Thank you both. Got it.
I'm by no means an expert in this department, but I am a little confused by this. Why would the overall weight of a valve spring be a factor in parasitic drag? Isn't it the spring pressure that would be the primary factor? Granted, a heavier spring may have the ability to generate higher pressure than a lighter spring (if so designed - which seems to be the case with the stock springs, based on your data), but I wouldn't think that the actual spring weight would matter with respect to valvetrain drag. Or I could have no idea what I'm talking about!
A lighter valve spring would technically mean lower/lighter reciprocating mass meaning it would require less spring pressure to pull the spring and everything else up after depressed by the camshaft. I forget the calculation, but it's something like for every gram lost from the valvetrain the redline can be raised 'X' amount. Obviously a lighter valve would be more effective (I have those too) as the weight of a spring rebounding is sort of a diminishing return compared to a constant weight loss such as lighter retainers, valves, shim buckets etc. What confuses me about what these fellows are saying is that their springs, although significantly lighter, employ even less spring pressure than stock springs which I do not believe is the way to go. I'm currently searching for a spring which has slightly higher seat pressure yet similar open pressure. Valve bounce occurs when landing back on the seat and the stock 62lb seat pressure might not cut it with this significantly more radical camshaft profile I am going with. I'm thinking 80-85lbs at the seat should be about right, but I want to keep the 200lbs or so open pressure.
If I remember my physics correctly, any spring system will have some hysteresis (bounce back you called it) and usually another spring with a different frequency is used to dampen this. Do they do this in automotive systems like valve trains?
Absolutely. Dual spring valves were designed for that specific purpose. Imagine a slinky stretched out a bit laying flat while one end of the slinky is depressed and retracted a bit. This creates a bit of a wave in the entire piece. This is normal spring harmonic operation. When the springs really start going, often times single spring systems (and some dual systems if pushed hard enough) begin to bounce a bit causing harmonics from both ends meaning the slinky is now not just waving in one direction, but in both directions. If this happens enough, the spring will snap. Dual springs wound generally in the opposite direction as the primary outer springs dampen or eliminate this effect.
Here's an example of one of my seat cuts and the beginning pic prior to the port work taking place. The ID and OD of the intake seat I had installed is slightly larger than stock giving me some meat to remove around the bowl ID where it meets the seat to increase flow. The new intakes I have are 44mm (stocks are 42mm) with some fancy back cuts. The installed height from the cut in this pic is right within spec at 1.516" (specs are 1.5-1.54). The cut is one of those infinite radius deals and looks perfect. The 45 is cut right up top and is a bit difficult to see in the pic, but it looks good. As a general rule, I try and keep the pinch point as far outside as possible, but in this instance I had it right in the center due to the backcuts and seat area on the valve being so small and as the OD of the valve is getting close to 90% of the ID which is certainly something I don't want to go outside of (rule is usually to have ID be not more than 88-90% of the OD of the valve head). Image Unavailable, Please Login
The answer has been found, and it was not easy! Ok, so these springs are made by Eibach and are absolutely perfect for just about all 2v Ferrari applications, what's funny I Eibach had zero idea that these fit such an application (of course). The bad side is Eibach springs are a bit pricey, but these guys have the perfect spring package and I am sort of tickled over the finding them as this little search took absolutely forever. Anyway, these springs employ slightly more seat pressure yet about the same to slightly less open pressure which is excellent. Eibach part number is: 20450.02 76lbs seat pressure @ 1.54" 245lbs pressure @ .950" bind: .830" OD of outer spring: 1.26" ID of outer spring: .944" ID of inner spring: .710"
Here's an example of a couple spring samples forwarded to me. The idea was essentially to find a spring made from small gauge steel, yet with a slightly longer free length. This allows for more lift before bind yet the smaller gauge keeps the pressure in check. The spring on the right is the unit I will use and weighs a scant 50 grams opposed to stock which weighs 112 grams. Image Unavailable, Please Login
