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| 1965tbird |
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Hey guys im usually in the 6 cylinder section lol. I have a 65 thunderbird with a 390 FE block in her. im inthe process of doing some shopping in the carbie market and i really dont know what to buy. Here is just a little about the motor, its getting re-built blueprinted, decked honed, slightly higher comp, new cam slightly lumpier, new intake manifold (edelbrock street master i think) so its not a high rise, custom made extractors oh and changing the points system to the electronic module. i want to have a nice cruiser with some punch.
Thanks in advance. PS no budget lol |
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| XRfairmont67 |
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holley has a formula to work this out. engine cubes - (390) x max rpm - (6000) then divide by 3456.this will give you carb cfm size if running at 100% efficiency,a healthy motor runs at around 80%,race motor runs at just over 90%. this will give you a rough guide. watch out for weak conrods in the 390 motor. still a good motor though, mate had a 390/fmx in his xk falcon, pulled nice third gear burnouts.
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| 1965tbird |
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yeah lol i can mage. thanks for the info appreciate it. can wait to get this thing on the road and start cruising around.
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| Macca |
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elf100capri wrote: holley has a formula to work this out. engine cubes - (390) x max rpm - (6000) then divide by 3456.this will give you carb cfm size if running at 100% efficiency,a healthy motor runs at around 80%,race motor runs at just over 90%. this will give you a rough guide. watch out for weak conrods in the 390 motor. still a good motor though, mate had a 390/fmx in his xk falcon, pulled nice third gear burnouts.
 That formula isn't exact either, sometimes you fit and jet a carby much bigger than required in theory and find a good performance increase, I have had healthy Clevelands that would prove that wrong.
Trying to remember the details, Joe Sherman has a write up about a 302w 400hp, I think top rpm was 6500rpm, going from a 650cfm DP holley to 750 DP he picked up 10hp (I do remember that bit  ), not saying this engine would be ideal on the street with the bigger carby but it proves the theory is flawed.
_________________ 93 Ford Maverick LWB automatic petrol guzzler (gets stuck where Deli doesn't, big pumpkins |
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| 1965tbird |
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yeah i did the the calculations and worked out i need a 650 holley. So i called hume performance and had a bit of a chat and he reccomended the 670 street avenger or the 770. ftr a bit of a chat he realised that holley's guidline for that series is that anythin under 400ci the 670 is ok and anything over is the 770. now thinking about it if i have a 390 that has gone out 20 thou im getting close to the 400 side of things, soi figued id get the 770 to be safe id rather down jet something than have to run it at close to its max all the time, plus gives me options if i change anything down the track.
have any of you guys had any dramas with the street avenger series? it seems to be a good carby, but at $540 i want to be sure. cheers |
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| XR9UTE |
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Need more info. Cam specs? are heads ported? RPM range of engine?
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| 1965tbird |
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finding it hard to determine the rpm range of the engine but my estimation is between 5000 and 6000 rpm, cam is still being decided but it will not be much different to stock maybe slightlier lumpy and thats a real maybe, heads have been ported and polished inlet manifold is being match ported the extent of the porting i dont know, but like i said the car isnt being built for hard revs and huge horespower, but thats not to say im not going to give her stab evey now and then
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| XR9UTE |
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Sounds like something around 700cfm would do the trick then.
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| 1965tbird |
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hmmm thats what i thought thanks again for your help, i just didnt want to put my self in a situation where i get a carbie that is just adequate id rather have the lee way. so i guess now i wait till the engine is done!
cheers |
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