Big cam idle adjustment, Holly 4150

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Another thing that helps with big cams is to drill a very small hole in both primary throttle blades. This allows more air in so you can close the throttle blades and get better idle mixture adjustment. If the throttle blades are open too much it exposes the transfer slot rendering your idle mixture screws useless.
 

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lilcuda said:
Another thing that helps with big cams is to drill a very small hole in both primary throttle blades. This allows more air in so you can close the throttle blades and get better idle mixture adjustment. If the throttle blades are open too much it exposes the transfer slot rendering your idle mixture screws useless.
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This modification should be a last resort fix.

Usually the reason the blades are too far open is the engine isn't as efficient as it should be which is centered around the ignition.
 
crackedback said:
This modification should be a last resort fix.

Usually the reason the blades are too far open is the engine isn't as efficient as it should be which is centered around the ignition.
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Yep! I did the blade drill a few times early on for moderately cammed engines.....until I got my mind right. :D
 
crackedback said:
I sell those bushing and for a lot less than FBO.
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Really? Damn!.... Pm me. Got some customers cars I might need a few.

We have a customers 66 Nova witha 427 small block and a .630 solid roller. Initial is at 24*/total at 34* with a 10* bushing. Idles pretty good @ 900rpm considering that cam. Didnt drill the throttle blades either.
 
OldmanRick said:
Yep! I did the blade drill a few times early on for moderately cammed engines.....until I got my mind right. :D
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So Chrysler didn't have their minds right when they put holes in the throttle plates from the factory even on some 318 BBD applications? Sure you can get a little bypass by cracking the secondary seat screw but the vortex through the hole if positioned close enough to the idle fuel port helps aerate the mixture... Just start small. The main thing is not to expose the transfer slot at idle or you will never get a good mixture.
 
Sure you don't have a vacuum leak some where. Last time I was chasing a no idle issue the intake gasket was sucked in at the bottom.
 
mguner said:
So Chrysler didn't have their minds right when they put holes in the throttle plates from the factory even on some 318 BBD applications? Sure you can get a little bypass by cracking the secondary seat screw but the vortex through the hole if positioned close enough to the idle fuel port helps aerate the mixture... Just start small. The main thing is not to expose the transfer slot at idle or you will never get a good mixture.
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That may have been part of an emissions package, very low idle/initial timing. If you don't have to do it, it's best to leave them complete.
 
We'll I work out of town and won't be home for a few more days, I will order this pro billet now and also order this bushing and try that. But I'm getting rid of the 650 for a holly 750 race. I will be checking back next week once all this is done!
 
Well i just the call from my mech and he worked his magic with a new Holley 750 DP race style 4150, and he also rebuilt the distributor (not sure everything he did but he did say he worked some magic) said initial timing is 24* and total is 38*. He said it idles right around 650-750ish, also said she just runs like a dream. Smooth idle (for a big cam) and response is super crisp & clean. Im too excited to get home now and have 2 more days till i am, but i will def take some videos and post them up on here!
 
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