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Old 03-30-2003, 09:41 PM   #1 (permalink)
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302 tuning question.

My freshly rebuilt 302 started driving like crap last week, and I finally got around to seeing what happened. It was running like it had a vaccum leak, but it was still pulling 18in. I pulled the plugs, and they were all carbon fouled, this occured with about 200 miles on the engine.

So, what should I do next? Engine is a stock 302 bored .030, mild cam, Windsor Jr. cast heads, Edlebrock intake, Holley 4150, stock exhaust, Pertronix ignition, stock coil.

I currently have the timing set around 16 deg., and went one step hotter with the plugs. Parts store was closed for the day, and I couldn't do anything else.

I think that my problem may be two-fold, weak ignition and carbs jetted too high. I checked the resistance on the wires I have now, and measured between 7K-9K ohms, depending on the lenght of the wire. According to Holley's site, my carb has 64s in it right now.

Since I don't want to spend the dough right now on upgrading my ignntion system if I don't have to (my boiler went out Saturday night, and I had to spend 3K on a new one), what's the cheapest hing I can do if I end up fouling the plugs again? The carb was set with a tach and vaccum gauge, and seemed to perform fine, until the plugs fouled out.

If I do have to do something to the ignition, what's safe? I know the Pertronix ignition can only be used with points style coils, but would that be enough to do anything? I'd like to avoid moving to an electronic ignition system for the present time if at all possible, just don't have the cash right now.

TIA
GregG
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Old 03-30-2003, 10:41 PM   #2 (permalink)
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302 tuning question.

retorque bolts especially intake manifold.
possible weak coil-check by using an oscilloscope. Go to the local high school or community college auto shop.
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Old 03-30-2003, 10:45 PM   #3 (permalink)
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302 tuning question.

Do the plugs have wet, oil carbon or dry, gasoline carbon? Probably gas-caused carbon. Did the engine pop back thru the carb when starting or accelerating? If so, the power valve could be blown out, letting in way too much fuel. Floats sticking or set too high will cause a rich mixture, fouling plugs. Look at the venturiis with the engine idling. If you see any fuel dripping off them the float level is too high. No fuel should flow thru the venturiis until the throttle plates start to open. If the carb sat a long time the bowl gaskets could be shrunk, allowing internal leakage. Allan
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Old 03-30-2003, 11:07 PM   #4 (permalink)
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302 tuning question.

I second that carburetor check as a possibility.
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Old 03-30-2003, 11:47 PM   #5 (permalink)
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302 tuning question.

Is the engine overheating?
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Old 03-31-2003, 12:03 AM   #6 (permalink)
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302 tuning question.

Are you using a PVC valve and do you have baffles in the covers? No baffles can cause the plugs to foil if the PVC is sucking oil in. I had this happen once. Intake gasket can also seep in oil on the bottom side. Could be the carb too.
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Old 03-31-2003, 02:41 AM   #7 (permalink)
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302 tuning question.

The engine is not overheating as far as I can tell, I don't have any gauges, but the idiot light is working, and has not come on. Plugs are definately carbon fouled from gas, and not from oil. I am using the PCV valve, and I do have baffles in the stock Ford valve covers.

As far as the power valve goes, how can I check it? I ended up backfiring through the carb a number of times the first time we started the motor due to having the ignition wires on wrong, and a couple of times since playing around with the timing. I'll check the venturis to see if I can see anything. Also, I should have mentioned this before, on ocassion I'll have gas coming out of the tube right next to the choke plate after I shut it off. I was under the impression that Holley added some kind of something or another to keep the power valves from getting blown out from backfiring? Does anyone know if this is true, and if it is when they started doing it? I can double check the date code and figure out how old it is.

My carb is new, but I got a deal on it, my guess is that while it wasn't sitting around in my posession for very long, it might have been sitting on the shelf from the place I bought it from for a while. If my powervalve is vulnerable to backfires, is there anything that can be retrofitted to keep this from happening in the future?

Many thanks to all.
GregG

[ This Message was edited by: ggroth9 on 3/31/03 2:41pm ]
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Old 03-31-2003, 02:57 AM   #8 (permalink)
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302 tuning question.

