Setting Right Side Cam #4

GotaT · 10-28-2007, 09:35 AM

I just put in my E cams in my 2.4 and was able to finally Correctly Set the Driver side Cam on Cyl. #1. It came out Perfect!

Im now going to set the Pas side came using #4 Cylinder but Dont understand Exactly where to begin. Where should I position the Crank, I know at TDC.

To make this a Simple Q/A If I have the Crank at TDC for #1 how many Turns Will I need to rotate the Crank to Set up my Dial Gauge to 0 for Cylinder #4 (passenger side cam)?

... And from this point I'll just Turn it 360 to Set the Valve Overlap.

THANKS.. Hoping for a quick response...

Jeff Alton · 10-28-2007, 10:19 AM

360 from TDC on #1. When at TDC overlap on #1 you are at TDC on #4. Then justd 360 more to measure the lift.

Or put another way, if doing both cams, one right after the other. Measure #1, then without turning the crank, remove the "Z" block and place it on #4 and set dial indicator to "0", then turn crank 360 and take reading.

It helps to remember that all of the valves will open and close once for every two turns of the crank.

I use 2 "Z" blocks and indicators so that I don't have to remove them and put them on the other side. Plus, I like to make sure I rotate the engine a number of times to pull the cahain all the way through its length to see if the readings change at all.

Cheers

GotaT · 10-28-2007, 01:07 PM

Ok... I've figured out how to set the Cam for #4.

I set the #1 first and did my clearance check using the "cheat" way of turning in the valve adj screw 1+ turns in the Valve overlap position and I was able to turn the Intake in 1.75 turns. According to the person I bought the cams he said 1 turn on the Intake and 1.5 on the exhasut will be Plenty of clearance. Therefore, This driver side checked out fine!

I next set the Cam for pas side #4 (first front right hand cyl as looking into the engine bay.) On this side I was only able to turn in the Intake valve adj screw .75 turns IM CONCERNED ..... So I decided to set the Valve Overlap to be a Lesser value within the Range of adjustment and still the Intake Valve adj. screw would only turn in .75

Recent engine work... From what I was told the Heads were flycut only .010 on all 6 from a Factory spec head. I used a .25 base Gasket on all 6 and running T pistons. Many of you might instantly say.. Well theres your problem.. gotta have E pistons. However, I still dont understand why If all parts have been cut the same and Equalities have been set on both sides WHY the #1 side would Check out Fine with Plenty of Clearance and the #4 side comes in a little shy.

AS a NOTE the #1 side chain does have some Slack in it that cannot be taken out whereas the #4 side Is Extremely Tight

What am i Missing? To me If I got the #1 side working properly I should be able to get the #4 ... Please Help!

304065 · 10-28-2007, 01:54 PM

Stop.

With Nr. 4 cylinder in overlap TDC, if you can only get the valve adjustment screw to turn three-quarters of a turn, this means you only have .75mm of piston-to-valve clearance on the the intake. The valve adjustment screw is on the half of the rocker that contacts the valve stem of course, so you disregard the rocker ratio, it's a direct measurement.

A clearance of .75mm is HALF the factory recommended value. The reason is the E cams have more lift. I thought you were warned of this and concluded the same thing in the thread below.

Cam Failure !! .. Solex Upgrade ? STORY

And that's only at TDC. Where the real clearance issues come in is before and after TDC a few degrees. And that's measuring cold.

I wouldn't even turn the engine over with a breaker bar until you investigate the clearance thorougly using the solder method.

GotaT · 10-28-2007, 02:20 PM

Thanks John.. I agreed that the E cams would prob not work until I was convinced otherwise and am at no risk if they didnt work, being I could send them back... so based on him telling me these work all the time.. I figured I would try.. Now, back to topic at hand...

Still, why would one side check fine before and after TDC while the other did not based on all ther other mentined things done above?
Could it be a Chain Issue seeing that the #1 side has some level of slack and the#4 side looks and feels fine on being able to adjust it tightly!?

304065 · 10-28-2007, 02:32 PM

Tolerance buildup. Even if the chain is worn it wont reduce the clearance. Were the spigots decked? What was the cylinder height?

camgrinder · 10-28-2007, 03:03 PM

I would go back in and check the cam timing on number 4 cylinder. Sounds like its off. Could also be the deck height?

