Leyland P76 Owners 2004 | 
		Question Holley carbys   | 
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Question
  - Sunday, November 06, 2005
 
  
  - Right oh , i just found the problem (I think).
 
  - I had a go at retuning the holley 600 carb and found that when i turned idle screws back in and only turned them out half a turn   the motor started to run smoother and now theres no smoke out the pipes.
 
  - Now the question is i thought that these carbs had a one and a half turn idle ajustment?? could there be another prob?(leak?)
 
  
  - cheers niko.
 
 
 
Reply
  
  - Monday, November 07, 2005 5:06 PM
 
  
  - Hi Niko
 
  - One question, why are you running such a high CFM Carby when their is no way in the world that your 4.4
 
  - can flow that much ???
 
  - If you want it to boogie down low and up high,don't go larger than a 465 Holley.
 
  - So many people think bigger is better and end up driving a fuel guzzling pig instead of a torquey street sleeper.
 
  - I have the figures here to work out your CFM requirements if you provide me with some details about your motor..
 
  - Cheers Anton...
 
 
 
Reply
  - Monday, November 07, 2005 8:44 PM
 
  
  - Hi Anton, i think from memory i had been told that the 600 would work fine, but im not sure by who its been in the car for a while.
 
  - When i had the motor recoed they (speedpro) did do a fair bit to it.
 
  - It was bored out to 4.8ltrs and flattop pistons were fitted.
 
  - The heads have been ported/shaved and the manifold is a custom number (4barrel)
 
  - Other mods include
 
  - jethot coated extractors, electronic distributor,and a cranecams sparkamplifier.
 
  
  - Im not sure of the power out put but the biggest problem has been the transmission its blown up three times( one time really blowing up!!)
 
  - Its all going to change as im going to fuel inject the motor sooner than later.
 
  - cheers niko.
 
 
 
Reply
  - Mon, 7 Nov 2005
 
  
  - Sounds good in the motor department Nico, but i would still like to see a 465 holley set up properly for the motor
 
  - mods, recon you would think twice about fuel injection then. I would imagine that the 600 holley you have on at
 
  - the moment would be running a heavier spring on the vacuum secondarys to negative any of the ill effects of the
 
  - large carby, opening the secondarys too quick which would play havoc with your airspeed.
 
  - The formula for working out your CFM is-----   Engine CID X  Maximun RPM   Divided by 3456 .......
 
  - This formula assumes 100% Volumetric efficiency, which off course you will only have if your motor is blown. \
 
  - Yours is probably working at around 80 to 85%  realistically.
 
  
  - For example a 350 chev X 8000 rpm  Divided by 3456  = 810cfm at 100% VE
 
  - Where at 85%  VE its CFM is 689 quite a difference.
 
  
  - So your motor would roughly come out at  290cu X 5000rpm  divided by 3456 = 420cfm at 100% VE........
 
  
  - Hope this helps & Happy Peeing.................
 
  - cheers Anton.
 
 
  
Reply
  - Tue, 8 Nov 2005
 
  - Your Holly 600 isn’t too big for the capacity (4.4) but the P76 ports in the heads are too restrictive to allow
 
  - the flow rate the 600 needs, hence try using a smaller CFM size and it will probably go better and use less fuel .
 
  
  - You can enlargen the ports for more flow and fit bigger valves , cam etc and the horsepower will go up but low down toque will suffer , also don’t expect it to be a cheap option .
 
  - By the way – Holly lies about the CFM rate on  their carbies (they have a creative way of measuring their CFM rates to get higher figures)
 
  
  - Hope all this helps , now where was that coma .......
 
  
  - Rick
 
 
   
Reply
  - Mon, 7 Nov 2005
 
  - With a mild cam, extractors and few head mods  a 390cfm would do nicely, I reckon.
 
  - Mick.
 
 
 
  
		
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