A little more pep for all of you Carburated folks Out there. |
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A little more pep for all of you Carburated folks Out there. |
pcdarks |
Mar 18 2021, 02:43 PM
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#1
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Member Group: Members Posts: 80 Joined: 22-June 13 Member No.: 16,037 Region Association: None |
This is something for you to try to get more pep when you first hit the gas. First of all read it through until you understand what I did. I switched over from FI to a center mount progressive two barrel carb but this would work with any carb configuration. I had the stock distributor with vacuum advance and retard. I hooked up the vacuum retard to ported vacuum on the carb. What this does it retards the timing at idle. I then timed the engine with the vacuum hooked up to factory specs. The engine idles as it should at around TDC. As I start to accelerate from a stop the vacuum drops and the retard in the distributor releases giving me a little timing advance and the engine takes off with more pep. This advance works until the engine catches up and vacuum increases causing the distributor to retard to stock timing. Now the mechanical advance works for the rest of the acceleration. If I am cruising in a higher gear and give it gas the distributor again advances when the retard losses vacuum when the pedal is pushed giving the car mare advance again until the engine increases vacuum where it then retards to factory timing. At cruise speeds. the distributor mechanically advances to 27 degrees and runs there until again acceleration causes the vacuum to drop and momentarily advances the timing. The car has very noticeably better take off from a stop and accelerates quicker at speed. try it.
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PlaysWithCars |
Mar 20 2021, 10:14 AM
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#2
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Senior Member Group: Members Posts: 524 Joined: 9-November 03 From: Southeast of Seattle Member No.: 1,323 Region Association: Pacific Northwest |
Be sure and check your total advance. Its been too long since I worked on a -4 to remember exactly what the timing curve looked like. But, if I understand what you've done correctly, you are getting more advance at low speed acceleration which will make it peppier but you might also be getting excessive advance at high rpm WOT acceleration that could lead to pre-ignition. Check your total advance at 4000 rpm with the vacuum line disconnected.
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pcdarks |
Mar 20 2021, 04:04 PM
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#3
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Member Group: Members Posts: 80 Joined: 22-June 13 Member No.: 16,037 Region Association: None |
Be sure and check your total advance. Its been too long since I worked on a -4 to remember exactly what the timing curve looked like. But, if I understand what you've done correctly, you are getting more advance at low speed acceleration which will make it peppier but you might also be getting excessive advance at high rpm WOT acceleration that could lead to pre-ignition. Check your total advance at 4000 rpm with the vacuum line disconnected. Been there done that. The timing advances to 27 degrees at 3200rpm. If the pedal is floored at cruising speed it will momentarily advance it further but for so short of a time it will cause no problems. I stated this in the original post. Had you read it entirely you would have seen it. |
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