Q&A / Tech

Ask Away! with Jeff Smith: How to Decode a COMP Cams Camshaft

I purchased a used hydraulic roller camshaft from a friend that was originally used in an LS1 engine. My buddy says it’s a mild cam that’s bigger than a stock LS6 version, but he didn’t have any more information. The end of the cam is stamped 3709/3711 HR 114 followed by CC and 7661-11. Can you tell me the specs on this cam from these numbers? On other cams I’ve looked at, they just list the part number – which is easy to look up, but this cam has a bunch of numbers I don’t recognize.

D.S.

thumpr-camshaft-group-421w-219hJeff Smith: First of all, the CC refers to COMP Cams. That gives us our first clue where to look for the rest of the numbers. If we didn’t already know this was an LS cam, the first thing we would want to do is determine the engine family. COMP Cams uses two-number designations for all its engine families. The LS engine is designated 54 and this number is generally the first two numbers that define the actual cam part number. Other examples include small block Chevys -12, big block Chevys -11, and 5.0L small block Fords -35.

The 3709/3711 numbers are references to lobe designs. Each family of cam lobes has its own numerical designation with the same basic configuration, usually encompassing multiple individual durations that also might include changes in lobe lift. To decipher these codes, we accessed COMP’s website at compcams.com. On the home page, we looked for the “Information” tab and then clicked on “Catalogs”. Under that heading toward the bottom we found a tab for the Cam Lobe Master Catalog. This is the COMP Cams equivalent of the Rosetta stone for cam lobes.

In the catalog, you will see the cams listed by configuration starting with flat tappet hydraulics and then hydraulic rollers–which is what we want. Once we found the hydraulic roller section, the first column lists each lobe by number. We continued down the list until we found the 3709 number, which because it is listed first on the camshaft, is the intake lobe. We found it under the heading of Xtreme RPM for LS1 lobes, Hi Lift.

The 3709 lobe is listed as 265 degrees of advertised duration with 212 degrees at 0.050 and 0.328-inch lobe lift. The lobes are also listed with various theoretical valve lifts–the one we’re interested in would be the LS1’s 1.7:1 rocker ratio that delivers 0.558-inch of lift. All you have to do to determine valve lift is multiply the lobe lift times the rocker ratio. With this intake lobe: 0.328 x 1.7 = 0.5576-inch, which COMP rounds off to 0.558-inch. The second lobe number 3711 refers to the same family of lobes–this one spec’d at 269 degrees advertised with 216 degrees at 0.050-inch tappet lift with a lobe lift of 0.330 and a theoretical valve lift of 0.561-inch.

The next information engraved on the cam was HR 114. The HR refers to this as a hydraulic roller camshaft while the 114 refers to the lobe separation angle (LSA). When referring to LSA’s, the larger the number, the more degrees of separation between the intake and exhaust lobes. The greater number of degrees means there is less overlap between the intake and exhaust lobes. If the number was 110 degrees, this would increase the amount of overlap. Less overlap generally produces a more stable idle while more overlap makes the idle lumpier. Stock GM LS engine cams feature LSA anywhere from 116 to 121 degrees because GM is concerned with creating a very smooth idle. But this comes at the cost of reduced torque in the middle of the rpm band.

The only thing we don’t know from these number is the cam’s intake centerline. We have a hint because if a camshaft if ground with no added advance, the intake lobe centerline will be the same number as the LSA–114 degrees After Top Dead Center (ATDC). However, most cams intended for street use are ground with several degrees of advance. This advances the intake centerline by that number of degrees. We investigated a couple of our Comp off-the-shelf LS cams and found they were ground with 5 degrees of advance, but that is no guarantee that your camshaft is ground that way. The 7661-11 is a serial number specific to that camshaft only.

We compared these specs to the catalog and because there is no list number on the end of the cam, we will assume this was a custom-ground camshaft. COMP offers this  as a service to anyone who is looking for a custom combination of specs that are not listed as an “on-the-shelf” cam. This requires a little more time but COMP does not charge extra, which is a great service if you are into tweaking the cam a bit to do something special.

If you want to know where the intake centerline is located, all you have to do is install the cam in the engine and then degree the cam. Some enthusiasts just compare the opening and closing points of the intake with the cam card but this isn’t as reliable as the intake centerline method. In this case, we don’t know what the opening and closing points are – although you could compare the intake lobe points to an off-the-shelf XFI RPM Hi-Lift cam and probably be pretty close.

For the intake centerline method, once the cam is installed and TDC is established on the degree wheel, then roll the cam around until the dial indicator signals maximum lift. Now zero the indicator and turn the engine backward until the dial indicator reads roughly 0.100-inch. Now turn the engine clockwise and stop at 0.050 on the opening side of max lift and record the degree wheel reading. Then do the same process with the lobe at 0.050 on the closing side. Add the two numbers together and divide by 2. This will give you the intake centerline. With your cam it might come out to somewhere between 114 to 110 degrees depending on if the cam was machined with advance.

Hope we’ve helped you with a little more camshaft knowledge. For as simple as this product appears, it is actually a very complicated piece of engineering if you study it closely.

