Thought I had stock cams...?

[foxystealth]

Back in 2005 or so when I was getting into the 3s platform I had purchased a set of heads from a forum member of 3SI. As far as I remember the heads were only lightly ported but other than that stock including the cams. I have the engine pulled I am doing some cam timing with 3sx's adjustable cam gears and my results are not quite what stock cam specs are. This is a 1st gen TT motor and timing was done at 0.050 after open and before closing.

Front Intake Front Exhaust Rear intake Rear Exhaust
Open @ 14.25 ATDC @ 19.5 BBDC @ 13.0 ATDC @ 20.0 BBDC
Close @ 24.75 ABDC @ 13.5 BTDC @ 25.5 ABDC @ 13.75 BTDC


(following measurements from Web Cam's calculator)
Front bank Rear bank
Overlap -27.75 Overlap -26.75
Int duration 190.50 Int duration 192.50
Exh duration 186.00 Exh duration 186.25
Int center line 109.5 Int center line 109.25
Exh center line 106.5 Exh center line 106.88

Just for shits and giggles I tried getting a reading at 0.001 after open and 0.001 before close and got 8 BTDC and 67.75 ABDC and put that into Web Cam's calculator and came up with 255.75 degrees of duration which is more than the stock total duration for intake of 251 degrees. So its saying I have more total degrees of duration but at 0.050 I have less than stocks 208 degrees?

I didn't write down the max lifts but I remember the intake being .374 or so and exhaust around .350 ish I think
I tried looking up how the letters correspond to what cam goes for what engine and int vs exh, but too many different answers so for someone who might know they are labeled as:
front int. A-B
rear int A-C
front exh J-J
rear exh A-B

I cannot figure out why the open and close figures are so far away from stock figures and most of everyone's I researched, as well as the duration. I have checked top dead center several times with a dial indicator and piston stop, I am using a Ford adjustable solid lifter with 0 lash and I have set up and re-setup each cam but still come up with the same results. We've been driving on the cams for several years now and haven't noticed any issues until I saw these figures. There are paint marks on them, similar to a friend's that were sent off for a regrind.

Has anyone seen these kind of numbers before and what is your opinion? I don't really know what to think at this point.

[sergechronos]

Interesting...IIRC, I believe J was the intake cam for 93+ turbos and B was the intake cam for 91-92 turbo and nonturbo.

Not to ask a stupid question, but have you thoroughly inspected that hexagonal area there? Perhaps you overlooked the usual B,C, J, K, or N designations on the others?

At any rate, if they were regrinds, the letters on the cams would just tell you position, not the actual profile information. Since it ran well, I wouldn't worry too much about it.

[foxystealth]

Ok I was looking at the wrong markings. Thanks sergechronos. Int is "v" and exhaust is "d".

I probably will continue to use them for a little longer but I'm not sure what it's doing to performance. To my understanding I have less overlap which is more pressure in the cylinder but the valves opening and closing points being so far off I'm not sure if I'm gaining or losing. I will keep researching but any comments will help. Thanks

[RealMcCoy]

I'm betting they're stock cams... The factory specs are not a cam card, they are advertised numbers. Many advertised numbers start from a couple thousandths up. We really have no idea how they measured it... The only thing you can use from advertised numbers with confidence is the lobe center data.

You're only a few degrees out from advertised, and from the variation in your intake data, you could have a couple degrees margin of error. Aftermarket cams would be at least 264 or bigger, which you aren't anywhere close to...

[GTOJOE]

Just remember the 3sx adjustable cam gears are all wrong. You need to compare them to the stock gears to find the true "0" point. There is a thread on here about it.

[spaceace60]

for noobies and since im not up on adj cams what is all wrong on 3sx cam marks?

[sergechronos]

3sx cam gears are not actually at 0 when the gear says that they are. If you held them up and compared them to your stock ones, you would see that they are off..Being off more than 2-3 degrees isn't unheard of. The fix is to use the stock gear as a base, then adjust the adjustable to where the pin spot and the timing mark are in the same place as stock to get to the actual zero, then adjust from there. Of course, doing actual timing (like OP is doing) should have the same effect since the gear/cams will be degreed in.

Additionally, they had runs where the spacing of the teeth was off and it was chewing up timing belts (so if you buy a used set you should ask to see a picture with a timing belt wrapped around the gear to make sure it seats properly.)

And of course, there is the persistent issue of gears slipping, for which pinning is pretty much the best fix. Allegedly the new BC gears won't slip, but I'll wait and see.

[GTOJOE]

****-major-issue-3sx-adjustable-cam-gears-zero-not-zero**** - 3SGTO (http://www.3sgto.org/3000gt-stealth-gto-related-topics/10754-****-major-issue-3sx-adjustable-cam-gears-zero-not-zero****.html)

**** Major Issue with the 3sx Adjustable Cam Gears - Zero is not Zero**** - 3000GT/Stealth International Message Center (http://www.3si.org/forum/f35/major-issue-3sx-adjustable-cam-gears-zero-not-zero-545631/)