R33 Rb30 Conversion

[Cubes]

Swen.. The hot exhaust gas passes the exhaust valves.

Good point Steve, Matlow is basically running a stock head with gtr cams i think.. then again I 'think' I remember him mentioning something about needing to enlarge the block head bolt holes which would mean that it is a RB26DETT head he is using?!?!

When you create more power don't you also create more heat?

Why is there a need for S/Steel Valves or better valves if standard valves can handle as much power as you throw at them?!?! Might do a bit of googling.

I'm really not sure as in all honestly a street car shouldn't be getting heated up that much anyway, unless you were looking at racing the motor then maybe that is when better valves are in order?!?!?!

[Cubes]

I've found a good read on Valve Failures.

Skim down to Why Valves Fail and Valve Breakage.

Note from Valve Breakage..

excessive heat and/or rpm

- MattR 9000rpm..

[[SweN]]

this answers my question before quite well

Let’s talk about burning first. Exhaust valves are the ones most likely to burn because they run hotter than the intakes. The intake valves are cooled by the incoming air and fuel, and consequently operate at about 800 degrees F. Exhaust valves, on the other hand, receive little such cooling and are blasted by the hot combustion gases as they exit through the exhaust port. Exhaust valves run at 1200 to 1350 degrees F. on average, which makes them much more vulnerable to erosion and burning than intakes. The higher operating temperature requires a tougher alloy, so exhaust valves are usually made of stainless steel or have stainless steel heads (typically 21-2N or 21-4N alloy with a high chromium and nickel content). For heavy-duty gasoline and diesel applications where heat is even more of a problem, a tough Stellite facing (cobalt alloy) may be needed on the exhaust valve face to control wear.

http://members.aol.com/carleyware/library/ar1192.htm

[alkaline]

I was about to say pressure and rpm, but pressure equates to heat in the end anyway...

[JNR24]

Originally posted by Steve

Isnt Matlowth running around 340rwkw with stock head?

I still cant get my head around a vavle dropping because of a particular hp - how so??????

Steve im with you on this one,

Where did this HP Figure come from? and wheres the weakest link, to prove that standard RB25 Valves drop off at around the 300RWKW mark?

In that webpage that Joel posted, he mentioned "Why Valves Fail". Under there, he explaines why exhaust valves fail more than intake etc. What i found more intresting was the 3 main reasons valves will fail: (Quoted from his page) These are Directly related to the head. (There are other reasons like engine cooling etc.

1. A buildup of deposits on the valve face and seat can have an insulating effect that slows cooling and makes the valve run hot. So too can poor contact between the valve and seat if the seat is too narrow, nonconcentric or off-square. If deposits build up in one spot or flake off in another, it can allow leaks that create hot spots on the valve and result in "channeling".

2. Weak springs or insufficient valve lash can also prevent good valve-to-seat contact and allow excessive heat to build up in the valves. A loose seat or poorly fitting guide can also hinder heat transfer to the head and contribute to burning.

3. Valve recession can cause the same kind of problem. As the seats wear away and the valves recede into the head, valvelash is lost. Eventually there’s little or no lash left and the valve makes poor contact with the seat, overheats and burns.

Reason 1.

He is making refrence to Carbon deposites on the valve face, creating a insulating barrier, causeing the valve to overheat & burn out. Cause: Bad tuning, Rich fuel mixtures, poor fuel octane, cold spark, etc.

Reason 2.

Weak springs and dodgey seats, pretty self explanatory. If you springs arent heavy enough your valves wont seat properly, or quick enough. Either causeing the piston to start touching your valves (On highly advanced timed motors & long duration & Lift cams) Cause: Springs not having the correct pressure rating for your application, This falls under the initial build, if its not built properly, its going to fail.

Reason 3.

This reason wouldnt really apply to any of us, mainly because were actualy building the head and hopefully you guys are going to at least replace the seats & guides (Dont forget to get some heavier springs) when you put it on the new motor. But once again this comes down to the initial build of the head.

All his reasons, (Go through his page) are related to either the initial build of the head (Having it correctly setup the first time) or tuning. Not once did he make refrence to Valve metal density or valves failing on a MD vs RPM?. There are alot of other factors as well as to why they will fail on that page but they seem to be relevant to how the valves are lined up, Stem geometry, engine cooling etc.

Make sure your head is %100 including all the Valves, take it somewhere respectable. Put some heaveir springs in. Make sure your cars tuned properly. And you should have no problems.

m2c

[Cubes]

Lol.... It was late... I forgot to past the link but yer it was the link that alkaline posted.. http://members.aol.com/carleyware/library/ar1192.htm

[Cubes]

Put some heaveir springs in. Make sure your cars tuned properly. And you should have no problems.

I was told that putting new springs in will do jack by Milton Engineering who worked on my head. If there isn't enough valve lash then they shim the vavle springs. New valve springs will have the same problem as the old valve springs if there isn't enough lash there isn't enough lash it isn't due to the springs its due to the position of the valve sitting in the head. i.e higher or lower in the head and as the read stated after a valve job the valve will sit slightly higher up in the head hence resulting is less lash or less pressure of the valve upon its seat.

This is also making sense with LPG cars now as I remember I had a burnt valve in my TE 250 Cortina many years ago due to lpg, I was told I needed to shove hardened valve seats in to it.

