I sent an email to Malvern Racing ordering one of their catalogs. I satated thatI wanted pistons and a few other goodies to build a street engine. Steve replied that I should build an A15 bored to 97mm and use 1600 pistons. I still am not sure if it can be bored that much. It looks like there just isn't very much room between # 1 & 2 pistons and # 3 & 4 pistons for very much boring. Those cylinders are Siamesed pretty tight.

My question is "How much can an A15 be safely bored?"

If I can bore one to a 1600, I want it for sure but I am not boring to strike oil, I am boring for longivity also. The most that I have ever had one bored was .010 oversized on an A14. I don't want it to run hot.

Steve is going on vacation this week and he will get back to me on this later. I am just trying to find someone that has bored an A15 and see what problems that they have had.

Mareo

they are 87 mm std arnt they if they are there is no way that u can take 10 mm out without running very very hot and not a long life expectancy i think

If the 1600 he's talking about is the L16, I'm pretty sure they are 85mm, and the L18/L20B is 87mm. I'll double check my 1600 service manual, though. Still, 8mm is ALOT to take out of any engine. That's around .355 over! Alot more than .020 over. Are you sure the A15 is 85mm bore?

I just looked in my Datsun book, A-15 stock bore and stroke is 2.99x3.23, that's a 76 mm bore. I called and talked to the guy at Malvern racing before and he was trying to talk me into boring the A15 out to basically an A16. To get 1600 cc's would require boring an A-15 out to 3.215" which is 225" over, almost a quarter of an inch! Basically the bore would be another 1/8 of an inch bigger around in all directions. I haven't looked at how much metal is between the cylinders in a while, but I have a Comp head gasket that measures 3.125" bore, and there isn't very much materiall at all left between #1/2 and #3/4 cylinders. Boring the A-15 out like that would make an almost square bore/stroke ratio like the A14 (2.99x3.03) but I don't know what that's worth. You'd definitely need a good, large radiator to keep it cool if it was bored out that much. I don't think it's worth it, but that's just my opinion. Anyway in a few years I'll be putting a different, bigger engine (CA18DET?) in my 1200 to get the right kind of power out of this car. The A series would just take too much to get anything close to an engine like that and yet retain it's legendary reliability and efficiency. Until I can afford such a project though, I'm in the same boat and will try to get as much power from my A15 as I can afford.

-Andy

That is a pretty ambitious size in a standard block. I would bore the cylinders even larger and fit sleeves. Also to beat the cylinder spacing problem offset the bores slightly. This alters the efficiency of the filling action of the chamber but it's bugger all. To get the capacity I'd also weld the crank and offset grind it to change the stroke. Look around and some other rod lengths and piston diameters and pin heights and work backwards from there.

Hey fellas, An A16 would be nice but obviously cant bore it to that degree! My A15 block has been bored 120thou and keeps cool no prob. I doubt taking it past 140 thou but have heard it done. With the A14 crank capacity is around 1530cc. It hauls and revs real hard. Major headwork and twin 45s help aswell but its a neat little engine.

Scott
Davo

I know of several race A15 engines that have been bored to 1608cc this is as far as they normally go and Im pretty sure they are offset bored so 3mm or 120thou over is about the limit for reliability. Davos engine (my old race a14) is 120thou over and it hauls pretty hard i miss the sound of it actually.Now I just have the big whoosh of the turbo and around an extra 200hp so i cant complain.
Andrew.

PS: will be posting some pics soon of the latest engine mods crank is getting worked over with nitriding shotpeened and a linish the rods are also getting the once over with some ARP chev rob bolts and a polish ect.Bottom end shoudl be good for close to 450-500hp. No more power yet until I save and get some JUN wobbly sticks and valve springs will probably have to upgrade the injectors too :-0

the biggest i would bore your a15 is to 78 mm which is obviously 2mm(80 thou) over.you could go to 79 mm,but pistons in that size seem hard to come by unless you use forged pistons.i have an a14 that is 79 mm bore,but the block was very carefully checked out before hand to make sure there was enough metal.the pistons i used were japan castings from a nissan catalogue,& they also listed pistons for a15's,but this is almost 10 years ago,& i can't find the catalogue anymore(i put it somewhere safe).i friend of mine here in australia uses 78 mm aftermarket pistons to suit a mazda engine (i think they are for an e series engine).his engines are quite good(hasn't blown one up yet), so this might be another way to find pistons reasonably cheaply.a 78 mm bore gives you approximately 1570 cc's,a 79 mm bore is 1608 cc's,like andrew (ca18det) mentioned,but some of these 1608's tend to be grenades.

also noticed someone suggesting offset grinding the crank,please don't.the a15 crank isn't as tough as an a14,& by offset grinding you weaken it further.have seen too many cracked cranks,in fact the first a15 i bought came complete with one,to not mention this.looking at the crank shows how little support there is between big ends & journals,in fact i always get any a14 or a15 crank i use crack detected then nitrided as added insurance.sure they always seem to bend during nitriding,but they can be straightened afterwards(wilkins performance in seven hills has straightened all 3 of my cranks for me).

When Steve a from Malvern Racing suggested boring to 1600 , I rejected the idea as not very cost effective. I have my old extremely high revving A12 but it has a burned piston and scarred cylinder wall. I have always assumed that the wall was so badly scratched that it couldn't safely be bored out without sleeving it. I really had not thought of offset boring but that may be practical for the old A12. I will have to check out the block when I get back home.

There is a notch at the top of each cylinder on the intake side that I had always assumed to be the safe boring diameter. I really haven't measured the notch to see how large the cylinder can go. There is only about .250 between 1&2 and 3&4 cylinders so boring to 1600 CCs is not practical and Steve at Malvern Racing is not what I consider reliable information.

You were very right about the A15 crank, B310GX, they are cast (and not as reliably), not forged like the early A14 and A12 cranks. I have seen a lot of 79 - 82 A14 cranks that are cast also. The only stock cranks that I would even consider using are the forged A14-H72 cranks from the 80 HP engines.

When I first contacted Malvern Racing, it was for pistons for the A14. Steve there suggested the A15 bore and I ran the idea here for input because I didn't think it was feasible. I still don't. 97mm is Chevy/Ford size, not A-series size.

I am now waiting on Malvern Racing to reply with my original question and a catalog. I think he just wants to sell more parts, not sell me what I want. I just want to have a fun motor, not a monster.

My friend that has the machine shop that I have used since the 60s has retired this year so there goes a world of knowledge that is now unusable. I have to go outside his realm now and I just do not trust everyone's knowledge. I have heard too many nightmares to take one person's opinion at this stage of life.

I love this club because there is very reliable knowledge here on the 1200. Thanks everyone.

Mareo