Hey all. Upgraded to mid-range comp cams for my 2004 Cobra DOHC heads and am dialing them in. Passenger side was right on the money at 114* for both cams with a 4* bump on the adjustable timing gear. Driver's side has me spinning. Exhaust cam is right at 114* with a 2* bump, but the intake was consistently showing a centerline of 123* or 124*. Cheated it down with the slag in the keyway to about 120, but would like to get it to spec. Given that it is driven by the exhaust cam, I'm not seeing a lot of options. I froze the primary tensioner with a hose clamp and always went clockwise anyway, so chain slag isn't impacting my readings. I'm getting consistent numbers, so the readings are on. Tried swapping out a couple of other secondary chains I had kicking around and either they are all stretched the same amount or none of them are, because the readings stayed the same. I'll go with the latter as more likely. Sprockets look fine and I swapped those out too with no changes. Tried skipping a tooth on the secondary sprocket and it was way to far. Spoke with Comp and they swear up and down the grind can't be off. I'm just about out of ideas. Before I pull out the die grinder to the keyway of a couple of old gears and tinker with that I thought I'd reach out. I don't think they sell adjustable secondary sprockets, do they? Any troubleshooting or fix ideas? Thanks.
Degreeing my cams and my left intake is late 12*
- Thread starter Happster
- Start date
I e never done cams on our cars but can you have the intake and exhaust swapped?
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Thanks for the thought! I checked that, but the exhaust centerline is spot on at 114 ATDC and the intake is supposed to be at 114 BTDC. They both install with the keyway at 6 o'clock and the lobes are drastically different at that same position, on opposite sides of TDC. Supposed to be 228 degrees of rotation apart (114 + 114, split by TDC), although mine are 234 apart (114 + 120) with the intake cam lagging behind 6 degrees.
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Both cams do not degree to the 114. The exhaust cam is a calculated value. You need to take the difference of your intake cam (114 you said) from the separation value (not sure what yours is on cam card). Should be 4 or 6 or something. Add that value to the intake cam value and that is what you set the exhaust cam to.
My cams were 110 intake with a 114 lobe separation. So 114-110=4. So 4+114=118. My cams are set at 110 intake and 118 exhaust.
Hope this helps. I called bullet Racing cams because I had the same question and they explained it to me.
My cams were 110 intake with a 114 lobe separation. So 114-110=4. So 4+114=118. My cams are set at 110 intake and 118 exhaust.
Hope this helps. I called bullet Racing cams because I had the same question and they explained it to me.
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Thanks 03! My cam card doesn't list lobe separation. It has:
Intake
Advertised duration at .006 is 258, duration at .050 it is 222. Opens .050 at 3* BBDC, closes at 45* ATDC.
Exhaust
Advertised duration at .006 is 260, duration at .050 it is 224. Opens .050 at 50* BBDC, closes at 6* ATDC.
I'll go back and spec out these valve events. One strange thing is that the specs on the cards are listed as being for 118* centerline exhaust, 114* for intake. (So LSA is 116*?). Comp cams said that was an error and they should all be set at 114* centerline. That was a bit concerning that they are banging out cam cards with errors like that. (There were typos abound too, with all four cards having a header "left exhaust". I had to use the part number suffixes, LI, RI, LE to RE, figure out which were which.) But maybe there is something there? I asked Comp to explain and the tech said he's dialed in cams on these motors hundreds of times and always uses 114* across the board for street applications on mid-range cams. I was still a little uneasy with this explanation. Thoughts are welcome.
Two thoughts... First, the right side came in at 114 for both. Second, that my intake is late. If I bump the exhaust from 114 to 118, I'd expect my intake to bump likewise to 124. As I mentioned, right now I'm at 120 cheating with the slop in the keyways as much as possible. There is no other way to adjust the intake beyond filing the key that I am aware of.
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With this example
Using the lobe center of 110* with a lobe separation of 114* would put the exhaust lobe center at 224*
Start with the driver side bank #6 cylinder remove all rollers except #6 including the all passenger side rollers until you get driver side done
Using the lobe center of 110* with a lobe separation of 114* would put the exhaust lobe center at 224*
Start with the driver side bank #6 cylinder remove all rollers except #6 including the all passenger side rollers until you get driver side done
I have adjustable primaries and I ground the keys right off my secondary gears when I degreed them. Todd Warren (the mod motor cam guru) has a guide posted on his facebook group that says to do it this way. (or grind all the keys off if you don't have adjustable primaries.) Install ARP bolts in the cams and torque them to 125 lb/ft.
Are you sure there isn't a couple typos in there? I think the intake valve open spec should read "-3* BTDC" or "3* ATDC". The exhaust valve close spec should be "-6* ATDC" or "6* BTDC" See chart below.
Here's a handy chart to help visualize what's happening. CamChart
Plugging in the numbers for your cams and it looks like this:
According to the specs on your cam card listed in post #5, the exhaust centerline is definitely 118. Installing all 4 cams at 114* centerlines will still work. Our engines are not very sensetive to exhaust cam timing. Intake timing has a greater effect.
I just installed a set of Crower Stage 2's which are very similar to yours (222/222 duration,.475/.475 lift) and degreed then to Crowers specs which were 110* ICL, 118* ECL, 114 LSA. Were just finalizing the tune and hope to get some dyno time before winter so I can't comment on the performance yet.
