Author Topic: Cam and stock power brakes  (Read 8611 times)

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Cyclone Joe

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Cam and stock power brakes
« on: July 05, 2016, 08:09:40 PM »
So I've been kicking around a couple of cam selections for the 390, but am concerned that too big of a cam will negate the factory vacuum assisted power brakes.  I dont know enough about cams to balance out all the different variables and end up with enough vacuum to operate the brakes. 

Car is a 1967 Cyclone convertible, factory Kelsey Hayes power disc's up front.  It appears the factory GT cam was borderline too big (possibly) to warrant a vacuum reservoir (at least thats all we could figure out what the rectangular container was on the drivers side of the engine bay)?

I bought the 2.20/1.65 valved BBM heads, and have been looking at a couple of Bullet hydraulic roller cams.  My concern is that the cam wont allow for enough engine vacuum to operate the power brakes. 

From Bullet's website I was looking at:
HR297/3334:
Cam details: 297 adv duration, 240@.050, 154@.200, lift is .587"

What are your thoughts, is this just way too much cam to end up with any vacuum for the brakes?

Joe


fryedaddy

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Re: Cam and stock power brakes
« Reply #1 on: July 05, 2016, 08:26:22 PM »
im no engine builder but i think those 2.20 intake valves are too big for a 390s bore.caution!
1966 comet caliente 428 4 speed owned since 1983                                                 1973 f250 ranger xlt 360 4 speed papaw bought new

cjshaker

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Re: Cam and stock power brakes
« Reply #2 on: July 05, 2016, 10:08:16 PM »
I think it depends on how you'll use the car. My 260/264 cam allows my power brakes to work fine with only about 5" of vacuum, BUT I don't putt along in parades and slow traffic. I don't think you're cam choice would be much different than my situation since you would have a limited amount of vacuum at idle, so I'll compare yours to mine...

When you're slowing down, vacuum is high, so you'll have all the vacuum you need to operate the system. If your system is good and sealed tight, meaning no vacuum leaks in the booster, you'll still get a couple of uses before the vacuum is gone, even at a stand still. If you have any leaks in the diaphragm or the seal between the master and booster isn't good, it'll probably only last once, if that, depending on how bad the leak is and how long you sit idle.

Since I never use my heater system (I don't drive the car in the winter) I used the vacuum reservoir for the plenum servos, which I think is what you were describing (not sure if they were using vacuum servos in '67 or not), and plumbed it into the brake system. It probably doesn't add much, but I'm sure it helps a little. At a stand still I can pump/use my brakes 3-4 times before the boost is gone. My system is pretty tight with no leaks. I can pop the car into neutral after a 1/4 mile run and still have plenty of power brakes to stop the car from 112 mph. On a manual car, it's easier to build vacuum by letting the engine slow the car down between stop lights, if that's what you deal with. In a small town like I live in, it's not an issue at all. If you live in a city and encounter stop and go traffic, it may be.

Doug Smith


'69 R-code Mach 1, 427 MR, 2x4, Jerico, 4.30 Locker
'70 F-350 390
'55 Ford Customline 2dr
'37 Ford Coupe

Cyclone Joe

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Re: Cam and stock power brakes
« Reply #3 on: July 05, 2016, 11:27:03 PM »
Thank you Doug for the comparison.  I do live where there is a lot of stop-lights (Sacramento, California area) so I probably need to give some additional consideration or some manner to hide an electric system 'elegantly'.  Given there was only 400 big-block GT Cyclone converts made in 1967, I'm trying to keep it as original looking as possible.  The system isn't 'tight' right now since its all in pieces currently, but the plan is to make it so upon reassembly.

66FAIRLANE

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Re: Cam and stock power brakes
« Reply #4 on: July 08, 2016, 12:42:08 AM »
I have a 240@.050, 110sep in my 390. I get about 7" at idle. Brakes are ordinary until you get some vacuum from trailing throttle. I installed a reservoir so you get more than one push. You also get used to driving as to 'ration' the vacuum.

