Author Topic: Dailing In Cam Results (Read 1911 times)

mike · « **on:** February 06, 2005, 02:58:43 PM »

Hey guys, I

Cameron · « **Reply #1 on:** February 08, 2005, 08:51:46 AM »

IMO your motor won't care. Use the washers that came with the cam gear, to get the cam as close to the cam spec card. Cams have some variations built in from the manufacturing/ grinding process. Most of our VW high performance cams are still ground by a guy standing at a manual grinder, nobody wants to invest several hundred thousand dollars in a CNC cam grinder. Things to also think about: How accurate is your pulley? Your own measuring skill? What are you measuring the lift with? All of these little things contribute to variations from the cam card.

mike · « **Reply #2 on:** February 09, 2005, 12:49:13 AM »

Well, I

jim martin · « **Reply #3 on:** February 10, 2005, 08:54:57 AM »

no you don't need a new cam , just a new approach .last night i posted and today its gone ? i have the answer you need.will see if it returns today ,if not i will have to repost. let me know if you are still interested and a will repost it

mike · « **Reply #4 on:** February 10, 2005, 10:28:01 AM »

thanks jim! ^_^

saw your post on stf and couldn't find it here.

probably because of your login issues.

jim martin · « **Reply #5 on:** February 10, 2005, 11:57:04 AM »

lets try again,first there is many things that dictate cam selection-rpm/heads/displacement/intended use etc.those topics are a huge post in themselves relating to cam selection.what you need to understand is why your cam is ground the way it is and how to adjust it .first put yourself in the position of the cam manufacturer.ever day you get calls on cam recomdation and in the end customers don't lissen and buy what they think or what is recomended from a friend.end result is the customer buys a cam that doesn't deliver what they want ,so now that customer is upset and tells his friends about how crummy this cam is and you can see why customers and friends turn to other suppliers. to combate this many suppliers got smart .first ,grind the cam with a 4 deg advance as well as a few deg earlier closing and they acomplished alot.the advanced cam nets better low end power and the earlier closing event builds higher cylinder pressure which boosts performance as well. now the customer is happy with his new cam. but the suppliers are smart and they know that if you know what you are doing you dial in your cam propperly.
now i'm going to pass on my methods and ways i look at cam degreeing and look at your supplied numbers only.
22+180 +58 = 260 deg duration
24+180+54=258 deg duration .
26 +180 +52+258 deg duration.
this is how i look at it .both your intake lobes run the same duration of 258 but,are seperated by 2 deg.no problem split the differance and make your own numbers up.
25+180+53-=258 deg duration .but is still advanced from the cam card specs so !use a 4 deg washer and retard the cam 4 deg and you get
21+180+57=258 deg duration with a differance of 1 deg later openning and a 1 deg earlier closing no big deal.so now you can see this cam is damb close !!!not bad for a mass produced product.
like i said earlier there is alot more to it than this ,but this will get you going.
good luck

mike · « **Reply #6 on:** February 11, 2005, 04:58:33 PM »

Thanks for the excellent post Jim. Very informative! I

jim martin · « **Reply #7 on:** February 12, 2005, 10:52:17 PM »

mike , pm me your phone number ,i just typed away here for over 20 min and like before for some reason i can't sudmit posts .
sorry

jim martin · « **Reply #8 on:** February 14, 2005, 10:24:04 PM »

***Now I understand the shorter duration on the intake side. Builds more cylinder pressure at lower rpms resulting in more torque. Correct.***

close but ,you need to understand something first .which is dynamic compression and how cam timing effects it. lets put it into terms that everone can figure out ,or this is going to fly over alot of heads .imagine a syringe that is 10\" long with markings from 0\" to 10\" ever 1\".unscrew the needle and pull back on the plunger so its at the 0\" mark.grasp the syringe so the removed needle end is straight up and cover it with your thumb.now push the plunger end against a table top.guaranteed you will not be able to push the plunger in very far or you will blow your thumb right off the end.
now set the plunger at the 5\" mark and repeat.this time you can move the plunger almost to the end as well as being able too keep your thumb on the end.you have just discovered how cam timing effects dynamic compression.lets look at it relating to your numbers/my numbers .when the intake valve closes at 53deg abdc advanced 4 deg] that is equal to the plunger being at the 0\"mark.you can see now that because of the earlier intake closing event you have buildt higher cylinder pressure which will yield a higher energy output.but when the timing is retarted back to the closer #'s of the cam timing card ,in this case 57 deg abdc it is equal to the plunger being at the 5\" mark.this yields a lower cylinder pressure and will also give a lower energy output.
so its not the shorter duration that gives a higher cylinder pressure .but in fact its the earlier intake valve closing event.
duration is nothing more than the amount of time in deg's that the intake starts to lift until the time it fully closes.so why do we need cams with a longer duration .easy RPM!!! .but this is a hole new topic.

***So by retarding it 4 degrees, it'll bring the intakes closer to spec.[CORRECT] however, by doing so, this would retard the exhaust as well.[CORRECT] Which would then be out of spec.[SEMI CORRECT] however, if I

mike · « **Reply #9 on:** February 17, 2005, 05:52:46 PM »

Jim,

Thanks for your post. It's very informative. But it looks like I

jim martin · « **Reply #10 on:** July 25, 2006, 11:09:55 PM »

bump, this may help

John W. Kelly · « **Reply #11 on:** August 01, 2006, 08:30:39 AM »

Why are you degreeing the exhaust? You'll be fine with doing just the intake.