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#1
04-28-2011, 11:25 PM
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Power Brake Booster
What's the size of the factory power booster on a 66? I measured across the housing and it was 8".... so is that the size or is it smaller inside? Has anybody installed a larger one? I was thinking of doing this to help out with my disc brakes, however there appears to not be enough room before hitting either the steering column, washer motor, or pedal linkage... Thoughts?
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"A bend in the road isn't the end of the road unless you fail to make the turn." |
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#2
04-28-2011, 11:30 PM
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Maybe dual diaphragm ?
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#3
04-28-2011, 11:35 PM
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I don't think installing a 'larger one' is going to solve your issues...what kind of manifold vacuum are you pulling? Maybe your cam is causing a weak vac situation...
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RediRad circuit designs, branding and intellectual property are for sale. Serious inquiries only. |
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#4
04-28-2011, 11:57 PM
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about 14 at cruise, 11 in gear at idle. It's the old faithful cam.
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"A bend in the road isn't the end of the road unless you fail to make the turn." |
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#5
04-29-2011, 12:11 AM
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11 at idle seems low...I would think you should have at least 18 in hg at idle. Maybe a vac leak somewhere?
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RediRad circuit designs, branding and intellectual property are for sale. Serious inquiries only. |
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#6
04-29-2011, 06:41 AM
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Quote:
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"If you do everything you'll win" -LBJ 13 Smiles per Gallon: 66 Bonneville wagon 66 Bonneville 2d HT - In perpetual progress 2005 GMC L-33 |
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#7
04-29-2011, 08:35 AM
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11" seems a bit low for that cam, but not by much. when I bought my cam from Dave, he said that his stump puller cam would get very slightly better vacuum than ol faithful. i put in stump puller and got this data from a datalog using a map sensor - on a 462 (which I think you are running too?):
750 rpm = 12" 830 rpm = 13" 900 rpm = 14" 950 rpm = 15" Think it will also depend on heads, manifold, etc... Anyhow that's pretty low vac. Might be able to improve a bit with timing/mixture at idle? Check out this article has some math on boosters: http://www.deanoshiro.com/brakes/bra...e.html#booster Dual diaphragm doubles assist based on square inches of circular diaphragm. Double 7" has same boost as a single 10". I have a dual 8" booster with the vacuum outlined above and it works great. |
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#8
04-29-2011, 09:22 AM
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I'm not very familiar with the power brake systems on 1966 cars, but in 1961 they included an reservoir to increase the vacuum capacity. It looked just like a big Hi-C juice can with a hose barb soldered on one end, and it was connected to the booster with a rubber hose. The can was hidden up inside the fender.
If your car doesn't have something similar, I wonder if you could add one. |
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#9
04-29-2011, 09:19 PM
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Well, I'm going somewhat off of memory on my vacuum numbers as I haven't had the car out of storage yet this year, but I do believe those are close. I do not have any leaks and I have thoroughly adjusted the timing and mixture on my engine. It's a 461 with KRE 310 cfm heads, torker II intake and holley 850dp.
Stuart, the 66 didn't have the resevoir you speak of. Was that something like an electric vac pump? I've heard of these being an option as well.
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"A bend in the road isn't the end of the road unless you fail to make the turn." |
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#10
04-29-2011, 09:34 PM
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It's just a can that acts like a reservoir. '63 has it under DS fender back by the firewall. I have seen them as options avail on '65-6 but never on the car that I know of. Would be really easy to try.
__________________
"If you do everything you'll win" -LBJ 13 Smiles per Gallon: 66 Bonneville wagon 66 Bonneville 2d HT - In perpetual progress 2005 GMC L-33 |
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#11
04-29-2011, 09:50 PM
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I got a chance to read through a good majority of that article. Very good info, thanks for that. What car do you have this dual 8" on? How do I know the size? Does it just go off of the diameter of the booster? Mine measures 8" across.....
Where did you get your dual 8" booster from? Is it in the same size case as a single 8" booster or is it deeper? Are there any other issues with the MC or push rod when installing one of these?
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"A bend in the road isn't the end of the road unless you fail to make the turn." |
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#12
04-29-2011, 10:27 PM
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http://www.summitracing.com/search/D...Rank%7cAsc
If the link works - these are the aftermarket cans that others have referenced. If you want to go that route I may have one available. Just PM me. Jom
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65 Catalina sedan. Allen Thomas Performance 495. KRE Heads at 310cfm ported by SD Performance, ProSystems Dominator carb on ported Victor intake, P-Dude custom grind hydraulic roller, MSD ignition, 3.50 Moser/Ford rear. F-Glass front bumper by son Rob, rear by the old man and joint effort for trunk lid. 3950# w/driver. Best of 9.5761/139 on 175 shot, 6.01 /114 in 1/8. |
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#13
04-29-2011, 10:35 PM
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Why is that most tech articles you read, they say a minimum of 16-18 in vacuum must be present for the booster to do its job, yet most people that have larger cams and lower vacuum say in the 12-15 range say they never have any problems? Is it just a marketing tactic or.....?
__________________
"A bend in the road isn't the end of the road unless you fail to make the turn." |
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#14
04-29-2011, 10:46 PM
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Quote:
i can't remember what i had to do to get it fit, but i think i had to oblong the holes through the firewall - but not by much. it's on a 61 fullsize, and i got rid of the original vacuum reservoir. you're right about people saying how much vacuum you need for brakes... i thought the same thing about having enough vacuum, but i'm really happy with mine. main test is the wife.... she hasn't driven my car yet, but i think the brakes would be one of her last complaints. brakes are great. |
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#15
04-30-2011, 12:42 PM
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there's a thread going on the ol faithful cam, and a guy in Florida is pulling 13-14" but it's through a tri-power intake. i didn't realize it can make that big of difference, but I started poking around some tech articles and found that dual plenum can increase vacuum over single plane by couple inches. has to do with double 180 reversion pulses or something
 also- when you converted to disc, did you change MC to match, or change valving? there's some particulars with residual pressure valves depending on where you have discs. the above referenced tech article has a bunch more information brake information on his site that is really helpful. |
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#16
04-30-2011, 09:38 PM
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Here's the deal. After reading through that article, there's a lot of information that I was unaware of with the braking system. I didn't think it through or study it very well. My brakes weren't terrible the way they are, but I knew they could be better and I suspected a couple things not right with them.
Basically I've got 4 wheel disc brakes, a proportioning valve to the rear brakes, all new steel lines, and a new MC. The MC I purchased was one that I read in the full size forum that a couple people have used. It's a dual chamber MC from a 68 camaro with all drum brakes. Now after reading the article, not only is this MC not correct in that it probably has the residual valve built in for the drum system, but also it only has a 1" bore. I'm coming up with the fact that I need 1 1/8" bore for disc and a larger volume MC with no residual valve. However, now that I read that article and looked through the one website, that twin MC setup has me very curious. If I'm going to be making the changes with an MC and booster anyway, for just about the same amount of money why not go to their twin setup and save the space under the hood and eliminate the worries about vacuum at the booster...
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"A bend in the road isn't the end of the road unless you fail to make the turn." |
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#17
04-30-2011, 09:43 PM
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Quote:
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