Cam timing Alignment Question - See Photos

Tom, I can't make head nor tail of what you have done.

The shop manual has point of initial opening and point of closing with EXACTLY 0.50mm valve clearances, or you can plot a timing chart and calculate point of max lift as halfway through the duration, which negates the need to have a false clearance and also renders any wear irrelevant to timing.

You must verify true TDC, then turn the engine in correct DOR and repeat your timing check.

I do maintain that the marks are more accurate than many consider them to be, but if you're going to check for yourself, do it properly, or in a way we can understand!

Phil

 

Interesting to read this thread and the precision that Dave and Brian are applying to cam timing. I have a viewpoint from where the "rubber meets the road" as of the this weekend. Dr. Helms just completed a major on my 11K mile 355 and I've just had the chance to drive it for the first time since I picked it up.

The car ran really well before. Excellent driveability all though the range and no CEL's or other bad habits. Just a really solid running 355. As good as it gets, I thought.

After getting the car back from Dave there is a marked increase in torque in the 3-6K RPM range. Hard to quantify but from a seat of the pants perpsective it about like the + differance between sea level and Colorado. It's that noticable. The thought is that it will only get better as he's set a smidgen, find that on the degree wheel Brian, of advance in so as the belts settle it will fall to dead perfect.

It makes a difference.

 

Not trying to stir the pot here..would it be possiable for you to post some pictures of your set up and how you got this result??

 

Hey Dave you should quit this slackin' crap and get back to what your gettin' paid to do. Do your "bosses" know your wasting this time on us? Wow, sorry I blew up there! HaHaHa Regards, Vern[/QUOTE]

Hell, Niki looks for any excuss to kick my backside. Life has now come full circle, I am now able to be a PITA to my kids!

 

Hell, Niki looks for any excuss to kick my backside. Life has now come full circle, I am now able to be a PITA to my kids![/QUOTE]

Yea Dave, what comes around goes around, of course we as parents wouild tell our kids we were doin' what we did because it was good for them, they do stuff to us for s@@ts and grins. crap life never seems fair. HaHaHa. Regards, Vern

 

I dialled in another 360C engine today.

The 1-4 bank cams were both on the outer limits of the "goal posts", while the 5-8 bank was near perfect dead centre to the reference marks.

(FYI 360 has 1.66mm valve lift at TDC on Inlet during transition and 0.60mm Lift at 9 deg before TDC on exhaust on transition.)

 

How do you guys mount an 18 inch degree wheel to a 308/328 engine?
I assume it goes on the crank damper?

Thanks in advance.

jwise

 

It can go on either the crank damper, or the flywheel.

Not sure if there's clearance for one that large with the engine in the car, going to be tight. That's 9" on each side of center! A 12" one should fit w/o a problem.

To mount a timing wheel on the damper you have a couple of mounting options:

1) Use an extra-long damper bolt with a sleeve that pressess th damper bolt washer against the damper & crank timing drive gear. The timing wheel becomes a rathar large washer between the bolt head & the sleeve. I understand this is the way the factory timing wheel mounts.

2) Attach the timing wheel to the rim of the A/C belt flange using screws. To do this you drill the timing wheel with a 3 or 6-hole pattern with the inside edges of the holes exactly on the diameter of the flange.. If the hole pattern is kept sufficiently precise & holes are kept small, you can use the heads of flat head screws to pick up the flange. Otherwise you'll have to use washers under the screw heads to clamp the flange against the wheel.

 

Verell, when I timed my 348 I attached a 12” degree wheel to the damper. Used 4 bolts with nuts washers etc. Sandwiched the damper between the degree wheel and small clamps on the back edge of the damper. Indicated the wheel to center, established TDC via dial indicator in the #1 spark plug hole(split lag number) and set the pointer to 0. Crude but accurate variation of your #2 procedure.
I should have degreed the cams as well but worked to set all the cam reference marks between the end cap “goalpost” marks. No excuse for my error. As you are aware my background is manufacturing. A reference mark is just that, not a definitive feature with a defined tolerance range.
Thanks to the experts who share their knowledge here, I will know better next time!

 

"The 1-4 bank cams were both on the outer limits of the "goal posts", while the 5-8 bank was near perfect dead centre to the reference marks."



My point exactly. Now divide that 1" dia shaft into 360 degrees and how many degrees differance is it between "outer limits and dead center" (one would need a microscope to see degree hash marks on the diam. circle)?
I have many photos of the marks well outside of the "goal posts" once properly degreed in. If the cam timing would have been set dead on the marks on the 1/4 bank, you would have had the 5/8 bank making power and the 1/4 bank just going along for the ride.
Splitting hairs? Yup! But these cars were not purchased for "transportation", they are a passion and should run like it. As Tom stated, it CAN be felt seat of the pants.
Dave

 

The std dial indicator stands have magnetic bases.
What do you use mount the dial indicator you're using to measure valve timing & piston TDC with?

I'm guessing you have something that goes onto a cam cover stud?

 

TDC indicator screws into the plug hole and has a long extension. Cam cover stud is correct for the cam indicator.

Calculations:
The notch in the cam cap is about .050"'s wide which equates to roughly 4.6 camshaft degrees. Eyeball that one!

 

Tom,
Assuming your original pix are at least 2 Mpix or more,
could you crop the original photos so they just have the cam marks, then resize down to 640x480 (if the cropped pix isn't already down to that size), & post the enlarged area.

Not a microscope, just a digital camera with macro capability will magnify the cam marks so that their alignment is easily visible. When the marks are enlarged so that they're half an inch wide, then it's easy to see a 1 degree (~0.010") miss-alignment as one mark will be ~0.1" off center.

Tom,
Reason I'm asking is that I downloaded & enlarged the 1-4 Exhaust picture (below) & it looks like the cam mark is right on the edge of the cam cap mark. ie: The cam is off by ~3 degrees, however the resolution is terrible.

BTW, what did you use to make the marks more visible?
Image Unavailable, Please Login

 

Tom,
3 holes on the cam gear sure limits the adj. range, that's probably your problem.

One solution would be to take the cam gear to a machine shop & have add'l holes machined in. The shop manual gives sufficient dimensions for a machine shop to correctly add more holes.

Another possibility is to try switching that cam gear with the corresponding gear for the other bank.

 

I consider myself very fortunate to have shard a workshop with an "old school" engine tuner, who had his own dyno.

He spent all day every day building Lotus Twin Cam engines, and BDA series too.

He built engines for many race teams in UK and Europe, and his engine were winners in every class entered.

I personally witnessed, and often helped, perform tests and adjustments on cam timings, for different tracks and different use requiremets, and different cars etc.

He changed both inlet and exhaust cam timing and also changed overlap to suit whatever was required.

Cams on these engines could be moved many degrees (over 20 crank/10 cam) one way or the other for different output requirements, but amazingly, the peak figures often stayed pretty much the same (+-2%~), but the rpm at which they were produced varied greatly, as did the drivability.

It is he that instilled the "max open" method I use religiously.