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Redblock stroker kits: what are they like and who are they for?

S

sspiff

New member
Joined
Aug 17, 2020
Hi all,

I noticed that quite a few race or higher end products seem to target a 2.5 stroker engine for the red blocks. I also noticed there's a plethora of stoker kits available in Sweden. There's 2.5L, 2.8L, 3.0L and even 3.2L.

I've always been told that noone makes a 4 cylinder over 2.4L because the vibrations become very uncomfortable. How are these stroked redblocks? I'm assuming they have increased torque and lower end, but higher vibrations? Are they driveable on the street or really only make sense in a race or drag context?
 
Here, read this

Redblocks are pretty "over square", meaning they have a shorter stroke to bore ratio. There are plenty of sub 2 liter 4 cylinders with more stroke than a redblock. Honda K24's had a 99mm stroke with a rod ratio of 1.58:1 and you see how people run those. Penta AQ151/171's have a 86mm stroke with 1.91:1 rod ratio and are 2.5 liters. It's apples and oranges of course but you get the idea. I've wondered how a 3.0 rotating assembly would work in a B234F block, which used balance shafts. Redblocks are buzzy as they are, I'd most be concerned about the idle characteristics of a 3.0 8v redblock if you wanted peak power at 5500 rpms. If you increase the pumping ability of the motor but don't do anything to the head, your powerband will shift downward. Increasing just the stroke (2.3L redblocks are bore limited to 97mm, or .040" over), doesn't allow any more room in the combustion chamber for much more chamber and valve work and the 8v heads are limiting as they are.
 
sspiff said:
Hi all,

I noticed that quite a few race or higher end products seem to target a 2.5 stroker engine for the red blocks. I also noticed there's a plethora of stoker kits available in Sweden. There's 2.5L, 2.8L, 3.0L and even 3.2L.

I've always been told that noone makes a 4 cylinder over 2.4L because the vibrations become very uncomfortable. How are these stroked redblocks? I'm assuming they have increased torque and lower end, but higher vibrations? Are they driveable on the street or really only make sense in a race or drag context?
Click to expand...
I've driven a 2.5L B20 Amazon, the thing moves fast enough that I never noticed the vibrations. The bored and stroked B20 setup built either by Tinus Tuning or Swedish Relics seems to be the new hotness in the OHV redblock space. The good old Penta 2.5L stroker crank has been a thing in the OHC engines for a while now.

Early Tacomas got 2.4 and 2.7 liter flavors of the RZ engine family. The 2.7 had balance shafts but the 2.4 didn't.

Overall most modern four cylinder engines will feature balance shafts.
 
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OttoB said:
I just found a tempting stroker kit for my DD.
Cast 86 mm stroker crank and -3 mm H-rods. Just under 800 euro. I'm getting one!
Click to expand...
That is the standard Volvo Penta 2.5L. Make sure you get pistons, as the pin location is different. Rods are the same length as stock.

And damn, I got 2 2.5L engines for 500 bucks, with v cams and 531 heads
 
Pietercc said:
That is the standard Volvo Penta 2.5L. Make sure you get pistons, as the pin location is different. Rods are the same length as stock.

And damn, I got 2 2.5L engines for 500 bucks, with v cams and 531 heads
Click to expand...
This is aftermarket thingy. Not Penta, marine engines are not so cheap here Finland. "Everybody" knows to look for Penta engines and prices are high.
 
OttoB said:
This is aftermarket thingy. Not Penta, marine engines are not so cheap here Finland. "Everybody" knows to look for Penta engines and prices are high.
Click to expand...
I understand it's aftermarket, does it say if you need pistons? As if it's modeled after the OE setup then the pistons may be different. Just stating that 86mm is a solid stroke, as even Volvo did it
 
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