Please help me check my cam timing logic.

Speed Buggy · Speed Buggy's Garage

Hi all. I have a 3.0 L stock SC motor, 930/16 series. I set the valve gap on #1 to .004 then set crank at TDC. Both pins in, both 930's up. I rotated the crank twice and moved the cam to the lift in Wayne's rebuild book, 1.4 to 1.7 -I got 1.55 (digital mm) the last time. Went to the right side and put both 930's down. Set the crank to TDC and set the cam with the pin to .061 (decimal by dial indicator). SO, when I rotate the crank, I get ~1.55 on the left and ~.061 on the right on alternating TDC marks. Does this sound correct? TIA.

Also, when I get hear TDC on the right bank, it gets difficult to turn. I am using a standard 1/2" drive ratchet, so I doubt I can bend something and it is the same resistance every time around. Is this spring tension on the cam lobe? Thanks.

ZOA NOM · ZOA NOM's Garage

Looks good, but to be clear, you put the crank at TDC for #1 cylinder for the left side cam, and the #4 cylinder for the right side, correct? I think if you hadn't, you wouldn't get the alternating values, so I think you're ok.

Speed Buggy · Speed Buggy's Garage

Yes, 930's up on the left, down on the right. Thank you. It is very nerve racking doing this the first time. I don't want to have to do another engine drop...ever. Haha

ZOA NOM · ZOA NOM's Garage

As for the resistance, if you have the rockers installed for all six cylinders, the overall resistance would increase a little, but should be balanced. If only the #1 & #4 rockers are installed, the resistance would increase as you climb the cam lobe for those cylinders.

Flat6pac · 07-01-2014, 06:25 AM

I cant agree, your numbers dont look correct
you have 1.55mm or the left
.061mm? you need to be in the area of 1.55.
If you were to move the left pin one hole advance you would be right on the high side of spec at 1.70.
If you cant come in close with the cams, drop the tensioner on the right and rotate the teeth gear one tooth and that will give you a whole new area of numbers.
Personally, I like to see the cams as close as .05mm
Bruce

Speed Buggy · Speed Buggy's Garage

Bruce, I am using a digital dial set to mm on the left and a decimal dial in thousandths on the right. I believe 1.55 mm approximates to .061 thou. Is this ok now? I don't have access to two metric dials. Should I change the digital to decimal and see if they match? Hmmmmm...didn't think of that, forest...trees and all that. Duh. Thank you for the check. Am I alright?

Flat6pac · 07-01-2014, 07:49 AM

I dont have 2 dial indicator setups but I find using metric 100% of the time permits me to know what I am doing. I have a small SAE indicator but for setting valves its too close looking for .1mm in inches....
Sorry I missed the conversion.
Bruce

Speed Buggy · Speed Buggy's Garage

Next step is priming the new tensioners and installing them, correct?

Flat6pac · 07-01-2014, 01:00 PM

Prime them?
you need the pin in to install. If you fill them with oil then you have to put them in a vise and squeeze the oil out to put the pin back in so you can install them.
When you install the engine and spin it with the plugs out you will have oil flow to the tensioners.
Bruce

Speed Buggy · Speed Buggy's Garage

Ok. New ones have the pins installed. The book said to dunk and squeeze them to prime them and get the air bubbles out. Is this required?

Speed Buggy · Speed Buggy's Garage

For want of one tensioner o-ring...urg! Well I guess I can change out the exhaust studs. Tarter sauce.

ZOA NOM · ZOA NOM's Garage

You should consider the jerry woods tensioner mod while youre at this stage. Simple peace of mind. Search for it here.

edit: check post #34 in this thread: Shops that don't recommend Carrera Tensioner Update?

Walt Fricke · 07-04-2014, 08:39 PM

You do not need to prime the pressure fed tensioners. It won't hurt anything but your time if you do, but you don't need to. Like Bruce said, the normal priming of the oil system generally before starting a rebuilt engine before firing it up will take care of that. And if it doesn't, the first few seconds of running certainly will, and at start-up speeds having no oil in the tensioners isn't going to hurt.

This was not the case for the older tensioners, or at least it took rather longer for them to fill from having splash oil get pumped in via one way valves.