adamky wrote:Checking cam timing on my JWT S1 cams:
This was a bit more of a chore than it's been in the past, but I'm sure some of that has to do with only getting 4 hours of sleep for the past few nights. Regardless of the cause, my results were... interesting.
Also, a little warning before you start reading: this is going to be a bit long, and possibly a bit pointless since I think I know what I am going to do (although I am still open to any and all advice). But, here's a peak into what has been going on in my head all day while checking cam timing and trying to decide what to change.
So, for starters, in case you haven't seen it yet, one of our members, Dustin, made a great thread on setting valve lash and cam timing:
viewtopic.php?p=337400
If you get
really bored and read through that whole thread, you'll see that at one point there was some confusion over the JWT cam card. The reason for that is the way that JWT had their cam card set compared to Brian Crower, Kelford, and really... most other companies that make aftermarket cams. BC cam cards have timing events (intake open, intake close, etc) specified at .050" of lift. Setting cam timing at .050" of lift is pretty standard in the industry. Kelford's cam card specifies the timing events @ 1.0mm or 1.27 mm of lift. 1.27 mm of lift is .050". But for some reason, the JWT cam card specifies events at only .001" of lift. If you take the numbers on the cam card and put them into a cam timing calculator, the duration comes out to 272 for both intake and exhaust,
which is their advertised duration.
Here's the JWT cam card:
Kfred was the first one to notice this and thankfully he made a thread about it, which helped to clear up some of the confusion I was having with setting my cams up:
viewtopic.php?t=48513
So, when I went to set timing today, I decided too measure @ BOTH .001" and .050". I took my time doing this and I was really careful to get my dial gauge in line with with valve travel. I was really slow and careful about spinning the crank and measuring and checking
everything 3 and possibly even 4 times. In other words, this was the most careful and precise I have ever been when checking cam timing.
Important information:
-Valve lash is @ .010" for both intake and exhaust
-I'm using a set of Greaser's awesome mechanically-locked timing chain tensioners. I set them as tight as I thought was necessary while trying not to overdo it. Bottom chain was easy. For the top chain, I rotated the crank until I had valve spring tension keeping the chain tight between the 2 cams and also keeping the right side of the chain tight to the idler gear. In other words, all of the slack was located at the tensioner. Then I simply tightened it up to get rid of the extra slack. BTW, I'm only mentioning this to say that while I'm not an experienced engine builder and have never set timing chain slack before, I got it pretty snug but I tried to let the valve spring tension do the majority of the work. And the only reason that I mention all of this is because I actually got MORE duration than advertised @ .001" of lift. Yeah, I know... WTF?
Anyways, here are my results:
@ .001" of lift
Intake Opens BTDC (ATDC is -) : 20
Intake Closes ABDC : 87
Exhaust Opens BBDC : 79
Exhaust Closes ATDC (BTDC is -) : 29
When I plug those numbers into
http://www.wallaceracing.com/camcalc.php, this is what it spits out:
Intake Duration is 287.00 degrees.
Exhaust Duration is 288.00 degrees.
Installed Intake Centerline is 123.50 degrees ATDC.
Installed Exhaust Centerline is 115.00 degrees BTDC.
LSA is 119.3 degrees
Overlap is 49.00 degrees.
Comparing these to the cam card, my opening and closing events are 5-10 degrees off, but my centerline for the intake is only 2.5 degrees off, and the centerline for the exhaust is only 1 degree off.
What I don't understand is how I got more duration that what is advertised, but like I said, I was
very meticulous and careful, checking everything over and over again. Also, the duration for both the intake and exhaust ended up within 1 degree of each other, so...
If only one of them was 287 and the other was 272, I'd be more likely to attribute it to me screwing something up.
As I mentioned, I also checked events @ .050" of lift. Here are the numbers:
Intake Opens BTDC (ATDC is -) : -17
Intake Closes ABDC : 51
Exhaust Opens BBDC : 45
Exhaust Closes ATDC (BTDC is -) : -9
Results from plugging them into the calculator:
Intake Duration is 214.00 degrees.
Exhaust Duration is 216.00 degrees.
Installed Intake Centerline is 124.00 degrees ATDC.
Installed Exhaust Centerline is 117.00 degrees BTDC.
LSA is 120.5 degrees
Overlap is -26.00 degrees.
Obviously, the opening and closing events are waaaay off, but the centerlines are only 3 degrees off for the intake and 1 degree off for the exhaust.
So, that's where I stopped and I'm not sure if I'm going to adjust either of them. I've seen various opinions on setting cam timing. The ones that come to memory were from Derek (Greaser) and Duron (duncan351)
BTW, PLEASE don't think that I am calling either of you guys out by posting your replies here. I'm just trying to show some of the information that I have gathered and share how I am applying this info to my motor and my needs/goals.
Derek says that maxing out your advance on intake and maxing out your retard on exhaust is the best because you end up with really good hp gains from 2K-6K. That makes sense and he's got dyno proof and many years of experience to back this up. The trade off is a rougher idle and you will lose power above 6K. Here are the two threads where he discussed that:
viewtopic.php?p=529536#p529536
viewtopic.php?p=529158#p529158
Long time and respected member Duron has dyno'd his car with various cam timing settings and I have seen him recommend retarding the intake 2.5 degrees and advancing the exhaust 2.5-7.5 degrees. He wrote:
duncan351 wrote:Turbo size doesn't even matter. This was the best happy medium for low end and top end power along with very good drive ability.
viewtopic.php?p=525015#p525015
viewtopic.php?p=529662#p529662
So, given this info, how should I set my cams up?
To recap my setup, my motor has:
-JWT S1 cams
-JWT cam gears
-BC valves (stock size)
-BC springs and titanium retainers
-Head has a 3 angle valve job, but the ports are untouched/stock
-ATI Super Damper
-Eagle rods, Wiseco 9:1 pistons
-Equal length exhaust manifold with a PT5857DBB (4" ported inlet and .64 A/R hotside)
-Xcessive Intake manifold with Q45 throttle body
While my initial goals are going to be mild due to running 93oct pump, I will eventually be installing my new fuel setup for E85 and cranking up the boost to 30+ psi. While I like the idea of gaining lots of power from 2K-6K rpm, I would prefer to have a decent idle. Also, with the built head and ATI Super Damper, I have plans to spin the motor to close to 8K rpm. So, I don't want to choke it off on the top end too much.
Applying this all to my car
The car will be a weekend fun car with occasional trips to the local 1/8 mile strip and probably a lot of roll races (in Mexico). So, I'm looking for a good middle ground for the cam settings. This leads me to believe that I should just leave them where they are at right now since they are about as close to the cam card as I can get them.
I appreciate and welcome any opinions for or against my thinking here.