Replacement Cams and Pulley's

If I get a 256 intake and a 264 exhaust cam (with the adjustable pulley's what real world change am I going to notice. I'm not really talking about power but a guestimate wouldn't go a miss.

Would the car lose some drivability?

Would it be less smooth at idle?

Will it be louder?

What else should I consider doing at the same time as the fitment (new valves, guides and springs, fuel re-map, timing change, spark gap change?)

Will the car be more responsive?

Will it try to guzzle more fuel or just pull in more air, and allow the car to breath easier?

Would I be better off with a different combo. I was under the impression that the 272 was for racing and that most people went for the longer exhaust cam than the intake - I assume to make sure the chamber is cleared more effectively.

Can I just replace the exhaust cam with a 256 or a 264 and the adjustable pulley's?

So many questions...

All of your collective input and experience as always is most welcome.

Cheers

I don’t know about the Supra but we have taken my son’s car from 98bhp (dyno) to 138.5 by changing only the cam. that in a 1.4 NA engine.

Sorry I know this is a supra site.

This is just for example.

Reading the cam companies book was a real eye opener regarding the gains that can be made in NA engines by altering cam profiles.

If you have stock turbos and a J-spec car then keep to the 256's. If you have stock turbos with a UK-spec car then it's not really worth swapping the cams.

Reason being, the HKS 256's are not all that removed, spec-wise, from the UK-spec cams. Okay, the HKS 256's have a little more duration and fractionally more lift over the UK ones, but nothing to write home about.

The HKS cams are designed for use with the *stock* pulleys. Well, that's what it says in the HKS fitting instructions that I had translated from the Japanese.

I suppose only if you were constructing a built motor would you consider going to all the trouble of using accurate dial gauges and so forth, in order to set the valve timing.

My answers to your other questions are as follows..........

Would the car lose some drivability?

No, not with the 256's.

Would it be less smooth at idle?

No, the same.

Will it be louder?

No, the same.

What else should I consider doing at the same time as the fitment (new valves, guides and springs, fuel re-map, timing change, spark gap change?)

There's no point changing the valves, or valve guides or doing any kind of re-mapping if you are simply swapping the cams for 256 duration and keeping the stock turbos.

We have done a range of mods. to Justin's head, despite him having the stock turbos. But the turbos will be changed sometime in the future, and we thought as the engine had to be split in order to repair some other fault, we may as well do the head work while it was dismantled.  

Will the car be more responsive?

The cams give a nice extra surge in power from about 3500 rpm.

Will it try to guzzle more fuel or just pull in more air, and allow the car to breath easier?

Like any tuning exercise, if you cause your engine to make more power and you use it: more air gets sucked in, more fuel gets gobbled.

Would I be better off with a different combo. I was under the impression that the 272 was for racing and that most people went for the longer exhaust cam than the intake - I assume to make sure the chamber is cleared more effectively.

I'm not sure whether you would want the cylinder clearing quite so effectively mid-range. With a longer duration cam, the cylinder may be cleared so quick and so effective, a significant percentage of the intake charge can get cleared with it.

Can I just replace the exhaust cam with a 256 or a 264 and the adjustable pulley's?

The general concensus is, as you say, longer exhaust than the intake. But I'm not convinced that combo is a good idea on a road-going stock turbo'd MKIV. Swapping the Intake for a 256 and leaving the exhaust stock could well work better.

If you are looking to save money by only swapping one cam, and you are wondering which would be the best, then swap the intake first.

To my mind, the stock cams work best. Unless, of course, you are building something even more radical, with a range of head mods, ECU swap, bigger fuelling, bigger turbos, etc., etc.

Now, when I say "stock cams" I regard the UK-spec cams as being the stock-cams.

Reason why I say that is because I consider the J-spec cams as something of an anomaly.

It is against Japanese law to advertise a car that makes more than 280 HP. After studying the differences between the UK and Jap cam specs, it appears to me Toyota curtailed the power of the J-spec car 30HP or so, by simply reducing the cam duration and shaving off some lift.  

To my mind, the UK-spec cams are the cams best suited to the stock engine. As I say, the HKS 256's are a fairly close match to the UK cams, and it comes as no surprise that they perform well. The only thing that doesn't quite sit right is that Toyota would have made slight changes to the ECU mapping in order to suit the new profile.

I ran the 256's in my car with the stock turbos just after I first got it, and they felt okay. But that was just before I bought the UEGO sensor setup, so I haven't got any test data.

I'll have Justin's car as a test-bed soon and he runs 256's with the stock turbos (for now) so that'll give me a chance to data-log the A/R and publish my findings.  

HTH

Yours,

J

So, I've got a jap spec Supra with (we believe) modified jap turbo's (larger compressors etc), UK spec injectors...do you think that the person who fitted this stuff was making it UK spec in more respects and therefore I could have UK spec or even HKS cams.... would it be the logical step as the guy has obviously spent alot of money in japan on my car. If I take the cam cover off will I be able to tell?

Also if 256 is normal how much different is 264 on intake and exhaust?

Cheers

It could well be worth checking what cams have been fitted. I doubt whether the person doing the work would have replaced the cams with UK-spec as HKS tuning gear must litter the streets in Japan.

The HKS cams have "HKS" stamped on them together with the actual duration, i.e. 256, 264 or 272 degrees. Failing which, all you need do is measure the duration with a degree wheel and a dial gauge, which should give you a fairly close indication of the cam spec.

When I say 256 is "normal" it's a fairly agressive cam for the stock motor. 264's I wouldn't contemplate unless I was prepared to do a lot of fiddling about getting the fuel and ignition mapped to suit along with a turbo upgrade.  

Yours,

J