So there is more than just slap s/steel valves in it than meets the eye.. I'm glad I started on this topic as I've ended up learning a little..

[JNR24]

Hmmmm, wouldnt it work the other way round?

higher the valve the more pressure the valve upon its seat?

As the valve falls into the CC via the lobe on the cam compressing the top of the valve spring?

I might attempt a paint drawing

*puts L plates up"

[JNR24]

like this?

cam rotates, cam lobes compress springs, valve drops, cam lobe passes, spring uncompresses, valve seats??

[Belly_up]

I think they're talking about valve recession, not the normal operation of the valve. As the valve seats wear away (or are ground deliberately), the valve spring will be allowed to expand slightly, and will thus not be pulling the valve back into the seat with as much pressure as originally. Which is why they were talking about shimming the valve springs to maintain a constant spring pressure on the valve.

[JNR24]

Yeh, but what im saying is if you physicaly move the valve further up, wouldnt that create more tension on the spring creating a harder seat.??

cheers,

trev

[Cubes]

The Spring wants to pull the valve up in to the head.

The higher the valve sits in the head the less compressed the valve spring is there for there is less tension in the valve spring.

[Bl4cK32]

So what did we all decide was the solution?? -or haven't we got there yet?

a)Proper head work

b)hardened valves

Im following this very closely......

[GiJOr33]

i was told that it's a good idea to put higher pressure springs in. Especially with the N/A head. As the more boost you run the more pressure is on the spring to hold the inlet valve in its seat. I'm going to put heavier springs in. The last thing i want is to have to pull the head off again cos of valve bounce or leaking from 20psi boost that's being fed in! And for $300 or so i think it's a good idea. There is some rule... for ever 1psi of boost you feed in you need 2psi extra in spring pressure... i can't remember exactly what it is.

[GiJOr33]

i'd say proper headwork (porting & match porting manifolds, cc'ing, radiusing, triple angle cuts etc) standard valves, heavier springs, and then top it off with a day of good tuning.

[JNR24]

I thought the standard springs are rated at around 44PSI anyways arent they?

I got the workshop manual at home, il check that tonight. im pretty sure that the pressure is in the 40PSI mark.

[[SweN]]

-Joel-. there are a couple of things in this thread that would be good in your pdf too. a few things come to mind right now.

1. more info on the PowerFC ecu and what its capable of (if possible, im going to do someof MY OWN research ) also what other ecu's are worth looking at, and can the stock ecu be used for the interim period without problems? (R33 doesnt specify in the pdf, just says you recommend the PowerFC)

2. fuel system upgrade? what would be a set of injectors worth looking at? what about fuel pump? the Bosch 044 pump got a bit of a rant in another thread i looked through. maybe its worth including as an extra?

3. sump choice? aftermarket or getting baffles installed and maybe enlarging?

4. oil cooler choice?

there is a wealth of knowledge floating around here, may aswell tap it

oh, if your having trouble with webspace you con put it in mine till you figure out yours PM me if you want

EDIT: i do IT and STILL i cannot type

[GiJOr33]

Power FC is as capable as the tuner behind it. It's a full plug and play replacement. The standard ecu should be fine for run in etc, as most of it's controlling duties are with the rest of the electrical system and cylinder head. Get a GTR pump and fuel regulator, and if you can get some RX7 13BT 550cc injectors they would fit. The standard sump should be fine, if you are going to race it often then maybe look at an aftermarket sump, but i'd go an oil cooler as well if that was the case. There is a mob that does oil coolers pretty cheap, i forget the name but someone here will know. Get one that has a thermostat in it so that when you are just cruising around, the oil bypasses the cooler. Just means the engine warms up quicker and stays at it's optimum operating temp. When you start giving it a bootful and the oil heats up, the thermostat opens and oil goes through the cooler.

[Steve]

to use RX7 injectors you will need to replace the plenum.

GTR pump is only good for around 250rwkw, so if you use this pump you will not need to upgrade the injectors.

oilcoolers, so many optoins. if you dont want to spend a fortune there is probably two ways I can think of:

1. get a grex one with sandwich plate and built in thermostat - cost around $650 delivered - only a 10 (or 13) row cooler, so ok but not optimal.

2. buy a serck or mocal cooler (34 row on special at GCG for $275 delivered - supposedly the one nismo used for its N1 cars),

then buy a sanwich plate for around $50 (mocal in uk can build the thermostat into the sandwich plate - investigating that option currently and will update),

inline thermostat (also called an oilstat) around $80,

fittings can be bought from pirtek or enzed for around $4-6 each x 8,

hose is around $10/m for internal braid rated at 2000psi max - probably need around 2.5m to be on the safe side (havent measured it yet),

then you will need aluminium strap (40mmx3mm seems ok) at around $5 per metre - I could only find it in 4m lenghts, but you may be able to find offcuts at a salvage yard.

Probably need to add a few dollars for decent nuts and bolts and you are done.

Option 2, although a bit more stuffing around and you dont get pretty stainless braided lines (to wear holes in anything they touch:)), is definately a better option from a cooling and cost point of view.

[Guilt-Toy]

Can someone tell me the alloy cement for blocking the VCT hole in the head is called? i need to buy some tomorow. the one that expands with alloy?