83hurstguy

Has anybody measured the vacuum on a 455 with 308* cam installed? Just curious, as that's the cam the '68 H/O came with from the factory... mine won't be running for a while. The 328* cam wouldn't support power brakes, but the '68 H/O came with power brakes and the 308* cam, so it had to be somewhat better.

Thanks!

costpenn

Funny you should ask. On my 68 W-46 (A/C) Hurst, everything - carb, dist, exhaust manifolds C heads is original to the car (still had the lower end at STD/STD - lower end had never been apart), but I did install a 402194 cam in it instead of the 400165 and tuned it to the W-46 specs. It runs very well and has a KILLER exhaust tone at idle, but like everyone says, vacuum assist to the booster at low engine speeds can make slow speed stops, if you are puttering along at anything under 20 mph, a little scary. You quickly get used to it and begin to anticipate when it might happen!! Next time I have it out, which might be a while, I'll put a gauge on it and see what it says.

64Rocket

Luke,
For what you are going to use the car for, I'd run manual brakes.
Take your booster off.

Gene

coppercutlass

Couldn't you just make a vacuum canister to hold a little extra vacuum. I mde one from 5 in. Pvc pipe and 2 end caps with the pvc cement. Never used it but I have it lol.

grampy

I ran one a long time ago .it worked with power brakes and a stock converter but it had a 411 gear. If you have a lower gear you might need a little stall.

83hurstguy

Thanks guys. Costpenn, appreciate your offer to measure, I'd be curious for the vacuum values at idle and also 1200 rpm.

This will eventually run at the Pure Stock drags, so I may have to run the power brakes unless they were optional on H/O (believe they were standard, but I'm out of town so I can't check documentation). The rules require 16 in-hg @ 1200 rpm (with exemptions for factory combos that can't meet that rule)... I am suspecting the 308* cam will be an exemption.

I have 3.91 gears in it, so I'm not worried about the power band aspect.

costpenn

All 68 HO's - A/C or not - had power disc brakes. I'm pretty sure my car would be at or below the 16 inches at 1200 rpm.....

oldsmobiledave

Use Rhodes lifters & you will be fine.

grampy

A 1200 rpm idle it should pull 16 inches. it helps if you use manifold vacume on the vacume advance .BTW I do know that I have had a camshafts with 230 @ 50 cut on a 110 lobe separation run 14 to 15 inches @ 700 out of gear.

83hurstguy

Thanks guys. The rhoads lifters aren't legal, I've gotta run the stock cam and was curious to see if it met that rule or not... Sounds like it will be just on the edge. Dave H provided some feedback that his ram rod got exempted.