We like big Ferrari lobes here. Also is a pic of a Si exhaust valve I am using. Much better than Ferrea IMO. The Ferrea exhaust valves I used before after just 3k miles were practically junk. Also, the seat area on the Ferrea valve causes the valve to sit into the head about 10 thou more than stock or the Si valves, and that's before the seat is ever cut! The black funk they have on the lobes is an anti-wear type break-in stuff. Typical for new cams. Image Unavailable, Please Login Image Unavailable, Please Login
Block bored and honed with deck plates. Without getting into too many details regarding deck plates, there is a difference. Note: there is no difference when a dummy head is bolted on one side and deck plates on the other side. It was finished last week but I finally had a chance to pick it up today. Running .003 clearance. The Rottler machine which performed the finish hone was specifically programmed to take into account that the hone could not make a complete stroke due to the location of the main saddles (in the way of the hone stroke) therefore; every other stroke the machined performed a smaller finishing pattern concentrating at the bottom area or the bore to account for the difference lost in not performing a full stroke. So in other words, they came out perfect. Image Unavailable, Please Login Image Unavailable, Please Login
Are you saying the dummy head was not required? (edit: judging from the pic I guess it wasn't required because it didn't fit in their machine ) ... so what was the actual distortion ... I'm looking forward to measuring it again with my new head gaskets ... get those tq plates back to me . Good progress ... should have 'er together this weekend . cheers
I was there when we measured for distortion with just torque plates and torque plates with a dummy head. There was no difference. The distortion was about .0009 on all cylinders except for 3 and 6 which had .0014 ish. The measurable amount was near the bottom of the cylinder with almost none at the top. interesting stuff. I will have them back to you this week! I can just barely squeeze a .003 feeler gauge between the piston skirt and the liner. Clearance is probably just below .003.
Thanks for sharing John ... interesting ... that is totally different from what I measured. I saw .0015" distortion on all the bores only at the top and it diminished as I went down the bore. I've also seen the distortion remaining during teardown until the sleeves "relax". If the distortion is only happening in the bottom it's not a big deal 'cause the rings never make it down there FWIW. The distortion also was such that the sleeves grew in the plane of the skirt, but shrunk normal to that ... in which plane did you see the distortion? I'm glad you measured it ... you're the only other person I know that has posted real data with regards to this. Stock sleeves just bored out right? cheers, Sean
How did I miss all of this ?? Cams look good . As always your project seem to keep moving !! No news on the crank ?
Sean, you're exactly right. I had it bass ackwards. We didn't quite measure that much other than in one cylinder on each bank for some reason. I do not recall which plane.... Wish I could now as it would be useful information.
I took some time this evening to carefully measure the camshafts to make sure the cam manufacturer sent to me what they said they had (hey, everyone makes mistakes right?). What I noticed is the intake cams is 11.5mm lift and the exhaust is 10.5mm lift. These lift figures are substantially higher than the 10.75mm intake lift and 10mm exhaust lift these cams are supposed to be..... There is no other cam on their website which this could be so I am sort of wondering what they did here. The lobes don't tell me they have a giant amount of duration like a race cam, so the could have made me some sort of custom grind they thought would be adequate although I still cannot find out why they would not tell me...... On another note, I absolutely love the large bolt pattern the placed at the end of the cam before the cam gear. This deletes the need for the ridiculous Ferrari tool which holds the cam while it's being torqued. Image Unavailable, Please Login Image Unavailable, Please Login
Pardon my ignorance but the measuring device in the picture is placed on the rough surface and not the bearing surface to the left of it. Wouldn't the lift be measured from that point or at least from the equivalent distance circumference from the other side of the lobe?
If you measured lift as the picture suggests then you will get wrong results. A quick and dirty way to measure lift would be to measure by clamping with your calipers the width of the entire lobe from the peak top to back side and then at 90* to that (your base circle) and subtract.
