[Rob79]

Trying to degree my cam. Speed Pro 224-234@ 50 thou. 465-488lift. Installed dot to dot. and on center keyway(has 4 adv and 4 retard positions also) Cam timing spec is 106 to 108 intake center line. Followed timing proceedure at Bill Boyles web site. First part of my confusion was that my degree wheel has 4 90 degree quadrents but after sorting that out my first number was 67 deg before TDC second was 157 add together and divide by 2 gives me 112 (Am I doing this right so far ?) now if I retard 4 degrees that gives me 108 right? As per the guy who did my heads and sold me the cam dot to dot usually ends up about 107 why and i seeing this variation or am i missing something? also cam lift spec is 310 but measured with a dial indicator it is 318. Will this cause me that variation? If anyone else has abetter method or even a different one I would appreciate it.
Thanks
Rob

[Rob79]

Trying to degree my cam. Speed Pro 224-234@ 50 thou. 465-488lift. Installed dot to dot. and on center keyway(has 4 adv and 4 retard positions also) Cam timing spec is 106 to 108 intake center line. Followed timing proceedure at Bill Boyles web site. First part of my confusion was that my degree wheel has 4 90 degree quadrents but after sorting that out my first number was 67 deg before TDC second was 157 add together and divide by 2 gives me 112 (Am I doing this right so far ?) now if I retard 4 degrees that gives me 108 right? As per the guy who did my heads and sold me the cam dot to dot usually ends up about 107 why and i seeing this variation or am i missing something? also cam lift spec is 310 but measured with a dial indicator it is 318. Will this cause me that variation? If anyone else has abetter method or even a different one I would appreciate it.
Thanks
Rob

[Rob79]

Please guys a little help here. First Engine build and I am not so sure of myself. Need all the help and input I can get.
Thanks again
Rob

[PROBRD]

Sounds like your doing it right to me although I don't know what Bill Boyles site tells you to do. The only problem I see is that you will need to advance the cam 4 degrees to get to the 108 reading that you are looking for. Make sure you are at TDC when your wheel is at 0. Double check to make sure. Turn the crank clockwise until you get a reading of .250 lift. Make sure it is exact and write this # down. Continue to turn the crank over the top of the lobe and back to the .250 lift on the other side of the lobe and write that # down. Add the two together and divide by two. This will give the current installed intake lobe centerline. Some gears are not exact and some cams are ground a little off. That's why it's a good idea to degree the cam. Good luck.

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PROBRD
(probrd1@aol.com)

[Old Man Taylor]

Rob - I think you need to give more information. Measure the opening and closing of the intake valve at 0.050, then measure the same for the exhaust valve. Draw the results on a piece of grid paper by measuring 720 degrees of crankshaft rotation. Then place your measurements on the chart. It will be very easy to identify the parameters you want from this chart. If you are still confused, post again with the new data and we can tell you the results you are after. You will also need to include the specs from the cam sheet, and the manufacturer’s recommended installed position.

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Jim

[Bill Boyle]

Probird here is the URL for the details I provide on my site for degreeing a Pontiac cam. It's basic stuff as you will see.http://www.boyleworks.com/ta400/psp/camshaft.html

[Bill Boyle]

Rob--I read your post and decided to reply. First and foremost, you need to understand the information contained on the cam card provided by the manufacturer. Many grinds are ground with a 4-degree advance. You have to know that information as it is needed to fully understand the degreeing process--which I might add is not difficult, just a little perplexing at first. Hopefully, the cam manufacturer has also provided a recommended intake degree location for the cam. In the example on my site, I am working with an off-the-shelf Comp Cam grind. Comp grinds most of their cams using a 110 lobe separation angle. They also machine them with a 4-degree advance, hence, they recommend the cam be installed "dot to dot" or straight up. That translates into 106 degrees using the intake lobe centerline process. On timing sets having 3 keyways, "dot to dot" or straight up is in the middle keyway and stamped with a circle (usually). Lining up the dots should produce a verified 106 degrees in that case--as it did in the example I wrote about. So, knowing what advance is ground in is important. If I had used the advance keyway on the timing set, the cam would have been at 102. If I had retarded the set, the cam would have resided at 110.
Rob if you can't get the amount of advance, if any, designed into the cam, call the manufacturer and get that info directly. Things will fall into place once that information is verifed. If your cam is not designed with a 4-degree advance already, dot to dot on the timing set will likely give you the lobe separation angle From there you will have to go to the 4-degree advance keyway on a 3 key timing set. One other thing. Take your time. Get the numbers down correctly. Verify everything twice and by doing that you will learn a lot and won't forget it either. Hope this helps a little more. Bill Boyle

[Ed Neasham]

Rob,

Another thing to be aware of, when you get a little further along. When I degreed my cam, it came up that I needed to advance it 2 degrees to meet the specs (I had a 110 degree intake centerline cam and my calcs came out 108 degrees). Went to the local parts store and asked if they had 2 degrees off-set keys. Turned out they could order them from Mr. Gasket. When I got the key in, tried to "science out" which way the offset on the key should go. Put in in and measured and had 112 degrees. Said, Oh S***, and pulled it apart and want the other way. Came out 104 degrees. Turns out it was a 2 degree key based on the crank. Remember, 1 degree on the crank is 2 degrees on the cam, so my 2 degree "crank" key gave me 4 degrees on the cam.

