Anyway to calculate vacuum from camshaft overlap?
03-15-2017, 10:07 AM
#1
Anyway to calculate vacuum from camshaft overlap? As the title says... is there any rule of thumb way to do this?
I know rings, compression, engine size, and intake manifold design all play a role in vacuum... but the cam is still the biggest variable in how much vacuum you'll pull.
Is there a way to calculate this?
I know rings, compression, engine size, and intake manifold design all play a role in vacuum... but the cam is still the biggest variable in how much vacuum you'll pull.
Is there a way to calculate this?
03-15-2017, 10:18 PM
#6
Restricted User
It is just math, but some of the factors you need to know to make it easier to calculate can only be gotten from an engine that's already running, at which point you won't need to do the math in the first place.
Cam specs will be biggest factor, idle speed being 2nd, idle airflow being 3rd.
Cam specs will be biggest factor, idle speed being 2nd, idle airflow being 3rd.
03-15-2017, 10:50 PM
#7
I'm curious as to what a 244/256 114 cam would do on a 12:1 CR 408 with TFS 245 heads.
With the 373s I'm installing, I'm setting it so lockup won't happen until after 50mph. So, I'll never cruise below 1800RPM. So I can run almost any reasonable hydraulic cam and with that much engine speed, it should drive fine. The only issue is what will it pull at idle? 10" of vacuum?
Still weighing the Procharger on the current setup vs a big motor. Price is better on the 408...
I don't have to lockup at 50... but with the Kooks drone at 1600-1700rpm, I actually clear it by locking up later. Can't do that right now with the 323s unless I want lockup at 65.
So it does present some differences in what I can do for streetability.
Of course, the easiest issue is to cut off the bullets and put some Magnaflows in there. With the Procharger, I'd probably do that and lockup at 40 with the current setup. That's still 1400rpm. I figure the 244/256 114 would drive fine there too. My 234/242 111 drove fine above 1400 and it had 16 degrees of overlap in a 346 and had 9.5" of vacuum with 11.2:1 CR. I figure the 244/256 114 would drive better than that with the added cubes and compression. But I'm just wondering how much better?
With the 373s I'm installing, I'm setting it so lockup won't happen until after 50mph. So, I'll never cruise below 1800RPM. So I can run almost any reasonable hydraulic cam and with that much engine speed, it should drive fine. The only issue is what will it pull at idle? 10" of vacuum?
Still weighing the Procharger on the current setup vs a big motor. Price is better on the 408...
I don't have to lockup at 50... but with the Kooks drone at 1600-1700rpm, I actually clear it by locking up later. Can't do that right now with the 323s unless I want lockup at 65.
So it does present some differences in what I can do for streetability.
Of course, the easiest issue is to cut off the bullets and put some Magnaflows in there. With the Procharger, I'd probably do that and lockup at 40 with the current setup. That's still 1400rpm. I figure the 244/256 114 would drive fine there too. My 234/242 111 drove fine above 1400 and it had 16 degrees of overlap in a 346 and had 9.5" of vacuum with 11.2:1 CR. I figure the 244/256 114 would drive better than that with the added cubes and compression. But I'm just wondering how much better?
Last edited by JakeFusion; 03-15-2017 at 10:57 PM.
Trending Topics
03-17-2017, 11:21 AM
#11
FormerVendor
iTrader: (1)
Join Date: Nov 2008
Location: Santa Ana, CA. USA
Posts: 2,157
Likes: 0
Received 16 Likes
on
16 Posts
SC Camshaft Design Hi Jake, yes your SC choice may be WELL educated.
I have had good luck with turbocompressor pumps.
I have NRAC design software.
I have installed them the Pantera, over the transaxle, belt drive from a pulley on the flywheel.
I have also used them on boats and sold many ECU-882C's to LS/SBC/BBC Centrifugal users.
I have made Charge Coolers the use the AC system present on the car.
I have installed a SC on a Ford 5.4 supercharged Raptor Truck for Chet H. with that same Freon Intercooler with Charge Air COLDER than Ambient AIR.
I have had Crower Cams grind cams to my specifications.
My suggestion 224/256 .627/.550 @ 124 C/L.
Lance
I have had good luck with turbocompressor pumps.
I have NRAC design software.
I have installed them the Pantera, over the transaxle, belt drive from a pulley on the flywheel.
I have also used them on boats and sold many ECU-882C's to LS/SBC/BBC Centrifugal users.
I have made Charge Coolers the use the AC system present on the car.
I have installed a SC on a Ford 5.4 supercharged Raptor Truck for Chet H. with that same Freon Intercooler with Charge Air COLDER than Ambient AIR.
I have had Crower Cams grind cams to my specifications.
My suggestion 224/256 .627/.550 @ 124 C/L.
Lance
03-19-2017, 10:53 AM
#15
TECH Fanatic
Join Date: Aug 2009
Location: Coast of San Mateo County Between Pacifica & HMB
Posts: 1,815
Received 215 Likes
on
128 Posts
Just re-read other post with flow #s.
