degree cam by lobe center line
 

so i finally put my old 455 back together, and now im trying to time the cam. ive youtubed this process to death and i think i kinda got it sorted but figured i check my process.

1st i put #1 piston close to tdc, then set the degree wheel at 0 before bringing the piston down a bit. installed piston stop, rotated piston back up to the stop and wrote the number down which ended up 20° on the wheel. rotated the piston back the other direction and got 20° on the opposite side of tdc on the wheel. i think it was luck i got the wheel that close but i did check and double the 40° difference a couple times.

i dont have the card, i only remember i was told it was a 271/279@ .050 .426 lobe on 104 lsa. and that previously it was ran at 101.5° because that was as close to 101° as he could get.

with the dial indicator and the lobe attachment connect,i only seen a peak of .416 lift so maybe that was a typo back then on the .426 lobe but he did write it on the box too. next i put the indicator on 0 on bottom of lobe, cranked the motor over to peak lift of .426. after that i turned it .050 passed the peak lift and wrote the number down. next i turned it over to .050 before peak lift and wrote that number down. added it together and came up with 98° centerline using the 4° A key in an edelbrock gear drive. so i pulled the crank gear and went to dot to dot. and repeated the steps, came up with 101.5° centerline. i had an off brand ebay gear drive on the shelf without additional timing keys installed it and repeated the steps again, only this time my top numper was off by 1° and when averaged the 2 numbers together i got 101° thats not to say that .5° was not a margin of my piss por up close vision though. would it be safe to assume this cam has some advance built into it and my readings are right or am i missing a step?

i was thinking maybe now i should go back, measure the 1st .050 of lobe lift on each side of the lobe from the bottom instead of after peak lift and see if i still come up with the same 101°


when i use summits calculator it shows with no advance this cams centerline would be 104°

I usually zero the dial indicator at max lift. Than coming around till you see lift, I thinks its easier to count and get it all on one rotation, before and after .050 lift.

i was reading a post on anotger forum where a guy said the same thing to someone. im gonna double check myself this evening

I almost always check .050 points and centerline .... Then check the exhaust for the same along with lobe lift.

True story, I knew a guy that only checked intake centerline. Cam company mis boxed his two Pontiac cams and the customers got the wrong cams. One was a HR and one a SR. At least the intake centerline was correct

Paul, the .050 points you mention...are you refering the opening/closing event on the cam card? i dont know how summits calculator populates that field by just the having the duration@ .050 and lsa. it does tho, since i dont have the card, i coukd just check and see if i get close to what their site says.

Correct I'm referring to the numbers on the cam card. If you don't have a cam card, Jmo it's more important to check the .050 points that way you can double check the duration.

i was messing with it a bit more, i think my lobe centerline is right, but the timing events are not the same as the calculators..since my timing/degree wheel is set at tdc of 0. it seems i need to mark down the degrees each lobe opens at .050, and closes at 050. add the 2 numbers plus 180 and thats duration . i may have been ahead to experiment with a cam that i do have a card on 1st

Good job, Your process sounds good. I'd go wider on the lobe ramps to find each "virtual" LC, due to long Dur & possible lobe asymmetry, and;

Since the valve open-close events (IC, IO, EC, nevermind EO) define the Lobe Separation EFFECT moreso than the actual LCs.

My opinion: 101-104 LCA LSA sounds like a worthy goal.
Easy in text, maybe as-easy in practice. OMG, just noticed you figured it out last night.

I do it like Paul as a double check. Ultradyne's assymetrical lobes wanted the 0.050 on either side.

im gonna give it another go this evening. worse case ill put another cam with spec card just so i know ive done it all right

Sometimes maybe we think about degreeing cams too much.
I have done it, bought a bunch of stuff to do it. But always run them straight up as intended. Just pick a known goo shelf cam. Or buy a custom one from a guy who knows what he is doing.
Ed Smith does not put a whole lot into it. Either you are going to run it straight up, advance for more low end, retard for more top end, or buy a new cam.
https://www.youtube.com/shorts/B1-qXSmroTA

Same could be said about bearing clearance. After all they're usually STD, 010, 020 or 030 ..... But I sleep better at night knowing it's correct.

"Same could be said about bearing clearance" Yep I'm chasing that right now! Good thing I did not just toss in the same bearings !

for the most part, i think im stuck with whatever i can get using a 3 key geard drive, i know the 9 key way timing chains does give you a bit more adjustability. still kinda nice to learn it and do it though. i can see it being even more bennificial using the bop belt drive where you can dial it in even closer with the adjustable cam gear, i think milodons gear drive has that too....of course in my case....i still need to get the basics down before i get ahead of myself

Have you ever had a cam that was not made correctly ? I am sure it happens and you have built a lot more engines than I have.
Clearances, well... a lot more important than where your cam is at. Cam is not blowing your engine up, clearances might.
I ask the machinist where they ended up at and go from there. Ended up putting some coated bearings on the rods to get them where I wanted.

after re checking, from what i measured i came up with these numbers.


[email protected]/279@050

intake open 33° btdc close at 58° abdc
exhaust open 67° bbdc close at 32 atdc

intake centerline 101.5°

the screenshot is summits calculator, and it looks to be a degree different than mine but i figure thats just error from my eyes and to close to matter. what is confusing is the exhaust centerline. no matter what i do i get 155° and 65° .050 before and after peak exhaust lift. divided by 2 gives me 110 centerline but summits calculator gets 107. when i go to 110 on the degree im at peak lift, but it also stays at peak lift right down to about 106.5° ish.

i mean i guess the small amount its off probably wont affect it one way or the other though...i hope

Looks like your doing good..... If it's still set up check the numbers fifty thousandth before and after peak lift .... Those are the ones that will tell you the lobe centerline..... It's normal to be off a number or two from the cam card

Define correctly.... I've seen cams that are off enough that one calls the supplier to find out they lowered there "plus and minus" acceptable numbers due to lack of skilled labor, I already mention the mis-boxed cam deal, I've witnessed cams the were stamped with the wrong grind number and I've had cams that the lobes were ground wrong, making them taller than the bearing journals. Btw when that happens the cam won't fit in the block but they're fun to roll across a flat surface a hear them wobble.

Nowadays if you check everything chances are you're going to miss something.

i left it all set up, so im gonna double check again. seems i was able to find the center of the intake lobe easy, but not tge exhaust. but it was late too.


also, i wish i had checked sooner but while i was at it, i measure the deck clearence. looks like these pistons are .019 in the hole. so if i used edelbrocks .038 gaskets i would still have a quench of
057 which from what i read isnt good. the heads are 78cc speedmasters putting it around 10.5xx cr

do you think it will detonate on premium? or should either pull apart and shave .010 or try the .027 cometics? ive not seen any other options besides the cometics

Hard question to answer.... Generally it's well worth the effort to bring that piston close to the head .... Unless it's a power adder build.