Cam for 340/416 Six Pack

[erik70rt]

This weekend I am picking up a 340 to build for my T/A convertible project.  As I am debating what to do with it - keep it a 340 or stoke it to 416 like I did in my Barracuda, I would like to add power brakes to the car like a factory T/A.  The cam I had in the old 416 was a Comp Magnum series 292H and it produced only 5 lbs of vacuum w/ a performer RPM dual plane manifold.. 

I was looking at this cam from MP:  https://www.manciniracing.com/hyd280280dur.html  is this still too much for creating enough vacuum for power brakes?  Should I be looking more at the Lunati Voodoo cams for more vacuum?

Thanks!

[autoxcuda]

Stroke it.

Sounds like an under 500 HP build.

Use a Scat Kit.

So your choice for forged or cast crank kit.

Comp cam would be a XE275HL should give you enough vacuum. I have the 274-Solid version and get 12 in vacuum with a single plane and maybe too big of carb; 750 Demon

Would go dual plane air gap or performer rpm. I'd think it would help vacuum a little

Lot of people like the Lunati cam in that range.

[autoxcuda]

Here a thread from a few weeks ago talking about a range of mid range cams that seem to be in your target wheelhouse

https://forum.e-bodies.org/engine-transmission-and-rear-end/4/planning-for-my-warlock-basic-la-408-stroker/12159/

[Chryco Psycho]

I would stroke it for sure ,
Here is the cam discussion from last week https://forum.e-bodies.org/engine-transmission-and-rear-end/4/which-comp-cam/12229/

[7212Mopar]

I went with Hydroboost. I got 8 inches of vacuum at idle.

[erik70rt]

I want it to appear totally stock, so no boosts or anything.  I like the 416, and I also always build with a forged crank.  I've had good build using Eagle products.  I've heard the Scat brand is hit or miss from my engine builder/machinist friends. 

I'm also definitely running a six pack, and I already have the intake manifold. 

Some other specs to consider  - stock exhaust manifolds and 2 1/4" pipes like original, manual trans, 8 3/4 rear with 3.23s for cruising.  I don't want a tall gear because it won't be track driven.  As far as heads, been looking for the 308 but haven't found any yet.  I have a set of 915s currently that I will get worked to accept the larger valves and maybe get them ported, if needed. 

[Chryco Psycho]

I added the link to the other post from last week in the post above

[Arctoad]

I wish I had the cam specs to mine but I just purchased the car last November. It does have a flat tappet Purple Cam and it runs perfect. Nice Idle and Loves the RPM..if your staying with the stock stroke.Check out my Video in the Gallery.

[73_Cuda_4_Me]

IMHO...

340's are GREAT runners, but definitely NOT torque monsters... If you are looking for a cruiser with some more giddy-up now and then, I'd stick with something with a little less duration...

I put in a comp 274, and have second-guessed that ever since...

I'd say the 268 would be much better in my case... similar to the Voodoo 701, just to keep as much low-end torque as possible with the 3.23's (which I also have)...

[Shane Kelley]

The old what cam question. That's the million dollar question with countless threads and various answers. Somebody like Hugh's Racing engines would be a good place to ask. They are Mopar guys that build and dyno motors so they know what's going work best with various combinations. IMO    I have seen some the dyno numbers and they are quite impressive.

You definitely don't want anything that's choppy and a lot of lope running 3.23's and a manual trans. At low speeds it will jerk and buck. Automatics don't have that issue.

[erik70rt]

Thanks for all of the replies, everyone.  But back to the original questions, will a cam at 284 produce enough vacuum to run power brakes?  Would the Lunati Voodoo produce more vacuum than the similar Mopar cam?

[73_Cuda_4_Me]

My comp cams 274 does not make enough vacuum to correctly handle power brakes at 650 rpm in gear with A/C running (950 in neutral and A/C off) when engine is cold... like idling back out of the driveway right after starting, I have to pedal the gas to rev it up around 1200-1300 to keep brakes from fading...

Once engine is warm, it's okay.

I have 14 inches of vacuum at idle.

But that is a comp cam, not yours, and I don't know enough about the Voodoo version of a 284 to say whether it would have more or not... but I doubt it would be dependable with either without a booster. That is an option you can add if you really want to run that much cam and still have dependable brakes.

[7212Mopar]

I read from Hughes that minimum 14 inches of vacuum required to run power brakes. They make electric vacuum pump that can be hidden so not to change the stock looks. Most cam manufacturers would list the cam's vacuum range. I would pick the cam to make the power you want.

[Shane Kelley]

I have run that exact cam before in a 340 with power brakes. It was in a 73 Road Runner with a manual trans. 90% of the time the power brakes worked fine. Every now and then you would notice something. Still very manageable. Cam has some pretty good lope to it in a 340 and might buck at low speeds with 3.23's. Nice sounding cam. 

[Chryco Psycho]

The Lunati should do a better job even at the same specs , Keeping the centerline in the 112-113 range really helps vacuum