This is topic Spark plug gaps!?? in forum Tech Talk at Northern California Ford Owners .
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Posted by kuku93 (Member # 14014) on
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Question. I've built a 347 stroker N/A, and wondering why my car does not like to turn on when it's hot. Cold starts it'll run ok then turns off. But when I try starting it up it won't turn over. My question is, can a spark plug cause this to happen? I believed my gap is at .40 NGK UR4IX #7401. I've check every ground and everything is ok. I'm stuck on this. Any help would be awesome!
Posted by SLOWSN95 (Member # 8269) on
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Tuned? Aluminum heads? Injectors? MAF? New issue? Persisting issue? Need more info.
I have AFRs running Autolite 3924s gapped at .035 with my 347.
Posted by kuku93 (Member # 14014) on
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Not tuned yet. Dart eagle iron heads. 36lb injectors MAF converted. Forged bottom end. When I pull the number one spark plug. Its black and with the smell of gas. It's been an I'm going issue for a while. It's a new fresh build. Haven't even broken it in with 1 mile yet. Still trying to get it to the right degree but it won't stay on for a while for me to get it. I'm using a megasquirt ecu tuned for the injectors and the base map.
Posted by kuku93 (Member # 14014) on
:
Not tuned yet. Dart eagle iron heads. 36lb injectors MAF converted. Forged bottom end. When I pull the number one spark plug. Its black and with the smell of gas. It's been an I'm going issue for a while. It's a new fresh build. Haven't even broken it in with 1 mile yet. Still trying to get it to the right degree but it won't stay on for a while for me to get it. I'm using a megasquirt ecu tuned for the injectors and the base map.
Posted by SLOWSN95 (Member # 8269) on
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You need to pull fuel out. If you have a wideband, use it. If you don't have one, get one. There should be a table for cold start fuel and warm start fuel. Other than that, you need to base your idle and air/fuel on maf transfer functions as well as high and low slopes.
But you do not want a new motor that rich. If it's not starting because there's too much fuel, you can wash out the rings.
Posted by kuku93 (Member # 14014) on
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Ok thank you
Posted by Martinna (Member # 12493) on
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Listen to SLOWSN95. With out a tune, your new injectors are squirting twice as much fuel during startup than the motor needs. Tell your tuner to cut it in half. Another thing that makes a difference on startup is your timing advance.
Posted by kuku93 (Member # 14014) on
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I have a mega squirt and it has something called the live tune and tunes the tables for you as the rpm's go up. But I think I have the wrong spark plugs on there. I still need to tune my FPR. But without my car staying on when it's hot, I can't do those. Currently have the NGK IRIDUM IX #7401 in them and those are not the right ones. The guy who told me to get them is an idiot. And sadly i listened
Posted by kuku93 (Member # 14014) on
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So I talked to the people about my engine specs. Dart recommends to use the Autolite ar23 for those heads. So I guess I'll try those out and see how they perform.
Posted by SLOWSN95 (Member # 8269) on
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Give us some more info about your setup. I can possibly help you out a bit.
What I need to know is what...
Cam specs
Compression ratio
What maf?
There is a calculation for everything. But before you start experimenting, get an AEM wideband and have it installed. Aggressive cams like timing, some injectors need higher base pressure for better spray patterns (I'd set it to 45lbs with no vacuum)
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