390 Carb choice
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From: Bozeman, Montana
390 Carb choice
I have a 1976 390 stock as can be accept for an Accel Super Stock coil, I wish to put a new carb i.e. the Edelbrock Thunder Series AVS Offroad carburetor #1825 650cfm, I was wondering if anyone has any experience with this carb, and if I want to put it on the stock manifold will it bolt on or do I have to get an adapter of some sort. Right now I have a 2bbl of unknown cfm but I know it is robbing me of performance. (possibly any other carb suggests.?) One last thing, do you think I might get away with a 600 cfm carb if I wanted to do a mild build on the engine or should I shoot for 650-750 cfm.
Last edited by 4x4madness; Feb 29, 2004 at 06:06 PM.
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From: Louisville,Ky.
I wouldn't install it on a 2bbl manifold. Those adapters will really choke it down. I would either get a 500 cfm Holley 2bbl or get a 4bbl intake manifold, then use the 650 AVS or a 600 AFB.
You would have to turn over 5500rpm to use over 650cfm.
390 @ 5000rpm requires 564cfm.And that's on a very efficient engine.
On a stocker, yours will run fine with any of the 3carbs.
Jimmy
You would have to turn over 5500rpm to use over 650cfm.
390 @ 5000rpm requires 564cfm.And that's on a very efficient engine.
On a stocker, yours will run fine with any of the 3carbs.
Jimmy
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So Jegs has the holley 500 cfm 2bbl carb for around $220 remanufactured at $150 <-- (Is there anything wrong with theses?). Now do you think that this upgrade will provide a noticeable performance gain or should I wait and save (something that is really hard to do ) for lets say a Edelbrock Performance set---------------> = $$$$$$$$$$$$$$$
Lxman1, is there a formula how you calculated rpm to cfm intake
Lxman1, is there a formula how you calculated rpm to cfm intake
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4x4madness
The Holley 500 cfm I put on my 390 made a big difference in performance. The engine was fresh also, headers, 2 1/2" duals.
I cannot guarantee the same for you though.
It bolted right to my stock cast iron 2bbl intake that was on the 390.
BTW, I would not be afraid of a re-man unit.
You can also catch these on e-baymotors about all the time.
The Holley 500 cfm I put on my 390 made a big difference in performance. The engine was fresh also, headers, 2 1/2" duals.
I cannot guarantee the same for you though.
It bolted right to my stock cast iron 2bbl intake that was on the 390.
BTW, I would not be afraid of a re-man unit.
You can also catch these on e-baymotors about all the time.
Last edited by Superdave; Mar 1, 2004 at 10:49 PM.
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So I finally popped the lid today and checked out the carb and it is a Motorcraft, now could this carb be tuned to match/exceed the performance of a Holley 2bbl, or should I just scrap it and go with the Holley. One last thing, when I give it the onion it just seems to slug until it hits a higher rpm, is that something that can be improved with the Holley?
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If your 390 is still stock go for the Holley 500..If you are going to build it up it anytime soon save your money and go with a 4..JMO..The problem you have could be a # of things from ign. to fuel..What rpm and gear are you in when you "give it the onion"?..You may want to come over to the FE forum for help with the 390..
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Alright fellas, just put the order into Jeg's for a reman. Holley 2bbl, one last question then this monkey will be off your back. I live at approx. 6000 ft above sea level, will I need to tune this carb before install, and if so is there a "manual" to describe what jets/metering rods/or fantastic new parts I need (new to the carb world, used to let the EFI do all the work for me)
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Thumb rule coming up:-)Jet size should be reduced by one number for each 2000 foot above sea level.
Power valve should be increased by 1.5-2.0 in. Hg. for each 3000 foot above sea level.
The list 4412 500 cfm comes with 73 main jets and a 125-50 power valve sooo... if you stay at 6000 feet ALL the time you could use a set of 70 jets and a 125-75 power valve.
CAUTION-if you drive down to sea level(or near) you will prolly be running lean and could have problems, so only retune if you really do stay at 6000 ft.
It's always best to start with the tune in the carb and test, before changing.
Power valve should be increased by 1.5-2.0 in. Hg. for each 3000 foot above sea level.
The list 4412 500 cfm comes with 73 main jets and a 125-50 power valve sooo... if you stay at 6000 feet ALL the time you could use a set of 70 jets and a 125-75 power valve.
CAUTION-if you drive down to sea level(or near) you will prolly be running lean and could have problems, so only retune if you really do stay at 6000 ft.
It's always best to start with the tune in the carb and test, before changing.
Last edited by Putt; Mar 5, 2004 at 12:07 AM.
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Well the carb finally came in and I took a two hour lunch break yesterday to install it. I a very pleased with the results (10 ft. burnout in front of my house, bet my neighbors love me now, lol) The only other changes I had to make were a new choke cable because the old one wasn't strong enough to push the choke plate to the full open position anymore, I had to ream a hole in the throttle lever in order to accept the pin that my throttle linkage hooks up to and 3ft of fuel hose and a 90 degree elbow to reroute my fuel line so it doesn't run right along my heads <---- great for vapor lock and hot fuel but all in all I am very sastisfied I still have to adjust the idle screws and the float bowl. ??? One last question, under hard acceleration (pedal to metal) the engine seems to backfire, what are possible causes???
Last edited by Ford_Six; Mar 13, 2004 at 03:38 AM.