Cams choice, Low CR vs VE%

-
go to .275 (no use using .300 on a .305 cam) he is 50% bigger than the MP 260 which is about 268 in .006 degrees
Whoa! 50%! On a FTH, that would be amazing. I have seen a motorcycle cam like that once for a CB350,lol, The noses were kindof squared off. I still have that cam somewhere.
 
He's talking about today's fuels.
 
Must be impossible because you can't do it right?
 
Must be impossible because you can't do it right?

I didn't say it was impossible. I said I'd have to see it. Aren't there some things in life you have to see to believe? No need to be an *** about it.
 
I had a 360 with 205 PSI cranking pressure that would run on 93 pump gas. It protested if I really poured the coals to it without a few gallons of 114. I'm sure I could have tuned it better but never took the time.
 
I recently measured the 2.4liter in my 2014 Chevy Orlando. She's a DI-VVT and posted 220psi in every hole. I give her nothing but 87E10, and she never complains. But she has a 6 speed and a pretty low starter gear.
The VVT comes in at 4500, and then hang the heck on. Ok, that's a bit of an exaggeration ..... but she is rated at 174rwhp at 6700 .......... and I think she weighs about 3650.
She rarely gets into the VVT ; just when passing at hiway speeds. Otherwise that 6 speed is always in the right gear, it's simply amazing.
And on the hiway at 65mph, point to point, I have measured 32mpgUSg. At 3900lbs loaded, IMO, that's pretty darn good for a 2.4 humming along at just over 2000 rpm. Ima guessing the 220psi has something to do with that,lol.
Now remember; at one time, I got the same fuel economy in my 68 Barracuda (also 3650 unloaded) , with a 367 and geared 65=1600rpm, and my pressure was just over 180psi. IMO the aero on my Barracuda has got to be far far better than on the Orlando.
If/when this current 367 gets tired I will be upping the pressure and lowering the flow.

280px-2012_Chevrolet_Orlando_LTZ_VCDi_Automatic_2.0_Front.jpg
images?q=tbn%3AANd9GcQkIvuLUeIzI_GX_gcqMom-cZNoKBq_oLw58A&usqp=CAU.jpg


from WIKI:
The LAF is a direct injected 2.4 L. It uses technology based on GM's other four-cylinder direct injection applications, but with unique features designed for its specific application. This includes an 11.2:1 compression ratio that helps build power, slightly dished pistons that increase combustion efficiency and injectors with an application-specific flow rate.
 
Last edited:
So I have actually bought a camshaft from Jones a few months ago, to replace my Hughes Whiplash roller camshaft (208/214) in my 9.6:1 CR 318.

What surprised me, is that he actually recommended me a higher duration camshaft.
HR68340-69340-110
216/220 @.050"
.340"/.340" Lobe Lift
110 LSA

I was expecting a lower duration camshaft for my "low" compression 318.
The .050" duration is a little deceiving, because the seat duration is a lot smaller then most 216/[email protected]" cams. The seat duration is only 264/268.

This will be interesting for sure.
 
Well, looking at DCR, I sure expected a lower duration cam.
 
Did you perhaps check the Dcr using the Ica @.050 numbers? That will inflate the number impossibly high.
You have to use the advertised numbers ........ and your intake valve is NOT closed at even that number. So your calculated Dcr is always higher than your real-world Dcr.
Your Dcr can NEVER be higher than your Scr, and is usually near 1.5 or more points lower, with a typical street cam.
At 9.6 Scr, I would be looking for a Dcr near or less than 8.1, so if my calculator spit out a number too far from that, I would call bs and start over.


here is an LA318+.020 example;
Static compression ratio of 9.6:1.
Ica of 59*/600 ft elevation
Effective stroke is 2.68 inches.
Your dynamic compression ratio is....................... 7.95:1 .
Your dynamic cranking pressure is 159.01 PSI.
V/P (Volume to Pressure Index) is 124

I grossed up your 216*@.050 cam to 262 advertised. and installed it at 108 to come up with that Ica of 59*; I have no idea if that is accurate; it's just an example.
Also I guessed at 600ft elevation.

Notice that 7.95 is ~98% of my estimated 8.1.

Wallace Racing: Dynamic Compression Ratio Calculator

If you had used the .050 numbers, you might have got;
Static compression ratio of 9.6:1.
Ica of 36* @ sealevel
Effective stroke is 3.08 inches.
Your dynamic compression ratio is ....................... 8.99:1 .
Your dynamic cranking pressure is 190.34 PSI.
V/P (Volume to Pressure Index) is 171
And that would likely be impossible to drive if true. Thankfully it is not correct.
 
Last edited:
Jones recommended a hft 264 lobe for a 9.7 383 over at FBB0 it does not have the lift of the HR version where .904 HFT do. 383 owner is going with Vooeoo or Crower 267HDP (stock rockers)
you can directly compare Jones hft hr solid roller and sft as he uses lash + .006 for everything (lash = 0 for the hyd cams)
I like his 256 mopar .305 lobe lift hft
grind for 9:1 and lower motors
AJ your post 76 the 260 mopar @ about .008 is about 268 in .006 terms typical of its era it is not a high lift cam but for stock heads
it wears very well with a big fat nose- but not compare well in the .300 lobe .450 valve lift area
 
Jones recommended a hft 264 lobe for a 9.7 383 over at FBB0
you can directly compare Jones hft hr solid roller and sft as he uses lash + .006 for everything (lash = 0 for the hyd cams)
I like his 256 mopar .305 lobe lift hft
grind for 9:1 and lower motors
AJ your post 76 the 260 mopar @ about .008 is about 268 in .006 terms typical of its era it is not a high lift cam but for stock heads
it wears very well with a big fat nose- but not compare well in the .300 lobe .450 valve lift area
Can you remember the spring specs for that cam?
 
273 post 73
.200 data is redily available in most lobe catalogs
insist on it and seat timing at .004 or .oo6
.050 is pretty worthless given the wide variance in lobes say factory to Howard or Engle's or Crane's race lobes
 
Are you serious? But 240 is is hard to believe..........

I just said I'd have to see it, that's all. Why is that so difficult for you? Geez man, don't worry yourself so much. lol
 
I had a 360 with 205 PSI cranking pressure that would run on 93 pump gas. It protested if I really poured the coals to it without a few gallons of 114. I'm sure I could have tuned it better but never took the time.
i beleive that , had a 340 with 195 psi ran okay on 93 unles it was lugging up a hill in 2nd gear a few gallons of 112 sue woke it up . but 240 **** that is high did they use methanol injection to run on pump gas ?
 
i beleive that , had a 340 with 195 psi ran okay on 93 unles it was lugging up a hill in 2nd gear a few gallons of 112 sue woke it up . but 240 **** that is high did they use methanol injection to run on pump gas ?

I'm sure it's possible. I just want to see it.
 
i beleive that , had a 340 with 195 psi ran okay on 93 unles it was lugging up a hill in 2nd gear a few gallons of 112 sue woke it up . but 240 **** that is high did they use methanol injection to run on pump gas ?

Read the link in post 21 on page 1.
 
-
Back
Top