FElony

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Re: Cam and stock power brakes
« Reply #5 on: July 08, 2016, 02:21:07 PM »
Thank you Doug for the comparison.  I do live where there is a lot of stop-lights (Sacramento, California area) so I probably need to give some additional consideration or some manner to hide an electric system 'elegantly'.  Given there was only 400 big-block GT Cyclone converts made in 1967, I'm trying to keep it as original looking as possible.  The system isn't 'tight' right now since its all in pieces currently, but the plan is to make it so upon reassembly.

Before I "tamed down" my '69 XR7, it had a solid-lifter Crane CompuCam in it with about .575/.590 lift. It had a fairly aggressive idle. And dual quads. And, it stopped on a dime, all the time, every time. I was amazed about that for a bit, but then it dawned on me that Cougars have a vacuum tank to operate the headlights, so maybe...?

Do you have a Marti for your car? I have the same model, but with a factory stick. Years ago some Net info yielded 27 made for the manual trans cars, but I have yet to confirm that with a Marti.

I assume you are not going to choke off the BBM heads with correct #'s iron intake and exhaust manifolds, so I'm thinking the "stock appearing" idea is already a moot point. Make it work to your satisfaction and safety.

Cyclone Joe

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Re: Cam and stock power brakes
« Reply #6 on: July 08, 2016, 07:09:14 PM »
Thank you Andy and FElony for your feedback.  It sounds like its worth it to go with it, so thanks to everyone who chimed in.

FElony,
I dont have a Marti report for it just yet.  Its a 1967,390FE/C-6 convertible, stock glass hood, PS/Power Disc brakes up front.  3.25 rear open 9", medium metallic blue exterior, blue vinyl/cloth interior.  Once I do have it, I'll let you know what it shows though. 

As I stated, I want to try to keep it as original as possible, but there are some items that are simply unacceptable.  There are some things that just wont do, one of which is the exhaust logs, another is the intake, and the Autolite 4300 that sat upon it.  But the body color, striping, interior will be original, although the wheels may be bumped to 15's, if only to get a reasonable tire anymore.
« Last Edit: July 08, 2016, 11:19:43 PM by Cyclone Joe »

FElony

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Re: Cam and stock power brakes
« Reply #7 on: July 09, 2016, 02:57:44 PM »
As I stated, I want to try to keep it as original as possible, but there are some items that are simply unacceptable.  There are some things that just wont do, one of which is the exhaust logs, another is the intake, and the Autolite 4300 that sat upon it.  But the body color, striping, interior will be original, although the wheels may be bumped to 15's, if only to get a reasonable tire anymore.

If you are just concerned about the originality of the exterior and interior, why claim you have to take extra care in an under-hood modification because of the rarity of the vehicle?

The correct original wheels would be the 14" simulated chrome-reverse wheel covers on 14x5.5" steelies...



If you have those, I suggest looking at Coker Tire for correct-appearing reproduction tires. I suppose you can get somewhat in the ball park with 15" actual chrome reverse wheels, though. Then it boils down to your version of a "reasonable" tire, and whether that looks period correct. Just my opinion. I had Magnum 500's with lettered tires on mine; not sure what I'll use for the resto version.

64bird410

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Re: Cam and stock power brakes
« Reply #8 on: July 10, 2016, 01:08:58 PM »
Another option to think about would be to wire up an electric vacuum pump from a 99+ powerstroke. The electric vacuum pumps can be readily bought from the local parts stores for around 75 bucks I think.  A guy could wire and plumb one of those in and hide it well enough to not look out of place in a build.   Good luck on your build!

