Vacuum guage fluctuates
Thread Starter
Senior Member
Joined: Jun 2008
Posts: 660
Likes: 1
From: Corning NY
Car: 86' IROC
Engine: 388
Transmission: Built 700r4
Axle/Gears: 3.08 non-posi
Vacuum guage fluctuates
Ok so I just got my top-end back together and in the car. Its a 388 with a lopey cam (240/246 @.050") and the vacuum gauge fluctuates between 7" and 9" of vacuum. I assume this is normal for this cam. All the lifters look perfect and the lobes all had the same amount of lift (eye balling.)
I just wanted to make sure this is normal for a large cam.
I think I got the valve lash set correctly at least seems right.
I just wanted to make sure this is normal for a large cam.
I think I got the valve lash set correctly at least seems right.
Thread Starter
Senior Member
Joined: Jun 2008
Posts: 660
Likes: 1
From: Corning NY
Car: 86' IROC
Engine: 388
Transmission: Built 700r4
Axle/Gears: 3.08 non-posi
Re: Vacuum guage fluctuates
Right now base timing is 16* and 900 rpms mechanical doesn't kick in until 2900.
Moderator
Joined: Jan 2000
Posts: 20,981
Likes: 11
From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Vacuum guage fluctuates
You mean mechanical is fully in by 2900?
How is the vacuum advance set up?
How is the vacuum advance set up?
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Joined: Nov 2001
Posts: 2,428
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: Vacuum guage fluctuates
Ok so I just got my top-end back together and in the car. Its a 388 with a lopey cam (240/246 @.050") and the vacuum gauge fluctuates between 7" and 9" of vacuum. I assume this is normal for this cam. All the lifters look perfect and the lobes all had the same amount of lift (eye balling.)
I just wanted to make sure this is normal for a large cam.
I think I got the valve lash set correctly at least seems right.
I just wanted to make sure this is normal for a large cam.
I think I got the valve lash set correctly at least seems right.
You might be able to increase that a little and get it a little more steady if you use an adjustable vacuum advance unit on your distributor so that you get another 10* advance or so at idle.
