520 CI Stroker 440 Engine Problems In 1967 Fury

[65CopCar]

It was a great pleasure to help today!

Yes there are things that could be improved (my ultrasonic probe indicated potential significant vacuum leak in one corner of the carb and an electrical abnormality at the coil), but they probably are not the main issue.

The spark plugs are probably WAY too hot. They are Champion RN14YC. The engine just quit while idling after we took it for a nice spin. When tried to restart it and it sounded like it wanted to blow up and it spit some smoke out of it to boot. Started it up again and it died after a minute or two.

So decided to see what it sounded like while only cranking it. So I pulled the spark plug wire out of the coil so it would not fire - impossible for it to run with the coil wire pulled.

Much to our surprise it basically ran for a couple of seconds. Ok - THAT'S A PROBLEM! The most obvious cause is too hot of a spark plug. 14 is too hot. 440 Source says 12 is their standard recommendation, and I think that is too hot for a 10.5:1 motor. This is a 520 CID. To put it in perspective, granted it was better heads and higher compression, I ran a 7 heat range in my 528. I recommended a 10 heat range, and the NGK should be a bit colder than the 10 so should be a good start in my opinion.

Will it totally solve the problem, maybe or maybe not. But for sure its a major problem and it needs fixing before any other troubleshooting takes place. Pretty obvious the dieseling is being caused by the spark plugs, but if its not the cause, then there is a serious combustion chamber problem and I seriously doubt that.

 

[Don Frelier]

It was a great pleasure to help today!

Yes there are things that could be improved (my ultrasonic probe indicated potential significant vacuum leak in one corner of the carb and an electrical abnormality at the coil), but they probably are not the main issue.

The spark plugs are probably WAY too hot. They are Champion RN14YC. The engine just quit after we took it for a nice spin while idling. When tried to restart it and it sounded like it wanted to blow up and it spit some smoke out of it to boot. Started it up again and it died after a minute or two.

So decided to see what it sounded like while only cranking it. So I pulled the spark plug wire out of the coil so it would not fire - impossible for it to run with the coil wire pulled.

Much to our surprise it basically ran for a couple of seconds. Ok - THAT'S A PROBLEM! The most obvious cause is too hot of a spark plug. 14 is too hot. 440 Source says 12 is their standard recommendation, and I think that is too hot for a 10.5:1 motor. This is a 520 CID. To put it in perspective, granted it was better heads and higher compression, I ran a 7 heat range in my 528. I recommended a 10 heat range, and the NGK should be a bit colder than the 10 so should be a good start in my opinion.

Will it totally solve the problem, maybe or maybe not. But for sure its a major problem and it needs fixing before any other troubleshooting takes place. Pretty obvious the dieseling is being caused by the spark plugs, but if its not the cause, then there is a serious combustion chamber problem and I seriously doubt that.

The weak spark should be corrected as well.
Orange/ yellow is inadequate

 

[65CopCar]

The weak spark should be corrected as well.
Orange/ yellow is inadequate

I agree. But Its a secondary issue in my opinion.

 

[MarPar]

Great News!! Headed in the correct direction!

 

[Lefty71]

I agree. But Its a secondary issue in my opinion.

Probably, maybe lol.

This is the motor built by a well known buider, now having odd occasional yet persistent issues? I havent reread the thread again.... Do we know the particulars of the ignition system, what has been replaced, and is the current coil 100% compatible??? Could be key, and maybe the current unit is just failing as well, or overheating itself.

BTW, glad to hear some real members got hands on.....this has been a tricky one.

 

[pnora]

Hi Everyone,

I have a long overdue update on the 520 stroker Fury and thanks to Mark or @65CopCar s help, it looks like we may actually hopefully have it figured out. He can chime in here if he would like to. Turns out it may actually be the spark plugs. The plugs in it now have a 14 ceramic and according to Mark and other knowledgeable engine people he knows and talked to, it looks like that is too big and we need a 10 or 12 ceramic with our 10.5:1 compression. That being said we just ordered these NGKs here…. Amazon.com: NGK (7131) BPR6ES Standard Spark Plug (8 Pack) : Automotive. We tested fuel pressure and it was about 7ish at idle, here is a picture.

View attachment 1954118



We did a spark test and it had a weak spark and the spark was a yellow orangey color, and the coil was a bit warm too. We also did some multimeter testing and some was good but some was a bit weak. We also did a vacuum test and it showed it good, but there is a leak somewhere on the right side of the engine according to Marks special stethoscope tool. The timing chain is good, but we need to retard the timing on the carburetor a bit. We need to improve the ignition a bit too and ground some stuff better. Here is some stuff I wrote down….

View attachment 1954128

We did the tests and we shut it off in park and it shut off fine like it should do. We took a test drive around the block and it ran great like normal, until we pulled in the driveway and thats when it messed up. We drove around the block and it ran great like normal, then we pulled in the driveway and it “dieseled” when my stepdad shut it off, we took a plug out and thats when Mark told us about the spark plugs that he thought the ceramic was too big and we needed smaller, then confirmed it with the people he knows and 440 source. Well anyways, it looks like we are finally headed in the right direction.

Where is that electric choke pulling its power from? If its on the coil it could be an issue.

 

[65CopCar]

Where is that electric choke pulling its power from? If its on the coil it could be an issue.

Its not connected right now.