Help !!! Camshaft problem =(

[Philouw]

Hello everybody,

i recently installed a new camshaft in my 86 K5 blazer, I chose the "compcam 12-210-2"
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=73&sb=2

So the cam broke in good, and after the break in, I had to remove to heads to change my springs (I kept the old, softer springs to break in the cam) and after i put everything back, i timed it to initial 10 degrees BTDC, however, while trying to find TDC on compression, i noticed that I also had a small compression zone on the exhaust stroke, right when the piston is almost at 20 BTDC exhaust stroke. I noticed that the exhaust valve closed at around 20 BTDC, but the intake valve opens up only at around 5 BTDC, so there is that 15 degrees where both valves are closed and since the piston is on it's way up, there is a fraction of second of compression...(I can hear air comming out of the spark plug hole) I doubt that this is normal (or is it ??) there's no overlap, meaning intake valve starts opening while exhaust is not yet fully closed. Thing is, I don't remember having that small compression on exhaust stroke before removing the heads. Or maybe it did happen but i didn't notice, which would surprise me.

The cam specs says that:

exhaust opens at 68 BBDC, closes at 20 ATDC
intake opens at 28 BTDC, closes at 60 ABDC

but I don't have that at all, what I roughly have :

exhaust opens at 15 BBDC, closes at 20 BTDC
intake opens at 10 BTDC, closes at 11 ABDC

I read that roughly on my balancer, those are not precise values, but I wanted to have an estimation/idea of what was going on in my engine. I would understand if I had 5 degrees of difference between what i read and the official cam specs, but the difference I have is really big

I'm lost... did comp cam mislabeled their camshaft and they sent me a wrong one ? Would they make such a huge mistake ? Or did the timing chain skipped a tooth ? but Timing chain, crankshaft gear, camshaft gear are all new... and even if it did jump a tooth, it wouldn't change the specs that much !! So i really don't know...
I need help !!
Thank you !

 

[big dan]

Sounds to me like you need to put a degree wheel on and check the specs.

I don't recall ever having compression on the exhaust stroke but I've never looked for it either.

Regardless if your cam specs don't match the card you need to check it with a degree wheel to make sure then go from there.

 

[76zimmer]

I've had two cams that weren't what was printed on the cam card....many years ago a Crane, and more recently a Melling cam.
In any regard, are your lifters adjusted right?
I agree with Dan, use a degree wheel, and confirm piston at TDC before going any further.

 

[Philouw]

thank you for your replies !! yes, the degree wheel will be pretty usefull I guess, but I asked a compcam tech, and this is what he said:

"Hi Philippe,

On that camshaft, cylinder #1, the intake valve should start to open at 3* before top dead center and the exhaust valve closes at 5* before top dead center. Now these are measurements @.050" of lift. The ramp rates are slower starting off so you may not notice the valve moving until you get further up on the ramp. The most accurate way to check this is to have a degree wheel and record the measurements at the timing events stated. Let me konw if you have any other questions.

Thanks,
Adam"

and what he said matches with what I have (and I didn't even tell him when my intake valve opens and exhaust valve closes), but still doesn't match with the specs on their website... I'm really confused

 

[Philouw]

I've had two cams that weren't what was printed on the cam card....many years ago a Crane, and more recently a Melling cam.
In any regard, are your lifters adjusted right?
I agree with Dan, use a degree wheel, and confirm piston at TDC before going any further.

how do you adjust a lifter ?? or you mean the valve lash ?

 

[76zimmer]

Yes valve lash!