FWIW, I have been making "E on T" cams since 1990. I have never heard of a valve to piston problem putting E cams into a carb T engine.

GotaT · 10-28-2007, 07:37 PM

John, You have a PM. As a note, I have a 72 T MFI motor w/ Carbs on them now. Thanks

Eagledriver · 10-29-2007, 08:12 PM

Just a clarification. The factory spec is not half of .75mm. There is only one factory mention of valve to piston clearance and it is for the early 911S. It says that you need a minimum of .8mm on the intake. There is no mention of a spec for the exhaust. Having said that I would want at least 1mm on the intake and 1.5mm on the exhaust. Also as has been mentioned you have not measured the minimum clearance if you are at TDC when you do it.

The sides are different sometimes due to differences in the case halves or the depth of the valve seats/valve grinds, or machining of the heads.

-Andy

dtw · 05:37 AM

Andy's comments bear repeating - if you are only turning in the screws at TDC overlap, you are basically fooling yourself into getting a 'go' measurement. The valves come much closer to the pistons before and after TDC than at TDC itself. If you have Wayne's book, there's a really good diagram in there that should help you visualize the relationship. The valves and the piston 'chase' each other. If you are going with the 'cheat' method, you have to turn the engine all the way through a cycle for each increment of the screw. I start with 0.5mm (one half turn) and slowly and carefully turn through 720'. I increase in 0.25mm increments until 1.5mm, when I go to even smaller increments. I continue the process until I encounter interference/resistance - it bears repeating that the crank must be turned very gently and slowly. When I encounter resistance, I record the position on the crank pulley with a sharpie and take notes on the final clearance. This process must be completed a minimum of four times, obviously you cannot double up and try to do more than one screw on each run or you won't know which valve is interfering if you encounter resistance. Upon completing the process for each valve, you can then compare notes and see how consistent your measurements are from side to side. Interference should be encountered fairly consistently w/r/t crank position and valve lift from left to right.

Next - I tend to agree with comments above that some clearance differences left to right is possible. However, due to the fact that a whole millimeter is observed (seems like a lot to me), combined with your first time through a build, I am more skeptical of your situation. I'd advise some really careful re-review of your build and your measurements. Did you forget cylinder base gaskets anywhere? Did you install any of your pistons upside down (potentially very easy with T pistons)? Are both of your cam 'dots' facing up at TDC? Are the cams oriented correctly in the engine (did you put the left cam on the left side or did you cross them up)? When you timed each cam, did you set enough pre-load on the dial gauge?

GotaT · 10-30-2007, 06:36 AM

I was able to check the Cams the way a knowledgable friend described to me yesturday. I first Marked the 10 degree ATDC and the 7 BTDC on my Pulley, which was as Accurate as I could get it ( I took it off and used a protractor ) which was said to be the to points of most likely intrusion. Exhaust at the 7 degree mark BTDC and Intake at the 10 degree ATDC

After this, I set the #1 Cam to TDC for piston #1 and turned in the Valve adj screw on both intake and Exhaust so that the elephant foot was touching the top of the Valve, and backed it off until I would see a very small movement in the screw and elephant foot... which basically left no free play between the elephant foot and top of the valve. Definitely not a Feeler guage spec, much Tighter

I then did this same procedure to #4 side

Keep in mind my #1 side is set to .130 = 3.3 and my #4 to .126 = 3.2004

I then brought the Crank to the 7 degree mark BTDC for cyl #1 and Turned in the Exhaust Valve adj screw until it intruded with the piston but could Not turn it in to the 1.5 Turns. : / I loosened it up.

I then Continued turning the crank to the 10degrees ATDC and turned in the Intake Valve adj screw, to my best knowledge, 1.16 - 1.2 turns before it intruded with the piston. Turned it back out.

On the #4 side I also did not come up with the 1.5 turns in on the Exhaust side at 7 degrees BTDC, but did come up with 1.2 - 1.23 turns in on the Intake at 10 degrees ATDC

So, my Intakes seemed to pass the check by just turning them in.. I didnt feel too comfortable Turning the Crank over w/ the Intakes turned in @ 1 turn, only because it naturally takes some force to turn the motor over, but felt that coming in over the 1mm would be sufficient. I could "force" the intakes to turn in more than this before they would Actually come to a Physical Stopping Point but the #'s mentioned above were where I felt they had some level intrusion.

