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I have a 1982 GPZ 1100 that I had in my old garage for a number of years neglected. I finally got it running and have taken it out for a couple for rides. The engine is leaking oil (worse than when I tore it apart 10 years ago) and I am trying to plan out my next move. I am thinking that I would like to take advantage of the tear down to put in larger pistons and upgrade the bottom end. I am like the APE 1170 kit for this engine as it appears that it won't require new sleeves and it comes with new valve springs and .410 lift cam with identical durations to the stock cam. I just want a solid, powerful engine that will keep pace with most modern bikes.

I am not sure that I want to bump up the valve sizes as I am looking to maintain the bottom end grunt that I am used to. Also, I am an MSF instructor and this will probably will be the bike I will use when teaching BRC-2 classes so I want something that will idle nicely and won't need to be revved to the heavens to make torque. Your thoughts are appreciated. I do plan to keep the stock fuel injection. whether I use trickery to manipulate the existing ecu or a microsquirt is still undecided.

What you propose isn't a bad setup for a mild upgrade and you keep shim on top valve adjustment. Cost is not significant either.

Larger valves aren't going to hurt the bottom end torque.....so long as it's done properly. 38.6 Intakes is a nice upgrade from the stock 37 intakes and you don't have to go to 33 on the exhaust side.

If it were me, I'd go for the K435 grind but then you need buckets & retainers. You DO NOT NEED Ti Retainers though. OEM SOB retainers are perfectly fine for a street motor.

Are you keeping the DFI? If yes, and if you can afford it, The Pogue taper bore setup is a great upgrade. Not certain if Sid is still doing them but here's the contact info. They will work good with anything you do to the motor...

3700 S High Ave, Oklahoma City, OK 73129
(405) 677-9397

Please enlighten me, I have been trying find a source that tells me if you cam is ground like this, you can expect this to happen, how much gain does the extra 25 thousandths provide? Also, at what point do I need to start clearancing the head and cam cover? Would I have has to do that for the 410 cam? I ask because I am engineer that likes to understand the fundamentals.