Tags: , ,

28 Comments

  1. Pingback: PERFORMANCE PARTS | My great WordPress blog

  2. to may word in this i need pics lol

  3. I bought pair of cams for my 99 mustang 4.6 i was told they are stage 2 cams but i wanted to be sure before taking old ones off can u please help me identify them will they improve my pony thank u very much sir. back of cam has 660 371079 front of cam has s42008L

  4. LARRY HOOKER says:

    i have a 572 hemi and i am in the process of pulling the cam but the harmonic damper is being a pain . i have some stamps on the cam that i can see EP236 and CWC can these be used to idetify the cam

  5. Piotr Ksiazek says:

    i have a 383 chev engine ibought and would like to know what cam is in it. i have removed camshaft welsh plug to see numberbut can’t identify numbers help would be appricated.i nee to see what size converter i would need.

  6. Piotr Ksiazek says:

    i have a 383 chev engine ibought and would like to know what cam is in it. i have removed camshaft welsh plug to see numberbut can’t identify numbers help would be appricated.i nee to see what size converter i would need.numbers on cam end are z102 and also 14p

  7. I have a cam trying to set startup timeing hr112 intake hyd .555 ext .576 duration .006 valve tapping lift 287 in 293 ex valve timing .050 open int 10 close btdc46 abdc exh :57 BBdc 5 ATC. These spec are for cam install @108 intake ctr line duration @.050 intake 236 ext 242 lobe lift .3470in .3600 ext lobe selection 112.0 where do I set my timeing for first start ?

  8. Ed Johnson says:

    I have this small block chevy the guy says is a 418 strocker …a lifter lifted off at the track but now im looking at the cam and all it has on it is a S then another set of numbers is CH2 ..its a roller set up lifter ar comp cams and so is the rockers but i have no cam spec with car when i got it so im lost ….

  9. Curtis Robinson says:

    can you help me to decode this cam . 139536 93B2B

  10. Sonny cox says:

    I have a solid roller cam has cc 950 k5462 r6 292-5 296-6 stamped on front help with specs

  11. Corey Adams says:

    I am just trying to decode the cam out of my 400m. Stamped numbers are 529506 and 031531. Grind numbers are HR 224/339. 25-12.
    52.01.07
    And there is a CR inscribed as well off the lower left
    Thanks for any info I “”Think”” it’s a crane cam but I can’t match the stamped numbers anywhere

  12. Tim Gideon says:

    I have Comp Cams camshaft. The markings on end of cam is 300C6 and X6733. Trying to find the specs on this camshaft.

  13. Robert Seaman says:

    I have a fessler roller cam trying to identify the grind specs. Rear cam bearing journal is etched/engraved “Fessler Killer Cams #38” Any info is appreciated.

  14. Pelon Baeza says:

    Hey I have a cam I can identify

  15. I have a new cam was told it was a comp cam # 1136 230780 any ideas on cam specks

  16. Looking for 4311-4314-r106 Q 7388-04 CAN ANYONE TELL ME WHERE I CAN LOOK THE SPECS UP!

  17. I have a cam I need to I’d I need the specs and if it’s a solid or hydraulic it’s a ua9450 a4250h11 can someone help me with this I am building this junk yard over night Grease monkey maid 10/4 I need it if possible

  18. Jimmy Johnson says:

    I have a bbf429 numbers on rear of cam359356 can you tell me what cam I have

  19. Hi, I have a cam that trying to figure out the specs on. The numbers on it are, 3734R/3377R, HR13, I 3996-06. Is there any way anyone could hp me out?

  20. Randy Witt says:

    I was given a can that has the #’s
    4270 H11 then letters CC vertically, then CB6554 can you tell me the specs on this cam? Thank you in advance

  21. Chris Lee says:

    Gday mate trying to decipher this comp cam to no avail, # 2-018b 1295 3106-rb 046987 any help on duration and lift lobe centre and rev range would be greatly appreciated

  22. Keith Jones says:

    114568. What specs solidroller

    • Hey Keith, we did some quick sleuthing and your cam MAY be for a BBC Marine (boat) motor application that’s been discontinued. A call to Comp at 1-800-999-0853 will probably give you some more details.

  23. Ford Au part no ! 4226 what kind of camshaft is it

  24. i have a hr8ty 3050s/305is y7379 cc 212203 2811 out of a 1999 360 dodge magnum i cannot get any info on lift duration or center line also has cc letters asume comp cam ?

  25. I have this in a recent purchase…5.3 cast-iron ls engine numbers are…256373-18…and 32340135…I’m at a loss..can you please help Jeff?….cheers dave

  26. Bart Beeman says:

    I bought a 34 Ford pickup with a 302 installed. I have no idea what’s on the inside. On the outside there is a Carter AFB 9637 (625CFM) sitting on an Edelbrock manifold.

    It’s got a great loping idle (“big cam”?? – no idea) and only pulls about 10psi vac at idle.

    Looks to have stock cast iron heads and exhaust.

    Old school Comp 9000 Mallory Distributor and coil.

    No smoke, but I have not checked compression yet.

    I just rebuilt the carb as it was pretty dirty and leaked at the accel pump. I was pretty careful with the float settings etc and it fired right up when put back on!

    Only thing is the idle mixture screws have little effect (oh no timing pointer either – on order) so can”t really tell timing.

    Any advice? Any way to to determine the type of cam from the outside?
    Cheers Bart

Leave a Reply to Mike evans Cancel

Your email address will not be published. Required fields are marked *

*

This site uses Akismet to reduce spam. Learn how your comment data is processed.