Valve spring heights and pressures

[DangerousDerek]

My heads are going back to Dave Knight tomorrow. He has kindly offered to sort them out properly and to open up the chambers in order to reduce my CR into the 10's.

I have a Crower 50304 solid cam and am unsure on the spec required for spring heights.

The valve caps i have are only the sintered type so i will be purchasing the dual spring steel caps along with new double springs and a shim set from real steel.

What i am unsure of at the moment is the installed height required for the Crower cam.
Any ideas or advice?

[Brummmie]

You need to consult the spring manufacturers, on the box it will give you a pressure at an installed height, but this is not the installed height you need, my cam was a lot higher lift on intake so needs shimming less than the exhaust.

[DangerousDerek]

I wonder if i had valve float previously due to slack springs.
I left the heads as they were with the old double springs.

The engine did rev to a peak power point at 6300rpm but the power curve didndt climb much after 5900.
Maybe new springs and setting them correctly will make a difference.

[Brummmie]

It's the coil clearance at max lift that is the key, this is what drives the installed height.

[Sardonicus]

40/40.5 mm IIRC springs to mind (would need to check notes) with the Comp Cams double valve springs and caps from R.S and I had no issues with coil bind but I did have to shim to get to this measurement

[DangerousDerek]

Time to start fitting and measuring. Any tips?

[BoostedChim]

What was the issue with the Yella Terras Derek?

[Brummmie]

DangerousDerek said:

Time to start fitting and measuring. Any tips?

Sober..

[DangerousDerek]

BoostedChim said:

What was the issue with the Yella Terras Derek?

I don't have issues with the yella terra's.
I have had problems contacting Paul at V8tuner though.

[DangerousDerek]

Brummmie said:

DangerousDerek said:

Time to start fitting and measuring. Any tips?

Sober..

I best get a move on then. Not much of dry January left

[rev-erend]

What is your CR?

What issues was it giving?

[DangerousDerek]

Bobby Shaftoe said:

Get the req'd seat pressure and full lift pressure off crower.

Use valve height mic or snap gauge to measure your current installed height. (Keep each valve, retainer & collets labelled and matched to each port as there is some variation/tolerance in each)> installed height will probably be different from valve to valve unless your machine shop were very good.

Real Steels duals are roughly 90lbs@ 1.575" , 200lbs@1.18" ,but you may want to measure your own as i've noticed a +/- 10 lbs tolerance in RS 's springs over the years. The relationship is linear so graphing it out will let you know your req'd install height to hit crowers recommended figures.

Then just check you've got no coil bind at full lift with a minimum of say 60 thou ish clearance between the coils on both inner and outer spring, then jobs a good 'un.

I run 100lbs seat on RS's duals and don't hit valve float till 6700rpm+. I have noticed that all Rv8 valve springs seem to go soft reasonably quickly no matter if they're stock singles, double or triples, just pulled a set of Kent Cams triples that have only been in there a couple of years and they're down to 50lbs seat pressure already.

Edited by Bobby Shaftoe on Monday 11th January 20:33

Thanks for that.

[DangerousDerek]

rev-erend said:

What is your CR?

What issues was it giving?

CR will be about 11:1 if I fit thicker MLS gaskets.

When the previous build was on Dales dyno (Bailey performance), the power curve climbed quickly then linear to about 5900 rpm with 290 bhp then tailed off suddenly but still climbed to 6300 only reaching 310 bhp.

[DangerousDerek]

Scratch that I found the printout. It all goes flat at 5000 rpm as you can see. Theories please

[rev-erend]

DangerousDerek said:

rev-erend said:

What is your CR?

What issues was it giving?

CR will be about 11:1 if I fit thicker MLS gaskets.

When the previous build was on Dales dyno (Bailey performance), the power curve climbed quickly then linear to about 5900 rpm with 290 bhp then tailed off suddenly but still climbed to 6300 only reaching 310 bhp.

That is pretty high

What is the advantage of lowering the CR?

[DangerousDerek]

rev-erend said:

That is pretty high

What is the advantage of lowering the CR?

Due to a mix up, a rushed build and Roland at ACR assuming my heads had much bigger chambers we actually had a CR of 11.6:1 when we ran the dyno above. The engine ran great NA but melted a piston on the 3rd run at TOTB when I used the nitrous. I am sure the high Car was a contributive factor. I was also running lower fuel pressure due to the new jenvey injectors. AFR was around 11:1 on that run but I obviously suffered severe det

[DangerousDerek]

Bobby Shaftoe said:

From that graph it looks like cam is too mild, peak torque comes and goes very early in the rev range. Looks like you could do with bumping the torque curve 1000rpm up---------> but then you may end up being limited by head flow if only running 1.63"/1.4"

The cam was advanced 2 degrees and I know that won't have helped but I don't see it explaining this. It's a Crower 50304 so fairly wild.
The heads are the biggest valve '500's that have additional work. I know now that they had a lot of issues however but Dave Knight assures me they are much better now so let's see what happens com dyno day. I now have a new vernier timing set so wii set the cam straight up or maybe a tad retarded to urge that power curve up.

[DangerousDerek]

Bobby Shaftoe said:

From that graph it looks like cam is too mild, peak torque comes and goes very early in the rev range. Looks like you could do with bumping the torque curve 1000rpm up---------> but then you may end up being limited by head flow if only running 1.63"/1.4"

The cam was advanced 2 degrees and I know that won't have helped but I don't see it explaining this. It's a Crower 50304 so fairly wild.
The heads are the biggest valve '500's that have additional work. I know now that they had a lot of issues however but Dave Knight assures me they are much better now so let's see what happens com dyno day. I now have a new vernier timing set so wii set the cam straight up or maybe a tad retarded to urge that power curve up.

[rev-erend]

DangerousDerek said:

rev-erend said:

That is pretty high

What is the advantage of lowering the CR?

Due to a mix up, a rushed build and Roland at ACR assuming my heads had much bigger chambers we actually had a CR of 11.6:1 when we ran the dyno above. The engine ran great NA but melted a piston on the 3rd run at TOTB when I used the nitrous. I am sure the high Car was a contributive factor. I was also running lower fuel pressure due to the new jenvey injectors. AFR was around 11:1 on that run but I obviously suffered severe det

Did you retard the ignition timing when you injected the timing.. I know MSD have this functionality and I guess something like Emerald could be made to switch maps.

Source info:
http://www.noswizard.com/nos-technical-information...

[DangerousDerek]

Bobby Shaftoe said:

2 degrees advance 'll make naff all difference, but all crower cams have 4 degrees advance already ground in so you may have 6 degrees advance, depending on how you set/verified the timing.

Who did the heads originally, before Knight fixed 'em?

Yeah I think I will aim for 4 degrees retard, piston to valve clearance allowing