[pastry_chef]

Originally Posted by Jay S

================•
XTQ solid
272* at .020”, 242* @ .050
Loose side of the lash, .021” lash
IVC = 66*
.021” lash removes 12* from .050”= 230*
Intensity out at the valve. 40*

=================.

Max Area solid
269* at .20, 242* @ .050
.021” lash
IVC = 64*
.050 duration at the valve 230*
Intensity. 35*

Decent estimations Jay.

XTQ solid lobe 16259 - 241.8 @ .050

After .021 valve lash (1.5 rocker) the "hyd equiv" @ .050 is 232.3

The valve seat duration at hot lash is 281 - good for 5000 RPM with 4.21 stroke.

--------------------------

MA solid 6137 - 242.6 @ .050

After .021 valve lash (1.5 rocker) the "hyd equiv" @ .050 is 232.7


XTQ is the dark, both on 107 intake centerline. Same rocker - same valve lash.

[Jay S]

Originally Posted by Stan Weiss

Cam selection can be a bag of worms.

What you want is a valve lift curve which meets the engines needs.

Looking at the cam lobe data from a RAIV cam (if my data is correct) and adjusting it to give the same valve lift curve with 1.5:1 rocker ratio I see a problem. The cam lobe would run off of the lifter face. Back when Pontiac designed the RAIV engine / cam there was no option for hydraulic roller lifters. So they went with the 1.65:1 rockers with the lobe design they did. Their only other option to use 1.5:1 rockers would have been been to use a larger diameter lifter.

This is my long around way of saying don't just look at what a cam profile will do for you with only using the stock 1.5:1 rocker arms

Stan

I agree Stan, trying to duplicating the valve curve of what a ra4 did with 1.65s using a 1.5 it would likely run off the lifter. It is one of the reasons that old dinosaur of a cam can still out muscles these fast rate cams with 1.5s.

I think Chrysler took their 426 hemi solid grind in the late 60s and put the hydraulic lash ramps on it just like what was described in a earlier post. It didn’t seem to change the Hemi much. I guess the lash and the hyd shock absorbers cancelled out.

I just did a cam for a RA4 engine with a 4.25” crank. It’s a Melling SPC-8 grind with Rhoads Vpro lifters and 1.65s. Rhoads Vpro super lube lifters are pretty trick. Done a couple of the Vpros now. On the street they are my favorite flat tappet lifter, very versatile lifter.

Thanks Pasty... I did some rounding

[Stan Weiss]

Some of you may find this interesting

The Best Engine Development Tool You've Never Heard Of! Spintron

https://youtu.be/Xzt6np8N3p0?t=187

Stan

[Jay S]

Originally Posted by Stan Weiss

Some of you may find this interesting

The Best Engine Development Tool You've Never Heard Of! Spintron

https://youtu.be/Xzt6np8N3p0?t=187

Stan

That is AWESOME! Real time data logger software they developed and the ability to recreate engine cycles is amazing!

[mgarblik]

Originally Posted by Stan Weiss

Some of you may find this interesting

The Best Engine Development Tool You've Never Heard Of! Spintron

https://youtu.be/Xzt6np8N3p0?t=187

Stan

Good info, Thanks. If I could just win that lottery!