Cam question

[Steve]

Just curious really, when asking about changing cams, people have said about re-shimming. What is this?

 

What should the valve clearances be?

 

Thanks

[Miguel]

Shimming is the is the method of ajusting valve clearances. There are small shims on the top of each valve bucket that can be swapped out for thiner or thicker shims to obtain the correct valve clearance . Stock clearances are intake 0.15-0.25mm exhaust 0.25-0.35mm . After maket cams specify their own tolerances when it comes to valve clearance , if you get them too small it can hold the valve open on combustion and too wide they will not open the valve enough ...as well as sounding like a Singer sowing machine .

[Steve]

So what would the clearances be for HKS 264 cams??

[Guest Usmann A]

Youd have to use a feeler gauge, and measure the distance from the cam to the shim top off lift ovbiously.

 

You then need to look into the book, and use the table to establish what toyota No, shims you need.

 

HTH

[b_have]

think the rec clearance for HKS cams are different than oem, seem to remember when i fitted mine it was at the top end of the oem spec. Can't find the HKS specs at the mo, will have a look tonight.

[Guest Usmann A]

Well, I got a pair of HKS cams the other day and no clearances.

 

The cams are ground already to give larger lift, all were doing is to make sure that the valves all have the equal lift which the HKS cams give.

[JohnA]

What most people don't know is that valve clearances are a function of operating temperatures --- on racing setups temps after the intercooler might ask for different intake gaps, and it goes without saying that higher EGTs will demand different exh gaps.

When you're off-stock you can't just assume that the stock clearances are still valid for your engine. (and that's even for stock cams!)

[Guest Usmann A]

Yes, I agree,to a certain poimt, thats why it says Warm/Cold for clearances.

 

So, what gaps would you use then John?

 

I for one an going with TMC charts for int. and ex.

 

what do you class as racing spec?

I assume you mean gasoline,I know some guys that build 6 seconds motors with 2JZ engines and they use the stock shimming tables,(ok I agree these are for only a few seconds)

 

Letss if you are running race fuel anyway, the chamber temps will not rise as much(chambers temps refelct EGTs), as all the heat energy is being used up to actually ignite the fuel in the first place, and on a properly mapped EFI system,with correct ignition maps, it should all be ok.

Remember, all these racing spec cars have bigger A/R hotsides, huge tubular manifolds, all less restriction in the exhuast= less chamber temps, I dont think you have quite seen the stock manifold yet have you?

 

On cars with small hotside=more restriction in the exhaust, and with aftermarket(longer duration) cams, more chance for reversion to occur as there is more backpressure on the exhaust side, which infeccts the intake charge and thus higher chamber temps=Higher EGTs. But not the extent of having your shims regapped IMO.

 

If you mean racing as in track cars which are operating at these temps for hours then yes, but are any of these cars were talking about racing cars, that see hours on end of abuse ..

[Steve]

think the rec clearance for HKS cams are different than oem' date=' seem to remember when i fitted mine it was at the top end of the oem spec. Can't find the HKS specs at the mo, will have a look tonight.[/quote']

 

 

If you can let me know that would be great

[JohnA]

Yes, I agree,to a certain poimt, thats why it says Warm/Cold for clearances.

In a way, yes, but that is the difference between a cold engine and a warm one.

what do you class as racing spec?

If EGTs are 100C over stock, do you really believe that the stock clearance is optimal?

 

.., I dont think you have quite seen the stock manifold yet have you?

Not mine, but I've seen pictures from here and the States.

It's horrible, if the sequential system is not taken into account

 

But not the extent of having your shims regapped IMO.

Opinions are nice, measurements are better

To give you an idea, I used to have an aircooled kawasaki750 turbo, which I knew inside out, like the palm of my hand. It was the best factory turbocharged engine, straight conversion from the n/a 750, which had a few previous incarnations in various states of tune, all derived from the 650 of a decade before.

I had the full manuals and specs of all models, so could see what the factory had done (and why)

Exh valves always had larger clearances than intake ones. In the case of the turbo the exh recommended clearances were the same as the n/a version 0.08mm-0.18 IIRC (despite the presence of the relatively small turbine) but the intake were 0.13mm - 0.23, significantly larger. That was a non-intercooled engine mind you, but you get the picture.

 

(I can't remember what I ate yesterday, but still remember the clearances of the Kawa almost 20 years later lol...)

 

Those were DOHC under-bucket shimmed designs, and changing a single shim meant dismantling the cams etc.

When running slightly higher boost, I found experimentally that I had to operate at the top end of the clearance range, and when running significantly more boost (with primitive water injection) I had to go at least 0.05mm up and I still couldn't hear them ticking.

Expansion, expansion...

 

HTH

[Guest Usmann A]

It depends on what source the opinions are coming from.

