Race Engine Forum UK

Hello,

I just bought another Delta HPE last week, and I wanted to ask your advice about camshafts comparison and recommendations.

the car has the 2.0 16v turbo engine, I am going to replace the stock turbo since its smoking a bit, with a Holset HX30W,the plan is to run about 1bar boost, this time, I am concentrating on on the looks of the car, at least for now, but I would like to know, if I should use the N/A 16v camshafts, or I should go with a set from Colombo & Bariani or Gozzoli? will I to notice a difference in the behavior between these cams? in what sense?
P.S. (if no one has any experience with Gozzoli cams, just compare N/A to C&B street series cams)
I noticed that C&B has 3 types or road series camshafts, so for a daily driven which would u recommend (most fun to drive around at teh same time good power, without having to use adjustable camshaft pulleys), keeping all engine internals stock, max boost 1-1.2bar, custom mapping of ECU.BTW I have been told that the HX30w turbo should boost at low RPM.

Kind Regards
Nabil

Nabil, hi

the easiest question to answer in general terms, but one of the most difficult to consider in detail, so I'm not going to try. Actaully in that latter respect dyno testing or simulation is really the only way and whilst I can get top-level sim done on n/a engines I don't even know anyone who has the trubo add-on software capable of modelling it.

So, how do you choose? Very simple. Beyond putting a nomrally aspirated inlet or pair in there, which, yes, works and is documented on this forum, there are apparently 3 choices of cams from the reputable and proven C&B source. Or so you say their website says which may be another thing altogehter. The other firm I don't know and don't need to. The cam with the lowest (peak and tdc) lift will give the best low-medium rpm torque characteristic. The higher the lift, the more top end it will have and the worse 'below peak-torque' and off-boost behaviour. So if you want driveable, don't pick the most radical...

(this incidentally, is common to all engines)

Also be aware:
1. The more peak lift and duration the higher the lift at tdc is going to be and you might have piston-valve clearance problems.
2. The standard 16v Fiat/Lancia Integrale type dual valve springs with standard caps and spring bases coil bind at 11.6mm true lift, and bearing in mind that you must have at least 1mm clearance between coils (2mm is preferable) this means the max lift the 16v head will take is about 10.6mm.

As for not wanting to fit adjustable cam wheels all I will say is I would never make that stipulation. Don't ask 'why?' - I'm a race engine builder, I just would never would. And it's asking a bit much from the cam grinder to tell you you won't need them... (it happens).

So, all in all, unless you want to dismantle the whole engine and build it from scratch, maybe fit the mildest cams. All the same I would want to dry build it and ascertain what the valve-piston clearance actually is. Details of this are in GC V/W.

Hope this helps,

GC

Guy, Thank you so much for clearing this up, I need to ask you another Question if I may.
assuming I chose to go with C&B Road medium or Road max, will I have to change the valve springs? and do you advise to modify the stock pulleys and make them adjustable? or I better buy a set of these?

Kind Regards
Nabil

Hi

This question is for GC but I think I can answer it.

For me camshaft "choice" is pretty easy.
You need to perfectly know what you will do with the car and which different kind of circuit are in relation with.
From there you will be able to find a set of camshafts suited for your particular application. That serve nothing to invest in high duration camshaft if the car will race at AutoX event for example and the first thing I think you need to take in consideration is this engine is turbo...
I would first check the turbo on the engine before taking a decision about camshafts since I would want to match perfectly the boost curve by finding the ideal duration to match the rpm and after finding a cam that will give the highest lift at this X duration.

I will suggest you to change your spring anytime you install camshaft even a model with 1-2mm lift more.
If you invest money in camshafts and install them with factory used spring right there you will not get there full potentinal.
New race springs will give you a better valve closing time and sealing "force" applied to the valve If I can tell it like this.
With high lift camshafts I would suggest to carefully inspect your camshafts bearings caps and new bolts/studs if you can afford.

For the adjustables pulleys I would suggest you to got a set eventually or modifying the stock ones. If you know a machinist this is a simple part to modify. I can't really talk from experience on turbo setups but with an n/a motor on certain circuit these parts can provide the "top notch" ajustments..
But at the end this is your choice

Hope thats help
Hugo

If you're interested in making adjustable cam pulleys I can provide you the information you'll need. Its just a bunch of easy small tasks but overall it can be some work..

