STROKING (a Buick 215 or a Rover 3.52)

Webmaster note: Stroking is a process where the capacity of the engine is increased by varying combinations of different crankshafts, conrods, pistons, piston head shape and over-boring. By changing the length of the "stroke" of the pistons, the effective combustion space is increased with benefits to the power the engine can produce. The work must be precisely done. Here are some notes...

from a gent down under
My personal experience was with the original Buick 3.5 V8 casting. I don't know where you are, but I see the Servicesoft company is based in the states. So the following makes and models may not mean a lot to
you, but you should be able to get the parts imported or whatever.

It is not recommend boring  the Buick/Rover 3.5 block out past 0.020" (20 thou) but I went for coma and bored it out 0.063" (63 thou) with no problems. I used 179 Holden pistons as the compression height was spot on. They are a flat top piston but sit down lower in the bore. The standard Buick/Rover piston has a higher compression height, but is a "bowl in piston" type, so they lower the comp that way. Using the Holden piston's was good in a couple of other areas, Cheap, readily available and because they sat down lower in the bore you can put a big bump stick in it without having to worry about the valves hitting the pistons. Also the Holden pins are smaller so I was able to convert them from a press fit to fully floaters and fit bushes to the rods - blessed!

This is what you will need.
8 x ACL P/N#     3623B or 3625 Sleeves.
8 x ACL P/N#     RY3000 060 piston set. They come in a set of 6 so you will have to buy 2 more with pins, rings etc. Go for the Duralite slugs, there better and chrome molly rings.

I am an Automotive Machinist by trade and had all the gear at my disposal and years of experience around me to call on, it was pretty simple. I used a AMC overhead boring bar which uses the sump face as the index. The sump face is used as the index for all engines as is the rocker cover face for the heads.

Whoever you get to do the work for you, make sure they have an overhead bar, period. If they have a portable bar and index off the head face - expect problems, it's a no no!! Go somewhere else. OK they will know what to do, bore the sleeves off center, collapse them, remove them.

Next: index up the bar to the bore centers and bore out the parent alloy to take the "B" sleeves. The B sleeves are thicker in the wall and provide more strength. This is why this has to done on an overhead bar as the you need to go in perpendicular to the crankshaft in both the X & Y planes so the that the slug will travel up and down perfectly square to the mains. If you don't understand this and your machine shop can't explain it to you leave as fast as you can, you are talking to Aliens!

Once the sleeves are fitted, the main caps should be fitted and torqued up while all this is going on. Now a good idea is to fit a set of head plates to the head surface for the same reason, no distortion, then just bore the sleeves to suit and hone of course. They might have to machine a bit off the bottom of the skirts so they don't fowl the crank, but they will know all this.

You will need to work out the compression ratio and either machine the tops of the pistons or open up the chambers. Fully balance the motor and all the things that hang off the crank, goes without saying.

Result 4899cc or  298.8 CID that's some mumbo. You can stroke them up to 5.2 litre but that involves more dosh. The way I suggested is pretty common and cheap."

Good Luck.

Webmaster Notes Stroker Kits are available from D&D Fabrications in Michigan or Rimmer Brothers in UK, both capable of increasing a 3.5 to a 4.4 or a 3.9 to a 4.8. However, at the time of this writing (July 28, 2001), the price of a factory new 4.6 block has dropped to the point where it has become competitive with the stroker process.