tektic
(Senior Member)
03/12/15 09:06 AM
this is tdc

Now am I off a tooth or is the cam timing just this far off from machine work?


Edit: just checked the cam card. Exhaustcenterline is out 6 and intake is out 1.5 degrees. What's a full tooth?


Whoodoo
(buff guys = good time but my dream is to fondle 1051)
03/12/15 11:27 AM
Re: this is tdc

There are 48 teeth in a cam sprocket, so each tooth is 7.5 degrees.

prove_it
(my racist jokes aren't actually funny)
03/12/15 12:35 PM
Re: this is tdc

It looks like normal machined head to me. Your maybe 1/4 tooth off, or about 3 degrees. My stock gears line up like that with a machined head. You had the block decked didn't you?

tektic
(Senior Member)
03/12/15 02:36 PM
Re: this is tdc

Both surfaces have been redone. I will time it from here then. Thank you.

prove_it
(my racist jokes aren't actually funny)
03/12/15 03:28 PM
Re: this is tdc

In reality, if you were doing a timing belt with stock gears, you would just rotate the crank CW a tiny tiny bit and the cam marks would line up fine and the crank lines would be just barely off to the side.

Double check all your measurements to be safe though. Also I'd like to see what Evan has to say.


CutlassJim
(poop load of room)
03/12/15 03:54 PM
Re: this is tdc

This is the exact reason for adjustable cam gears and degreeing.

tektic
(Senior Member)
03/12/15 04:07 PM
Re: this is tdc

No, I get that. I was just making sure I had the belt on right.

GSTwithPSI
(A hole)
03/12/15 05:50 PM
Re: this is tdc

I agree with Ryan. Looks to be slightly off, due to machining/tighter tolerances. I'd say you're fine.

prove_it
(my racist jokes aren't actually funny)
03/13/15 01:37 PM
Re: this is tdc

Wait?, We agree?


jk


tektic
(Senior Member)
03/14/15 06:35 PM
Re: this is tdc

I'm having a difficult time getting my open and close events to match the numbers on the card. I found it easier to match the center lines with the spot I found peak lift. Is that good enough? I'm tring to measure open and close at .04".

Also when I'm done are the timing marks on the cam supposed to line up again?


donniekak
(Member ++)
03/15/15 01:09 AM
Re: this is tdc

It's pretty rare for the opening and closing events to match with most cams. Use the centerline method. And not peak lift, the center of the opening and closing events.

donniekak
(Member ++)
03/15/15 01:10 AM
Re: this is tdc

It's really easy to use an online calculator.
click


tektic
(Senior Member)
03/15/15 09:10 AM
Re: this is tdc

So target the calculated centerline with the one on the card. Don't measure centerline. Don't worry about opening and closing events in relation to the card, but insted just use to find actual centerline.

Ok ill try again. That seems easier.


tektic
(Senior Member)
03/17/15 10:34 AM
Re: this is tdc

Ok.. . Now I forgot to take into account that I'm degreeing a stroked engine.

How should I adjust my target centerline while using a 94mm stroke crank?

I guess I should call GSC and see what they have to say. I'll report back.

Repoprt: I Talked to Gregg over at GSC, he's a super nice guy! Foremost he assured me that all his cams are sent out measured to the 5th decimal place in metric, and that any irregularity I'm getting is due to the equipment I'm using. If you saw my equipment you would agree with him too. He mentioned that a solid belt tentioner needs to be used and that his company made special flat top spring retainers so a perfect 90 degree angle can be maintained on the shaft of the dial indicator. Two things I have thus far overlooked.

So after all that he said I should concentrate on aligning my opening events to the numbers on the card. He also stated the stroke should have nothing to do with the targets.


tektic
(Senior Member)
03/26/15 08:50 AM
Re: this is tdc

I did this to death. I got the exhaust cam exactly where it is on the card. The intake cam doesn't match the card though. It opens 1* BTDC and supposed to close 35* ABDC when in actuality it closes at 42* ABDC. I measured many times. The card for GSC S1 cams is wrong.

After all this Exhaust cam 2* R Intake cam .75* Advanced. Complete waste of time money and and effort. One of my cam caps had a heli coil holding it in. Now it does not... Destroyed the set pin for that cap too. Going to try to stud it today. Trowing the nt engine back with a 14b is looking better and better.


EHmotorsports
(Capt Fabbin Stabbin)
03/26/15 08:59 AM
Re: this is tdc

Making the cam timing perfect is never a waste of time.

tektic
(Senior Member)
03/26/15 09:00 AM
Re: this is tdc

I truly hope your right

prove_it
(my racist jokes aren't actually funny)
03/26/15 11:19 AM
Re: this is tdc

It's not a waste. You'd be surprised to know that 1-2* cam change in the right direction can yield up to 20whp. Getting them set to where they need to be at will make the whole engine happier.

I'll be going down the same path you did. I'll be throwing on some gears and adjusting them to spec, your not alone!


biglady112
(or what)
03/26/15 09:34 PM
Re: this is tdc

My gsc stage 3's ended up at 8* advanced on the intake and straight up on the exhaust.

tektic
(Senior Member)
03/27/15 10:48 AM
Re: this is tdc

My intake cam seems to have 7* of extra duration not accounted for on the cam card. did you find anything like that?

This could be from my crap tools however the exhaust cam numbers all worked out perfect.
My machinist told me that small cam company hand index things and accidents happen constantly.
I know there's many other variables like valve installed height.

