R500 Duratec - Valve Spring Failure (yet another...)

[7 wonders of the world]

 

Love your calcs James  

I was meaning from a durability point as many race engines are refreshed annually or bi annually with valves, springs and retainers along with other compoments been discarded as consumables, and considering the track mileage you do this will far exceed this.

Road engines get a very easy ride by comparison

 

[aerobod - near CYYC]

I think I will be doing an annual check on the valve spring tension, Neil. I will take the accurate measurements on the retainers when I get them and convince myself they have enough inherent safety margin, but I think the aluminium retainers and a slightly higher spring rate would put my mind at ease on ensuring any resonance point is above the max rev range of the engine.

Raceline think (as was my reasoning before talking to them) that I should get a reasonable life out of the engine on the track keeping the rev limit at 8,200RPM. I would be happy getting 20,000 track km between top-end rebuilds (about 80 track days), compared with the 10,000km (besides 30,000 spirited road km) out of my current engine.

6061-T6 retainers should still have 90% of the original UTS when operated at 150C for 1,000hrs. At that point the pistons that are likely operating at a slightly higher temp at the cylinder wall (a lot higher at the crown) have probably lost enough strength to be about the same strength as cast pistons instead of forged, so a full engine rebuild would be appropriate.

[7 wonders of the world]

Ultimate P offer a double spring Duratec option too details below:

Maximum lift: 14mm.

Recommended fitted length; Outer Spring: 36mm, Inner Spring: 35mm.

Spring Rate: 43N/mm (245lb/in) +/-5%

Force at fitted length: 300N +/-7.5%

Force at minimum length: 900N +/-5.0%

Coil bound length: 19mm

Outer diameter: 27.6mm

 

SBD Double springs are rated at 210lb @ 13mm valve lift

 

[Shortshift]

Just updating and reordering the spring rate table I first posted above on October 11th (have we lost post #s in the new website?), reflecting the later information provided - just for posterity and for when others come looking in the future:

Kent VS60 single           33 N/mm          Kent VS59 double            37 N/mm          SDB double           37 N/mm          Kent VS51 single parallel           41 N/mm          Piper VSSDUR single           42 M/mm          Ultimate Power double           43 N/mm          SBD VLSK-DUR-01K double            44 N/mm          Piper VDSDUR double            52 N/mm          Cosworth YD0093 single                       tbc          Ultimate Power single              tbc   James (Apologies for space below; can't remove it!)

 

 

 

 

Edited December 9, 2023 by Shortshift

[Shortshift]

And, for completeness, I now have the car back from Stuart at Premier Power.  Top job carried out (seems to be his way... 😉) and, whilst I know that memory can be unreliable, the car seems to drive better now than at any time previously in my nine years of ownership.

As someone said to me - a tale of unlucky-lucky!

James

[bluenose]

Glad you got it sorted James. 

[aerobod - near CYYC]

Glad you have it in full working order again, James. I’m still finalising my engine and clutch rebuild parts availability to rectify the not nearly as lucky spring failures, hopefully parts are on the way soon.

[Shortshift]

Good luck James - I'm sure your engine will be terrific once you have it finished.  And then you will also have the satisfaction of knowing that it's been personally specced, exactly as you want it to be!

James

[aerobod - near CYYC]

I reviewed all the cam and valve spring parts I received from Raceline:

Cams are RLD250M / D-TEC35, 11.3mm cam lift (11.05mm valve lift), 280 degree duration, 68 degrees ATDC inlet closing. They are actually using the KC-1409 casting (refers to the Duratec fitment, as opposed to the cam grind, by the looks of it). I also have the S77 vernier pulleys for them.

Valve springs are parallel VS51 at 41N/mm spring rate with ST40 steel retainers, giving an initial load of 310N at 37mm and 845N at 24mm compressed length, which should give a maximum load at full valve lift of 765N.

[Shortshift]

Thanks for the update James.

So the cam you are using is the same as was fitted to factory-build R500s (Kent D-TEC35) and you've also helpfully identified the Raceline/Kent spring as a VS51 parallel at 41 N/mm.  I've updated the table a few lines above.

James

[aerobod - near CYYC]

33 minutes ago, Shortshift said:

Thanks for the update James.

So the cam you are using is the same as was fitted to factory-build R500s (Kent D-TEC35) and you've also helpfully identified the Raceline/Kent spring as a VS51 parallel at 41 N/mm.  I've updated the table a few lines above.

James

That is correct James, although there are 2 versions of the cam that are available with or without verniers (I picked the vernier version). Here are the relevant Kent Catalogue pages with the Duratec specs suitable for our cars.

Kent Duratec Cam Specs.pdf

[7 wonders of the world]

Quote

Just to clarify the Kents published spring rates:

VS51 singles        190 ib/in       33.3Nmm

VS59 doubles       210 ib/in       36.8Nmm

VS60 conical        188 lb/in        32.9Nmm

unless you've measured your springs James at 41Nm (234 LB/in) ?

I'm not sure If I would be comfortable with 190lb springs for your useage...

 

[aerobod - near CYYC]

1 hour ago, 7 wonders of the world said:

unless you've measured your springs James at 41Nm (234 LB/in) ?

I'm not sure If I would be comfortable with 190lb springs for your useage...

