carb idle
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Tuned
Joined: Sep 2006
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carb idle
I need a little help. I have just replaced a blown motor (460) in a 79 F350 camper special. I found a 87 ford truck motor-460 and actually was casted in 79 as well. I swapped all the accesories, pulleys ect from the old to the new including the exhaust manifolds, pan and oil pickup. The 87 was supposed to be a running motor, so I did not check the timing. I swapped my Holley 4 bbl off the old in place of the Edlebrock 4 bbl because the Holley looked in better shape. After changing the oil, I started the motor- started right up and reved to 3k or so. I backed the idle screw off and the motor still ran at 3k? I totally disconnected the throttle linkage- still 3k? Could a stuck float , vaccum leak, advanced timing be causing this? I getting ready to shoot holes in this thing- can someone point me in the right direction?
Tuned
Joined: Jun 2007
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Did you put the EGR spacer back on after the swap? I tried to ditch the EGR spacer on my Thunderbird's 302 once in favor of a new aluminum spacer and when I started it the idle soared to 2000 and wouldn't come down. Ofcourse you may have ditched it long ago for all I know. Other than that I'd make sure the vacuum advance on your distributor is actually getting ported vacuum, and also if this Holley has a secondary idle screw in the baseplate you may want to back it off a bit. Not too much at a time time though, that screw is sensitive.
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Tuned
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Thanks for the info
Yes- when swapping out the carb- I left the spacer with the vaccum port in it, plugged it- but the motor had a second solid spacer that I removed. Something that I just thought of is- the edelbrock carb is square and the Holley is more of a rectangle- with the spacer removed the carb might be hitting the back of the manifold- i did not take notice when I put it on- it was getting late- if it is not properly seated on the manifold- would this give it enough of a vaccume leak to
cause it to race? The exhaust pipe is still disconnected at the manifold so I could not hear if it was sucking air.
cause it to race? The exhaust pipe is still disconnected at the manifold so I could not hear if it was sucking air.
Tuned
Joined: Jun 2007
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If the carb didn't seal well enough it could definately cause a vacuum leak and the symptoms you describe. However I don't know how likely it is that a Holley would strike a stock manifold. The fact that you removed a spacer interests me though I couldn't say precisely what the effect is. Adding or removing spacers can have a large effect on idle, I'd be curious to see what it does if you put the second one back. Is the Holley the original carb you were using on the old engine?
Last edited by sum_weirdo; Jul 18, 2007 at 01:23 PM.
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That carb is still delivering the amount of fuel to run that fast.
Timing would change it by about +500 rpm Max.
Cast as 79 or Designed in 79 ?
a 79 casting would read as : *9(A-M)digit(digit)*
That still could be an 80's 460 with a different timing setting.
Timing would change it by about +500 rpm Max.
Originally Posted by 0351mike
I need a little help. I have just replaced a blown motor (460) in a 79 F350 camper special. I found a 87 ford truck motor-460 and actually was casted in 79 as well.
a 79 casting would read as : *9(A-M)digit(digit)*
That still could be an 80's 460 with a different timing setting.
Last edited by Mil1ion; Jul 18, 2007 at 01:39 PM.
