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?

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.

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

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)

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.

Re: How much cam is too much cam for power brakes
 

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.

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..

Re: How much cam is too much cam for power brakes
 

Thanks Guys.

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.

Re: How much cam is too much cam for power brakes
 

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

Shawn