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So i was palning to put a dual weber, new headers and intake to my 3k to gain some extra omf, is it worth it and does the dual carbs give me too worse mpg. new to these things so thanks for any tips.

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"Wasting your time without head work, cam and compression. Fuel economy will deteriorate.  "


Just assume Toyota had the carb, the head, the cam, and the exhaust perfectly set up for power and economy up to say.. 4000rpm.  So anything you gain will be above those revs, not where you drive very often. The first trade-off will be economy for power over 4000, so as Parrot said, it will give you more power and more revs, but use more fuel.

Its much harder to get more torque, which is what you need for daily driving, than more power, which just comes from more rpm. If you get a cam cut, pick one that opens quickly, opens a long way and has little overlap, in other words designed for torque not rpm. Around town that will get you off the line quicker than a racing engine.

Don't forget to do a compression test before touching it, decide then if you need new rings or a rebore before taking the head off. Its no good putting a skimmed head on a leaky set of rings. If you're fitting extractors, remember they only work with a full exhaust replacement, and once again they will flow more air at higher rpm. 

Of course the fastest way to power is fit a 4K!

Have a read though here, I did all you are planning to do.



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Of course the fastest way to power is fit a 4K!

Fully Agree !

Now, don't get me wrong, the 3k in it's day, was a great engine.  There was a speedway series once, where the engines were limited to 1200cc, & I've seen some amazing pictures of 3K engines that produced amazing results, but that was at very high revs, & after a lot of  expensive modifications.  A fully balance & engineered 3k, could produce twice the number of revs, Toyota designed it for.

However; as the yanks have always said "There's no substitute for cu inches (CCs)"

I drove an early Corolla for 18 months once, with a 3K engine, & frankly it wouldn't pull the top off a custard.  Alright on the flat, if you got it wound up, but as soon a hill appeared, it was not up to it at all. 

If your Rolla is a "daily drive", then keep a lookout for a 4K-C, which was probably the most popular 4K produced.  If you need more torque, then consider a 5K, which has always been my favorite.  There was a 4K-U, which nearly produced almost as much HP, as a 5K, but they are a bit hard to find.

Even with a 4K engine, there are a lot of things you can do, to make it a more enjoyable drive, but at least with a 4K, you are at a much better "starting point", than with your 3K.

Cheers Banjo




Edited by Banjo
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Turbo the sucker!  A suckthrough SU carb and no intercooler, it doesn't have to be efficient or giving max bhp, just double what you have.

"Instead of the old car’s 185bhp 1.6-litre petrol engine the new car will have a 1.2L turbo. Peugeot Sport director Bruno Famin says the new R2 car will have a “substantial increase in performance.” It’s fair to expect a power figure close enough to the outgoing model’s, but with much more torque. " So Peugeot have a 3cyl turbo with a couple of hundred bhp.

or buy yourself  a little Cherry 1.2L turbo straight out of the box, shipped from China..  220NM torque, 100KW.

Box Cherry.jpg

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