 

John, thats all good an all, but when say you want to adjust all your shimmings anyway,youd have to spec them back to normal specs using the book first, and then work your way from there. As its a benchmark to follow, each seat wears differently, and all valve lifts never stay equal on say a 70K motor.

So using the book to shim all the tolerances back to the way TMC intended it,and then IF you are expereing a problem, adjust away(although I highly doubt it,I for sure found out later that our 2J had not been shimmed and was running 264s, from a "Supra-God" tuner, and it ran fine)

 

I highly doubt that a few slighty off tolerances will give you problems on the 2J.

 

Have you tried A/M cams on a stock head? checked the tolerances on your head?

 

I havent expereicned the problem your describing with the 750 etc,etc on the 2J, but if I do then you will be the first to know.

[Steve]

So am i right in saying that its usually ok to run 264's without re-shimming.

Slap me if i'm wrong

[Guest Usmann A]

Yes you can, but its NOT the proper way of doing things ... get them shimmed.

[Steve]

Thanks again Ali

 

Does anybody know the what the clearances should be with 264 cams??

[JohnA]

It depends on what source the opinions are coming from.

yes of course.

Trouble is that everybody's got a few to spare

John, thats all good an all, but when say you want to adjust all your shimmings anyway,youd have to spec them back to normal specs using the book first, and then work your way from there.

eh?

you measure the existing gap, and calculate shims for whatever the stock gap is + your offset.

With the cams out, you just keep a record of the existing shims, as well as the ones needed to get to your 'target' clearances.

If you're lucky some existing shims might be able to be swapped about.

 

So using the book to shim all the tolerances back to the way TMC intended it,and then IF you are expereing a problem, adjust away

Not a wise practice mate.

Valve clearances too large : you can hear them tapping like a sewing machine.

Valve clearances too small: you hear nothing, silence can be deadly, and end up with burnt valves if you're unluckily too far off.

 

That's why those who know prefer to have them sliiiiiiightly on the wide side, just a bit audible. At least you're safe.

Well at cold idle they'll probably be audible anyway, it's at full boost that they should have enough room to expand.

 

As always, it's a free country and people can do whatever they like.

[Guest Usmann A]

What do you know what target clearances are without the TMC chart?

 

I measure the clearance first, then the used shim, then look at my chart and it gives me a nice shim to choose from, so that I have equal lift on all valves into the chambers, like toyota intended.

Now, remember that seats,guides,etc all wear, and if go around just making the cclearances bigger, you would not have dealt with the tolerances in the head.

Thats why im saying, go back and spec all the valve clearances to stock, then work your way from there.(if you belive so)

 

Intake valve clearance .. (Cold only) 0.15-0.25 mm(0.006-0.010in.)

 

eg, 2.800mm(0.1101in.) sim is instaleed, and measured clearane is 0.450mm(0.0177 in), replace this shim with a No 12, which is a 3.050mm(0.1201in) and that will spec that clearance back to stock.

Now once youve done this, go about making the learances slightly larger if you wish so.

Its a plateu to work from.

 

I think were saying the smae sorta thing here.

[JohnA]

What do you know what target clearances are without the TMC chart?

of course you need the TMC chart mate, who said you don't?

(I'm kinda dizzy, I was out in the sun, had a few beers now, so may not be thinking clearly )

 

You just add the (potentially) extra clearance on top and replace with shims that will give you that.

 

I think were saying the smae sorta thing here.

Probably

[Need4Speed]

A quick question to all you with HKS cams. If I fit 264s, does it make a big difference to bottom rev performance and do they have a noticeable power band? What sort of bhp gain am I likely to get?

[b_have]

Does anyone have dyno graphs for before and after 264s? I remember fitting mine when i had (Leons) hybrids and was kinda dissapointed. Seemed a little more mid and top end, but lost my silk smooth idle. I also have experimented with the cam timing adjuster, settled with 4deg advance on the exhaust. Anyone else dialed these in?

[Ian C]

Best I can do is the attached picture. Setup 1 was my hybrids, Setup 3 was my hybrids + 256in 264ex HKS cams. The graph shows how long it took to traverse 10mph blocks.

 

My data comes from an Apexi AVCr digital display, that is accurate to 1mph with my Road Angel II GPS. A friend video'd it while I did the runs and then I played it back and got the exact frame timings that it ticked over to each 10mph, so the timings are accurate to 0.04s - way beyond the accuracy of the rest of this

 

Gear changes may skew some 10mph results, it's quite obvious when it does.

 

If anyone is interested, setup 2 was the same as 1 but running 1.5 bar instead of 1.35 and setup 4 was a 80% mapped T67

 

-Ian

[JohnA]

...Seemed a little more mid and top end' date=' but lost my silk smooth idle. I also have experimented with the cam timing adjuster, settled with 4deg advance on the exhaust.[/quote']

Charlie, if you retard the intake by 3-4 degrees, I'd expect you to get better idle and better top end too (at the expense of midrange though, that's where VVTi can be helpful)