 

Hi Neil, the Kent rates are quoted at installed height and maximum pressure (minimum) height, as opposed to quoting the spring rate which most manufacturers do, leading to:

VS51s are 70 lbs at 37mm / 190 lbs at 24mm to give 120 lbs over 13mm or 41N/mm

VS60s are 56 lbs at 38mm / 188 lbs at 24mm to give 132 lbs over 14mm or 42N/mm

VS59s are 64 lbs at 37mm / 210 lbs at 23mm to give 146 lbs over 14mm or 46N/mm

The VS51s with ST40 retainers are the recommended combination from Raceline for all their Duratec-R engine builds from 250bhp up to 280bhp, with the RLD250M, RLD270M and RLD280M camshafts, so I'm trying to use the internals from their Duratec-R 250bhp build as closely as possible, other than using higher compression pistons to compensate for my normal 1,250 metre altitude.

I've attached a different page from the 2019 Kent catalogue that shows the Newton load values, too, to confirm the pound values are not rates.

kent_cams_brochure_2019_1.pdf

Edited December 10, 2023 by aerobod - near CYYC
Add cam catalogue page

[7 wonders of the world]

Well spotted James, I misread the Kent data, ...... 

[familymad]

New to the R500D family and have bought a low miles machine. Keen to avoid the rebuild scenario, has anyone done this work preventatively to life the engine and has a rough costing? Assume it’s Raceline only now since Premier Power closed?

[Shortshift]

Congratulations on becoming an R500D owner! 

Would love to see a photo...

I'd absolutely recommend that you have the valve springs replaced so as to not be playing Russian Roulette with your top-end.  I have no experience of Raceline but replacing the springs is not a tricky task (and can even be done with the head in place, I think) so you should have plenty of options. 

Whereabouts in the country are you?  I may be able to suggest some reputable specialists (as will others, no doubt).

James

Edited April 7 by Shortshift

[familymad]

Hi James,

That’s encouragement enough for me then. I’ll plan it in as the first job. She came to me with 2304miles on the clock and is lovely. I’ve added another 20% to the total miles in the first week. Looked at a few, plus some 420R’s (one on throttle bodies) and a 620R. The R500 had always been on my bucket list, after reading Evo’s review, so I thought best I just got it done! Bucks near Denham.

 

 

 

Edited April 7 by familymad

[familymad]

[Shortshift]

Lovely car - maybe see you on some Club trackdays with it?

Not sure who to recommend for the valve spring replacement work in your neck of the world.  Is Ratrace Motorsport nearish?  Otherwise, perhaps other members will be able to come up with recommendations for you.  At least you have a wealth of information in this thread to help you decide on which springs to select, etc.

James

Edited April 8 by Shortshift

[Dan R]

9 hours ago, familymad said:

Hi James,

That’s encouragement enough for me then. I’ll plan it in as the first job. She came to me with 2304miles on the clock and is lovely. I’ve added another 20% to the total miles in the first week. Looked at a few, plus some 420R’s (one on throttle bodies) and a 620R. The R500 had always been on my bucket list, after reading Evo’s review, so I thought best I just got it done! Bucks near Denham.

 

 

 

What a lovely car, and welcome to the 500D club!  I saw that car for sale recently and the mileage caught my eye as mine was equally low mileage when I bought it!

I have looked at getting the valve springs done and got a quote from Premiere Power not long before they closed.   The only other place =I have been recommended for work (Not specifically for valve springs) is Northampton Motorsport, who seem to have a very good reputation. 

[Shortshift]

Ah yes, of course, Northampton.  Good call!

James

[familymad]

Thanks both. Ratrace are 40 mins. PGM about the same. PT sportscars 25 mins.

[familymad]

4 hours ago, Shortshift said:

Lovely car - maybe see you on some Club trackdays with it?

Not sure who to recommend for the valve spring replacement work in your neck of the world.  Is Ratrace Motorsport nearish?  Otherwise, perhaps other members will be able to come up with recommendations for you.  At least you have a wealth of information in this thread to help you decide on which springs to select, etc.

James

Yes, track days are the plan. Not done one before in a car only on bikes. 

[Shortshift]

Look forward to seeing you at one or more; Club trackdays are simply the best...

But you will need to replace your standard rollover bar with a 'trackday' or so-called, 'FIA', bar.

James

Edited April 8 by Shortshift

[aerobod - near CYYC]

In terms of doing the springs with the head in place, after removing the cams (using a jig to hold the timing sprockets in place to preserve timing) and carefully labelling the bucket tappets for return to the same position, an adapter that screws into the spark plug hole and pressurises the cylinder with compressed air (to about 8 bar) can be used to keep the valves in place. Instead of a conventional ‘C’ clamp style spring compressor. A plate bolted to the cam bearing shell bolt holes with a bolt threaded into it to align with and compress the valve springs is then used. Keeping the piston at TDC and transmission in gear to stop engine rotation will stop the valves dropping in if the air pressure is less than required to stop the valve moving when the keepers are removed.

Without using this technique or a modification of it (such as the piston at TDC and waxed string stuffed in the cylinder on top of the piston to keep the valves in place instead of compressed air), an engine out job will be likely be needed, as head removal without removing the timing case is likely difficult, then if it is removed timing has to be redone due to the crankshaft bolt being disturbed.