Technical Vacuum hose length for brake booster, does length effect diameter

I am currently tying up all the loose ends on my 38 coe build. I have mounted the engine in the bed of the truck.
I am wanting to run some steel fuel line under the truck as my vacuum line for the brake booster. The line will end up being 8 feet long or so. I have a roll of 5/16" line. The original booster hose was 3/8" .
This may sound like a stupid question but at this point i dont want to experiment.
Over a long distance like that, does the diameter of the line effect the amount of vacuum it will pull?
Thnx☺

 

Not really, vacuum systems are like hydraulics in that equal pressure is felt everywhere in the system. I would use a hose the size of the fitting on the booster. It might work better to fabricate a steel line for most of the distance then a short rubber connector at either end.

 

That was my plan to put a piece of rubber hose at each end.
I just happen to have the 5/16" line and didnt want to buy the 3/8" if not required

 

Its funny i have dumped a ton if cash and time into this thing and now im getting all cheap at the end☺

 

Doesn't affect the amount of static vacuum it can pull. But it might affect the time it takes to pull that vacuum. I don't know if you'd notice the difference...but there must be some reason why all OEM brake booster vacuum lines are 3/8", and why they run larger line on things like hydrovacs under older trucks?

 

I was thinking there may be a slight lag in vacuum upon engine start but i font start and imediately go anyways.
Ok, thanks guys im going for it
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engine start up isn't the problem, the problem is panic stops

 

I agree. I'd run the 3/8 like it should have. It won't cost that much for a length of 3/8 pipe to do it right. Don't skimp on brake stuff.

 

more like a multiple pedal application in a short period of time might cause problems ,its the press and release not the steady application .

a vacuum reserve canister near the master can help the situation , IMo I would run the 3/8 line so the vacuum can not have any restriction and using hard line is a good Idea over long lengths

 

Good idea, ill pick up some 3/8" on tuesday, monday is a holiday here in canada so nothing is open. And ill score a vacuum canister from the wrecker as well.
Thanks

 

I peeked under the old bus, it has 1/2" steel line to the hydrovac which is near the transmission. Probably a similar setup to yours.

 

I actually have a ton of 1/2" copper, it wont even look like a boiler room if i paint it chassis black.
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