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Re: 440 jerking/surge while cruising and light acceleration [Re: Supercuda] #1920946
09/28/15 12:05 AM
09/28/15 12:05 AM
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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RapidRobert Offline
Circle Track
RapidRobert  Offline
Circle Track
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
Quote:
I was trying to enlighten the OP.
Oh OK, I misinterpreted. I apologize, my bad/my mistake


live every 24 hour block of time like it's your last day on earth
Re: 440 jerking/surge while cruising and light acceleration [Re: CoDart] #1920975
09/28/15 12:47 AM
09/28/15 12:47 AM
Joined: Sep 2007
Posts: 14,889
up yours
Supercuda Offline
About to go away
Supercuda  Offline
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Joined: Sep 2007
Posts: 14,889
up yours
Nah, I poorly wrote it is all


They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
Re: 440 jerking/surge while cruising and light acceleration [Re: CoDart] #1921499
09/28/15 10:39 PM
09/28/15 10:39 PM
Joined: Oct 2011
Posts: 318
Fort Collins, Colorado
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CoDart Offline OP
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Posts: 318
Fort Collins, Colorado
I appreciate the comments. Supercuda, I did rear the link you sent me, that helped me understand the system a lot better.

I have the distributor still blocked off and I think Ive been reaching the limit of pinging with the blocked off distributor. Ive been cruising it at different speeds and getting a good reading and adjusting the carb accordingly from idle-cruise-acceleration and wot.
Now my specs with 76/84 jets are:

Idle- 13.8 af 10" vacuum
Cruise 30mph-13.2 af 11" vacuuum
Cruise 50mph-14.1-14.5 af 12-13" vacuum
WOT-12.7-13.0 af

Since I have leaned the primary jets, I noticed if I go half throttle in 3rd gear or so(if your trying to pass someone) the AF ratio is about 13.3-13.5 but I hear pinging pretty bad. Since I know this now, I will now get the timing set which should help with the pinging...I hope! The wild thing is that I calculated my MPG and with this motor combo and slippery stall, I get right at about 10 mpg for 1/2 town driving and 1/2 50mph cruising.

Re: 440 jerking/surge while cruising and light acceleration [Re: CoDart] #1921519
09/28/15 11:08 PM
09/28/15 11:08 PM
Joined: Jan 2003
Posts: 31,081
Oregon
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AndyF Offline
I Win
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Posts: 31,081
Oregon
The power valves and the power valve restrictions are how you tune the AF ratio for WOT on a street car. Drag race guys cheat by changing main jets but that is just because they don't drive around town.

The power valve spring sets when the extra fuel comes in. The power valve restriction sets how much fuel comes in. If you need more fuel at WOT then you put bigger jets in the power circuit or drill out the restrictions. If you need the power circuit to come in sooner then you put a PV with a stiffer spring in (opens sooner).

Re: 440 jerking/surge while cruising and light acceleration [Re: CoDart] #1921526
09/28/15 11:13 PM
09/28/15 11:13 PM
Joined: Jan 2003
Posts: 31,081
Oregon
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AndyF Offline
I Win
AndyF  Offline
I Win
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Joined: Jan 2003
Posts: 31,081
Oregon
Originally Posted By CoDart
After some more cruising I found that if I plug off the manifold vac advanced on the distributor the car does not surge when accelerating or cruising. I think I need to hook the advanced up as PORTED but I do not have a ported port on my Holley. What do I need to make it ported?

Thanks!


Street cars should almost always use ported vacuum to avoid cycling the vacuum advance at low throttle position. Adding a ported vacuum port to a HP Holley isn't easy though. Basically you need to buy a different base plate. You might be able to find an old time carb guy who can modify your base plate but it is probably cheaper to buy a new one. I think the HP main body will be drilled for the ported vacuum but you should probably check first. I've converted them over before but that doesn't mean that all of the main bodies are the same.

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