318 poly plug fouling

Rooster34

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Hey guys and gals hope all is well! It's about coming that time here in the northeast to put the ole girls away for the season. I have been chasing 2 plugs fouling #7 and #2 here for the last month or so, Autolite 85s. I've run compression test on all cylinders and they are all within what they should be from one another. I've adjusted the carb with a vac guage which is a holley 2bbl 500 cfm, squirter size is a 45, power valve is 7.5, 72 jets and the accelerator pump cam is the yellow one, that sits on a transdapt adapter for the stock 2bbl intake, stock heads have been milled for 10:1 compression, cam profile is 264 .450 222 @.50 with solid lifters and a set of tti headers. I'm just trying figure out why just those 2 plugs are fouling. I'm not sure if I need to get a new metering block that has adjustable IFRs or go with a step up for heat range on those 2 cylinders. I've attached some photos of the fouled plugs in cylinder 7 and 2 and 2 more of what all the other plugs look like. Any guidance is much appreciated!

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gyknot

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Just a thought, but if compression is good, and there is no sign of oil fouling, I'd suspect maybe a couple bad plug wires, or distributor cap.
I'm no expert on carb and ignition issues, but if 6 cylinders are firing fine, I would find it hard to believe you need carb adjustments, or 2 hotter plugs.
 

Rooster34

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Just a thought, but if compression is good, and there is no sign of oil fouling, I'd suspect maybe a couple bad plug wires, or distributor cap.
I'm no expert on carb and ignition issues, but if 6 cylinders are firing fine, I would find it hard to believe you need carb adjustments, or 2 hotter plugs.
I should have mentioned that the plug wires are new and the cap and rotor are as well, however I do have the original coil and distributor which I thought about changing out, just haven't got there yet.
 

Davea Lux

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I do not think fouling only two plugs is likely to be a carb problem. If the carb is too rich, they would all be fouling. #7 and #2 are the last two cylinders in the firing order, check to be sure you do not have their wire position reversed on the distributor cap. The after market carb adapters can cause a lot of issues with erratic fuel delivery because of turbulence between the throttle plate and the manifold. This in turn can cause the end cylinders to have an improper fuel ratio while the middle cylinders are fueled properly.
You might also want to get out your digital caliper and measure the cam lobes on the distributor, if they are excessively worn or the distributor shaft is bent, this can cause two adjacent cylinders in the firing order to fail to fire.

Dave
 

Rooster34

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I do not think fouling only two plugs is likely to be a carb problem. If the carb is too rich, they would all be fouling. #7 and #2 are the last two cylinders in the firing order, check to be sure you do not have their wire position reversed on the distributor cap. The after market carb adapters can cause a lot of issues with erratic fuel delivery because of turbulence between the throttle plate and the manifold. This in turn can cause the end cylinders to have an improper fuel ratio while the middle cylinders are fueled properly.
You might also want to get out your digital caliper and measure the cam lobes on the distributor, if they are excessively worn or the distributor shaft is bent, this can cause two adjacent cylinders in the firing order to fail to fire.

Dave
I'll check wire to make sure they are in right order, pretty sure they are as I jave triple checked but it doesn't hurt to look again. Funny you mention the distributor shaft being bent, that's is a possibility as I took engine out to seal the cam plug that was leaking oil and when putting it back in the distributor hit the firewall and my cap and rotor got all messed So i got a new one. If that is the case I'll just get a new dizzy. If all checks out how would I remedy the fuel delivery turbulence to the 2 end cylinders?
 

Davea Lux

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I'll check wire to make sure they are in right order, pretty sure they are as I jave triple checked but it doesn't hurt to look again. Funny you mention the distributor shaft being bent, that's is a possibility as I took engine out to seal the cam plug that was leaking oil and when putting it back in the distributor hit the firewall and my cap and rotor got all messed So i got a new one. If that is the case I'll just get a new dizzy. If all checks out how would I remedy the fuel delivery turbulence to the 2 end cylinders?

Address the potential distributor issue first. I mentioned the turbulence issue because with an after market cam and headers, you should really be running a 4BBL carb and an appropriate after market manifold. The stock 4BBL manifold did not flow very well at higher RPMs. The stock 2BBL manifold was geared and flow matched as an economy setup and does not work very well with a larger than stock carb.

Dave
 

Rooster34

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Address the potential distributor issue first. I mentioned the turbulence issue because with an after market cam and headers, you should really be running a 4BBL carb and an appropriate after market manifold. The stock 4BBL manifold did not flow very well at higher RPMs. The stock 2BBL manifold was geared and flow matched as an economy setup and does not work very well with a larger than stock carb.

Dave
Thanks Dave I really appreciate all your input on this issue and the many others you have commented on. I'll get a new dizzy and shaft and see where that puts me
 

Davea Lux

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Thanks Dave I really appreciate all your input on this issue and the many others you have commented on. I'll get a new dizzy and shaft and see where that puts me

Avoid getting a Car-Don't rebuild, they are a POS.

Dave
 

Davea Lux

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I use NAPA auto parts for generic rebuilds, but you need to check whose rebuilds they are. The other option might be to convert to an after market electronic unit which is readily available since you are already in the performance build area. If you go that route, be sure to also convert to an electronic voltage regulator. FuryGT a vendor on this site has a replacement electronic regulator that looks just like the original. The electronic ignition kits do not play well with the older style mechanical regulators due to static build up from the regulator point set, this can toast the electronic distributor.

Dave
 

Rooster34

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Ok, I was leaning toward an electronic unit. Could you possible send a picture or post one of the mechanical regulator?
 

Davea Lux

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Click on mail 040 not the icon. Located on the driver side firewall.

Dave
 

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Jakter

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I don't know if you're cleaning the plugs and returning them to the same cylinders or are you using new plugs that keep fouling in the same cylinders?

The reason I ask is about a year ago I had 3 Autolite 85's foul out like yours at three different times on two different cars.
I switched to NGK plugs and never had a plug foul on either car since I changed brands.

I asked around and nobody else seemed to be having the same problem with the Autolites.
 
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