Mechanical Roller Cam - Engine Vacuum Question
Thread Starter
Racer
Joined: May 2020
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Mechanical Roller Cam - Engine Vacuum Question
I’m looking to purchase a matched cam kit (cam, lifters, springs, etc..) for my engine, but want to make sure I have enough engine vacuum to run all the vacuum accessories. From what I’ve read, I need to stay under 240 @ 50 to ensure adequate vacuum. Is this an accurate statement? I know lobe separation also plays a factor due to valve overlap. I have found two mechanical/solid roller cams that look good, but with 11:1 compression of my LT1 short block, are these cams too mild? Looking at compression vs duration charts, it states I need to be at 240 degrees at 50 with 11:1 compression.
Thanks in advance!
https://www.lunatipower.com/voodoo-s...k-261-267.html
https://www.compcams.com/xtreme-ener...all-block.html
Oh, trans is a TH350 with 2200/2500 stall converter, 3:55 gears, the cars weights roughly 3,300lbs.
Thanks in advance!
https://www.lunatipower.com/voodoo-s...k-261-267.html
https://www.compcams.com/xtreme-ener...all-block.html
Oh, trans is a TH350 with 2200/2500 stall converter, 3:55 gears, the cars weights roughly 3,300lbs.
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
What heads are you running?
Is this a 350 still?
I built my Dad a 350 in 1999 with a 244@.050 cam in it and it pulled 11 inches of vacuum......the roller will pull more as you can't compare flat tappet duration to roller duration.....different worlds.
Jebby
Is this a 350 still?
I built my Dad a 350 in 1999 with a 244@.050 cam in it and it pulled 11 inches of vacuum......the roller will pull more as you can't compare flat tappet duration to roller duration.....different worlds.
Jebby
Had a 1976 L-82, 4-sp
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Those cam specs @0.050" are very similar to my Howard's hydraulic roller with a 112 lsa. I have 14-15" vacuum at 850 rpm.
Thread Starter
Racer
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They are Phase 2 Bowties- which will receive some porting. Unfortunately the information out on the web is very generic, which is why I come here to get better info!
Last edited by JC 1975; Feb 24, 2021 at 10:11 AM.
Thread Starter
Racer
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Intermediate
Joined: Jul 2019
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Likes: 11
I had no issues with vacuum. I ran the mildest solid roller from Comp Cams. I bought a complete kit from them with cam, lifters, springs, pushrods and timing set. I loved the sound and the way it revved, but after 3000 miles a roller lifter dumped it's needle bearings and destroyed my engine. I had bought the street lifter that were supposed to be long life. When I called Comp about the failure they just told me "sounds about right" for 3000 miles. I would stay away from CC entirely. They like to rush products to market and let the public be the beta testers. I went back to hydraulic rollers and I don't miss the valvetrain maintenance.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
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Thread Starter
Racer
Joined: May 2020
Posts: 498
Likes: 167
I had no issues with vacuum. I ran the mildest solid roller from Comp Cams. I bought a complete kit from them with cam, lifters, springs, pushrods and timing set. I loved the sound and the way it revved, but after 3000 miles a roller lifter dumped it's needle bearings and destroyed my engine. I had bought the street lifter that were supposed to be long life. When I called Comp about the failure they just told me "sounds about right" for 3000 miles. I would stay away from CC entirely. They like to rush products to market and let the public be the beta testers. I went back to hydraulic rollers and I don't miss the valvetrain maintenance.
Thread Starter
Racer
Joined: May 2020
Posts: 498
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Le Mans Master
Joined: Apr 2011
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From: Hermosa
As I recall for a solid lifter cam you can subtract 10* from the duration to compare it to a hydraulic lifter cam.
given that the larger cam you spec’d would be better, but I believe you could go with more duration if it’s a 383 even if a 350 depending on what you want performance wise.
be sure to check your DCR with an 11:1 CR. You may need more duration to avoid detonation.
DCR with iron heads max 8.5:1
aluminum 9.0:1
given that the larger cam you spec’d would be better, but I believe you could go with more duration if it’s a 383 even if a 350 depending on what you want performance wise.
be sure to check your DCR with an 11:1 CR. You may need more duration to avoid detonation.
DCR with iron heads max 8.5:1
aluminum 9.0:1
Last edited by REELAV8R; Feb 24, 2021 at 01:08 PM.
Safety Car
Joined: Oct 2004
Posts: 3,923
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From: Youngstown Ohio
I've had enough vacuum with a cam on a 108° LSA, 250/254° @.050 duration (11° vacuum)......all accessories worked fine. My current cam is on 112° LSA, with 259/265° @.050 duration and I have 12° vacuum with everything working fine. So it kinda depends on the grind and the total engine specs. If you see one you like at 110 LSA, but prefer it at 112, just have it custom ground......Comp Cams does this at no extra charge.