Camshaft help

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Lugnutz

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I am looking for a little help from the cam guru’s here.

When it comes to aftermarket camshafts, cam lobe over lap and or centerline how much is too much to where it creates issues for power brakes? I would rather not plumb in vacuum canisters or vacuum pumps.

I am planning a 318 engine build for the girlfriend’s car. It’s a 70 Dart, currently a slant 6 and 3 on the tree. She wants a V-8 with a 4-speed, power brakes and it has to have a rumble in the exhaust note at idle. She heard a friend’s 360 start (manual brakes, don’t know what cam) and turned to me with a big smile and said I love that sound.

Years ago, I ran a 318 with 360 (1.88 valves) heads and it had a 270/480 cam in it. I really liked the rumble it had at idle but it was low in vacuum. The car had manual brakes so it wasn’t an issue.

The plan is to build a 318, with 302 heads, 2x4 intake/ 500 carbs, A833, probably 3:23 gears and undecided on tire height at this point.

A mid 13 sec car would be plenty fast for her with a little coolness factor when she lifts the engine hood. Fun factor and drivability are more important than max cubic inches or max horsepower. :burnout:

I am undecided on camshafts at this point and I really like the dual pattern cams with more lift/duration on the exhaust side.

What would the cam experts recommend that would cover the rumble requirement at idle and create enough vacuum for power brakes?
 
I'll be listening in on this. I have an engine that hasn't run yet that has a 280/474 cam and power brakes that I wouldn't mind if they worked ...
 
Instead of how much is too much, give us some particulars and let us make some recommendations.
 
I like the Rhoades lifters. They bleed down at idle and take out about 15° and .025" of lift, but "pump up" by 3500 RPM to give full lift and duration. It's like having an adjustable cam for the low end without sacrificing top end.. It helps tame down a cam some. Read the second article here for more info:

http://www.rhoadslifters.com/Pages/Articles.html


I ran them on a 318 with 9.2 compression, 360 heads, stock 340 cam, with 4 bbl and dual exhaust and pulled 21.5" Hg at idle...


I put a MP .484"/284 cam in my 340 and it idled choppy at 1100 RPM and 11" of Hg. After installing Rhoades lifters, it idled at a more steady 13" Hg at 800 RPM.


Some people don't like them, but I've been using them for over 30 years with great success....
 
Put a cam in it that can run power brakes (mild 318 - I'd stay under 220° @ .050 duration). Idle it down a little and run louder mufflers. She'll love the noise and the fact you did it. The sound is nothing to concern yourself with - but tell her when she smiles that you knew it was critical...lol
 
Lugnutz said:
When it comes to aftermarket camshafts, cam lobe over lap and or centerline how much is too much to where it creates issues for power brakes?

This isn't a black and white one liner answer

it has to have a rumble in the exhaust note at idle.

rough idles, power brakes and Streetability aren't necessarily synonymous words

A mid 13 sec car would be plenty fast

again, more than one way to sin that cat

I am undecided on camshafts at this point and I really like the dual pattern cams with more lift/duration on the exhaust side.

why? Is your exhaust port deficient?

What would the cam experts recommend that would cover the rumble requirement at idle and create enough vacuum for power brakes?
Click to expand...

LSA and duration can have the same effect on idle and one can to some degree counter act eachother. Look at the comp cams thumpr series. They have mild to moderate duratons cut on really small LSA's. They idle like top fuel dragsters and don't work well with power brakes in my experience.

Tell us more about the combo as a whole like rusty said. then look at some actual cam recommendations.
 
Not sure what is meant by more information on the package as a whole or more particulars. I thought I laid out everything that worked with it as a combination other than I will probably use 340 exhaust manifolds, 2.5” dual exhaust with a more quiet than loud muffler and tail pipes.

Again, just a basic flat top 318 with 302 heads, 2x4 intake/500 carbs, A833, probably 3:23 gears and undecided on tire height. She wants to be able to cruise it to see her mom couple hours away on occasion over the summers and drive the sh*t outta it when not.

It’s going into a 70 Dart and will have power brakes so the engine has to make enough vacuum to operate them safely and as advertised.

I understand they don’t necessarily work with each other very well. More from one and you lose it from the other. I was hoping in the four decades that these things have been around that somebody would have stumbled across a camshaft that had a lil rumble to it and made enough vacuum to operate power brakes.

What that requirement is from aftermarket camshafts, I don’t know. And that’s why I am here asking for help from the experts. :cheers:
 
With 2 fours on a 318, you are gonna need some gears and progressive linkage. I would use 3.91s. That said, check out the Comp 275DEH. In any other instance, I would say it;s too big, but I think it will work well here with the right converter and 3.91 gears. As long as she drives with her big toe on the gas pedal, it will probably cruise along at a respectable RPM up to about 60.
 
