this is tdc

[prove_it]

Maybe they sent a larger cam by mistake.

 

[tektic]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

9 seconds or 9es?

 

[tektic]

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

 

[GSTwithPSI]

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]

" 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.