Engine Rebuilding Info

Woz · tinkerer Joined: 05 Oct 2001 Posts: 126

Im planning on building an engine up thats slightly up in the performance area, and ive got some questions...

(1) Ive been told by a few people here and there that the cheaper option on buying oversized pistons for a 1.6 is by buying 1.8 pistons for it. Is this an advisable option???

(2) Also; im aware that you can go out and buy full reco kits for engines that include much of the parts you will need for a full rebuild. What do these contain?? Is it just seals, gaskets & stuff like that or can u get them with new pistons etc.. ???

(3) IF i take the above idea in (1) and buy one of the kits in (2) for a 1.8, are the bearing sizes & stuff the same? I realize the cranks are different between models but is the rest of the bottom end parts the same??

(4) Crank Regrind: Yay or Nay? I assume if you regrind the surface of your crank you'd need bearings to suit??

Thanks guys.... Smile

-woz

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

(1) Yes you can do this, pistons for 1800 cost about the same as pistons for a 1600, and you will end up with around 1700cc of capacity.

(2) and (3) Yes you can buy complete kits, but you should talk to your engine machine shop and ask for a rebuild kit without pistons, but everything else for a 1600, and get 1800 pistons and rings to suit.

(4) you only need a crank grind if your journals are worn. In which case, they make the journals smaller and use thicker bearings to compensate. You might only need a linish, which is like a light clean/polish.

Ben Wight

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

hey ben can you offset grind the crank to increase the capcity on the 1600 or isnt it worth it.

also you can put the 1800 crank in too to increase capicty too

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Its been a while since I knew this, but I think if you use an 1800 crank, you can use 2 litre pistons on 1600 rods, or something like that, its a specific combination.

Also, I am sure you can offset grind the crank and fit oversize bearings, but you then have to find a rod that counters the extra stroke from the crank. I dont know the dimensions of all the rods, so this sounds like a research job for yourself.

Ben Wight

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

cheers ben
hey your turbo gem has how much hp?
and did you get that 12 se3c time card?

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

I haven't dynoed for a long time, not since installing intercooler and injection, but would guestimate at a bit over 200rwhp.

I never made it to the calder drags, but have raced around the long circuit at calder in 1:10's, which I am pretty happy with, seeing I have a pretty poor suspension and tyre setup, and given that a $200,000 GT3 porche was only doing 1:04's.

I will get to the drags one day soon, by then, I hope to be doing better than 12's though.

cheers
Ben Wight

Simmo · tinkerer Joined: 05 Oct 2001 Posts: 58

I know nothing, but i thought crank shaft lightening and balancing was essential in a performance rebuild, or is this only for high revving applications?

Is there any parts of the bottom end that its a good idea to get shotpeened or balanced while rebuilding?

Cheers, Simmo.

GasGem · backyard mechanic Joined: 05 Nov 2001 Posts: 755

Simmo,

My old Gem sedan was a 1600 bored 60 thou cheap Speed pro slugs, block was bored crank was machined, head was recoed.

other than that it was bog stock, added a warm cam, and 32/36, recoed the box and diff and drove it for 230,000 kms never touched it just regular tune up and oil change,

and cained the hell out of it all day long. pull the motor down all it needed was rings and valves, it was then recoed and balance rods shot peened and now is the turbo motor,

cheers eggy

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

You cant really lighten the crank, you can only get it balanced to make it spin more smoothly, regardless of rpm, but it is a common mod to engines with with high rpm limits in mind. Its only necesarry if its important to you. It wont really make any more torque unless there is a serious imbalance issue from the factory.

Everything that moves within the engine can be balanced, its only typical to shotpeen rods, particularly after beam polishing them, but I personally wouldn't bother. This only makes them stronger, and in standard form, they are plenty strong enough.

Ben Wight

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

yeah go the factory steel rods and crank