I run a Comp Cam 262 xe , power brakes work well , 15 vaccum seems to be okay , not sure about going any lower with power brakes . Best time 12.9 but lacking traction big time .
 
RustyRatRod said:
With 2 fours on a 318, you are gonna need some gears and progressive linkage. I would use 3.91s. That said,l check out the Comp 275DEH. In any other instance, I would say it;s too big, but I think it will work well here with the right converter and 3.91 gears. As long as she drives with her big toe on the gas pedal, it will probably cruise along at a respectable RPM up to about 60.
Click to expand...

True , but 3:91 gears are going to be hard on those few hour cruises , it's a 4 speed so 2x4's will work , but is it really needed ?
 
I would try a comp xe 268 or the 275 deh with Rhoades lifters. The lifters will help the low end and enable you to run the 3.23 gears and power brakes...

Or the Crane H-272-2 or Z-268-2 with Rhoades lifters...
 
Lugnutz said:
Years ago, I ran a 318 with 360 (1.88 valves) heads and it had a 270/480 cam in it. I really liked the rumble it had at idle but it was low in vacuum. The car had manual brakes so it wasn’t an issue.
Click to expand...


If you had stock 318 pistons in there, that could be your problem. Stock 318 pistons with 318 heads will end up about 7.6:1 compression. Read through this thread here:

http://www.forabodiesonly.com/mopar/showthread.php?t=278215


If you throw in a set of 10.5 compression pistons for a 318 with the 340/360 heads, you should end up around 9.2 compression.

The increase in compression will also help increase intake vacuum.


I ran a 318 with 10.5 pistons and 360 heads with a stock 340 cam and Rhoades lifters and got 22" vacuum at idle and could part throttle accelerate above 10" vacuum to keep out of the power valve and got 17.75 MPG on the highway also....

Rhoades lifters with a good cam in the 270° range should work well with the power brakes...
 
I ran the 292/509 cam in my [email protected],and my power brakes worked fine. Thing is, as soon as the vacuum goes up enough to evacuate the chamber, the check valve stores it in there, and you are good for at least one stop even with the engine shut off. That cam pulled 11 inches at 850ish. A couple of blips and away we go. With a manual trans, I am blipping the throttle to downshift anyway, so that keeps the vacuum up, ,and no problem.I think I measured that cam at around 241? @050, installed.
My current cam is a Hughes 230*@050,fast-rate.I have power assist right at start up.
The booster is off a 73Dart.
 
MP advertises the 508 at 248.5* @ .050 but I think that's a little big.
 
How about this to blow your mind: have it both ways. Throw the power brakes crap in the garbage; they don't need to be on an A-body. All they do is make the pedal have more travel and more spongy. Plus, you get all that space!
 
Thanks for the suggestions so far. I will look at the profiles when I get home tonight.

Also, somebody mentioned a converter with the right stall and the heads with the standard pistons.

Keep in mind it's a 4 gear car and the 302 heads are the swirl port closed chambers. I will be working with the machine shop and ideally I would like to get the compression in the 9.0:1 area.

The 2x4's are not needed. It's really just a cool factor for her when she opens the hood. I have access to one of the old Edelbrock D series manifolds and supposedly it hits the wall at 5k rpm, and that's totally fine.
 
Well,ummm; putting a 6500rpm cam into a 5000 rpm engine, would be quite a sacrifice just for the sound.The big cam will just kill off-the-line torque, and it will never get into the power zone.
If you're after the sound, a custom cam might be the answer, coupled with a careful co-ordination of Dcr/Scr/ICA and LDA.
Someone mentioned a 222*cam.
I had a 223/230 Hughes fast rate cam. It made torque right out of the gate, a very strong midrange, and with the aluminum Eddies and good springs, it rev'd to the moon. The idle was tame compared to the 292, but still had a bit of lope, and with 10.7cr there was quite a bit of energy left in the exhaust.It burned 87E10,easy. Full timing at 2800. There was plenty of vacuum,and idle could be set right down to exploit the rumpity-rump.
I loved the torque of that cam.With a stick car, I ran nearly every gear from 2.76 to 3.91s with that cam.With a 3.09low tranny,it pulled 3.23s easy, with 28s. If your 4-spd has the standard 2.66low, your teener may struggle with 3.23s. Better would be 3.73s, or at least 3.55s and possibly shorter tires.275/50-15s come in at 25.8 and should survive.
I should also mention that my 360 with that 223* cam pulled the 3.09-o/d box just fine. I just had to rev it a little higher before hitting second.If you use that box, you will want to run 3.55s at a minimum, to be able to pull the od, cuz 65mph will be near 2200rpm. I tuned that cam to hit 32mpgUS, using a Gear Vendor behind it ( Final drive was 2.23). Cruise was about 1900rpm.
The more I think about it, the more I think you/she would like a combo like that. It kinda depends on what tranny and gears that you may already have.If you already have the 3.23s, I would try them, for sure.
So to recap; a 223*cam with a matching Dcr,the other parts you mentioned, a 3.55 gear, and either 3.09 box (direct forth, or O/D).Tires could be short with either box.
Running the Dcr up, will put some energy into the exhaust, which sounds great.
I recommend headers for best results, or at the minimum, hi-flow manifolds, such as Trebleg sells. The headers and crossover separate the pulses, and that contributes to the, end-of-tailpipe sound. The thicker headers are much quieter than those two-season wonders that you buy on sale.
 
