Euro startup sounding like a diesel engine

[EUR003act]

What difference is there between "K20 spec" clearance and stock?

My understanding is that you want the minimum cold set valve clearance possible that allows some minimal clearance of the cam lobe base circle when all is at operating temp (with hotter and elongated valves etc...). The smaller the clearance the higher the valve lift and the longer the duration (ever so slightly for both), which should improve breathing just a gnat's whisker.

If this is what the 'K20 spec' is (i.e. a tighter clearance) then it should help power to an infintesimal degree so long as the base circle is not touching the follower. But if the K20 spec is a larger clearance that is not required to provide adequate clearance then it may infintesimally hurt power.

the K20 spec is tighter... and yes your right, thatll mean slightly more lift and duration on the cams... which should mean slightly more power...

the main problem you might face with the tighter settings is that the valve doesnt seat properly with the weaker K24 springs, equalling loss in power

Correction - K20 and AUDM K24A3 spec are the same... lol i was looking at the USDM K24A3 spec...

K20 spec:
Intake: 0.21-0.25 mm
Exhaust: 0.25-0.29 mm

K24 spec:
Intake: 0.21-0.25 mm
Exhaust: 0.25-0.29 mm

[tony1234]

the K20 spec is tighter... and yes your right, thatll mean slightly more lift and duration on the cams... which should mean slightly more power...

the main problem you might face with the tighter settings is that the valve doesnt seat properly with the weaker K24 springs, equalling loss in power

Correction - K20 and AUDM K24A3 spec are the same... lol i was looking at the USDM K24A3 spec...

K20 spec:
Intake: 0.21-0.25 mm
Exhaust: 0.25-0.29 mm

K24 spec:
Intake: 0.21-0.25 mm
Exhaust: 0.25-0.29 mm

Why don't you install some ITR springs while you've got everything pulled apart Justin.

[EUR003act]

Why don't you install some ITR springs while you've got everything pulled apart Justin.

lol what do you think was in the K20 head i bought?

lol my entire cylinder head is K20Z1 except for the cams... so my rockers/vlaves/retainers/springs all stock capable of 8500rpm all day long

[tony1234]

lol what do you think was in the K20 head i bought?

lol my entire cylinder head is K20Z1 except for the cams... so my rockers/vlaves/retainers/springs all stock capable of 8500rpm all day long

Ah,ok,then get ITR cams then.

[EUR003act]

Ah,ok,then get ITR cams then.

i have ITR cams... lol

K24A3 exhaust is better in everything, ITR intake cam is only better for VTEC, its primary and secondary lobes are smaller...

hence i stuck my K24 cams back in lol

[SPQR]

....lol my entire cylinder head is K20Z1 except for the cams... so my rockers/vlaves/retainers/springs all stock capable of 8500rpm all day long

But probably not the pistons, bearings and crank?

[EUR003act]

But probably not the pistons, bearings and crank?

lol no, probably not lol

although there is a guy in the states that runs his to 9000rpm for dynos...
(running K20 oil pump)

lol i think ill stick to 8000rpm however

sorry to hijack, im ashamed

[JohnL]

the main problem you might face with the tighter settings is that the valve doesnt seat properly with the weaker K24 springs, equalling loss in power

I'm having trouble seeing why that would be the case (with any springs if the only variable were the clearance), unless the clearance was so tight it wasn't really a clearance at operating temp...

The problem with weaker springs usually occurs at full lift as the valve train 'overshoots' the cam profile due to mass intertia, and perhaps a slight bounce as the valve seats, if it seats harshly (which should I think be more gentle with a lesser clearance).

[EUR003act]

I'm having trouble seeing why that would be the case (with any springs if the only variable were the clearance), unless the clearance was so tight it wasn't really a clearance at operating temp...

The problem with weaker springs usually occurs at full lift as the valve train 'overshoots' the cam profile due to mass intertia, and perhaps a slight bounce as the valve seats, if it seats harshly (which should I think be more gentle with a lesser clearance).

you said it right there yourself, with a weaker spring on a very tight clearance, the spring may not have enough pressure to push the valve all the way home...

its not going to be an issue as the AUDM K24A3 has the same spec as the K20 anyway... but if it were the K20A3 or the USDM K24A3, then yeah it might cause problems...

[JohnL]

you said it right there yourself, with a weaker spring on a very tight clearance, the spring may not have enough pressure to push the valve all the way home...

Then is that a problem with low spring stiffness or with inadequate spring pre-load. I'd suggest it's an issue with preload and the spring needs to either be longer or shimmed at it's base (so long as you could shim it without risking coil bind).

I'm all for using the weakest springs reasonably possible for the red-line the engine sees (+ a bit for safety), stiffer springs use power and cause greater cam wear etc.

It seems to me that so long as any clearance exists then the spring will be pushing (or pulling) the valve shut just as hard no matter what the clearance might be.

[EUR003act]

Then is that a problem with low spring stiffness or with inadequate spring pre-load. I'd suggest it's an issue with preload and the spring needs to either be longer or shimmed at it's base (so long as you could shim it without risking coil bind).

I'm all for using the weakest springs reasonably possible for the red-line the engine sees (+ a bit for safety), stiffer springs use power and cause greater cam wear etc.

It seems to me that so long as any clearance exists then the spring will be pushing (or pulling) the valve shut just as hard no matter what the clearance might be.

you may be right, it was just interesting to me that the engines which have the lower redlines/weaker springs all have slightly looser clearances...

and true, hard spings to use up valuable power

[JohnL]

you may be right, it was just interesting to me that the engines which have the lower redlines/weaker springs all have slightly looser clearances...

I suspect it might allow more time to safely ignore the valve clearance?

Sometimes valve clearances open up with wear, sometimes they close up with wear, depending on what surface is wearing the most quickly (i.e. wear on lobes / followers / valve stem tips causes clearances to open up, wear on valve seats causes them to close up).

My gut feeling is that it's probably safer to allow the clearances to get too big than too small, hence a larger clearance on a lower perfomance engine with a longer clearance service interval(???).

Or, maybe one engine model wears the lobes / followers etc faster (than the seats) and can tolerate smaller spec clearances because they tend to get bigger in service, but the other engine model tends to wear seats more so the clearance tends to get smaller in service, thus requiring a larger spec gap...???

Dunno, just thinking out loud..