Ed

[Will]

Smallblock Mopar cam keys work in our Pontiacs. For about $12 you can get a set of them from a Mopar Performance parts dealer, they come in one degree increments and since they fit the cam keyway, you're advancing or retarding the cam by the amount that you want in relation to the crank.

[Skip Fix]

As was said above, use you wheel and find the highest lift point on the intake. Then go 0.050 both ways. Add and divide by two. That will be your intake centerline. I have had some that were right on with no key way and ones that needed a 4 degree cam key to be correct.the chain and gears as well as the cam give the tolerances that change.

Do the same for the exhaust. Add it and your intake together and divide by two gives lobe separation angle. Something ground into the cam.

[Rob79]

Thanks for the replys. Much appreciated! Am going to have another crack at this tommorrow. May be back with another question or two. LOL.
Thanks
Rob

[Rob79]

Bill
After I reread my original post I realized it may have sounded like I took issue with the method you had posted on your site. Just wanted to let you know that is not the case. I am with out a doubt a novice and find that the info available to me at sites such as this one, yours, and others like it is truely indespensible. I was somewhat confused as to why my calculation came up 112 intake centerline and I was under the impression that when installed dot to dot it should be 4 to 6 degreees less than that. I dont have the cam card accessable right now but will look at it again. Although I dont recall a intake centerline spec on it. The 106 to 108 position was given to me buy the shop who did the head work and sold me the cam. Guess I can give him a call. also will call Federal Mogul. The other specs on my motor can be found under the posting ( HP/Tourque guesstimates) in the street forum.
Once again thanks Bill and everyone else for the help
Rob

[Bill Boyle]

Rob--I didn't interpret your question as anything but a question. No offense with anything you wrote or think was implied. Hope it all makes sense to you on you next cam degreeing effort. BTW, lots of good advice on this thread by all participants.

[Rob79]

OK after deciding I am reasonably sure I am degreeing this thing in the right fasion I called Dave Bisschop (did my heads and sold me the cam) Asked him about the intake centerline number He said that when he installs dot to dot he gets 107 and that It may be a variation in the timing gear set. So I switched the crank gear to the 4 degree keyway remeasured and ended up with 100 degrees intake centerline.measured and remeasured. The 4 deg. keyway apparenty changed the cam timing 12 degrees. Called federal mogul for a intaked centerline spec (they had no clue) called milidon and the tech rep said it could be a miss marked gear set. Anyone else ever have this happen? also, and this is probably a dumb question but if my intake duration is 224 would that make the intake centerline 112 when intalled dot to dot or is there more to it than that.
Here is all the info supplied with the cam.
Speed Pro CS-1175R
.050 dur 224-234
sae dur 298-308
cam lift .310-.325 measured 318 intake
valve lift .465-.488
lobe centers 107-117

Intake
@.050 cam lift 5 BTC 39 ABC
sae j604 37BTC 81 ABC

Exaust
@.050 cam lift 54BBC
SAE J604 86BBC 42 ATC

Not listed with cam but 112 LCA as per Dave Bisschop and I believe the Federal mogul Guy said the same thing

Hope Someone can give me some insight

[Floyd Hand]

Rob, Remember that a 4 degree key makes 8 degrees. Use the set that MOPar sells,5 or 6 keys to the pack.They check right on the money. Most aftermarket keys are off, a 2 might check out 3 1/2. Recheck after installing any key. Floyd Hand

[Jim Hand]

Rob,
The lobe centers for your cam are for the peak lift points, which are also the lobe centerlines. So, the lobe centerline (CL) for the intake is 107 degrees after top dead center (ATDC). The exhaust CL is 117 degrees Before Top Dead Center (BTDC). To determine lobe separation, add the two numbers and then divide by two - the result is 224 divided by 2 = 112 - the lobe separation is 112 degrees (Just as you noted). I use the term Lobe Separation - The LCA (Lobe Center Angle) means the exact same parameter. For estimating purposes, the midpoint between the opening and closing points is very close to the lobe centerline, but as some lobes have a faster opening rate then closing, the designed CL may not be exactly centered between opening and closing. That is why UltraDyne and others companies recommend you accurately locate the lobe centers by finding the peak lift point, and then reversing rotation back past at least .050" less then peak lift. They then advise to select a major point on the dial indicator, such as 50, 65, 20, or whatever major number is close to the .050 difference down from peak lift (can be .045 or .055 down, but stay within that range). Then rotate clockwise to that major point, record the crankshaft position as indicated by the degree wheel. Continue rotating clockwise past the peak point and stop on the same major lift number identified above. Again record the crank position from the degree wheel (Assure you are accurately reading the degree wheel for a total amount of change from either TDC or BDC for both readings). Add the two crank degree values, divide by two, and that will be the lobe center. (The procedure is almost identical to finding TDC on the crank in order to correctly position the degree wheel.)

