Cam timing

[racydave]

I am helping a local friend with his 75 Spider. It has been "saved" and a 6 year resto. It has a 2L engine with a milled head. I can not be very specific about how much was shaved off,or even what head it is. But, we did finally get it running. It sounds as if the cam timing is off, as it runs poorly, and the only way it runs is with the ign timing mark way off target. The cam marks are aligned also. We are pretty sure everything else is opperational... Could this be a result of a shorter head somehow???

[manoa matt]

When the timing marks are aligned what does it look like? Line up the cam timing marks with the pointers and then check where the crank is in relation to TDC. The intake and exhaust cams are still in the same relation to one another and always will be, its how they relate to the crank that gets changed when the head or block gets shaved.

The cams may be set up right, but the crank is either too advanced or too retarded.

[racydave]

The number 4 piston is at the top when we are checking the cams! But it seems to be the cam timing. I have a spare crank pulley, maybe the wrong one is on the eng, does not not explain it thou.

[kilrwail]

Dave - Missed you at FFO - it was great! Could it be that you need the adjustable cam pulleys, to compensate for the shaved head?

[ventura ace]

If one of the cam pulleys is the wrong style (intake vs exhaust), this could make the engine run rough and timing way off, if it would even run at all. If both cam pulleys were swapped, I doubt that it would run (don't ask me how I know!!).

You could try resetting the timing belt to put the crank pulley one tooth over to see if that makes a difference. One tooth would equate to about 17° crank motion. If the timing mark is off that much, then maybe that is the problem.

A

[racydave]

I was not around for the engine build. I hope they used the 2L cam gears. Would that make a difference? Peter, Its been a bummer not attending the FFO again. We did get to see alot of friends at Dixiefest. And we might go to WI for the fall FUN event hosted by the Chi guys. Reigonal events are good, and you do get more quality one on one time... Thanks for the help!!!

[narfire]

I'll second Alvon's recomendation. My cams were dialed in and thought the crank was as well.. nope a couple/one anyway tooth out(TDC).I had painted the mark on the crank and the pointer. To run properly (sort of) the timing was around 20 deg out. Noticed a lack of power compared to times past,so changed belt and got the crank where it shoud be and the cams then timed 10 deg adv. and i think a very noticable difference in power.
One tooth out on the crank seems to give a big difference in timing and the engines performance.

[racydave]

I missed shop night, but was informed that the cam gears were loose, accounting for the metalic noise we needed to fix. And the fellas said it runs alot better! Bad news is that the trannie will not go into 2nd or 4th... Best part, it gave me a chance to chat with my bro Alvon!

[MNspiderman]

with the shaved head and or block, you really need to get the adjustable pulleys, your probably off by 5 - 15 degrees instantly. You really need a dial caliper to find true tdc and mark it then you really need to find the center of dwell on each cam for an absolute true dead on timing which is needed anyway. The dwell is when you put a dial caliper on the valve face iteself and when you turn the camshaft there is a moment in time where the cam turns and the dial caliper stays still for about 5 degrees or so. It's the center of the flat area. Mark it, put the engine together, install the belt, and tighten the pulleys so crank and both camshafts are in true alignment. Its well worth the effort

[spiderrey]

so how is this done when the engine is already assembled?

[Rmprotune]

two dial gauges with the cam covers of. position the dial gauges on top of the cam followers(lifters) on both intake and exhaust side and equal the overlap ( same lift readings on both intake and exhaust).

[maytag]

I realize I'm resurrecting a very old thread, but from my search, this thread most closely gets to my topic.

I'm getting ready to install my cams & Millers' Mule adjustable cam gears.
My cam-grinder / "motor-mentor" has recommended that I install the exhaust at "zero" and the intake at 3d advanced.
I'm cool with this... BUT:

I need to find "zero".

Somebody check me, but if a cam is dialed-in and degreed to "zero", then when the timing marks are all lined-up, #4 piston is at TDC and both valves in #4 are open. RIGHT?

So at "Zero", my cams would both be half-way through the short duration that they are at full-lift, ... right?

So I'm cool with the mechanisms of how to measure all this out with a degree-wheel, piston-stop and dial indicator... I just want to make sure I understand where it's all supposed to be before I start moving it from there.

thanks.

[narfire]

I watched my motor mentor degree my car in last fall. Found tdc on #1 with a dial indicator.He set the wheel & pointer to 0. The cams were at the marks on the cam tower. the cams were adjusted as needed from there to get the 109 centerline as spec'd.Not sure what cams you have but the ones I have , I just had them dialed in when they were lined up with the cam tower marks and adjusted.
Chris

[maytag]

well, the adjustable cam pulleys from Miller Mule don't have timing marks on them to point at the marks on the cam towers. But even if they did, that'd only be considered "rough" anyway.

[So Cal Mark]

is your cam grinder basing this advice on the cam specs? Normally the cams would be ground to be used as-is and you would vary from the specs to mitigate some issue