Thread: tuning issue

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I just installed a worked pair of exhaust manifolds on a 454 that previously had headers. The carb is a rochester that was rebuilt by jet performance. The engine ran perfectly with the headers but now seems to be loading up (fuel) and seems to miss slightly when revved. I'm thinking i need to lean a 1/4 turn on the screws. I have timing at 34 total with 14 initial.What do you all think? thanks

I know that when you go from cast iron exaust manifolds to full length headers, you must compensate for the scavenging affects of the exhaust pulses. This means you need to go at least one or two sizes bigger for the jets to compensate for the extra air being sucked into the cylinder. Since I have never gone from headers back to cast iron manifolds, I can only speculate you perform the opposite change (smaller jets).