namasgt

Im still looking for a good short block for my 88 S4.
if its doable is it a feasible replacement.

mark kibort

That would be a cool combination 11.5:1 compression! I think there are a few things you need to do with the block, like make a little spacer for the timing on the flywheel sensor, and a couple of other small mods

mk

Jim Morton

As Mark mentions, the compression ratio will be quite a bit higher. This should be taken into account with how you plan to use the engine. Could be good, could be bad... you need to consider what fuel you'll use as well as the cams / cam timing.

Also, if you plan to run the S4 intake manifold, you need to trim two button points in at the top of the valley, mid way. The protrusion will interfere with the S4 style manifold...nothing that a die grinder cannot take down without harm to the block.

Enjoy.

FBIII

I've been curious about this as well. Do the valve reliefs that are cut into the pistons align with the S4 heads?

namasgt

Thanks for the replies.
Im not trying to make a high performance engine, one of my friends sayed that he knows of two 86 short blocks that I may be able to use, had no Idea the compression ratio would change that much. It looks like no one has done such a swap on their car.

Hilton

From memory, John Gill has done it - although he used RoW '86 short block, which has lower compression from factory, so the net effect isn't quite as hairy as 11.5

The RoW 32V engines are reasonably rare - Australia and Japan both got 'em. A lot of European markets had the 16V S2 engine in '86 with the S4 suspension, brakes etc.

Vilhuer

Cuts are smaller in '85-86 32V as intake valves are only 35mm. Might as well make them 39mm as CR needs to be lowered anyway and then its easy to install 968 intake valves.

ROW '86 32V pistons will create around 10.8:1 CR without any piston top modification.

namasgt

I do have my 88 pistons, would those work, if I rehone the cylinder walls and install new rings, keeping the 86 crank and rods ?

mark kibort

If you care about performance, i would use the 85 pistons, if they are a set matched to the block and crank/rods, it will save you the balancing act. (more cost for less power if you use the 88pistons)

as far as the valve cuts, the cuts are very very faint. (less than 2cc) a dremel of the outer circumference will work just fine to give the emergency clearance . engine will run fine with the cuts the way they are, without ANY issues. if you dig them a little deeper, you might even be able to make a non-interference engine!

GregBBRD

OK, now that's just a bit too much "backyard". PUT DOWN THE DIE GRINDER!