Extract from a GC 'How to' data sheet re springs that may be helpful in the issue of installed height. I believe as an engine builder (which you are if you'r building an engine!) you have to make careful dimensional assesments yourself on your engine. Never assume things are OK. Check.

GC



GC 3VSR COMPETITION TRIPLE VALVE SPRINGS updated 27 Oct 07

Data

The minimum installed height of the springs is 23.2 plus 1-2mm safety clearance + cam lift. The installed height is distance from the underside of the spring cap (outer spring locating face) to the spring base/s used. It depends on: spring platform position (that¢ž¢s the alloy face in the head where the spring bases sit), the valve setup height, collet position relative to valve tip, spring cap design, spring base thickness.

The standard 8V and 16V valve setup (or tip) height (I call it VSH) is 40.7mm and will typically be about 41 ¢‚¬Å“ 42mm after valve seat blueprinting and valve regrinding. The more work performed on those parts the higher the VSH will be. You should always measure and record the VSH. A from is available from GCRE on request to do this.

Example of working out available lift with OE spring cap and dual spring bases:
With VSH 41mm.
Tip to underside of OE spring cap (outer spring region) 4.28mm
Distance to spring platform 41-4.28 = 36.72mm (the platform is the alloy section of the head around the guides where the spring bases sit)
Thickness of OE outer spring base 1mm
Installed height of outer spring = 35.72mm

When the installed height is compressed to 23mm with OE spring cap and BOTH OE spring bases fitted the coils ‹Å“box¢ž¢ or bind ie: will not accept more lift. So the theoretical maximum lift (not allowing any safety clearance between coils) is 35.72 ¢‚¬Å“ 23mm =12.72mm. That fully compressed condition must be avoided!

Maximum lift allowing for 1mm (minimum, 2mm is better) is 12.72mm ¢‚¬Å“ 1mm = 11.72mm (the maximum permissible valve lift in this case)
Max valve lift of 10.72mm ¢‚¬Å“ using 2mm safety clearance would be preferable.

If your cams have more lift you need a taller VSH, a lower spring platform (machining required) or race spring seats.

GC race spring seats will give spring inst height at full compression of 21.4mm, ie will allow 23-21.4 = 1.6mm more lift ie: with 1mm safety clearance between closest coils 13.3mm or 12.3mm with 2mm safety clearance.

About GC springs and what they can do for you:

GC triple springs have been exhaustively track and dyno tested including more than 2 years race and test in a 2liter Fiat 200bhp motor in NHRA (short oval) pulling repeatedly to end-of-straight 9500 rpm at 12mm true lift. They are lower poundage than OE Fiat TC and SOHC springs up to around 10mm lift (a thing some find very odd but it's true) and they rely on friction damping between coils to prevent damaging valve float and resonance in the valve event. The highest speed at which these springs have been run by GC is 13,000rpm in a Fiat 1600 TC hydroplane engine with 44/38mm valves.
Running 80-100thou‚ vertical piston to valve clearance at closest proximity no GC built engine equipped with these springs has ever dropped a valve.

Cautionary notes:

1. Beware of regrind cams with harsh ramps! They can fracture the springs. If using regrinds check springs periodically for fracture.
2. Low valve tip height and high valve lift especially with the OE spring bases can cause coil binding.
3. Contact GC if proposing the use of non-standard spring caps the damper spring tangs can fracture if the design is incorrect.
4. Race spring seats are available from GC. These are ‹Å“flat-base¢ž¢ ie: have no step for the inner spring.
5. Corrosion pitting due to damp storage will lead to growth of fracture zones in service ¢‚¬Å“ don¢ž¢t let the springs get rusty. Before installing strip and clean the springs with solvent to remove corrosion inhibitor and lubricate with WD40, Duck oil or engine oil.
6. Fit the small OE ‹Å“stepped¢ž¢ spring base firmly to the inner coil spring and reassemble. When offering up to the head make sure the inner spring base does not sit on the valve guide.

Lifing:

GC triple springs should be changed regardless of condition each year in competition engines. In a road or road-race engines they will last almost indefinitely but should normally be replaced at engine overhaul.