I am in the initial phases of rebuilding a Volvo B20 engine that will eventually go into Beck. It's a little larger than the B18 engine currently in there, and by carefully choosing components as I go, I can build a much more powerful engine tailored to my tastes. I'm looking for a "street monster" - an engine with a lot of torque spread over a broad RPM range. That is a lot easier to do with modern fuel injection and electronic ignition than this old-school equipment, but I'll do what I can, always within the constraints of my very tight budget.
Today I spent about an hour measuring and comparing three different heads I had in the shop. My explorations were informed by this excellent post that details how to identify the various B20 heads:
http://www.v-performance.com/articles/volvo_b20_head_identification.html
First, you need to know whether you're looking at a B18 head or one from a B20. That's easy. The cast VOLVO script is outside the valve cover on a B18, and under the valve cover next to the valve springs on a B20.
If it's a B20 head, there are four variants: A, B, E and F. The first two came from carbureted engines, and the others from fuel injected engines. The first thing to check is the input ports. A and B engines have a step machined in the input ports for a sleeve that matches the intake manifold. That's missing on the E and F heads, and in addition, on E and F heads, each port also has a hole on the top side for the fuel injector to live.
Mine was clearly from an A or B engine, and the instructions in the link above give measurements for the thickness of each head type. Mine was closest to the A head, which has a nominal thickness of 3.41".
I didn't clean the head much before measuring, so I can easily believe 0.006" of schmutz on there. So, I have a B20A head. This chart from a shop manual gives the specs for the various heads. Sorry it's a little wonky - that's a mash-up of two cell phone photos. Click to to expand so you can read it.
The chart says the B20A had an 8.7 to 1 compression ratio, and the B20B had 9.5 to 1. The B20A head will run great on regular gas, and the B20B will probably want at least mid-grade, and probably premium. However, high compression will help me reach my goals, so I'll have to ponder a bit more before deciding. I think milling about 0.020" off the B20A head will give it the B20B compression spec.
Incidentally, my explorations also show why it's best to use a B20 head when building a B20 engine. Volvo experts tell us that it's hard to get a B18 head to run well on a B20, and comparing the combustion chamber sizes tells the tale. The B20 head much better matches the B20 bore, which is 3.500" when stock. Mine will be 3.530" after the block is bored.
But I said I was pondering THREE heads. The third is a real outlier, a head that has been heavily modified for racing. Joe Lazenby gave it to me. When I was there picking up some parts, he just said, "Here, take this." Later I realized I don't have the skills to even figure out what to do with it. I tried to give it back, and he said, "Oh no - it's YOUR doorstop now!"
This little collage tells the tale:
Photo 1: The valves have been seriously enlarged - Joe thought they were from a Chevy V8.
Photo 2: Racing-style dual valve springs.
Photo 3: This confused me for a while, because this head has the same casting number as my B20A, but the intake port step is not there. I finally realized that those ports have been seriously opened up - almost half an inch!
Photo 4: The head thickness says that this is a B20A or B head that has been milled a lot to raise compression. I'm guessing 10.2 or higher, based on a linear extrapolation from B20A to B to this.
That one will remain a doorstop for a while longer, but it's interesting to better understand what it is. And I'm happy that I have an original "carb" head to rebuild for this replacement engine. We'll see what I can make of it.
Continue on to Part 64....
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