crankshaft and ended up with 88.8mm stroke. This could also be done to a B21 crankshaft, it has the same size large rod journals.
Stroke: 3.496″
Rod Journal dia: 1.771″
Rod Journal width: 1.130″
<hr> Pistons

The pistons are custom from Diamond Racing. I specified the dish shape to match the combustion chamber of the 16 valve head. And they fit the Mitsubishi 4G63 rods I am using. The piston to head clearance should be about .040″, just about right for good squish. This was a priority for me, since I?ll be trying to maximize power with this turbo motor running on pump gas. Tight squish motors help keep detonation away. As a curious observation, there are 3.800″ bore pistons for small block Chevy motors with very close compression height. It could be worth looking into if you are trying this type of build on a tight budget.
Piston Specs:
Diamond Racing Products Custom Pistons
Bore: 3.800″
Compression Height: 1.471″
Rings: 1.5mm,1.5mm,3.0mm
Piston Weight: 419g
Piston to Bore clearance: .006″
<hr> Rods

The engine uses a set of Scat H-beam connecting rods for a Mitsubishi 6-bolt 4g63. These rods are nice and strong with an ARP 3/8″ cap screw holding the caps on. They also have a small hole drilled in the big end that sprays oil on the pistons. A nice little bonus feature.
The rod dimensions are:
Scat Rods for 4G63 Mitsubishi
Length: 5.906
B.E. dia: 1.890
pin bore dia: .827
Big end width: 1.117
Small end width: 1.010
 <hr>Some pictures of the assembly coming together. The final displacement is roughly 2.65 liters. Enough for some extra low end grunt.
 
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Oh I love this project. I'm leaning in this direction more and more.

Ken, if you don't mind me asking, what does it cost for the offset grinding?

Mike
 
For comparison, the Volvo crankshaft started out with 54mm rod journals, they turned down to 45mm to get th extra 8.5-9mm stroke.
 
Here is some data I put in a spreadsheet when I was assembling in 2003/4. Adjust prices up for modern labor and metal price increases. (alot I think)

Part or Labor.........Notes.........................................Source...............Cost.......Subtotals
Custom Pistons.... .Pistons, Pins, Rings, and Shipping.....Diamond Racing.....$501.00
Crankshaft Labor....Magnaflux, stroke, heat treat......... Mile Hi Crankshaft..$350.00
B23FT motor......... lots of extras with motor................Pull n Save...........$65.00
Scat Rods.............Fit Mitsubishi 6 bolt 4G63 89-91.......ebay...................$280.00
Oil Pump...............New Oil Pump................................FCP groton $69
Balance Rot Assy.....................................................The Block Shop $115.00
Clean and Bore Block................................................The Block Shop $100.00
Hone wrist pin bores for floating fit..............................The Block Shop.....$12.00
Machine rod small ends to make them fit in the pistons....The Block Shop.....$40.00
Total $1,463.00 shortblock
 
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Anyone venture a guess on what this would give you on a fairly mild 8v? Such as with chips and one of the common cams?
Or an 8v turbo for that matter?
 
wolf_walker said:
Anyone venture a guess on what this would give you on a fairly mild 8v? Such as with chips and one of the common cams?
Or an 8v turbo for that matter?
Click to expand...

This setup with an 8v is going to be ridiculously choked by the head unless it's had something pretty drastic done to it.
 
wolf_walker said:
Damn, is it that bad? Even with a turbo pushing air in?
Click to expand...

Yes...plus, why would you do this on a mild build, when you can get the extra power from doing a few more easy mods? Anyway, that's a nice looking build, cool that someone figured all that out. Do you know how much extra power you're getting over a regular block?
 
wolf_walker said:
Damn, is it that bad? Even with a turbo pushing air in?
Click to expand...

No it's not that bad. It is comparing apples to oranges though. The 8V head benefits a lot from head work. The 16V head starts out so much better it doesn't need nearly as much work to make big hp numbers. So, that's apples to oranges in my book. The 8V is fairly simple to make some good hp with. The 16V is very good but takes a bit more work to utilize its goodness. There are people here on the board making about as much hp with 8V engines as others are with a 16V. The possible hp is higher with a 16V though and the 8V engines have had good head work to produce big numbers.
 
wolf_walker said:
Damn, is it that bad? Even with a turbo pushing air in?
Click to expand...

Volumetric efficiency is volumetric efficiency, it doesn't matter if you're running naturally aspirated or boosted. The 16v head is leaps and bounds better than any 8v casting.

Proper head flow becomes even more important with bored/stroked motors since there's more cylinder to fill/evacuate than before.
 
Good comments Dave,
And really at 300hp, You need to start considering things like rod strength, and better than stock forged pistons. 400hp it becomes pretty much a necessity. That was the underlying motive for alot of what you see above. The extra displacement was icing on the cake.
 
That's pretty reasonable for a bottom end.

Are there any downsides to the smaller diameter rod journals? Would one normally do this to a cast crank?

You also mention crank steered pistons. What is the difference between the Volvo setup and yours that make it crank steered?

Mike
 
740ATL said:
That's pretty reasonable for a bottom end.

Are there any downsides to the smaller diameter rod journals? Would one normally do this to a cast crank?

You also mention crank steered pistons. What is the difference between the Volvo setup and yours that make it crank steered?

Mike
Click to expand...

The Mitsubishi rod big ends are narrower than the factory Volvo journal by a good 3-4mm if I remember. And the situation is actually the same with the Volvo rods. They can slide back and forth on the rod journal quite a bit. When the journal was ground to a smaller size, only a stripe down the middle of the journal was ground down. So, the new journal now has radiused shoulders that hold the rod to one path down the middle of the journal. I had the pistons made with a little bit of clearance to the rod journal so that any misalignment could be adjusted for at the small end now. The piston now slides back and forth along the wrist pin a millimeter or two. The Volvo pistons/rods are tight a the piston end and floating on the crankshaft rod journal. I don't know if one way is better or worse. But the Volvo way is somewhat unusual. One thing my machinist mentioned is that a big end bearing that is captured should tend to hold oil a little better. It doesn't just spray out the sides like it does on a floating bearing.
I'm almost certain that my B23 stuff was piston steered too. Though it wasn't a huge float at the crank journal. I remember .015" side play on the stock stuff.
Canuckvolvo 0.006" piston - bore clearance??? I thought mine were loose at 0.004"!
Click to expand...

Yep, its a pretty classic forged piston motor. It rattles a bit when cold, but its good after it warms up. I think I went slightly tighter than that spec provided by the piston manufacturer. But compared to some of the pistons I see lately, namely CP and JE, its pretty loose. This is the high strength/high expansion Alloy though. Diamond also does a forging with a different material that can run tighter clearances. I just wanted the strong ones. Actually, I think Diamond wasn't going for even sell me the tight running slugs after I mentioned 30psi boost.
 
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