Cyclone Joe

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Re: Cam and stock power brakes
« Reply #9 on: July 10, 2016, 05:57:55 PM »
FElony,

You've asked a deep question.
My goal for this car has evolved over time as money and perspectives have changed.  Initially, this was going to be a 100% stock resto, because in my narcissistic mind there were so few made at least one should be preserved in perpetuity to document what 'original' once looked like.  I also didnt have a lot of money, and so it seemed to be the cheapest option (disclaimer: probably not an accurate statement) to restore a car without going the J.C. Whitney route.  Anyways I had in my head this glorious idea to have the one reaming specimen of a fully restored and correct 1967 Cyclone GT Convertible with correct paint dabs, stamps, and over-spray. The other objective was that if one day, I needed to sell it, it would bring the most money.

As we move closer to today, things have changed.  I've concluded that while I want things to be as close to as stock as possible, I wanted to make to make a few typical 'speed upgrades' that someone in the 1960's would have done to a car like this.  Exhaust upgrade, intake upgrade, carb upgrade (3-barrell Holley waiting to be installed, like my father had on his '66 Fairlane 390).  I also wanted to make changes that were 'reversible' such that if the next owner wanted to go back to fully stock, those parts could be swapped back onto it.  I've retained the original heads, intake, exhaust, carb for these reasons.  There is also a part of me that wants this car to be faster than a modern BMW, or Acura, to keep the allure that has defined  the American muscle car.  Again, probably more hubris on my part than logic.

With the modifications I mentioned above, there are the inevitable 'collateral' changes such as insufficient engine vacuum to operate the power brakes.  So as I continue to collect and work on a game plan for this fall/winter engine build, I want to look for and address as many of these before I sink money and time into an assembly that will yield an unacceptable result.

Regarding the wheels, the Cyclone GT convertibles had a different factory wheel option to my understanding.  They look similar to a Magnum 500, but with the Mercury Head center cap, and wheel recesses painted to match the body.  I have seen 1966 Cyclone Convertible advertisements with them shown on those cars, and the ones on mine are identical (perhaps not correct for 1967?).

64bird410, thank you for the idea of using the Power-stroke vacuum pump.  I'll be sure to keep this in my notes if I run into significant brake issues.

Joe

FElony

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Re: Cam and stock power brakes
« Reply #10 on: July 10, 2016, 08:19:58 PM »
You are referring to these wheels


which are not correct for '67. However, if you have them I would run them. I don't think they had any body color match in them but again, if you think they'd look cool with some blue in there, have at it. Not many people know the 68-69 12-hole GT wheels had a body color option from the factory, but I think that looks better than the generic argent silver.

I have run across a couple other cars like yours. I "think" another N54 member has a red one. However, your idea of having fun now and changing back to stock later is sound and realistic.

Joey120373

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Re: Cam and stock power brakes
« Reply #11 on: July 10, 2016, 11:23:33 PM »
Not sure if this really adds anything to the discussion, but most cars back then had a vacume resivor to keep all of the heater and air conditioning controls where you put them under acceleration.

Cyclone Joe

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Re: Cam and stock power brakes
« Reply #12 on: July 10, 2016, 11:50:05 PM »
FElony,
Hm, well that doesn't exactly look the same.  Here is a photo of the wheel (minus the center Mercury Head cap).  You can see a bit of body color on it.  Any thoughts as it what it was, either aftermarket or otherwise?

FElony

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Re: Cam and stock power brakes
« Reply #13 on: July 11, 2016, 12:37:46 PM »
FElony,
Hm, well that doesn't exactly look the same.  Here is a photo of the wheel (minus the center Mercury Head cap).  You can see a bit of body color on it.  Any thoughts as it what it was, either aftermarket or otherwise?

I know exactly what it is:   http://www.ebay.com/itm/151962594083

Very possible that your car had those added by the dealer during or after the purchase. Lots of people did not like the chrome reverse caps. I think the blue was done by the owner. Be interesting to see the Marti, 'cuz ya never know. If they clean up well, use them.

« Last Edit: July 11, 2016, 12:43:32 PM by FElony »

Cyclone Joe

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Re: Cam and stock power brakes
« Reply #14 on: July 12, 2016, 09:35:49 PM »
Thanks FElony.  I ordered my Marti report this evening, so we'll see what it shows.