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hi bear with me as this is kindof long but i wish to give all the info. i have a really well built 289 that runs low manifold vacuum because of the big cam (around 11 to 12). i have been fighting it all summer to perform as it should. it seems like it wants more fuel but when i give it more it seems choked. spark plugs read a lrean condition. my main irritation is that it does not have a good crispe throttle snap. my 302 in my 74 f100 snaps up to 4 and back down to idle lightning fast and its bone stock. the engine seems to rev up slow and seems to hit a wall at 2 grtand almost as if the pump shot is running out. but i am reluctant to adjust this because as i said the more fuel i give it the worse it smells and the more choppy it becomes. also the rpms come down fairly slow after i give it a bit of rev. all in all it feels as though i have no horsepower out of what should be a powerhouse. and lastly it seems to do ok cold but as the temp increases especially over 160 these issues increase in severity.

the engine has around 10 to 1 compression with factory 54cc heads that are ported with large valves. long tube headers into flowmaster 40s
the timing is correct idles at 14 and finishes out at 35 with all timing in by 3000.
i just changed the intake as i thought i had a vacuum leak but this did not change anything.
im running a 670 holley which i have altered the jetting squirter and pump cam numerous times on. as it gets warm i can switch to the pink pump cam and this helps a little which i find to be very strange.
i was running manifold vacuum but it actually is happier with ported for some odd reason.
i have also tried a holley 570 and this didnt help either
i do not have the throttle blades too far open on the transfer slots of the carb as i have checked this numerous times.
when i blow compressed air through the venturies it seems like it takes more to force gas out than what my manifold vaccum is capable of.
please i hope someone has someenlightening knowledge that they could share with me before i pull my hair out! im 19 and have always loved carbed engines but this is slowly turning me against them!
 

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Discussion Starter #2
oand i also compression tested it and that is not an issue there either
 

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not sure what all youve done. i did a 289 from scratch build (35 yrs ago). i had a crane solid cam/ lifters 290 dur 508 lift. even with the screw in rocker studs, mr gasket lock nuts on the rockers, i had to gap them all the time. once to get through the week to work, before hitting the streets fri night, sometimes again on sat if i got into a any races fri, before sat night, then again for the next week. it had a wicked lope but was real snappy on and off the pedal, but would get a little mushy if my gaps opened up. i got real good at it, but it did grow old.

the problem i had for a short while was i had guide plates for the pushrods, i had a bunch of sets of pushrods, bent standard pr`s, broke isky chrome moly pr`s. put a set of 289 hipo pr`s i had in it, never had another problem.

hydraulic cam? hows your lifters? valve springs? rockers? valve lengths? might be something along that line. just saw your post and throwing ideas :)

somehow you posted this in the 05+ v6tech forum so maybe a mod will move this for ya.
 

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also getting a cam card to set it straight up meaning having the right cam timing is important but ya I really haven't changed cams on my vehicle yet . but that is what im studying in school currently.
 

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cam timing lining up the spots on the gears is hard to mess up. but wore parts could be bad thing. i ran dual timing gears and a dual timing chain. in the day, that was the trick setup, not sure about nowadays.
 
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