Dbilas camshaft

[zaq123]

Put dial gauges on first cylinder with 276 Dbilas cam. For some reason I get peak timing 118' degrees for both IN and EX. Advertised is 108'. Basically I just clocked degrees at 1.5mm before and after max lift and split the difference. Dbilas cam card is a little limited with info. I wish the had some more info like lift at 0.050 etc.

I tried to verify duration but for some reason my numbers are way of. Not easy to duplicate. I get close to 304 on both IN and EX. I'm getting 34/90-90-34 by clocking degree wheel and dial gauge when IN/EX open and closes.

I checked Dbilas 304 cam specs and they are not even close: 47/77-77/47

I know that without lift at 0.05 is hard to verify the cam but my observations are still way of advertised 30/66-66/30 272 cam with 108' peak timing.

What gives? rocker ratio? something else is wrong?

[digger]

check it with clearances set and 1mm opening and 1mm closing as opposed to angle of peak lift

what lift at TDC in and ex?

are you referencing TDC correct? how are you determining the angle?

these are measurements i took several years ago

at 1mm the inlet opens 2* and closes 220* so the centerline is (220+2)/2 =110.
at 1mm the exh opens -218* and closes 2* so the centerline is (-218+2)/2 = -108

[zaq123]

I used degree wheel on the crank. TDC was found with the piston stop. I found peak timing with. 1.5mm before full open and 1.5mm after full open. Clearance is set to 25 as per can spec.

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[digger]

i would check the centre of opening and closing points say 0.1mm or 1mm check points, it is more accurate.

and also the lift at TDC of both valves, in the above it is 0.85mm inlet 1.05mm exh as installed once the clearance is subtracted as the graph is done with 0-clearance

[zaq123]

i would check the centre of opening and closing points say 0.1mm or 1mm check points, it is more accurate.

and also the lift at TDC of both valves, in the above it is 0.85mm inlet 1.05mm exh as installed.

valve lift registered as 11.6mm EX and 11.8mm IN.

what concerns me is that my measurement actually line up and point to 304 duration.
For example...IN side:
1.I spotted degree wheel when IN just began to open - 34 degrees BTDC
2.I calculated peak timing by observing degree wheel 1.5mm before and 1.5mm after full lift - 118 degrees.
3.I spotted degree wheel when IN just got closed - 90' ABDC.

2 was calculated independently from observing 1 and 3.

using observed #1 and #3 above:34+90+180= 304' duration

Or just using observed #1 and calculated #2 (based on 1.5mm before/after):

(34+118)x2=304 degrees

Both methods point to 304' degrees.

EX had identical observed number, symmetrical cam.

Do I have a flaw in my logic somewhere?

[digger]

if when you have 0.25mm clearance set and get those number just as the indicator registers 0.01mm opening and closing on retainer then yes that is alot of duration, something is off.

the 288 schrick inlet lobe is -38 (38 BTDC), 250 (70 ABDC) = 288 @ 106 centreline
stock cam is -18, 238 = 256 @ 110 centreline

but

the stock b23 cam -36, 262 = 298 @ 113 this cam has very long slow clearance ramps, it is not a big duration cam at 1mm it is same duration a stock b25

check duration at 1mm net lift open and close and at 5mm to see if it is something funny with the clearance ramps

sometimes peak lift can be different position than the middle of the opening and closing points if the cam is asymmetrical, the 276 i measured wasn't asymmetrical. your numbers also suggest it isnt asymmetrical.

[zaq123]

didn't have much...only was able to do IN side plot. What do you think? This is with HD rockers.

[digger]

at 0.5mm open is -12* and close is 240*. so that is 252* duration at 0.5mm. centerline is 114.

at 1mm open is -5* and close is 233*. so that is 238* duration at 1mm. centerline is 114

at 5mm open is 28* and close is 202*. so that is 174* duration at 5mm. centerline is 115

this isnt a big duration cam it is smaller than the 288

if the exhaust side is the same centerline then something is wrong (the lobe separation is too high), otherwise it could be retarded 6* or so

i would repeat measurements on exhaust side

[zaq123]

if the exhaust side is the same centerline then something is wrong (the lobe separation is too high), otherwise it could be retarded 6* or so

EX measurement are coming shortly..... fingers crossed, I would like to see close to 102 on the centerline

[zaq123]

Doesn't look too good, EX center line looks like 112

[zaq123]

can it be that I got their 284 cam?

Dbilas list their specs as following:

peak timing: 112
lift at TDC 2.1
valve timing: 30/74-74/30
clearance: 20/20
valve lift: 11.5

Looks lobe separation and valve timings are really close. Lift at TDC is way off though.

[digger]

for exhaust at 0.5mm open is -240* and close is 15*. so that is 255* duration at 0.5mm. centerline is 112

at 1mm open is -233* and close is 7*. so that is 240* duration at 1mm. centerline is 113

at 5mm open is -200* and close is -28*. so that is 172* duration at 5mm. centerline is 114

yeah lobes are definitely further apart than they should by about 4-6degrees. you could try contacting them, did it have any numbers on the cam, usually they put them on the end. it might be a different cam the numbers are more inline with what id expect with a 284 as the duration at these check points are only a few degrees smaller than a 288

[zaq123]

I recall etched numbers on it. Don't remember exact number but I think it matched up to 276 cam paperwork part number. Really don't want to pull the cam again, number is on the plug side....not the gear side.
2.9L 10:1 with long Bavauto headers and possible itb kit in the future. Head had Supertech valve fitted with zero port work.
would you run this cam? Should I give it a shot or it will perform terrible? would you run .25mm valve clearance or try 0.2mm as Dbilas suggest for their 284 cam?

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To sum it up: Looks like lobe separation is 112EX;114IN. Valve lift with 0.25mm clearance -11.7mm; 1.6mm lift at TDC, Duration: 284??????


here are 0.04" (1mm) numbers: EX side: -231EO/7EC................IN side: -5IO/233IC
here are 0.003" numbers: EX: -250EO/29EC..............IN side:-25IO/255IC

[digger]

if i ran id do it at 0.25mm and advance it a few degrees to about ~110 ICL.

it should make a lot more power at topend especially with ITB but will likely give up some midrange compared to the smaller cam due to the added duration and wide LSA. advancing should help mitigate it a bit but the exhaust lobe moves to so its a compromise.
It will still idle fine

[zaq123]

if i ran id do it at 0.25mm and advance it a few degrees to about ~110 ICL.

it should make a lot more power at topend especially with ITB but will likely give up some midrange compared to the smaller cam due to the added duration and wide LSA. advancing should help mitigate it a bit but the exhaust lobe moves to so its a compromise.
It will still idle fine

So basically advance it by about 4' degrees?

As far as midrange goes....I understand effects of wide LSA (decrease in overlap) or increase in duration (increased overlap)... What happens when you do both, increase duration and move LSA wider? Looks like overlap area in my plot is larger than in 276 plot you posted.