Cam timing with a degree wheel (7AGE specifically)

[70XIN]

Car - AE86

motor - 7AGE

use - skids

problem - cam timing

occurs/started when - today

personal situation - elite

Hi guys,

I'm currently working on a friends' 7AGE motor, we're up to doing cam timing.

I worked out 'true' TDC with a dial indicator and a degree wheel, but i can't seem to find the correct formula for working out the cams lobe centre (they are just standard cams, so should be 110deg)

I've been using this example (and others) but none seem to get anywhere right:

I've set the cams ROUGHLY in their correct positions, but i'm getting results like 150 degrees... I'm using the "valve opening and closing at 0.050" lift"

Can anyone tell me the right way to do this?

Thanks

[--Redwork--]

Pic of how you are measuring the lift with dial indicator on the top of valve..
I went to dial my cams in and gave up due to not having the correct equipment to do it properly..but apart from having that wrong.. If you follow those instrustions to the letter then you should be right..

[slide86]

ive done this before on a 327 chev.....but it was a LONG time ago.

from what i remember:
- you need to rotate the engine round clock wise to the 0.050thou OPEN on the bucket.
- then you take the degree reading on the degree wheel

continue to rotate the engine round till the valve is closing, when it gets to 0.050thou again, take that number from the degree wheel.

then the maths comes into play. i was so confused the first few times i did this but ill try to write it as easy as i can. actually, ill make a spreadsheet and you can enter the numbers and it should spit out the answer.....gimme a few mins

[slide86]

ok here is a REAL basic spreadsheet i made.....it should be working ok??

all you will need is the opening figure and the closing figure and it should give you the lobe centre...

is this what you even mean? sorry if you actually mean to do something else, i know your a smart guy so forgive me if we are getting our wires crossed...

LOBE CENTRE.xls

[70XIN]

Redwork: will take a pic soon, but basically i have my dial indicator above the cams, on the same angle as the buckets. i then have some wire (wrapped FIRMLY) around the indicator feeler so i could get in the narrow gap and get a reading. again, i will take a photo soon, should make more sense then.

slide86: exactly what i'm doing dude i used your calculator, and i'm still getting ~140 degree readings.

intake open at 0.050" - 36 atdc
intake close at 0.050" - 151 abdc

which gives me a lobe centre of 147

still almost "40 degrees" off

[--Redwork--]

Yeah.. I understand what your doing.. I tried this myself and got way to frustrated with the difficulty of it all... Really need to time my cams up though.. At least get them ball park before it goes off to the dyno..

hope you work it out bud... So you can come do mine.. HeHe..

Plus I wanna see robo's car skidin... And find out if those arms I did for him work... Or even fit for that matter..

[slide86]

hell, thats alot

its not something weird like one extra tooth on the crank pulley (im not heaps familiar with the 7age setup)

maybe it should be measured at 0.040 and not 0.050? i know alot of manufacturers specify measuring at 0.040thou....

i just found this info:

[--Redwork--]

Wheather its 40 thou or 50 it wont change it being wrong... would give identical results. Granted there might be a tiny difference but doubt you would even be able to see it..

could still be worth a try though... Just to see.. I could be wrong.. ???

[70XIN]

yeah exactly right redwork, near enough is not good enough for me (especially when it only takes a degree or two to alter power/idle drastically)

slide: tried the 0.040 thing, gives EXACTLY the same end result

and as far as i know we aren't out a tooth, basically put the cams in their "approximate TDC" position, put the crank to TDC, and put the belt on .. just had to advance/retard the gears a few degrees to make the belt line up

[--Redwork--]

Start skiping teeth my freind.. Back when I was playing the ALL MOTOR game. I went to the dyno with this new gun engine I built.. Never new about timing the cams with a degree wheel.. I thought you just dropped them in and played with them on the dyno...

Well off to the Dyno.. and well I came away VERY disapointed...
Went home.. started to skip teeth untill I found my limits of touching vavles.. Went back and within a few runs had gained 80whp... was much happier that day..