Good call. Had a chat with the shop and he also suggested tightening up the quench so we'll do it for sure. And you're right - gotta check pushrod length anyway.

 

Piston height relative to head's surface is what really affects quench. Milling the head won't change that relationship. You'd either need to deck the block, change piston pin height, or run a thinner gasket. So unless you're decking, consider a thinner gasket. Factory is usually way up around .051" compressed height. You'd need to measure how much above the desk your piston is proud and then do the math to figure out what gasket compressed height gets you in the .038-.043 range.

 

I'm not sure what we are looking at here, but it's obvious that the yellow graph is waaaay better for real life driving than the other two.

 

Got the additional details from Cam Motion this morning on the higher lift version of the cam:

We put a cam card in the box after the cam is measured.
The advertised duration will be 267 intake and 275 exhaust.
The cam timing events at .006" (advertised) are IO 21.5 BTDC, IC 65.5 ABDC, EO 79.5 BBDC, EC 15.5 ATDC.
The events on the card are at .050" so they will be different.

This puts the intensity right at 55, as you estimated, 68Formula.

 

Yellow is stock cam, but I haven't verified in detail that I haven't changed anything on the stock cam sim versus the others. It appears the sacrifice we make to have both a smooth idle and more torque, which more torque requires it to be made at a higher rpm. This as opposed to a "stage 1/2 cam that would have a slightly higher duration but less LSA which would make for more overlap and would bring shaking and roughness below about 900 rpms.

 

Cam Motion only gave me the specs at 0.050 on my sheet, but maybe I need to remind them and ask them again, but I measured it with a dial indicator and a degree wheel anyway and wrote them down. I'll put in the advertised stuff later and see if it changes anything.

What are ya'lll using to calculate intensity? I never knew there was any standard? I know the program I use gives you a unitless "acceleration rating" but unfortunately doesn't provide how it is derived or if it is used anywhere else in the industry.

 

Intensity is a term that Harvey Crane coined. It's just subtracting the 0.050" values from advertised seat to seat timing. The idea to give something to differentiate the valve opening and closing ramp. It's not great, but given the limited information from cam manufacturers it's better than nothing.

1. Not all manufacturers use the same valve lift for seat to seat timing. Most use .006", but Crane uses .004" for example. I think I've seen .005" used once. This will affect it a couple degrees.
2. Doesn't take into account asymmetrical lobes.
3. There's a lot of acceleration/deceleration ramp changes that can take place between the seat and .050." A cam from 2 manufacturers could conceivably have the same values on both seat and .050" timing, and still have a difference in speed at which the valve contacts the seat.

Think of it as a rough guide.

 

I feel so cam ignorant all of a sudden

 

I got my flow numbers from here:

Taken from: https://www.hotrod.com/articles/ccrp...ylinder-heads/

Do the LS3 heads flow the exact same as the L92/L9H? The ones from my link are a good bit lower than the ones on LS1 tech forum. Of course its a loosing battle trying to compare head flow data. Another thing that is missing is I don't know the advertised duration or valve event timing of the stock cam, only the 0.050 numbers anyone have those?

I know the program I have curve fits a cam profile from "specs" you enter. It will also estimate the seat to seat (advertised) numbers by trying to curve fit it, but it seems it outputs a lot more aggressive cam than the true measured advertised numbers.

The graph dosen't change with the new numbers but I think it may change a little with the correct stock cam advertised numbers, I also graphed charge loss which I believe is both charge loss to the exhaust and reversion loss:

 

I was pretty sure the only difference between the L92 and LS3 heads is a lighter valvetrain. Maybe someone else has better info.

Every bench is going to be a little different, the bore size, and the adapter entry plays a factor. Plus we don't know for sure what pressure drop they used (28"H2O? 25"H2O?), as not everyone uses the same standard. I assumed given the healthy numbers, the LS1Tech was @ 28". I've also noticed some of the MotorTrend numbers being a bit more pessimistic on different heads.

The other factor could be interpolation. For late GM heads, there's typically a bigger delta going from .500" lift and .550" versus between .550" and .600" lift. So if you only have the .500" and .600" and the program interpolates linearly, it's going to predict low. I try to find data with the .550" lift point whenever possible to better understand the flow curve.

The spotty information I've found on GM factory cam data has intensities going from as low as 63 to as high as 82 (typically varies intake vs exhaust on the same cam too). Don't have it for this particular engine, but around 66 intake and 65 exhaust seems to be the most common so you could start there.