Cam selection on a 390.
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Cam selection on a 390.
Scotty's right. I run a Carter 625 AFB which is similar and love it except for the secondary air valve. To tune the timing of it you have to grind off some of the counterweight. Problem is there is no turning back if you grind too much off (unless you guys know of any neat tricks.)
Barry
Barry
Thread Starter
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Junior User
Joined: Sep 2002
Posts: 75
Likes: 0
From: Monroe USA
Cam selection on a 390.
I talked to my mechanic about the 1407 and he gave me this thought. He said that he has had this exact carb on a few different motors cause he really like the way the carb did. He said if it has vacumn secondaries then how can you plug "every" hole in the carb and the secondaries still come in? This is just what he said. I am no know all about carbs by any means. I have always been open to any suggestions!
thanks
CHRIS
thanks
CHRIS
Post Fiend
Joined: Sep 2000
Posts: 8,238
Likes: 3
From: Oregon
Cam selection on a 390.
My God. Frankly, I would run screaming from your "mechanic". Of course no Eboks have mechanical secondaries. I only gently pointed it out originally in case you had done some incredible feat of engineering and created a unique carb. I'm trying hard not to be a jackass, but I sure wouldn't be taking mechanical advice from this guy.
Cargo Master
Joined: Aug 2000
Posts: 2,931
Likes: 12
From: SW Michigan
Cam selection on a 390.
Proel is right, you need a new 'mechanic' the guy you have doesn't know what he is talking about. In a vacuum secondary carb, the secondarys open when there is a high enough vacuum in the primary throttle bores. This is done with internal passages, there aren't any vacuum hoses to hook up to make it work. The Edelbrock carb, a fairly close copy of an old carter AFB, has mechanical secondary throttle blades but with a vacuum operated 'air door' above the boosters. Carter thermoquads and GM quadrajets operate in the same manner, as do some motorcraft 4 barrels. Your 'mechanic' should already know this stuff. Run away from him as fast as you can. DF
Senior User
Joined: Aug 2002
Posts: 309
Likes: 0
Cam selection on a 390.
What are single and dual pattern cam's? Is the single pattern when the duration is the same on both sides and the lift is the same on both sides? I am still learning about cams and I have never thought about this before.
Senior User
Joined: May 2002
Posts: 112
Likes: 0
From: aubrey usa
Cam selection on a 390.
The cam I use in the ugly truck nas a whole lot of low end grunt. It starts at around 1500rpms and can run up to 6500rpms. I also only run 9.5:1 compression with stock un-ported heads. I pull some pretty good numbers out of the hole at the drag strip. I have pulled a best of 1.69 60 foot time. This is with a 10" converter with a c-6. Here are the numbers:
.310 Cam Lift int.
.325 exh.
.536 Valve Lift
.562
290° Adv. Dur.
300°
224° Dur @.050
234°
Hyd Lash
105° Center
115°
75* overlap
.310 Cam Lift int.
.325 exh.
.536 Valve Lift
.562
290° Adv. Dur.
300°
224° Dur @.050
234°
Hyd Lash
105° Center
115°
75* overlap
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Thread Starter
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Junior User
Joined: Sep 2002
Posts: 75
Likes: 0
From: Monroe USA
Cam selection on a 390.
Now guys. No need to be rude and so inconsiderate. My roomate/friend/mechanic is very knowledgeable in alot of areas. He is ASE certified and has worked at a Chevrolet dealership for quite a while doing heavy motor work and the like. He may have decribed the carb thing to me in one way and I took it another. He was talking about how the doors were mechanical on the bottem. But we didnt talk about the rest of it. He told me that the secondaries take in only what the motor needs. As in the air demand of the motor.
Those posts were a bit much. But I wont hold it against ya ;-)
lata
CHRIS
Those posts were a bit much. But I wont hold it against ya ;-)
lata
CHRIS
Senior User
Joined: Aug 2002
Posts: 309
Likes: 0
Cam selection on a 390.
Hey Mr Econodrag, who makes your cam? I like the numbers and like the power band you are describing and i may want to re-cam mine with that one or one similar. Is it a Lunati bracket racing cam?
Senior User
Joined: May 2002
Posts: 112
Likes: 0
From: aubrey usa
Cam selection on a 390.
It is an ELGIN PROSTOCK cam. I pick the cam up through Flatlander Racing. It is pretty agressive and will require an adjustable valve train.....(trust me I know this from experiance.) First time I ran it down the track @ 6300 rpms it bent 10 push rods. It also needs 850-900 rpms just to idle and it is still pretty lumpy at that. Hope this info helps you out. Tony
Freshman User
Joined: Sep 2002
Posts: 40
Likes: 0
From: Mississippi
Cam selection on a 390.
Don'tmean to dropin themiddle of your conversation,b ut I have a 390 that is in need of lifters since they aremaking so much racket. I figured Imight just look at putting a cam in there while I am at it. It is a stock motor, intake and exhaust but would like to have a few more power. I figured the cam might get me through till I can rebuild the whole thing. Would a stock cam do enough or would it benefit me to go with one of the cams you mentioned here?