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Discussion Starter · #1 ·
Was wondering if it is possible to tune rather than install a vacuum reservior for your brakes when running a big cam.IE if I were to run a cam like cc306,could I adjust closed throttle spark advance and play around with idle speed to achieve adequate vacuum at idle.I know that a t56 helps a little,but I was basically wondering if tuning can overcome the need for a vacuum reserve.Can anybody take a guess how much vacuum a 355/t56 with cc306 cam would produce at idle with good tuning?Better yet does anyone out there have this combo,do you like it?
 
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Discussion Starter · #2 ·
I cannot imagine the vaccuum reservoir being that major a project that it would limit your cam choice. Is there a reason, other than unwillingness to add a bit more weight to the car, that you are asking this question?
 
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Discussion Starter · #3 ·
In my opinion, any tuning you do will not have a big effect on the vacuum reduction caused by the cam. I used to have a t56 with a stroker on the impala I used to own. I put a vacuum canister on to help the brakes - it made a difference, but my main problem was actually a bad brake booster so I took the canister back off. It was really easy to install. I still have it and will sell it to you for relatively cheap if you are interested - it's basically in new condition. It probably weighhs 2lbs and was mounted to the wheelwell. LMK if you are interested.
 
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Discussion Starter · #4 ·
Thanks for the replies guys.That was exactly the information I needed.Although it was not a question of whether or not I was unwilling to buy a canister or not,I didnt know if I really needed one and thats why I posted the question.Hey hvymtlwagon thanks for the offer,if you dont sell it by this summer I will probably take you up on that offer.
 
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Discussion Starter · #5 ·
While I can see how proper tuning could tame a big cam in terms of idle quality and drivability; I cannot see how it would change the amount of vacuum being produced.
 
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Discussion Starter · #6 ·
Originally posted by EricTheBald:
While I can see how proper tuning could tame a big cam in terms of idle quality and drivability; I cannot see how it would change the amount of vacuum being produced.
By adjusting timing and idle rpms.
 
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Discussion Starter · #7 ·
Originally posted by EricTheBald:
While I can see how proper tuning could tame a big cam in terms of idle quality and drivability; I cannot see how it would change the amount of vacuum being produced.
You start bringing the base idle timing up you would be amazed how much the idle vacuum will change.

I am not enamored with vacuum reservoirs though.
They just put off the inevitable. If you are jockeying a huge cam car in a parking lot at idle the brakes will still go away, you'll just get a few more pumps.
All that being said with a manual trans and its resultant higher curb idle I don't think you are going to have issue.
The biggest cam I have had behind a 350 had over 260 @ 50 on 108 and with a 1000 idle the brakes still worked.

Worse comes to worse a vacuum pump would solve all ills.
Gerry
 
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Discussion Starter · #8 ·
Originally posted by 95wagon:
I am not enamored with vacuum reservoirs though.
They just put off the inevitable. If you are jockeying a huge cam car in a parking lot at idle the brakes will still go away, you'll just get a few more pumps.
IMO, it's more important to have power brakes on the highway. This is where a vacuum reservoir shines by storing vacuum generated during coasting.

It's only neccessary if you have 11 or less inches of vacuum at idle. I have a fairly big solid roller cam (23x/25x @ 0.050") on a narrow (by the off-the-shelf cam standards) lsa and it still makes 12-13 inches of vacuum @ 950 rpms in a 383.

I have a vacuum canister. The brakes will probably be fine without it but it's very light, easy to install and does not hurt anything.
 
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Discussion Starter · #9 ·
IMO, it's more important to have power brakes on the highway. This is where a vacuum reservoir shines by storing vacuum generated during coasting.
I don't understand your reasoning.
When you close the throttle at speed you are going to have all the vacuum you could ever want.

Plus the booster and the production check valve would give you 3 or more pumps even if the engine was off.
Whatever, to each their own.
Gerry
 
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Discussion Starter · #10 ·
I'm with Gerry on this one. ESPECIALLY in a stick shift car on the highway too, you lift off the throttle and the brakes get plenty of vacuum...and the stock booster is almost a resevoir of it's own anyways.

Changing spark advance at idle, and raising the idle RPM up (if necessary) can work wonders for making vacuum at idle too...then you'll NEVER lose the brakes, and not need any nonsense plumbed into the system.
 
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Discussion Starter · #11 ·
You may not want to install a cam of that size in the first place.
You will have very little power/torque from idle to 2000 RPM.
You NEED power down low in a T56 car.

But what do I know


11.44 @ 120 says it all.
All with a lil 845 cam and no one has come close since.

I'm gone.
 
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Discussion Starter · #13 ·
I'm sorry... did you guys say that raising the idle and tweaking the timing will change the amount of vacuum a cam generates?
 
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Discussion Starter · #15 ·
Originally posted by EricTheBald:
I'm sorry... did you guys say that raising the idle and tweaking the timing will change the amount of vacuum a cam generates?
Don't be sorry, take your lap top and do up some idle flashes and see for your self.

Then you can see some hard evidence, just like you like to see.
 
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Discussion Starter · #16 ·
Well, he might be talking about reverse polarity cams...spark advance and idle RPM doesn't have any effect on those.

Nab, be honest, what'd it do WITHOUT nitrous?
 
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