Performance drop - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 03-31-2016, 05:11 PM Thread Starter
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Performance drop

Hello everyone,

I recently installed an Edelbrock 4-bbl intake and carb and a Pertronix billet distributor on my clone with a 350. The original distributor was working fine, but when I bought the car the PO had a ordered a the Pertronix, but never installed it. Since I was puling the original intake and carb (2-bbl) I decided to install the Pertronix.

Heres my issue: Before changing everything, even though the accelerator pump was bad on the 2-bbl, I could coax it into lighting up the tires. Now, with the 4-bb and Pertronix, if I stomp on the gas its like driving a golf cart. It goes, but not fast. The motor starts up and idles fine (doesn't start up as fast as with the old equipment though). I have the timing set to the factory specs of +9 degrees, though it would probably do better a little more advanced.

I've been reading the forum about the resistor wire that drops the voltage going to the coil to 9 or so volts so it doesn't burn out the points. I checked the volts on the wires with the motor off/ignition on and I got 12 volts. I also checked with the motor running and got 12 volts. Tried to follow the two wires, but lost them in a tightly packed bundle going to the firewall (too scared to unbundle old dry wires). Cant tell any colors because it looks like one of the POs sprayed everything in the engine compartment with black paint.

I'm wondering it I might have the new distributor installed one tooth off because the oil pump didn't like up perfectly with TDC. Can that happen? Would that slow the performance down Any other clues?

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post #2 of 4 (permalink) Old 03-31-2016, 05:30 PM
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As long as you can time it, it shouldn't make a difference if it's 1 tooth off. I've found that almost every engine wants it's own timing. I would keep bumping up the timing until it starts to ping, then back it off about 8-10 degrees. Also make sure there are no vacuum leaks.
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post #3 of 4 (permalink) Old 03-31-2016, 05:57 PM
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What type/style of Edelbrock intake and what type/size of carb? The wrong size/type of intake along with the wrong size/type of carb will kill your bottom end performance and it won't be responsive/snappy because you no longer have the high speed velocity of the intake charge you had with the 2 BBL set-up. This is where the Q-jet excels because you get the small primary's like a 2 BBL (which makes it responsive and snappy) coupled with the vacuum secondary system to provide more fuel to meet your engine's requirements. If it is just the bottom end you lost but the seat of your pants feel tells you you have more power once the engine builds RPM's, then this MAY be the problem and it may be possible to tune some of that out of the carb if its not a Q-jet.

Timing could indeed be part of it, as well as the distributor's timing curve - this is a little bit of trial and error as Rukee pointed out.
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post #4 of 4 (permalink) Old 04-01-2016, 07:48 AM
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what PontiacJim said, plus check your accelerator pump shpt, it should be a healthy squirt when you open the throttle... take the air cleaner off, and with engine off, do it by hand and see what you is very likely you can tune your combo back to performance.....a vacuum leak would also kill bottom end....
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