Quote:
A14force wrote:
D/Man, I 'spose .020 isn't much, but how much meat will that leave above the top ring? Probably wont create a problem, but with some senarios I looked at this was potentially an issue.
For a NA, mild street engine, there will be no problem whatsoever, but for a blown engine in competition mode I would be taking a second [& third] look at it.
The reason for the exercise is to boost torque & if I am successful, it will allow me to operate at lower rpm's generally across the board & this should translate into less stress & heat. Initial target is to be able to cruise at 3,000 rpm @ 100 Kph in top gear. In a lightweight like a KB10, I think it should be achieveable.
Edit, per Tapprts request.
The reply was directed straight at A14Force & he is aware of the engine that I will be building for my coupe, but basicly its an overbored A13 short deck block with a stroker crank. To make it work I have a set of 'replacement' A15 pistons. These have the bowl centralised in the crown of the piston while the originals have an offset bowl. This offset gives a wider flat surface area on one side & this is cleverly placed under the squish area of the head to maximise this feature.
The pistons with the central bowl have less flat surface under the squish part of the head, however, with the stroker crank, it's necessary to machine a small amount from the top of the pistons to bring the crown down flush with the block as it stands proud at TDC even though they have a lower crown height than all other A series pistons. As you rightly concluded, any machining will result in the crown of the piston, that band around the bowl, becoming wider & presenting a greater surface to the underside of the head, & this goes some way towards reducing the difference between the original A15 pistons squish area, & that of the replacement pistons.
Additionally, the distance from the crown of the piston down to the top ring is not particularly great in these Datsun engines & removing too much material from the crown can weaken the top of the piston. It then doesn't take very much detonation to cause a failure of this part of the piston, & he was asking about that.
A14Force has been through much of this with me before & [hopefully] understood what I was writing about.
If you scroll backwards to my previous post you will see the pistons in question. This modification works just fine in a normally aspirated engine, but I suspect that it might be a bit risky in a blown engine.
Transfer
