cam duration
Thread Starter
Instructor
Joined: Jun 2003
Posts: 143
Likes: 1
From: New Fairfield CT
cam duration
How high in cam duration @ 050 can I go in my rebuild of my 71 350 with a 400 turbo auto, before I need a after market higher stall converter? Will varible duration lifters fix a longer duration cam instead. Getting a lot of conflicting information from Jeggs and Summit. called Comp cams and also got 3 different cam grinds for the same rebuild. Once before on a camaro rebuild made a mistake with the wrong cam, I had to replace lifters with variable duration units. Do not want to make that mistake again.
Advanced
Joined: Jan 2005
Posts: 99
Likes: 0
Personally, I wouldn't go past 224 deg. @ .050. Check out Comps 270H, or their XE268 if you like dual pattern. Just make certain you match the cam with the rest of the components as well (i.e. CR, intake, heads, carb, rear gear).
Pro
Joined: Sep 2002
Posts: 690
Likes: 1
From: near Memphis TN
I agree with kcmk. Comp cams says a 270H (224 deg) is the highest you want with stock gears and stall. Even with that you will loose a bit of torque in the low range (below 1,800 RPM).
If you have a higher compression or lower gears (not sure what they are on a stock '71) that makes a big difference.
I've always read variable duration lifters is just a stop gap for a wrong cam selection, not a solution for going with a bigger cam.
If you have a higher compression or lower gears (not sure what they are on a stock '71) that makes a big difference.
I've always read variable duration lifters is just a stop gap for a wrong cam selection, not a solution for going with a bigger cam.
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Crane Energizer 272 advertised duration, single-pattern Hydraulic cam is a torque monster in my warmed over '80 L48 (9:1 CR, 1800 stall, 3.55's). 216/216 @ .050 with .454/.454 gross lift with 110 degree lobe separation. And it's emissions legal.
If I ever rebuild the L46 engine in my '69 (11:1 CR, 4-speed, 4.11's), I'll definitely step up to something in the 224-234 @ .050 range.
If I ever rebuild the L46 engine in my '69 (11:1 CR, 4-speed, 4.11's), I'll definitely step up to something in the 224-234 @ .050 range.
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
The Comp 270H was not a radical idle at all if that is a concern. Just a glug-glug-glug from my chambered exhaus when I had the L48 in the car. Sounded like my old 260 Mercruiser (boat I/O)
Check my sig below for the cam specs in the 383. This one sounds like rumpity-rumpity. My 1800 stall converter is too tight and the car pulls like crazy at 650 rpm in gear.
Check my sig below for the cam specs in the 383. This one sounds like rumpity-rumpity. My 1800 stall converter is too tight and the car pulls like crazy at 650 rpm in gear.
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
I think you are on the right track by asking the cam manufacture for a recommendation on the stall speed of the converter. Although there are other variables, they should get you in the ballpark. I don't think there is a hard rule that this duration needs this stall speed. At a certain point the cam will need the idle rpm's raised and it's powerband will also move up making a higher stall speed more desirable.
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