Will i have enough vaccum for brakes

[Austindarksaber]

Will I have enough vaccum for power breaks? I have listed all of my engine build below any help is appreciated

I got my 383 stroker chevy small block back from the machine shop 2 days ago.

Painted it yesterday and later put in the Crankshaft 3.75 stroke.

Pistons are dished 13cc hypereutectic.

I bought 195 AFR heads with a 65cc chamber 2.02 intake 1.6 exhausts .600 max lift.

Fel-pro 1003 head gasket so a estimated 9.88:1 CR

I will be getting my 700R4 rebuilt as I don't believe it will handle the power this engine will throw at it.

Rear gear ratio will stay stock at 3.42, don't really see a good reason to increase it.

I will be using this in a 88 GMC strictly used street use but who doesn't want more power

I was told by my Machinist that the comp cam 12-430-8 will have enough vaccum for power brakes, in my search I haven't found anything to support as such i have put the link to the cam specs below

https://www.compcams.com/magnum-224-224-hydraulic-roller-cam-for-chevrolet-small-block.html

 

[Sean Buick 76]

In my educated opinion the combination of relatively high compression ratio and the large cubic inches will give you adequate vacuum for power brakes given the cam specs. In a 8:1 350 it would be a dog, but in a 10:1 383 it would be good.

 

[PlayingWithTBI]

I was told by my Machinist that the comp cam 12-430-8 will have enough vaccum for power brakes, in my search I haven't found anything to support as such i have put the link to the cam specs below



https://www.compcams.com/magnum-224-224-hydraulic-roller-cam-for-chevrolet-small-block.html

I was running that cam in my 88 5.7 700R4 with no issues on vacuum - it ran ~47 KPa MAP at idle with 27° timing

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In my 383 10.3:1 CR I'm running the 08-432-8 cam (.510/.520 230/236 @0.050) at ~59 KPa at ~800 RPM, it doesn't like idling much lower. Duration affects vacuum more than lift.

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When running Lean Cruise it's ~ 49 KPa and plenty of vacuum - brakes work OK on all.

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[Austindarksaber]

I was running that cam in my 88 5.7 700R4 with no issues on vacuum - it ran ~47 KPa MAP at idle with 27° timing

You must be registered for see images attach

In my 383 10.3:1 CR I'm running the 08-432-8 cam (.510/.520 230/236 @0.050) at ~59 KPa at ~800 RPM, it doesn't like idling much lower. Duration affects vacuum more than lift.

You must be registered for see images attach

When running Lean Cruise it's ~ 49 KPa and plenty of vacuum - brakes work OK on all.

You must be registered for see images attach

Wow didn't know you could do this I appreciate it

 

[L31MaxExpress]

Depending on which brake system your 88 has, it may have a single diaprham booster. Those were terrible with stock engine vacuum. I am a huge hydroboost fan myself. In gear at 750 rpm with the ac on my 383 pulls like 11-12 in/hg vacuum, yet my brakes are far better than they ever were with the vacuum booster.

The 1987 G20 will get hydroboost when I manage to find the correct pedal but it has JB6 brakes with a dual diaghram booster and with nearly 20 in/hg idle vacuum the brakes are almost too touchy. Moderate touch of the pedal makes you feel as if you are going to face plant the steering wheel. JB6 brakes with the larger JB7 front piston calipers available for that setup, 11-5/32 x 2.75 rear drums, dual diaghram booster, and only ~4,700 lbs curb weight. The rears have a nasty habit of wanting to lockup prematurely though which is not exactly a great thing given no ABS of any kind, makes wet weather stops interesting to say the least. I might put a set of smaller diameter rear wheel cylinders in it to counter-act that tendency especially since it does not tow anything and typically gets run fairly empty. I have been on the hunt for a GM 9C1/Impala SS rear disc setup for that 1987 like my 1983 G20 has on it. Setup literally bolts on minus welding brake hose support brackets on to the axle tubes and swapping the proportional valve to a disc/disc setup.