Are you sure there isn't a couple typos in there? I think the intake valve open spec should read "-3* BTDC" or "3* ATDC". The exhaust valve close spec should be "-6* ATDC" or "6* BTDC" See chart below.
Here's a handy chart to help visualize what's happening. CamChart
Plugging in the numbers for your cams and it looks like this:
According to the specs on your cam card listed in post #5, the exhaust centerline is definitely 118. Installing all 4 cams at 114* centerlines will still work. Our engines are not very sensetive to exhaust cam timing. Intake timing has a greater effect.
I just installed a set of Crower Stage 2's which are very similar to yours (222/222 duration,.475/.475 lift) and degreed then to Crowers specs which were 110* ICL, 118* ECL, 114 LSA. Were just finalizing the tune and hope to get some dyno time before winter so I can't comment on the performance yet.
Very helpful stuff thank you everyone. I think my lobe separation should be 116 because my exhaust center line is 118 in my intake center line is 114. Am I correct then lobe separation is calculated by adding the center line for both and dividing by 2? The card does not list love separation.
Subscribing for any and all cam phasing and degreeing info!
Thanks
Ken
Thanks
Ken
Here is what my cam cards say exactly...I did miss the (-) sign...
Both exhaust:
Adv. Duration @ .006: 260*
Duration at .050: 224*
Valve timing: open at 50* BBDC, close at 6-* ATDC (does 6-* ATDC mean 6* BTDC??)
Specs are for cam installed at 118* center line
Both intake:
Adv. Duration @ .006: 258*
Duration at .050: 222*
Valve timing: open at 3*- BBDC (again, is this 3* ATDC?), close at 45* ATDC
Specs are for cam installed at 114* center line
I guess I'll just ask...WTF do I set the exhaust cams at? Lol
Both exhaust:
Adv. Duration @ .006: 260*
Duration at .050: 224*
Valve timing: open at 50* BBDC, close at 6-* ATDC (does 6-* ATDC mean 6* BTDC??)
Specs are for cam installed at 118* center line
Both intake:
Adv. Duration @ .006: 258*
Duration at .050: 222*
Valve timing: open at 3*- BBDC (again, is this 3* ATDC?), close at 45* ATDC
Specs are for cam installed at 114* center line
I guess I'll just ask...WTF do I set the exhaust cams at? Lol
Thank you. So my exhaust center line is 118 in the card, intake 114. I think that makes my lobe separation 116. So 116 -114 = 2. Add 2 to the intake centerline of 114 and set my exhaust to 116? Can't for the life of me figure out how that will get my intakes to the lower number of 114, but hell I'll try anything at this point.
Thanks again.
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Do you guys carefully check runout on these cams? It’s something I’ve talked to both Mihovetz and JDM about this and both have discussed it’s importance.
-J
-J
I checked about half of them...not a tremor on the needle.
From my understanding, LSA is always half way between ICL and ECL. So a 114 ICL with a 116 LSA means a 118 ECL.
As for your problem with the drivers side intake cam, I think the only way to fix it is to file the key or remove it completely.
As for your problem with the drivers side intake cam, I think the only way to fix it is to file the key or remove it completely.
Thanks. I'll try setting the ECL at 116 and see where I end up on the ICL. If I go with grinding off the key, I would want to set the ECL at 118 and the ICL at 114 per the card, instead of using the calculated value of 116 for the ECL, right?
114 ICL, 118 ECL is what is on your cam card and will be what you're shooting for. I think 03' White Snake has some typos in post #4. If you know the ICL and LSA, the "calculated value" for the ECL is (LSA-ICL)+LSA. (116-114)+116=118. In your case the cam card states the ICL and ECL so you're good to go. The LSA is just half way in between the 2 should you need that info.
This is the video I followed when degreeing my cams, very helpful.
This is the video I followed when degreeing my cams, very helpful.
Awesome. I'll get her tuned and dyno'd again and post. Was getting 475 to the rear wheels with 99 Navi heads, a stock Eaton blower and long tubes. Did the rebuild with the 04 Cobra DB series heads with the improved design (couldn't find 500Rs), ported, with the cooling mod and MAC long tubes. I took a conservative amount of metal out of the Eaton and had it ported too. Hope to be well into 500. Going to improve air flow too, suggestions welcomed. Hate to do all this and leave her with a little mouth to fill those lungs. The Navi heads are stripped, washed and up for grabs for a rebuild. Huge intake ports are a nice upgrade, especially for naturally aspirated applications.
When you advance the cams the intake CL gets numerically smaller and the exhaust CL gets numerically larger. The reverse is true for retarding. The intake CL gets numerically larger as the cams are retarded and the exhaust CL becomes numerically smaller. So, as you retard your exhaust cam to get to to a 118* CL, your intake CL will become smaller. Than that intake gear keyway will be need to be filed so you can get a 114 intake CL. You may be able to make up some of the difference by moving the gears against the far side of the keyway that favors your settings.
Good to know, thank you. Maybe I'll get lucky and not have to grind. I thought they'd both go up or down since they spin in unison, but glad to be wrong!
Here is my cam card and a round of measurements. I had a typo above sorry. Corrected it now.
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