How much cam is too much cam for power brakes - The 1947 - Present Chevrolet & GMC Truck Message Board Network

djracer · 04-27-2010, 09:12 AM

I'm talking about a 454 application this time but when is a cam too big to run power brakes without a vacuum canister?

Super73 · 04-27-2010, 02:11 PM

Not sure if this will help you or not but I was running a cam with 243/250 duration at .050 on a 108 intake center and a 111 lsa. I was able to run power brakes. But I only have 347cis..

I think the thing you need to look at is how much overlap the cam has and where the valve events are against static compression (leading to DCR). There is a lot that determines vacum at idle/cruise.

I'm assuming you will be running a hyd cam for maintenece reasons? Flat or roller? The lobe profiles will differ..

If you give me some more details I can put in it performance trends and give you an idea of vacum at idle. It may not be spot on, but might help a little.

djracer · 04-27-2010, 02:20 PM

Its a lunati 60212.

Hydraulic roller, lopey idle. High performance street cam. Likes upgraded intake, carburetor and exhaust system. Needs 2800 RPM or better stall speed converter, 9.75:1 compression ratio and 3.55-3.73 rear gears.

Advertised Duration (Int/Exh): 282/290
Duration @ .050 (Int/Exh): 231/239
Gross Valve Lift (Int/Exh): .600/.600
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2200-5800
Includes: Cam Only

Part Number: 60212

ripdog28 · 04-27-2010, 02:21 PM

Not sure but overlap and duration determine it. Roller cams, esp hyd i believe can take more then FT. not sure when you can not, all depends on the eng combo (Heads, carb)

djracer · 04-27-2010, 02:32 PM

Heads are 781 oval ports with 2.19 1.88 valves. It should be around 10 to 1 comp.

swb85 · 04-27-2010, 02:47 PM

Quote:

Originally Posted by djracer

Its a lunati 60212.

Hydraulic roller, lopey idle. High performance street cam. Likes upgraded intake, carburetor and exhaust system. Needs 2800 RPM or better stall speed converter, 9.75:1 compression ratio and 3.55-3.73 rear gears.

Advertised Duration (Int/Exh): 282/290
Duration @ .050 (Int/Exh): 231/239
Gross Valve Lift (Int/Exh): .600/.600
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2200-5800
Includes: Cam Only

Part Number: 60212

You won't have any problems with that cam in a 454. I run a hyd 247/255 @ .050 in a 370ci and I have no problem with power brakes.

Super73 · 04-27-2010, 08:16 PM

Yeah, that cam is rather small for a 454ci in regards to idle vacum issues. You have 66* of overlap at .006 and 15* at .050..

In my 347 I have 24.5* at .050 and close to the same 66* you have at .006 with 107ci less..

djracer · 04-27-2010, 08:38 PM

Thanks Guys.

Marv D · 04-28-2010, 12:25 AM

I agree with ripdog here Kevin, but keep in mind I don't know jack about the bigblocks and what is too much. That exhaust valve closing is going to be key in if it makes enough vacuum for PB or not. Could always advance the cam a little to get that exhaust closed a tad earlier and start building vacuum earlier too. Should help if it were marginal.

shawnt · 04-28-2010, 12:34 PM

Good to go DJ. And that's a very good cam choice

Shawn

04-27-2010, 09:12 AM	#1
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,892	How much cam is too much cam for power brakes I'm talking about a 454 application this time but when is a cam too big to run power brakes without a vacuum canister? __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

04-27-2010, 02:11 PM	#2
Super73 Registered User Join Date: Nov 2007 Location: Bay Area, Ca Posts: 2,841	Re: How much cam is too much cam for power brakes Not sure if this will help you or not but I was running a cam with 243/250 duration at .050 on a 108 intake center and a 111 lsa. I was able to run power brakes. But I only have 347cis.. I think the thing you need to look at is how much overlap the cam has and where the valve events are against static compression (leading to DCR). There is a lot that determines vacum at idle/cruise. I'm assuming you will be running a hyd cam for maintenece reasons? Flat or roller? The lobe profiles will differ.. If you give me some more details I can put in it performance trends and give you an idea of vacum at idle. It may not be spot on, but might help a little. __________________ ------Motor---------------Bottle 60'---1.53---------------1.41 1/8---6.58 @ 105.92----5.87 @ 118.41 1/4---10.38 @ 126.97----9.24 @ 142.49 Last edited by Super73; 04-27-2010 at 02:13 PM.

