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Rebuilt 460 lacks power

 
David289
New User
Posts: 16
Joined: 06/11
Posted: 06/10/11 07:36 PM

I took out the old 400 block (212k miles)on my 1977 F-150.Had a 1977 460 laying around,decided to rebuild it,sent it out...This was done:30 overbore everything insde is new except the crank (just polished)heads redone airgap intake,Holley 670 carb,largest cam available for a stock torque convertor (C-6 tranny) 3:50 gears out back.THE PROBLEM: This engine won`t even spin the rear wheels whereas the tired old 400 block would do that and have more get up and go.My stock 460 had much more power.I had put in an accell distributor but did not set the gear at the proper hight I believe since I chewed up the gear on it(cam gear seems ok.I put the distributor from the 400 block for now.This 460 has the want to feeling but lacks power. Most any engine in a pick up ought to at least smoke the tires.Any ideas out there???

Thanks in advance
David289  

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waynep7122
User
Posts: 146
Joined: 10/09
Posted: 06/10/11 09:23 PM

are you running the stock 400 exhaust system....   do you have an independent exhaust shop near by .. have them install an oxygen sensor bung... stick a narrow band oxygen sensor in it...  hook that up.. even temp to a 30 buck narrow band air fuel ratio gauge..  almost every parts store has it...  you might even want to think about a narrow band heated oxygen sensor... to keep it operating ...

you will also want to hook up a vacuum gauge to the intake..  mounted again..  temporary  or long term...  you can use one of the larger diameter fuel pump vacuum testers also.. that go from 30 inches of vacuum to 15 inches of pressure..

most stock performance carbs are jetted for something around a 350..   holley made special 4180 carbs for the 460.. i have one on my 460 powered van..  idle mixture screws in the base plate.. so they are much harder to get to...  they were used from 77 or 78 to 86 or so...  and will bolt right to the existing holley flange manifold..

its very easy with the mods you have done to exceed the stock converter...  how does it run from a roll .. or when pulled down into first gear???

a 460 takes a LOT of fuel from the idle circuit... from the idle transition circuit.. and from the primary mains...


this is just a place to start....

post your manifold vacuum readings...  

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waynep7122
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Posts: 146
Joined: 10/09
Posted: 06/10/11 09:25 PM

did you have one of these carbs on your 400 or the original on the 460???

http://www.mustang50magazine.com/techarticles/mump_0907_how_to_understand_the_holley_4180/index.html

and.. yes these same carbs with different jetting were used on the 5.0 HO motors of 85 and 86...  

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David289
New User
Posts: 16
Joined: 06/11
Posted: 06/12/11 04:50 PM

Thank you very much for taking the time to reply.   Installed on this 460 are a set of full length headers.The carb on the 400 block was a two Bbl.You mention installing an oxygen sensor bung so I must admit you got me on this one since there are no catalics on this otherwise old school 1977 engine.I do like your suggestion on the vac gauge. The carb is a new Holly 670 (ready to use out of the box they say,yea sure)As to the torque convertor,when money permits that will be changed.
I am not looking for a total high performer but expect much more performance than I had with the tired ole 400 engine stock to the bone.Considering the things done to this 460 it should perform much better than it does.
Thank you again,it was kind of you to take the time.
David  

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waynep7122
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Posts: 146
Joined: 10/09
Posted: 06/12/11 08:47 PM

most exhaust shops have oxygen sensor fitting they can weld into the sides of header collectors... there are also collector adaptors that have the oxygen sensor threaded bung already installed...   the sensor threaded bungs cost under 10 bucks.. plus welding..


there are wide band gauges and sensors...  

and narrow band sensors and gauges...   the narrow band gauges cost about 40 bucks...   the narrow band sensors about the same...

type in air fuel ratio gauges...   into the search window above.. there are a bunch of articles on it... i tried to post a link...

but the spam blocker got me...    you will find more after the first search by pulling down the menu where air fuel ratio is types in ... select performance group...   or select source media...  that will really turn up some results.. as there are over 50 magazines.. there has to be close to 40 on cars and trucks..  

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David289
New User
Posts: 16
Joined: 06/11
Posted: 06/13/11 01:56 PM

Thanks again Wayne,your input is appreciated as is the time you take to help!!!

David289  

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