Imput on building head!

[derk]

are they tomei procams? if so then run the tomei lifter buckets.

im running cosworth springs with stock retainers, and tomei buckets with the 260/10.8 procams

[gtrjon]

yea tomei pro cams. so ill grab the tomei lifters. what cosworth springs? dual or single? why stock retainers? and stock valves?

[derk]

cosworth only makes single valvesprings for the rb26 as far as i know, and stock retainers because cosworth doesnt make Ti retainers for their springs and i wasnt sure if the tomei/whatever other brand ones will fit, and im going with 1mm oversized valves + valve seats along with the cnc head port

[Bruizer]

I cheaped out on my engine so if I could go back and afford more, I woulda went with double springs, a stroker kit, +1 valves, N1 block, dry sump, triple clutch, hks or cosworth pistons, Carrillo H rods... That's what you should do, good for lots of power. I'm not going for much power so I can enjoy my car for a long time, not rebuilds ever 2-3 years.

[gtrjon]

I cheaped out on my engine so if I could go back and afford more, I woulda went with double springs, a stroker kit, +1 valves, N1 block, dry sump, triple clutch, hks or cosworth pistons, Carrillo H rods... That's what you should do, good for lots of power. I'm not going for much power so I can enjoy my car for a long time, not rebuilds ever 2-3 years.

thats not relevant at all i dont even know where that came from!

[Bruizer]

thats not relevant at all i dont even know where that came from!

Oh haha my bad, thought this was a "looking for input" kinda thread which that was my honest opinion, my bad if you got that wrong.

Anyway, I'm guessing That if you're going with double springs and +1pm valves, you have a monster engine, thats what I was getting at. Stock head is still Great above 500whp.

[GTR-Dad]

Bruizer, if your double springs were overkill for your application, you'd be rebuilding top end earlier than if the springs were optimum.

gtrjon, I don't know which are the right springs for you, but given a cam profile and valve mass you can calculate the rpm at which they'll float. Lift and duration are not strictly speaking enough info, but I'll bet someone has worked out a good rule of thumb.

Here's a writeup to consider. http://dairally.net/daihard/chas/Mis...alveSpring.htm
I don't know if it's right or wrong, but they key on the right variables.

Dan

[MarusGTR]

Bruizer, if your double springs were overkill for your application, you'd be rebuilding top end earlier than if the springs were optimum.

gtrjon, I don't know which are the right springs for you, but given a cam profile and valve mass you can calculate the rpm at which they'll float. Lift and duration are not strictly speaking enough info, but I'll bet someone has worked out a good rule of thumb.

Here's a writeup to consider. http://dairally.net/daihard/chas/Mis...alveSpring.htm
I don't know if it's right or wrong, but they key on the right variables.

Dan

Went through it quickly...it might be good from a practical standpoint but I'm not conviced on this paragraph:

Load at installed height = no medal for guessing what this is. Yes it's the force applied, generally measured in lbs or kgs on the spring to get it to the installed height. This is the figure head experts like to bandy about "you will need 85 pounds seat pressure. This one will need 105 pounds etc". What is apparently a black art is really just years of experience based on trial and error and a little bit of bluff. Now something to remember here is that if you are running boost, then that pressure is going to be acting on the backside of the valve, effectively reducing the seat pressure. This is not just applicable to the intake valve, but also to the exhaust valve on turbo applications. The exhaust side pressure can be equal too or more than the boost pressure up around peak power revs. Our rule of thumb head guys like to add a figure of twice the boost pressure in lbs i.e. if boost is 14psi they add 28lbs spring load.



First off, it's not black art, it's engineering. The preload helps extend the service life of the spring and to prevent it from getting sagged from applying a too great cam lift. It's not trial and error; it's based on projected life calculated for constant cycled service, e.g. 1x10^10 cycles.

Second, good point about the boost pressure negating the preload. The "twice the boost pressure gives the lbs pulling the valve" thing MIGHT work but can't you just, y'know , multiply psi per projected valve seat area in inch to get the lbs applied?


I'm just ragging on technicalities here, thanks for the link.

[Super_Dude]

alright you guys lost me now. so if i want to run my 280 cams with the 10.8 lift what would you guys reccomend for valve train? single springs and titanium retainers? stock or aftermarket valves? stock or tomei lifters?

What turbo are you going with? Assuming the 280 cam is the cam you want I would run stock valves, cosworth springs, factory retainers, tomei lifters.

[gtrjon]

What turbo are you going with? Assuming the 280 cam is the cam you want I would run stock valves, cosworth springs, factory retainers, tomei lifters.

borg warners s300x 91-79 with a race tune for ~30psi. why stock valves!? i still dont understand how there is any advantage to running stock valves

[GTR-Dad]

why stock valves!? i still dont understand how there is any advantage to running stock valves

Best arguement I've heard for staying with stock valves is that airflow going around the bigger ones can end up being choked by the proximity to the combustion chamber wall. I have not verified this possibility, but understand the solution would be to 'deshroud' the flow area around the larger valve.

To me, it seems self evident that derestricting airflow through the head would improve flow, possibly at the expense of low end response due to lower airflow velocities. There are many who have more experience than me in this area, so I'll just offer to post before and after dyno curves when the 'after' curve is available.

Dan

[Super_Dude]

borg warners s300x 91-79 with a race tune for ~30psi. why stock valves!? i still dont understand how there is any advantage to running stock valves

Because they work and you already have them. You don't need to spend money on something that works fine in the first place. Just because something is aftermarket doesn't mean it is better or required. Take the money you would have spent on valves (and the extra head work) and put it towards something more useful.

[Dragon Humper]

Hey Jon, would you mind explaining why? I'm guessing because it helps move the mixture away from the edge of the chamber, further avoiding detonation?

Quench pads cause turbulance inside the chamber and centralizes it as the piston reaches TDC (that is why there are two in an RB, the plug is in the center), this promotes a much better burn and helps dampen detination. The closer the clearance, the better. If you see a small clean spot on the pad(s) after a teardown, that's perfect, it's evidence that the piston was just barely kissing the head at max rod stretch and piston rock. If a combustion chamber was origionally designed to have the pads, you should never remove them (no matter what pistons you have). Nothing you can do with a piston will replace what quench pads do.

The only guys that run no pads in an RB are guys that are in the 1000+HP range and are running 116+ octane or methanol or both. One of the reasons to remove them is to unshroud the larger valves for max airflow. The bore is not really a shroud issue with an RB because the valves point to the center of the bore and move farther away from the wall with more lift. You can unshroud with bigger valves though, without removing the whole pad. I hope you are running race fuel DERK, because I can guaratee you that you won't be able to run as much ign. timing as I can on pump fuel.

The only "modern" local engine recently to use no pad at all was the 426 HEMI and the 429, 460 Fords, and they both sucked balls on anything under 92 octane. The HEMI was terrible because of the high compression, rattled like a bastard with any kind of timing that could make decent power. The Ford was better but only because they were a horrible 8 to 1 comp. (guttless turds).

If you want to make as much power as you can on pump fuel, DON'T remove the pads. This is one of the reasons I can run 32 deg. of ignition timing at 1.4bar of boost on nothing but Mohawk 94 (sadly, now a memory). I know they are still there because I peeked inside with a borrowed scope last year.

[Black BNR32]

^
that agrees with everything I've read (but no experience)