04-27-2010, 02:20 PM	#3
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,892	Re: How much cam is too much cam for power brakes Its a lunati 60212. Hydraulic roller, lopey idle. High performance street cam. Likes upgraded intake, carburetor and exhaust system. Needs 2800 RPM or better stall speed converter, 9.75:1 compression ratio and 3.55-3.73 rear gears. Advertised Duration (Int/Exh): 282/290 Duration @ .050 (Int/Exh): 231/239 Gross Valve Lift (Int/Exh): .600/.600 LSA/ICL: 110/106 Valve Lash (Int/Exh): Hyd/Hyd RPM Range: 2200-5800 Includes: Cam Only Part Number: 60212 __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

04-27-2010, 02:21 PM	#4
ripdog28 Registered User Join Date: Apr 2008 Location: Imperial Beach, CA Posts: 1,040	Re: How much cam is too much cam for power brakes Not sure but overlap and duration determine it. Roller cams, esp hyd i believe can take more then FT. not sure when you can not, all depends on the eng combo (Heads, carb) __________________ 69 c-10 BBC 462ci, forged crank, H-beam rods, 10.5-1 KB forged pistons, Dart Iron Eagle 308cc, Straub Cam, Comp Cams chrome moly full rollers, Weiand Team G, Prosystems 950, TH400/3500 Dalenzie stall, Currie 9+ Detroit Locker w/31spline axles.3.5/6in drop. My Build.

04-27-2010, 02:32 PM	#5
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,892	Re: How much cam is too much cam for power brakes Heads are 781 oval ports with 2.19 1.88 valves. It should be around 10 to 1 comp. __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

04-27-2010, 08:16 PM	#7
Super73 Registered User Join Date: Nov 2007 Location: Bay Area, Ca Posts: 2,841	Re: How much cam is too much cam for power brakes Yeah, that cam is rather small for a 454ci in regards to idle vacum issues. You have 66* of overlap at .006 and 15* at .050.. In my 347 I have 24.5* at .050 and close to the same 66* you have at .006 with 107ci less.. __________________ ------Motor---------------Bottle 60'---1.53---------------1.41 1/8---6.58 @ 105.92----5.87 @ 118.41 1/4---10.38 @ 126.97----9.24 @ 142.49

04-27-2010, 08:38 PM	#8
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,892	Re: How much cam is too much cam for power brakes Thanks Guys. __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

04-28-2010, 12:25 AM	#9
Marv D Registered Truck Offender Join Date: May 2008 Location: hells training ground (aka Ariz) Posts: 3,118	Re: How much cam is too much cam for power brakes I agree with ripdog here Kevin, but keep in mind I don't know jack about the bigblocks and what is too much. That exhaust valve closing is going to be key in if it makes enough vacuum for PB or not. Could always advance the cam a little to get that exhaust closed a tad earlier and start building vacuum earlier too. Should help if it were marginal. __________________ Still playin with trucks, even at my age! When you're dead, it's only a problem for the people around you, because you don't know you're dead. .....It's kinda the same when your STUPID. I just did my taxes and reviewed my SS statement. Thanks to the current administration it looks like I will only have to work till noon on the day of my funeral.

04-28-2010, 12:34 PM	#10
shawnt Registered User Join Date: Sep 2008 Location: sulphur springs texas Posts: 141	Re: How much cam is too much cam for power brakes Good to go DJ. And that's a very good cam choice Shawn __________________ Shawn 85 SWB 7.39 @ 93 Best so far with 0 tuning Lesson in life: Never fry bacon naked!



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