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Discussion Starter #1 (Edited)
Hey all,

I'm new to this forum, as well as carbed motors so I apologize in advance for my lack of knowledge.

I recently purchased an 82 Mazda RX-7 with a Ford 302 from what I believe to be a late 80s F-150. The motor is stock apart from a Holley carburetor. Lately I've noticed that its having huge hesitation issues on higher rpm/ hard acceleraton. It'll accelerate fine up to about 3000ish RPM, then it starts to break up hard and I lose almost all power. It's also backfiring heavily on deceleration when gearing down. I've researched a bit and a lot of guys are saying it could be that the vacuum advance on the distributor isn't functioning properly, or it could be a vacuum leak. I didn't notice any vacuum leaks, but I'm unsure how to check to see if the vacuum advance is working correctly. I also pulled plugs and they all seem fine as well as replaced plug wires. If anyone could help with some suggestions and on how to test the vacuum advance that would be awesome.

Thanks!

Cody

*edit

It also has started idling low (around 4-500rpm), and occasionally backfires into the carb as well
 

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Sounds like a timing issue. I had similar problems on the 302 in my '65 Mustang. The timing chain was just about shot. I had points in the distributor, and I had a heck of time setting the gap/dwell.
 

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I would check the basics first..Compression check on all cylinders..Check timing..Vacuum advance is easy to check..If the vaccum on the hose is full time (manifold) vacuum it should decrease the idle rpms when you remove and plug the hose from the distributor..You can also remove the distributor cap and suck on the hose and see if the advance plate moves..If not and you can easily suck or blow through the hose the diaghram has a leak in it..You said you replaced the wires but what about plugs,cap and rotor?
 

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If it is a vacuum secondary carb. put a paper clip on the rod going from the sec. throttle plate to the vacuum diaphragm so you can tell if the sec. are opening up. That could explain the problems on hard take offs. The back firing on backing off could also be a vacuum leak and I would check the throttle shafts on the front of the carb. It will suck in air and pop like crazy out of the tail pipes if they are leaking. Didn't say where it was back firing from I don't think.
The vacuum plate can cause a lot of this also like said above. Is it points or elec. ignition?
clint
 
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