Well... since I didnt have any advance ground in... I need to get some advance on the cam... thought I would go with a 4 degree advance and bring the peak down to 6400... or 6 degrees and get 6300.

Now... question is... how can I insure I have appropriate PtV clearance. Stock heads... 232/236 .585/.585 113LSA are the specs. I know +4 shouldnt be a problem... but I am wondering about +6 to get that peak down about 300rpm to 6300 then shift at 6500.

What do you guys think???? Should I have enough PtV clearance??? If any more info is needed on the cam... ive got the cam card in front of me.

Thanks

 

I've seen too many post that didn't simply check P-to-V. It sounds like it wouldn't be that much more work for you anyway.

 

You should probably be ok, but when its that close, I'd check it for sure.

 

No big deal for me to pull the crap off again... id rather pull the front apart again than spin a bearing. It's reving to 6800... which I dont like. Too high. Id rather have the power further down the power band. If anything I'll go +4 and rev it to 6600.

But... if +6 would clear... then I wouldnt have a problem with putting it at +6. How do you check PtV clearance???

 

caly is really the only way I know to check P-to-V.....

I have been trying to figure out how a person could check P-to-V with a dial indicator but have yet to figure it out....


I "think" a person could do the following:

- remove the valve spring off of one intake and one exhaust valve and put the retainers back on (to keep the valve from falling into the cylinder)
- put the rockers back on so the valve can "follow" the cam
- as you spin the engine, let the valve "drop" to hit the piston and then pull it back up to "touch" the rocker
- measure the difference and that would be P-to-V but it would take a LONG time and would need a LOT of data (readings) to make it work right

 

Hrm... Ugly.

Wonder if a computer simulation could do it...

I guess I would need how high the piston comes out of the block... the heights of the combustion chambers... valve angles... valve sizes... head gasket thickness... ugh... a bunch of ugly... but it could be done... hrm....

 

Here's how a buddy and I did his...Since .080" is about the minimum safe amount, we stuck a .085" feeler gauge in between the valve tip and the rocker arm and tightened the rocker back down. We then slowly rotated the motor over to check and see if the valve was going to hit. It didnt so we knew that their was at least .085" clearance in there. May be a rough way, but it was better than pulling the heads off.

 

If you are advancing or retarding your cam in any way, I would highly recommend the regualr clay method, it will defintely be worth it in the long run.

This might not help you with your current situation, but when you are installing a cam "straight-up" there is an easier way to check it using the "valve drop" method and a few measuring tools instead of messing with clay, solid lifters and a light valve spring.

Here is what I did with my G5X2 Cam and Absolute Speed 5.3L Stage-2 Heads:
LGM told me that the intake valve lift is .120" when the piston is at TDC. You want a minimum of .080" PTV clearance. So take the valve lift @ TDC (.120") + the min. PTV clearance (.080") and this is the min. amount the valve must drop before contacting the piston (.200").

#1 You need to find out from your cam mfg'r what the intake valve lift is when the piston is at TDC.
#2 Remove the valve spring from the #1 cylinder on your head.
#3 Using an indicator, rotate the crank to place the #1 cylinder to TDC.
#4 Install the head (using an old gasket) and tighten it down (no need to torque it).
#5 Lift up on the #1 intake valve and while holding it up, measure the distance from the tip of the valve stem to the spring seat and record this dimension.
#6 Let the valve drop down until it hits the piston and measure the distance again and record this dimension.

Now for the calculation: (Example)
In my case (using the #'s above) I needed a minimum of .200" valve drop.
Distance from the valve tip to the spring seat with the valve up = 1.850"
Distance from the valve tip to the spring seat with the valve down = 1.650"
Subtracting the 2 dimensions you have exactly .200" of drop and you're fine.

Actually in my case I had only .150" of drop and had to fly-cut my pistons .050" to use my G5X2 cam. I hope this makes sense.

 

Bergerman - I haven't thought this through, but it seems you should be able to check the drop +/- 10 or 15 degress from TDC, looking for the min and just measure it.

How did you notch? Engine out of car?

 

I am going to install my cam straight up in a few days. I should be good with the .588 lift.

 

It's fine as is... I just want to move the powerband down a bit... which I can do by advancing it by 4*.

Quick question... with a cam advance... you move the ICL down 4 degrees... it is currently 113... so it would become 109... correct?

 

I flycut them while the engine was in the car. Took about 2-1/2 hours per side, but I took my time and measured everything twice and then smoothed out all of the edges of my cuts with a dremel tool.

 

Yes, and the exhaust would go to 117CL.