PoisonDart74 said:
How about this to blow your mind: have it both ways. Throw the power brakes crap in the garbage; they don't need to be on an A-body. All they do is make the pedal have more travel and more spongy. Plus, you get all that space!
Click to expand...

Call RMS and ask him about "poor man's power brakes".

Essentially a 7/8" piston in a new style master cylinder. Gives you power brake feel and stopping power with manual brakes.

To me you have a poorly matched combo. twin carbs, tall gear, poorly flowing intake. I'm not seeing this combo work, especially with a girl driving. Not knocking girls or anything. My wife drives my car and my car does everything right, the way it should but if I built one for her I'd build it milder and simpler.

The cam I'd recommend for you. And it's a split pattern like you said you like is the crane cams 693801
 
This Comp was the very first performance cam I ever bought. It went into a 340, then in a 318. Both had a little bit of a note at idle, but enough vacuum for power brakes:
20-212-2 268H High Energy
 
moper said:
This Comp was the very first performance cam I ever bought. It went into a 340, then in a 318. Both had a little bit of a note at idle, but enough vacuum for power brakes:
20-212-2 268H High Energy
Click to expand...


Funny, I just degreed one of those exact cams yesterday.

It came out to:

.430"/.430" lift at valve

.304"/.303" at lobe

228.5°/226° duration @ .050"

277.5°/269.5 @ .001"
 
I had a chance to look at the cams that were mentioned and I did a bunch of searching for what the power brakes boosters needed for vacuum to operate correctly.

Everything I found showed 16 to 20 inches of vacuum was needed to operate the brake booster correctly and camshaft durations beyond 215 degrees @ .050 is where the vacuum starts to decrease.

I also found a little information that broke down the duration by groups for anybody searching in the future.

• Class I (200° - 215°)
Good idle quality. Low rpm torque and mid range performance.Will work with
stock or slightly modified engine. Manual or auto transmission. Good vacuum.

• Class II (215° - 230°)
Fair idle quality. Good low to mid range torque and horsepower. Will work with
stock or modified engine. For use with manual or automatic transmission with mild stall converter. Lower vacuum than stock.

• Class III (230° - 245°)
Rough idle quality. Good mid to high rpm torque and horsepower. For use with manual transmission or high stall automatic. Requires improved induction, exhaust system, and ignition system. Good street/strip cam, but has low vacuum.

• Class IV (245° - UP)
Rough idle quality. Good high rpm torque and horsepower. For serious racing.
Need proper selection of rear axle ratio and improvements in carburetion and exhaust systems. For use with manual transmission or automatic with very high
stall converter. Will not have enough vacuum for power accessories.
 
Hm. I'm in Class III with my Purple Shaft 280* cam, 238* @.050. Looks like running manual brakes to start with is a good idea.
 
Ditch the 2x4 idea. Run an edelbrock performer, 600cfm carb. I would runa small Lunati 262* Voodoo cam or one of the Summit Racing 216*/.454" cam kits or smaller. Run headers/duals and flowmaster mufflers and it will sound really good and perform well.
 
I'd call Hughes Engines and get their opinion on a cam.
 
Bear in mind that the vacuum numbers recommended is an idle vacuum number.
Also bear in mind that almost any streetablecam will pull those numbers sooner or later, as the revs climb. Even a Class IV will pull around 22 inches at 2200 in 4th gear.
I think all this worry about big cams and power brakes is almost unbearable. Like I said I drove that 292/509 for thousands of miles with no PB stopping issues. I certainly would not give it a thought, nor sacrifice performance for PB.
Now I realize your GF may be idling it around, but unless it never gets off the idle stop, and/or your checkvalve quits, it's not likely to be an issue, so long as the Dcr is up, and the ringseal is good.I would fugetabowdit.
 
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