Head for high rpm - What needs doing?

[spetz]

Hi guys,

Just a general question out of curiosity.

Of what I gather the redline/limit of an engine is governed by the first weakest link which (in most cases?) seems to be the valve-train.

So what would need changing to allow it to rev more?
Obviously valve springs to ensure there is no valve bounce/float, but I see (at least in B series) everyone always mentioning retainers. Are these really prone to fail? How about the valves themselves?

Please note I realize to rev high you need to make power there etc etc. This question is purely from a reliability perspective for the valve-train to sustain higher than stock rpm.

Thanks

[IV73CI]

To be able to rev past your current Red line limits you will need some or all of the below done.

1) Valve train - Retainers, Springs, Stems
2) Head stud bolts
3) Aggressive camshafts Hi / Lo profiles.
4) CNC Machining of the ports - possible port & polish is also an option
5) Upgraded oil pump
6) Bottom end build - Balanced crank, oversized bore/pistons, forged rods, HD bearings, ARP Bolts
7) Programmable ECU.
8) Bigger injectors
9) Bigger TB and port matched IM to suit.
10) Decent exhaust & intake.

The above will definately allow you to increase your rev limits and will have the bottom end to cater for it - which in theory will increase your power/torque.

just depends if your down on spending the money / rebuilt.

[spetz]

Thanks IV73CI for the reply.
I would like to focus more on the head for now, and ignore both the bottom end and everything that will shift the powerband.

So, can you tell me why retainers and stems would need changing (ie, the theory behind it)?
And why would the oil pump need swapping?

Keeping in mind this is not to rev to 10,000rpm or anything, but from say an engine which can rev to 8,000, to about 9,000rpm

Thanks

[egb16b]

If you are upgrading your cams then its a good idea to raise the rev limit.

Changing your cams with a higher duration and lift not only increases power and torque but shifts the powerband up the rev range..so you would need to raise the rev limit to take full advantage of this.

This puts stress on your stock valvetrain and won't be able to keep up..springs can't close the valve in time and it can come in contact with the piston and can break the valve.

So you need to at least upgrade your springs and retainers when upgrading cams. Cam gears is needed also to dial in the camshafts.

You also need to upgrade your ecu and get it tuned and to raise the rev limit.

[mocchi]

Thanks IV73CI for the reply.
I would like to focus more on the head for now, and ignore both the bottom end and everything that will shift the powerband.

So, can you tell me why retainers and stems would need changing (ie, the theory behind it)?
And why would the oil pump need swapping?

Keeping in mind this is not to rev to 10,000rpm or anything, but from say an engine which can rev to 8,000, to about 9,000rpm

Thanks

usually those cool springs like ferrea beehive will have different spring seating to oem. lighter as well. beehive type springs were said to reduce valve float. ie, happens at higher rev. I remember reading abt using hollow valves, filled with some powder to reduce heat transfer or using titanium alloy valves. less weight on valves, less weight on valvetrain.

sometimes in lower end engines like k24a3, they have smaller pump teeth and cavitate at lower rpm. they also use balancer shafts, a tad heavier to rev.
you can't ignore other things in bottom end because they all connected by timing belt/chain when you rev. I read abt how hytech modified one of the cam caps in their k series road race engine to provide better lubrication to camshafts on high rpm use.

you really need to google.

[DLO01]

everyone always mentioning retainers. Are these really prone to fail? How about the valves themselves?

Thanks

Regarding retainers. Its not that they are prone to fail as such, moreso because your going to higher revs 'lightweight' gear becomes more paramount. We are talking 10k rpm or more. TI retainers are a much lighter material than oem steel ones and will put less load/resistance on the complete valve train.

[IV73CI]

Spend about 5k on head work and u will rev like a muffakka..

Certain oil pumps are only capable of certain max revs due to the increase of oil pressure. Hence why its vital and a good idea to upgrade it.

Loss of oil pressure = loss of power and vtakkkk!! Lol

[spetz]

Thanks guys for the info.
So, the retainers are changed simply because they are ligthweight, not for any other reason?

And for engine where the rpm is raised some 1,000rpm, which means the cams only spin 500rpm faster than stock, I assume just valve springs and nothing else would be acceptable and reliable still?

[Bludger]

and for engine where the rpm is raised some 1,000rpm, which means the cams only spin 500rpm faster than stock,

wat??

[aaronng]

Thanks guys for the info.
So, the retainers are changed simply because they are ligthweight, not for any other reason?

And for engine where the rpm is raised some 1,000rpm, which means the cams only spin 500rpm faster than stock, I assume just valve springs and nothing else would be acceptable and reliable still?

For every cycle of the crankshaft, the valves open once. So the camshaft spins at the same rpm as the engine.

Edit: I was wrong. After thinking about it, the valves don't open during the compression and power stroke. So Spetz is right.

[mocchi]

I thought camshafts rotate at half speed of crank? if at same speed then e.g. int valves would open everytime piston goes tdc?

[Bludger]

I thought camshafts rotate at half speed of crank? if at same speed then e.g. int valves would open everytime piston goes tdc?

bingo