I think 115 rings a bell
What that wide LSA does is get rid of overlap.But this steals time from the compression and power events to do so. Thus you end up with a smooth running engine that sucks gas, and needs extra compression to not fall flat on take-off.
Check these specs out for the same 318 cam, with only the LSA changed, and measured at split overlap;
I will use a 248/256 cams with LSAs of 115,110 and 107
First the 248/256/115
Intake: 11 before to 67 after,exhaust: 70 before to 11 after, overlap 22
This has compression of just 113, and extraction of 115
Next the 248/256/110
Intake: 16 before to 52 after, exhaust: 60 before to 16 after, overlap 32
This has compression of 128, and extraction of 120
Next, the 248/256/107
Intake: 19 before to 49 after, exhaust: 57 before to 19 after. overlap 38
This has compression of 131, and extraction of 123
How to apply them;
A) The 115
would seem to be a race cam requiring plenty of compression to make up for the lack of TIME to build it naturally. But the total lack of overlap precludes it's racing aspirations. Here's what it looks like installed
Static compression ratio of 9.2:1.
Effective stroke is 2.50 inches.
Your dynamic compression ratio is 7.18:1 .
Your dynamic cranking pressure is
138.80 PSI.
V/P (Volume to Pressure Index) is 100 ....................................
100 ..
B) The 110
Static compression ratio of 9.2:1.
Effective stroke is 2.82 inches.
Your dynamic compression ratio is 7.98:1 .
Your dynamic cranking pressure is
159.36 PSI.
V/P (Volume to Pressure Index) is 130 .....................................
130 ..
C) The 107
Static compression ratio of 9.2:1.
Effective stroke is 2.87 inches.
Your dynamic compression ratio is 8.10:1 .
Your dynamic cranking pressure is
162.48 PSI.
V/P (Volume to Pressure Index) is 134 ......................................
134 ..
Where do you draw the line?
>Well I know that I can make pretty good fuel mileage with just 115* of extraction
so 123 might be more than a guy really needs.
>But you can clearly see the cylinder pressure progression, and 162 is about the max for pump gas and may need premium fuel when working hard. But that 134VP is hard to ignore.
>And I see nothing desirable in the 115 cam, unless your engine idles all day.
>So knowing this now, lets take the 110 and advance it 4 degrees to in at 106.
This will increase the compression event from 128 to
130, and decrease the extraction event from 120 to
118, and
D) Static compression ratio of 9.2:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is
161.70 PSI.
V/P (Volume to Pressure Index) is 133 .....................................
133 ..
Now you have a decent engine that burns regular gas on the hiway(Dcr of 8.07), can be tuned to get great mpgs(118* extraction), makes mega-torque (133VP), and has great passing power(162psi).
What you don't have is power after 4800/5200ish. It will still rev there with the right parts, it's just not gonna be pulling much anymore.
Now take a look at combo A with a VP of 100, and compare that to combo D with 34% more.
Read about VP here;
V/P Index Calculation
Recall that this is the same basic cam;a 248/256
Food for thought
