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We measured Redblock cam valve events; here's what we got.

We also have to advise you all on something unsavory we've observed. Many aftermarket camshafts (The IPD VX, this KL T3, the one from Jones) are ground with a BUNCH of retard built in. Like 10*, or thereabouts, and this is based off of measurements with a degree wheel. I won't bore you with the details but if you want me to, I will. If you're going to run one of these, there's a strong possibility that you'll need an adjustable cam gear.
 
Well, Volvo's figures are based on some weird, arbitrary checking number. The V cam, for example, is based on 0.7mm (0.028") valve clearance, at which point the intake valve begins to open at 11*BTDC. The H and K cams use 0.5mm (0.020") as a checking figure. Nobody anywhere uses these numbers, so they're not useful for comparative purposes. Just a couple weeks ago I checked the timing on my V cam in my 245 to make sure it was in the correct place according to this spec as the head's been milled a couple times, just to make sure it wasn't overly retarded, and found that I was on the money with regarding to the cam gear correction I'd set.

With regard to the archived CAMS.JPG, I looked at the A and B grinds compared to ours, and I don't see that they're off by much, if any. Intake on the A seems to be exactly the same. I see that the K that's on here is 10+ degrees larger at 0.050" on the CAMS.JPG, and I have to say that's much larger than what we got, yes. All of our named "Volvo" cams are original Volvo grinds, not repops or regrind equivalents or whatever. I've measured our K multiple times and I can confirm that our numbers are accurate as this is the cam we ran in our race engine. When I upgraded (the Jones cam) it was important to be absolutely certain as to what I had before I could make a decision where to go from there. Considering that we're using a dial indicator that's graduated to 0.001" and therefore has that much of a tolerance, some deviation is to be expected, but not 10 degrees worth. Additionally, while the valve event figures are measurements, the duration figures are manual calculations, and sometimes we goof those numbers (off by 10, whatever). Once in a while I throw a quick eyeball over those figures just to make sure they look right, sometimes I find an error. This many years in, there's probably none left. Probably. The valve lift at TDC was a later addition and the figures in red are estimations? reverse calculations? and shouldn't be taken as gospel. The same figures in black are measurements and can be trusted as they are now incorporated at time of measurement.

I compare our numbers to any Cam Doctor figures I see listed anywhere (rare) and I'm completely comfortable that we're within 1 or maybe 2 degrees from those, which for the purposes here is close enough. What we're trying to accomplish to have a control (Cam and I) using the same tools and the same methods so that the community has a way to directly compare one cam to another for the purposes of selection. I've seen tons of listings for specs on these cams where I've wondered "what did they use for a checking clearance because that doesn't jive with what we have at all". If you find measured specs but no information as to methodology, I'm not going to say those numbers are no good but they probably can't (or shouldn't) be compared to what's listed here.

Does this explain satisfactorily?
 
Actually, the overall 0.050" duration I have on the M is a bad calculation, it should be 201*, not 196*. As I said, sometimes the calculations are wrong. I appreciate pointing it out. I can't explain the difference in intake lobe center.
 
I said this on Facebook but reposting here:

For this one we did actually check from .010" to .016" as per culberro's suggestion (sort of). I totally forgot to add that to the sheet.

Intake/Exhaust

.010" 301/305
.011" 297/303
.012" 294/301
.013" 292/297
.014" 289/294
.015" 288/291
.016" 286/288
 
redblockpowered said:
I said this on Facebook but reposting here:

For this one we did actually check from .010" to .016" as per culberro's suggestion (sort of). I totally forgot to add that to the sheet.

Intake/Exhaust

.010" 301/305
.011" 297/303
.012" 294/301
.013" 292/297
.014" 289/294
.015" 288/291
.016" 286/288
Click to expand...
15deg of duration change is a lot! Thanks for doing that!
Shows why valve lash can really change how these engines run.
 
culberro said:
15deg of duration change is a lot! Thanks for doing that!
Shows why valve lash can really change how these engines run.
Click to expand...


Hi,

I'd like to understand the above statement a bit better. What makes the valve clearance variation reduce or increase the cam duration by that amount? If the valve is closed, the clearance doesn't seem to matter, however I can kind of understand that it will effect the valve timing once the cam starts to open and close the valve. I just cannot figure out how only 0.006" difference equals that much difference in how long the valve stays open.
 
hessam69 said:
Hi,

I'd like to understand the above statement a bit better. What makes the valve clearance variation reduce or increase the cam duration by that amount? If the valve is closed, the clearance doesn't seem to matter, however I can kind of understand that it will effect the valve timing once the cam starts to open and close the valve. I just cannot figure out how only 0.006" difference equals that much difference in how long the valve stays open.
Click to expand...
If you look at the advertised duration vs duration at a specific lift you'll see it as well. Like advertised duration might be 290deg, but at 0.050" lift it's 225-230deg.

This is due to the acceleration ramp profile built into the cams, and the transition to the lifting ramps.
 
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