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Discussion Starter #1
I have a 69 SS with a Vortec 383 stoker, carbureted. Cam specs are Lunati Hydraulic Roller 227/234 @ .50. I've been checking my vacuum to see if my engine can run a brake booster as I'm getting ready for a front disk brake conversion.

I want to know if 12-15 in. Hg is typical for this cam size or if it's considered low? If it's low then I presume that my timing is off or something. I'm in Dallas and altitude is 450 above sea level.

I'd prefer not to use a vacuum pump or a hydro boost if I can help it. If 12-15 is good for my engine, how can I manufacture vacuum another way?

Thanks,
R
 

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If you are talking about idle vacuum of 12-15 you'll have no problem with a vacuum booster...
So true!
I was only getting 8-9" with my 350 and was running a stock 11" booster, no problem. Went to the DSE dual 8" and it was even better! The 11" went out.
 

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Great! Thanks guys.
So everything the brake manufacturers are telling I assume is the "best case scenario" so their products work their best. I have tall valve covers so I'm thinking about something smaller than the stock 11" booster. I assume the dual diaphragm version works well with low vacuum?
 

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Think the situation thru.. your vacuum reading is at idle right? when do u need to stop at idle?
And when u do use your brakes u have your foot off the throttle right?..
Thnat means the butterflies closed, butterflies closed and car moving means engine braking... engine breaking is high vacuum.

The only time a low vaccuum MAYBE of a slight issue is if idling thru say a gas station forecourt and happen to press on brakes a couple times and then the go to manual hard... at walking pace or less.
So everything the brake manufacturers are telling I assume is the "best case scenario" so their products work their best
u are getting the idea.. marketing propaganda BS to sell product with the only interest being filling the pockets of shareholders....its called "business"
 

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If you think it through, when you are sitting at a stoplight at idle with idle vacuum, your brakes are doing about the least work they ever do, there is no inertia to overcome, no momentum to reduce. You need very little brake pressure to hold your car still at idle, so 12-15 inhg of vacuum will be quite sufficient.
Most every other situation will result in a much higher level of vacuum being trapped in the booster and your brakes will work just fine there, too.
 
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