What would be a normal vacuum reading at idle for a 396 with a comp 280H flat tappet cam.The engine has 10.25 to 1 compression. Thanks

I'd think 13-15

DAN is close but i would est 12-13"in a 396/402.

Why do ask,is it lower then in your motor or are you trying to find out the approx idle vacuum before ordering that cam?

Scott

Its a friends engine he thinks it has that cam.Or something simaliar? It does have around 11
or 12inch vac.But it does not have a very rough idle either.That kinda has me wondering.Maybe the idle would not be to rough with this size cam? Plus i have looked at the lifters you can see the 6 little holes in the top were the push rod sits.I am thinking there crane fast bleed lifters.No noise when cold. but when warm the idle smooths out more
and the sewing machine noise starts

280H has a great sound at idle. Ran one for years and loved the sound as well as the performance. To me it one of the best street cams ever.

10.5-1 is gonna be a lot of cylider pressure though.

280H has a great sound at idle. Ran one for years and loved the sound as well as the performance. To me it one of the best street cams ever.

10.5-1 is gonna be a lot of cylinder pressure though.


Agreed. Nice choppy idle. Very mild. Ran one in a 396, stock stall converter, 4.11 gears in a 66 Belair. Car ran 13.80's at 99 MPH with stock oval ports, small valves. I think my pistons were L2240NF30, which gave me 9.5/1 compression (99cc heads).