Dilema

I bought my 4s knowing it will need an engine rebuild in the near future for a good price, that i was prepared to pay. Well that time has come 5000 miles later and with winter quickly approaching, I have two options, 3.6, or 3.9. For the extra £1500, I could go up to the 3.9, but what do I get for my pounds. So, I put it out to the forum, does anyone have an increase of engine size in the 3.9 guize.? What extra power if any ? What extra torque do you get? I look forward to your replys.

Infrasilver's got a 3.9 Fully story here --> https://www.911uk.com/viewtopic.php?t=141208&start=260&postdays=0&postorder=asc&highlight=hartech This thread from Alex should be of interest too. --> https://www.911uk.com/viewtopic.php?t=125583&start=0&postdays=0&postorder=asc&highlight=capacity

Maybe this is my simpleton man maths...but at this stage, 1500 extra is probably not going to make a big difference. 3.9 for the win

3.9 owner here. Can’t compare it to a 3.6 as I’ve not driven one, but the 3.9 is great. Nice torque and power.

Expect a 20-30% increase in mpg too. Pays for itself in no time.

I would check with your insurance company first.

I have a Hartech 3.9 in mine and it's ace. 365 bhp and 345 lb ft of torque. It's the torque that makes the difference - it has been designed as a road engine so does it's best work in the mid range. It is more than quick enough on the road. My only compliant is really the tall gearing means you can't really wring its neck out but I guess that's true of the 3.6 too. For the additional cost it's a no-brainer.

True, but in all seriousness, how on Earth would an insurance assessor notice without stripping the engine and measuring? When I was a kid we all rode 50cc bikes with bore kits, the give away there was if you got caught going over 30MPH.

The Hartech 3.9 badge on the rear I just hoped that plod wouldn’t notice the 80cc on the upgraded barrel on my AR50

Well, to take Carroll Shelby’s famous quote: “Horsepower sells cars, torque wins races”. For me I'd say that £1500 get you lots of pounds of extra torque!! I know yours is a road car, but you get the point. Especially if you've ever driven a turbo version of a given car. It'd be a complete no brainer to me :thumbs:

Me too, if you're already pulling the engine apart, £1,500 for nearly 10% extra capacity is an absolute no brainer. It's about as cheap a bhp/£ upgrade as you're going to get on these cars. And whoever said "I wish my sports car had less power"?!

Unrestricted Yamaha DT50MX with a 70cc big bore kit. Did 55mph on the flat and 65mph down a steep hill. :grin:

Well, as you come to mention it... I've been weighing up whether to move to a 3.7 with my 3.4 during the rebuild and I'm coming to the conclusion that although the additional torque for most would be the 'no brainer' option it possibly makes for a one trick pony, a lot of the fun in the 3.4 comes from stirring the gears. :wink: So I don't 'wish my sports car had less power', but I'm quite happy for it to be rebuilt with the same as I think adding more torque would actually detract from the character of an all round fun road car.

Thankyou to all those who took the time to reply. You all very nearly raised the same points going around in my head, and yes who the hell would know it had a bigger engine than when it came out of the factory. So it is booked in for a scope check on cylinder 5, as they recon that cylinder will be the one which has a problem. That means only one thing, 3.9 it is.a

What is the difference in price between doing cylinders 5 and 6, I would do those two as they are the two that always go. In fact, even do 4, 5 and 6, vs going 3.9? I'm sure when I spoke to them it was around £4000 to do all that bank and get the car back up and running knowing the chances of scoring on the other minimal, and then around £13,000 to upgrade to a 3.9? What are your symptoms? If you are keeping it forever I guess the extra money is worth it. But if they are suspecting it is just cylinder 5 the jump in price is huge to do a conversion. Or am I missing something?