As the cam rotates at half speed from the crank, one degree change at the cam equals two degrees at the crank. Accordingly, a one degree change in location of the cam will shift the lobe center two degrees at the crank. So a two degree cam key will change the cam timing by four degrees! And many crank gears are offset in cam degrees, so if they are changed four cam degrees, the actual change will be eight degrees. Some of the more expensive billet gears are capable of one cam degree change, so will shift the crank timing only two degrees per jump. When you moved the crank gear one four degree step, you changed the actual cam timing by eight degrees - as there will be minor errors in both the machining of the crank gear offset, and of reading the indicator and wheel, the change from the indicated 107 to 100 is what would be expected with a four degree shift at the crank. The reference is from the intake lobe CL, not the lobe separation value.

So remember the above - we want the cam at a specific centerline, and I recommend it be put at the suggested point. If that is not known, stay close to 107 to 109 on the intake with a 112 lobe separation cam. And neither you nor the engine will know if it is one crank degree off from the desired number - obviously set it as close as possible, but when you get within one or one and one half degrees, there is no way to get closer without replacing major parts. It is a good idea to check the exhaust lobe position, but only after you have degreed the intake. That will assure you the cam is ground correctly, at least on that cylinder! Again, set the intake as close to 107-109 and put it together and have fun! (If you end up with the intake at 108, the exhaust CL will be at 116 with a 112 LS cam). Jim Hand

[Rob79]

I understand the one to two relationship between the crank and cam gear but assumed that the 4 degree advance and retard settings on the crank gear actually reflected a change in cam degree not crank degree since the cam degree setting is the one that we are trying to alter. So what we are saying is that by changing from the 0 cam setting on the crank gear to either the A or the R we are actually seeing a 8 degree change in the cam? Even with this being the case why did I see A 12 degree jump (from 112 to 100 buy changing from the 0 setting to the A setting ) It is a Milidon gear set with three keyway positions and three coresponding marks on the crank gear teeth. Can I just rotate one tooth at a time untill I see the 107 ICL I am looking for? Or should I try another Gear set.

[Old Man Taylor]

I have not had good luck with the three keyway gears being very accurate. Trust your measurement and use offset keys in conjunction with the keyways to get where you need to be.

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Jim

[Jim Hand]

Rob,
Here is what might be confusing the issue of degreeing the cam: All measurements you will make are in reference to crank degrees. We move the cam to accomplish the desired settings, but they are not to set the cam! The only specification that applies to the cam in the entire set of cam specifications is the Lobe Separation number, and it tells us how far apart the intake and exhaust lobes are in cam degrees. And the LS is fixed and will stay the same regardless of where we set the cam - on a 112 LS, if the intake is at 108 LC, the exhaust lobe CL will be at 116. If we set the intake at 104 CL, the exhaust CL will move to 120, but in both cases, the LS will remain 112. All other specs apply only to the crank position.

Accordingly, when you make a change that moves the cam any amount, the crank position will move double that amount. One degree at the cam is two at the crank and so on. First determine just where the intake lobe center is - if at 107 or 108, you are set. If it is at 104, you need to retard the cam so the LC moves to 108. To do that, use a 2 degree offset key in the cam. As most crank offset positions are four cam degrees, it cannot be used because it will move the LC by 8 degrees! As Floyd and others have stated, most crank offsets are not precise and may be three to five cam degrees, but that will still move the LC by 6 to 10 degrees. Although time consuming and confusing, it is sometimes possible to combine cam offset keys along with the crank gear offset positions to obtain more accurate final settings.

You may want to go to the following site and review the relationship of the cam parameters, and then the information provided by all the folks on this topic may be easier to follow. The material at the site, titled "Pontiac Cams - Shake or Roll" is extensive, so it is slow loading. Take your time and review it carefully. If you have questions, you are welcome to contact me directly. Jim Hand
http://www.cyberramp.net/~firebyrd/pontiac-cams.htm

[Gach]

Let's see I've been reading for two hours now, I'm still confuse. I think what he's really asking is my cam ground right, and how do I tell. Well a cam checker is the only way, timing gear sets are not always on the money. You also have to look at the quality of the cam company. Now here's the
other big question is this really only a street car question, or does it apply to race motor's as well. I guess because it's in street car, it won't apply to anyone who races.