My .02, 4-6* Split will hit your goal by
7000 RPM! in a hydraulic with your exhaust
port and system.
You have Way to much overlap for you're
E/I Ratio even with LLSR & 8000 RPM!
My .02, 4-6* Split will hit your goal by
7000 RPM! in a hydraulic with your exhaust
port and system.
You have Way to much overlap for you're
E/I Ratio even with LLSR & 8000 RPM!
03-19-2017, 10:58 AM
#16
11 Second Club
Man. That actually looks pretty good. My 383 with only 5* of overlap makes around 12-14in at idle. 750-800rpm. I wonder if it's the manifold you have on the car. Maybe smaller overall area inside? What rpm is it idling?
03-19-2017, 12:37 PM
#18
NAVYBLUE210 - it's a proven camshaft that makes 600rwhp in an F-body with a 416 with those heads. So that's why I'm considering it.
If I could hit 575 through a locked automatic, it'd be a lot of fun. And then throw 300 shot on top of it.
But of course the current setup with the D1 would do 650-670 on low boost and probably close to 800 with Meth and max boost.
The difference is I'm idling around 14" of vacuum now and the car drives pretty awesome. Going to a larger cam/motor combo - if I'm idling at 8" or so of vacuum - is not something I want to do since it's a street car. Though, the 416+nitrous would outrun the D1SC at the track. By a pretty wide margin.
If I could hit 575 through a locked automatic, it'd be a lot of fun. And then throw 300 shot on top of it.
But of course the current setup with the D1 would do 650-670 on low boost and probably close to 800 with Meth and max boost.
The difference is I'm idling around 14" of vacuum now and the car drives pretty awesome. Going to a larger cam/motor combo - if I'm idling at 8" or so of vacuum - is not something I want to do since it's a street car. Though, the 416+nitrous would outrun the D1SC at the track. By a pretty wide margin.
03-19-2017, 01:46 PM
#19
TECH Fanatic
Join Date: Aug 2009
Location: Coast of San Mateo County Between Pacifica & HMB
Posts: 1,815
Received 215 Likes
on
128 Posts
It may have made 600 RWHP NA but I still stand by my statement,
80% E/I ratio does not need more than +4-6* exhaust split NA,
HR, up to 7000 RPM through 1 7/8" LTs with 3" true duals.
More exhaust split then needed
= Lost/Wasted Torque & Vacuum!
64 Post with 243/251 with Dart 225s, maybe 75% E/I, 517/383".
Jeremy's 416", MAMOFIED AFR 230s, ~ 75% E/I, 243/247,
663 FWHP, 580 RWHP M6 Firebird.
SpeedTigger's 403" LLSR with 12* split designed for
300 shot N2O going bottom 10s NA with +400 lbs!
I would go MMS LS3s. LLSR 245/253, 114+3 .670"/.640",
FAST 102, standard runners on street, shift ~6600-6800,
Mid-Length @ Track shift ~7600-7800 RPM.
9 seconds at the track, mellow 12" vacuum on street.
With the 245s mentioned, LLSR, 247/251, & MAMMOFIED MSD.
80% E/I ratio does not need more than +4-6* exhaust split NA,
HR, up to 7000 RPM through 1 7/8" LTs with 3" true duals.
More exhaust split then needed
= Lost/Wasted Torque & Vacuum!
64 Post with 243/251 with Dart 225s, maybe 75% E/I, 517/383".
Jeremy's 416", MAMOFIED AFR 230s, ~ 75% E/I, 243/247,
663 FWHP, 580 RWHP M6 Firebird.
SpeedTigger's 403" LLSR with 12* split designed for
300 shot N2O going bottom 10s NA with +400 lbs!
I would go MMS LS3s. LLSR 245/253, 114+3 .670"/.640",
FAST 102, standard runners on street, shift ~6600-6800,
Mid-Length @ Track shift ~7600-7800 RPM.
9 seconds at the track, mellow 12" vacuum on street.
With the 245s mentioned, LLSR, 247/251, & MAMMOFIED MSD.
Last edited by NAVYBLUE210; 03-19-2017 at 01:57 PM.
03-19-2017, 06:02 PM
#20
TECH Veteran
If I was go do a hydraulic roller motor with a Fast 102 I see no need for a square port cylinder head for a 402-418ci setup.
Me personally I would do a set of Tooley 245 heads rubbed over with the intake ported to match then a badass setup from nitrous outlet if I was go spray. Maybe even a direct port nitrous setup.
Plenty of cars running 9s and 10s on motor with a Fast intake and hydraulic roller with cathedral heads 205cc-245cc intake runner.
Me personally I would do a set of Tooley 245 heads rubbed over with the intake ported to match then a badass setup from nitrous outlet if I was go spray. Maybe even a direct port nitrous setup.
Plenty of cars running 9s and 10s on motor with a Fast intake and hydraulic roller with cathedral heads 205cc-245cc intake runner.