What I know for sure is that in my setup I have 7 extra crank degrees of intake cycle over the specified duration on the card provided. I indexed the opening event with that on the card and thats where it going to stay unless it gets dyno tuned.


prove_it
(my racist jokes aren't actually funny)
03/27/15 12:13 PM
Re: this is tdc

Maybe they sent a larger cam by mistake.

tektic
(Senior Member)
03/27/15 02:57 PM
Re: this is tdc

Hmmm... The S2 intake cam is listed as a 230 duration and the s1 is only 216. That's a difference of 14.

I'm reading 7 extra degrees on the crank... which is turning half the speed of the cam. I have a S2 Intake cam?


prove_it
(my racist jokes aren't actually funny)
03/27/15 03:01 PM
Re: this is tdc

Sounds plausible. Are there any marking on the cams which would help identify this?

If it was the exhaust cam that was bigger, I'd say rock it. It would help, like a HKS 264/272 combo. Being that it's the intake, I'd try and deduce what cam it is.


donniekak
(Member ++)
03/27/15 04:36 PM
Re: this is tdc

Quoting tektic:

My intake cam seems to have 7* of extra duration not accounted for on the cam card. did you find anything like that?

This could be from my crap tools however the exhaust cam numbers all worked out perfect.
My machinist told me that small cam company hand index things and accidents happen constantly.
I know there's many other variables like valve installed height.

What I know for sure is that in my setup I have 7 extra crank degrees of intake cycle over the specified duration on the card provided. I indexed the opening event with that on the card and thats where it going to stay unless it gets dyno tuned.




That's why you degree with the centerline method.


tektic
(Senior Member)
03/27/15 05:33 PM
Re: this is tdc

I did it that way originally then gsc told me the opening event was more important. If I don't like how it runs I can retard it a degree to a degree and a half on the cam and that's about center. I'd do the math properly of course. I have it written down on the card.





tektic
(Senior Member)
04/25/16 04:11 PM
Re: this is tdc

I'm Revisiting this because I'm having knock issues and think this to be the cause. Can someone smarter than me please take a look at this picture and give me the mathematical solution to dialing in these cams to the factory spec. Everything marked is the actual measured events in my motor with the cam gears set to zero.

Thank You


GSTwithPSI
(A hole)
04/25/16 06:15 PM
Re: this is tdc

Hey dude, I'll break this down the best I can from what I see in the picture.

For the intake cam:

Intake (Card)
Opens 1* BTDC
Closes 35* ABDC

So:
1* BTDC + 35* ABDC + 180 = 216 Duration (like the card says)

Now, your measured results:
Intake (Measured)
Opens 44.5 BTDC
Closes 68* ABDC

So:
44.5* BTDC + 68* ABDC + 180 = 292.5 Duration...

So:
216 is not even close to 292.5

So, Basically, you messed something up. It's hard to say where, since any one of the steps done incorrectly can result in the measurement being off. You'll just have to redo it until you get it right.


Moving on to the exhaust:

Exhaust (Card)
Opens 42* BBDC
Closes 2* BTDC

So:
42* BBDC + 180* - 2* BTDC = 220 Duration (like the card says)


And, your measured results:
Exhaust (Measured)
Opens 44.5* BBDC
Closes 4* BTDC

So:
44.5* BBDC + 180* - 4* BTDC = 220.5 Duration

So:
220* is close enough to 220.5*

So, your exhaust cam looks to be advanced about 2 degrees.


Regardless, I doubt this is the root cause of your knock. What fuel are you on again?


tektic
(Senior Member)
04/25/16 07:23 PM
Re: this is tdc

I did it over and over. It opened and closed. There's not much to mess up. I got the same for my exhaust.

I'm running 93 octane and even with very little advance its regesters knock. I'm going to pull my plugs tomorrow.


GSTwithPSI
(A hole)
04/25/16 07:58 PM
Re: this is tdc

If your intake valves were opening at 44* BTDC they'd be bent. Not to mention, your calculated duration from the measurements you took is way off. If the picture you posted is accurate, the only explanation is something got messed up in the process of degreeing the intake cam.

Under what conditions is the car knocking? WOT? How much knock are you seeing?


tektic
(Senior Member)
04/27/16 09:48 AM
Re: this is tdc

About 8 counts above 5k @ 11* and over 22psi.

The open and close events are supposed to be in the range they fall in acording to the degree wheel.

I'm thinking colder plugs, 8es may help.


OldHairyBastard
(I take bottom on trannies)
04/27/16 11:41 AM
Re: this is tdc

Make sure you have them gaped and you could go to 9's but you will have to change them all the time if you don't romp on it enough.

tektic
(Senior Member)
04/27/16 05:55 PM
Re: this is tdc

9 seconds or 9es?

tektic
(Senior Member)
04/27/16 07:43 PM
Re: this is tdc

Those were the wrong numbers. Opens at 1btdc closes at 40abdc

GSTwithPSI
(A hole)
04/27/16 08:12 PM
Re: this is tdc

That still works out to 221 degrees of duration, which according to your cam card is wrong. Calculating the duration is a quick way to verify you did everything right. If your measurements = duration, you're good. If they don't, you either did something wrong, or the cam geometry is different than what the cam card says.

tektic
(Senior Member)
04/10/17 10:45 PM
Re: this is tdc

" cam geometry is different "
What If my valve install height was different? I had oversized valves put in and I'm pretty sure the valve stems weren't trimmed... Are they supposed to be? I know the exhaust still worked out properly... I don't know.

My notes say that my measured exhaust centerline was the same as the cam card when it was advanced 5.4 degrees.
My notes say that my measured Intake centerline was the same as the cam card when it was advanced 1.5 degrees.

This is based on the centerline not the opening events like the first time I did it. Does this reduce overlap?... No it doesn't, does it?

I have to look at what my gears are timed like now. I'm pretty sure its not this though.



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