yes I have an a14 with an a15 crank sitting in the shed thats going to go into the old beige sedan when it goes back on the road. It'll be 77mm bore with probably a factory 70 degree cam & a baby weber off a 1600cc escort (32dfv). This will give me another 2 overbores at 77.5 & 78 mm.Built right the first time it should last a few years, then with 2 other rebuilds it should outlast me. This is the engine i use to race in the biege sedan, & we used a14 pistons machined to slightly below deck height & it still pinged like a beaut on 98 octane fuel. Needed avgas & twin webers to cure that problem. it still killed the engine later, because we found bits of piston ring in number 1 cylinder. Problem was the ring was from number 3 piston, which was very melted. Pinging is called the Hiroshima Hammer Dance cause it's pounding the crap out of the pistons, rings & Block.

At least among the racecar set, the 79mm bore size is relatively common, but as has been said, racers are obliged to regard the block as just another consumable.

For street use in an A15, I personally recomend the second oversize of 77mm. This allows ready availability of both factory & 'replacement' pistons & rings & compression ratio's that can live with pump fuel.

This also allows for one more bore job in the event of high mileage wear or some mishap with a broken ring or dust ingestion.

For mild street engines, the smaller bore size will not be a handicap, but for a full blown race engine, well that's a different story.

79mm pistons will give you 1608cc on an A15.

there's an A15 that manages to get 1608 so it's one of the very few A16's.

i agree with Dodgeman that going to 80 mm isnt something i'd do for a road engine. I assume the 80 mm pistons were for a speedway engine, so they might run a bit cooler due to the fuel. The constant heat cycle of road use would probably create bore shift & cause blow by. So maybe use the largest stock pistons at 77.5 mm. When the bore wears you can then get a half mil clean up & use the 78 mm pistons. Get 2 lifes out of the engine. The philosyphy of maximum bores for race engines is because if the bore ever wears out, you get another block. A friend with an LJ Torana has problems because all the engines he finds in wreckers & such are at the maximum overbore. Also note the pistons suit an A14, to get it to fit an A15, you have to machine the piston tops to even get a flat top. Not something i'd be doing if i wanted a reliable engine, weaken the pistons & you get still get an astronomical compression ratio.

Quote:
Quote:Running an 80mm bore is pushing it right to the limit & then some in my view, & as it says in the post, block must be offset bored. The cylinder walls can get mighty thin at the ends & in the center of the block when this happens.
Even 79mm is pushing your luck in many cases. The problem mainly centers around the amount of material between the end pairs of cylinders for the head gasket to seal on. It starts getting awfully thin at these sizes. Awfully thin indeed, yet most racers seem to hold together most of the time.
Offset boring helps even at this size.
I doubt that thid bore size would constitute 'reliable' or 'not extreme' in a street engine but they will push an A15 to 1649cc

To answer a question I forgot to address earlier, the stock A15 pistons are not only dished, but have the deepest dish of the stock A series family in order to keep the compression ratio the same as the others.

I've ordered 78mm pistons for my A13 & this should be a good safe size for this engine as it's only a half mm larger than the third/largest standard oversize.

I have a set of A14 80mm forged pistons with rings ,the block must be sonic tested and bores offset to suit , can stroke or destroke to suit A15 for more info ring ernie 0412 864 741

The standard bore size is 76mm & there are three standard oversizes in half mm increments, so the factory supplies pistons out to 77.5mm.

Many racers regard 79mm as the 'racers standard' & while this pushes it over 1600cc, it's just a little, it's still legal in the1600cc class.

If your standard bore was worn 0.3mm, which is outside service limits, your smokey engine would displace 1499.72cc. Now that's 1500cc in my book, so to answer your question, yes 1500cc is achievable. The following bore sizes will give you the capacities indicated.

First oversize 76.5mm= 1507.6cc
Second oversize 77mm= 1527.4cc
Third oversize 77.5mm= 1547.3cc

If you want reliability & serviceability in a street engine, then any of the sizes above should do the job just fine.

3mm-120thou is the max.

I think my A14 is bored 120thou.. Wouldnt want to bore much more than that!!