If the fuel is blowing out the vent tube, the float is set too high. That's probably your problem. To check the power valve, try to suck on the diaphram side of it. If the plunger moves, it is okay. Several companies offer check valve kits to prevent power valve blow out, check a Summit or Jegs catalog.

My guess is that it is the front float level.
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Old 03-31-2003, 03:37 AM   #9 (permalink)
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302 tuning question.

I'll make sure to check the float level (again). I'll check the power valve too, probably taste better than the check valves on the air pump off of my Jeep's exhaust system.

Many thanks,
GregG
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Old 03-31-2003, 08:34 AM   #10 (permalink)
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302 tuning question.

I blew the power valve with one backfire on my 429pi. The carb was an older Holley 750dp. It wouldn't hurt to replace the power valve for reassurance.
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Old 03-31-2003, 10:15 AM   #11 (permalink)
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302 tuning question.

Also make sure the choke is set correctly if you have one.
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Old 03-31-2003, 11:28 AM   #12 (permalink)
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302 tuning question.

Electric choke. It's opening as the car warms up, I wired it to where the anti-dieseling solenoid was hooked up on the old carb, and watched it pull off with the car on, but not running. Is there a specific procedure at figuring out where to set it? I had nothing but problems with the mechanical choke on the Ford 2 barrel that was on there before. I think I have it set on the rich side right now, but I was having an awful time keeping it running when you put it in gear when the temp dropped below freezing, and it took a long time to warm up where you didn't have to drive double footed. Richening the choke did help quite a bit, but now I'm wondering if this is a symptom based on another problem, like the power valve, and I'll have to lean it out after I check everything out.

Thanks again,
GregG
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Old 03-31-2003, 02:17 PM   #13 (permalink)
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302 tuning question.

Holleys have come with PV blowout protection for over 8 years now so if you got it new you should be ok in that dept. Sounds like it is just too rich. What is the carb # you have? Do you have 64's all around? Shouldn't if you have a PV up front. Should be closer to 58/64 or 60/66 to start with IMO with the mild cam and heads. What cfm on that carb? I had a 750hp and could not jet it lean enough for my stock cammed 302. The 570 Holley I have on there now is set up with 55/64 and is still a touch on the rich side IMO.
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Old 03-31-2003, 05:58 PM   #14 (permalink)
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302 tuning question.

Carb is a 0-80497-S, which is a 4160, not a 4150 like I wrote earlier, 600 cfm, vaccum secondaries. Date code on the carb is 0483. I'm not sure what the jet sizes are, or how to check them. Per the holley manual the part numbers are 122-64 for the primaries, and 134-39 for the secondaries, does this equate to 64s and 39s? I replaced the primary power valve today, just for kicks, and found a vaccum port I had missed under the front bowl (Doh!). So I plugged that off, double checked that I didn't miss any more, and reset the timing and idle. I was able to drop the timing down to about 6deg with the vaccum leak fixed, and have the idle set around 900 in park. The old power valve appears to be fine, but I replaced it anyway. Car is running much smoother now, but I am still having a problem with it backfiring through the carb, leading me to believe I still need to do some more fiddling about with the carb. It will only backfire if you punch it hard, and then BOOM! If you raise it steady, it's fine. I also checked the float adjustment per Holley's manual, and everything looked fine to me. The cam is supposed to be very mild, 448/204 intake, 472/214 exhaust (not sure what all these numbers mean exactly, or if there are more numbers I need to dig up to do anything with them). So it appears I am getting closer to getting this thing running right, any clues where I should look next?

Forgot to add, car was warmed up when I did all this, and the choke was wide open.

As always, many thanks to all.
GregG

[ This Message was edited by: ggroth9 on 4/1/03 6:00am ]
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Old 03-31-2003, 06:47 PM   #15 (permalink)
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302 tuning question.

Lowering the timing is only gonna make matters worse. Those little motors like to be ran at 10-12 deg usually and the higher you can get it, the better the carb response will be. Back firing and sluggisness is a good sign of low initial timing.
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