Holley 4160 issues
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Joined: Nov 2010
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From: Rust/Salt Belt in SW Mich
desperado,
Is it still backfiring through the carb? I read that you have 21"hg that is good, however backfiring through the carb is a classic indication of a vacuum leak. Snug the carb down, snug the intake down and check all vacuum hoses and fittings. Just a thought from a guy who has not had a carbed vehicle in 20 yrs.
Is it still backfiring through the carb? I read that you have 21"hg that is good, however backfiring through the carb is a classic indication of a vacuum leak. Snug the carb down, snug the intake down and check all vacuum hoses and fittings. Just a thought from a guy who has not had a carbed vehicle in 20 yrs.
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From: S. Mississippi
Some of us choose the 500-600cfm carbs simply because the Holley 390 that is recommended is a pain to get dialed in right. I think this is because the carb is so close to what is required by the engine that there is very little "wiggle" room in calibrating it.
I could be wrong, but it seems to me that a carb slightly larger than requirements would be easier to tune that a carb that is precisely what is required.
I could be wrong, but it seems to me that a carb slightly larger than requirements would be easier to tune that a carb that is precisely what is required.
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From: Fresno, CA.
Interesting. I would have thought it the other way around. So, it sounds like the 300 would need more than 390, but is unable to get it, so you install a 500-600 for that little bit extra and it seems to help? Just trying to figure this out because I had planned on upgrading mine to a 390 when I get it, and now I am not sure.
Jim
Jim
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From: Earth
As long as it's a vacuum secondary carb it doesn't really matter what size you have. Within reason. The secondaries are only going to open as much as the engine can draw. A smaller carb should theoretically work better at low rpm - more air speed through the primary bores draws/atomizes fuel better.
Air flow definitely slows down when you snap open all four bores on a mechanical secondary 4-bbl. Not really an issue when you compare 390 vs. 600 cfm vacuum secondary carbs. Or even a 750cfm carb. It wouldn't be ideal but it would work. May be some tuning required. Maybe not if it's an Edelbrock. They're pretty forgiving. 600 cfm is probably the sweet spot - good size and there are millions of them to be had for next to nothing. I sure as heck wouldn't drop $400 on a new 390 cfm Holley.
Air flow definitely slows down when you snap open all four bores on a mechanical secondary 4-bbl. Not really an issue when you compare 390 vs. 600 cfm vacuum secondary carbs. Or even a 750cfm carb. It wouldn't be ideal but it would work. May be some tuning required. Maybe not if it's an Edelbrock. They're pretty forgiving. 600 cfm is probably the sweet spot - good size and there are millions of them to be had for next to nothing. I sure as heck wouldn't drop $400 on a new 390 cfm Holley.
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From: Earth
Another thing to keep in mind, a 300 has six 50 cubic inch cylinders. Dimensionally it's more like a 400 vs. a 302. A 300 isn't usually revved to the point it really needs a bigger 4-bbl but at off-idle and at low speeds it's sucking air pretty good to fill those big cylinders.
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From: Fresno, CA.
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From: S. Mississippi
NightEyez: I think that a 500-600 cfm carb would be perfect for your project. Couple that with a Offenhauser Dual Port (DP) intake and it should be about perfect for what you want to do. EFI exhaust manifolds work well as a cheap upgrade for the exhaust, without all the issues of having a header.
Believe it or not, my 83 once it is all done will be nothing more than a work truck. A nice work truck, but something I'm not afraid to take out and work hard if I have to, and covering DD duties as well. I guess that is the reason why I built the big six instead of putting a v8 in the truck, I wanted something capable of working hard all day, and still reliable and efficient as a daily driver.
Now that my taxes have shown up it is time to put the finishing touches on it and get to driving!
Believe it or not, my 83 once it is all done will be nothing more than a work truck. A nice work truck, but something I'm not afraid to take out and work hard if I have to, and covering DD duties as well. I guess that is the reason why I built the big six instead of putting a v8 in the truck, I wanted something capable of working hard all day, and still reliable and efficient as a daily driver.
Now that my taxes have shown up it is time to put the finishing touches on it and get to driving!
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From: Fresno, CA.
Well, with the price difference between the two, I will most likely go with the 600cfm Holley, unless I find a used 390 cheap. The Offy DP is a good choice I have heard, and the Hooker long tube headers will give more torque. However, if I have to notch the frame or bend a tube to get them to fit (like the Hedman header) then I may end up going with the EFI exhaust.
Jim
Jim
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From: Boise, Idaho
This is one of the main reasons I just skipped headers altogether and went straight for the EFI manifolds.
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From: S. Mississippi
When I got my intake/carb combo, I also got for free a split header for my truck. No idea who makes it but it splits the 6 cylinders into two separate banks.
I chose the EFI manifolds simply because I wasn't going all-out with my truck, and because I didn't want to have issues with changing my starter or the starter becoming heat soaked and dying prematurely.
EFI exhaust ftw!
By the way, I ordered my walker Y-pipe for the EFI mani's today. Time to get rid of all that leaking exhaust I fabbed up when I first swapped this engine in!
I chose the EFI manifolds simply because I wasn't going all-out with my truck, and because I didn't want to have issues with changing my starter or the starter becoming heat soaked and dying prematurely.
EFI exhaust ftw!
By the way, I ordered my walker Y-pipe for the EFI mani's today. Time to get rid of all that leaking exhaust I fabbed up when I first swapped this engine in!