Now the Exhaust sides came in Below the 1.5, and once again I could have gotten a bit more from where they began to intrude but still not enough to meet the 1.5......

So what Should I do? Is 1.5 turns an Exact measurement that MUST be HAD in order for it to Run Perfectly w/ NO intrusion?

I think I could set the cams to 3.0 (.118in) and get the 1.5 turns I need.

dtw · 10-30-2007, 07:29 AM

I'm not sure why you are resistant to turning the crank through 720'. With a good-sized wrench in hand, only four rockers installed (with only one at a time screwed down), no spark plugs installed, etc., your crank should be easy to turn with enough control and feel to sense resistance/interference. If you are only sampling the clearance at two points, I'm sorry, this is simply inadequate.

As mentioned, there's not a lot of documentation available from Porsche on what adequate clearance is. The clearance numbers that are currently used are 'generally accepted' based on the experiences of seasoned builders with a lot of builds and configurations under their belts. Note that cold, static clearances are not representative of what is happening in a hot, running engine. When the engine is running and hot, there is parts expansion, reducing clearances. There is (potentially) valve float, which can eat up most (or all $$$) of your clearance quite fast. And perhaps most often overlooked, the cams will not stay at the exact same relationship to the crank on each rev - as the loads on the chains change under acceleration/deceleration and the tensioners move up and down, your dynamic timing will change quite a bit. Tim For all these factors, minimum static/cold clearances have been estimated.

Upon reading your latest post, it does seem like your measurements were consistent side to side?? But just failed to meet adequate clearances? It seems like your intake is OK but again, I would measure a complete crank rotation, not just discrete points.

What is the timing spec range for your cams? If 3.0 is within the spec, you can try that - but keep in mind, when you are this close on you clearances, opening up the clearance for one valve can sometimes result in taking down clearance on another valve (again think back on Wayne's diagram).

Sometimes it helps to sit back and think about how little 0.8-1.6mm really is, and how much money you've got tied up in the engine. Here's an email I got from Bruce Anderson years ago when I was dealing with this:

Quote:

Hi Dave,

If indeed the Crane 288 cam is as aggressive as the Solex cam, you may have a
valve clearance problem. First lets make sure that you are checking the clearance correctly… I can’t be sure by your description. What you want to do is
start out with zero lash on the valve and then screw the valve adjustment screw in exactly one turn. The thread pitch on the valve adjuster is 1 mm per turn, so this will extend the valve by one mm. Then very slowly and carefully turn the engine over for two complete rotations (720 degrees) so that you go
through the complete operation of the valve being measured. If you can turn the engine over without interference you then have at least 1 mm valve clearance. Next you should turn the screw in another half turn and rotate the engine again. If the engine will still turn around without interference then you have at least 1.5 mm (or about 0.060") clearance, which is probably enough.

In one of the early Porsche workshop manuals they discuss a close clearance
situation that they had with the earliest 911 engines (engines up to No.
900927. They say that the engines have a slightly high intake valve pocket area.
If it becomes necessary to replace a cylinder head of an engine having these
pistons they want you to check the minimum clearance between the piston valve pocket and the valve. They say that the clearance must not be less than 0.8 mm (0.0314"), so I consider this to be the absolute bare minimum intake valve clearance. And probably double that would work for the minimum exhaust valve clearance, so 1.6 mm (0.063") exhaust valve clearance.

Bruce Anderson www.911handbook.com

Eagledriver · 10-30-2007, 06:12 PM

It's fine to adjust your timing to get the clearance you need, just be sure you do have that clearance. If you take a couple of measurements around the 5 to 10 degree area before and after TDC you will get a good feel for how close you are. Also do the 720 degree turn thing at the end to make sure.

I was almost able to do this with my 2.7 engine with "S" cams. In the end I had the pockets on the pistons machined deeper to make sure I had enough clearance. This is the best option and not that expensive when you look at the total cost of a rebuild.

-Andy

dtw · 10-30-2007, 06:35 PM

Another great point by Andy - I don't know how I forgot to mention, but I also had extra relief cut in my pistons. Crane 288 cams - basically Solexes but a touch more lift and duration - and 2.2T pistons. Even with additional relief, I am on the ragged edge of clearance, and had to retime the cams a couple times to get them there. Of course, my heads were also shaved net 0.75mm too.