New stroker engine burning oil

[74stroker]

Thanks to all for your perspectives. I don't have the equipment or experience to tear down and rebuild the engine.
Is it possible the engine could not run safely on premium pump gas with 10.5:1 compression? Bob Kammer who builds performance engines suggested this.

 

[Chryco Psycho]

Yes it is possible the compression is too high for the fuel but you would hear it knocking under load , depending on a lot of factors even an iron head engine with 11.7:1 can run on pump gas , if it is knocking under load it can damage the engine but it will take some time & the sound would be very noticable immediately .

 

[74stroker]

We pulled the head and found 2 burned pistons (6 and 8), apparently caused by car running too lean at WOT.
It seems that the stock fuel line (5/16) even with edelbrock mech pump and thermo quad 800 com carb was unable to deliver enough fuel. The builder and I discussed this a while back as possible cause for performance at the tail end of the 1/4. The plan at this point is to replace the pistons, check the other side for any damage, then run additional pump from tank probably with larger (3/8) fuel line. Would one normally increase fuel delivery capability when going from a stock 360 at 8:4 compression to a 415 stroker at 10.25? The guys that built this engine have a lot of experience (mainly with Chevy engines); the car was to be mainly a street car with a lot of torque but to be occasionally run at the track in the 1/4.

 

[Beekeeper]

I could totally be wrong here but that seems like a weak explanation. I would think that a lean condition would be caused by improper jetting rather than a fuel line that’s too small.

I have always heard that when properly jetted, the cylinders on the four corners, farthest from the carb tend to be a little leaner because of the extra distance traveled and I’ve seen this on heads Ive pulled. If the other head is removed and the damage consistent in cylinders 5 and 7, I might suspect that the secondary jets were too small creating a lean condition on all cylinders in the back Under WOT.

Thinking outloud here, I would guess that if the carb was jetted properly but the small fuel line the real problem, wouldn’t the piston damage be most apparent and fairly consistent in cylinders 1,2,7 &8?

Going to a 3/8” line is a good idea for your motors needs though but I’m skeptical about the smaller line being the source of the problem.

I am by no means an expert here but there are guys on this forum who are so I’m anxious to hear a professional’s viewpoint.

 

[74stroker]

Bent spark plug electrodes were from melted pistons. Engine builder concluded car was running too lean at WOT; which explains it laying down at end of 1/4. Fuel line and sending unit have been upgraded to 3/8" from 5/16". Engine has been rebuilt with new set forged pistons. Electric pump at tank was discussed, but not installed. I've seen mixed opinions on fuel line size... Hope this corrects the problem..

 

[74stroker]

Thanks Beekeeper! I will bring this up with builder.

 

[Juan Veldez]

I had an engine do that once and it turned out that a couple of the cylinders had rings that never seated properly, even after 1500+ miles. Removing the head showed that two of the cylinders were slick with oil and the walls still had the cross hatch hone pattern while the others did not.

A guy I know gave me some powder that I put on the walls (very sparingly) after cleaning the oil off. That did the trick.

I have heard (never done myself) that slowly dropping a couple teaspoons of Ajax down the carb while the engine is running will fix issues like this and other imperfections on the cylinder walls. Anyone else ever heard of this. It wasn't April 1st when I was told, BTW. - Never mind the Ajax, I just seen the pistons, wow.

 

[Juan Veldez]

Thanks to all for your perspectives. I don't have the equipment or experience to tear down and rebuild the engine.
Is it possible the engine could not run safely on premium pump gas with 10.5:1 compression? Bob Kammer who builds performance engines suggested this.

Depends on what octane the premium gas is that you used. Did it ever "knock" when you shut it off? That would be too low of octane. Do you have aluminum heads? They can handle a little less octane than iron heads as they dissipate heat faster. Do you have fuel injection or a carb? I will assume a carb, and the carburator was not jetted/adjusted properly. Could this have been originally jetted at a different altitude? Buddies of mine have problems running up and over the Sierra Nevada mountains all the time. Sea level to 7,000 feet is a killer.

 

[Chryco Psycho]

Ouch , I had a similar issue with a 440 it would lay down at full throttle because the fuel line was too small .

 

[74stroker]

Depends on what octane the premium gas is that you used. Did it ever "knock" when you shut it off? That would be too low of octane. Do you have aluminum heads? They can handle a little less octane than iron heads as they dissipate heat faster. Do you have fuel injection or a carb? I will assume a carb, and the carburator was not jetted/adjusted properly. Could this have been originally jetted at a different altitude? Buddies of mine have problems running up and over the Sierra Nevada mountains all the time. Sea level to 7,000 feet is a killer.

Minimum octane of 91, sometimes 93. Never heard any knocking. Iron heads, carter thermo quad (800 com) recently rebuilt. central NJ car elevation probably 200-500.

 

[74stroker]

Ouch , I had a similar issue with a 440 it would lay down at full throttle because the fuel line was too small .

Did you go to an electric pump back by or in the tank, or was mechanical pump off cam adequate?

 

[74stroker]

No electric pump at tank. Just bigger fuel lines and tank sending unit (now 3/8"). Have not run it in 1/4 yet.
Need to talk to engine builder ---I'm a bit gun-shy; don't want another piston melt-down!

 

[Chryco Psycho]

I was running an electric pump near the tank & it starved with 5/16 line

 

[74stroker]

The sad saga continues. The engine builder, Joe Lemley and his son rebuilt the engine in fall 2022, and I was changed for parts and labor (~ 2500). replaced pistons, rings checked cylinders. Put engine back in car and bare wire on alternator shorted the engine harness. Took me several months to straighten out wiring and instrument gauge problems. They replaced fuel line with 3/8" from pump to tank. I have driven it about 200 miles, with 1 or 2 wot to 60-80 mph. The car is now burning oil again from same side as it did when pistons were burned. I will pull plugs and do compression test later today. I cannot believe it.
These guys came highly recommended...I had several people advise me that the 3/8 line should go all the way through to the carb, but the Lemley's thought it would be adequate to just run it from the pump back to tank...
I retired this month and will have more time now to get uo to speed on this, and I'm counting on help from you experienced molar enthusiast..

 

[74stroker]

I discovered a few days ago that the fuel cap I got from a junkyard back in the 1980s was not vented. I wonder if this was the problem in fuel delivery at wot-- causing vacuum in tank and pulling fuel back from pump, causing engine to go lean...

 

[Chryco Psycho]

Could be part of the problem for sure but there was usually a vent system on the tank either to the engine or carbon canister assuming that line is also open still

 

[74stroker]

There is the original carbon canister with vent lines to the carb and tank. How would I know if they are blocked? Perhaps just blow into them? Would changing the canister filter do any good? Does the canister need to be changed out? Is it possible to burn the same piston (no 6 with 200 miles on newly rebuilt engine) or is it possible it was not properly repaired in the rebuild.
Again, these guys have a very strong reputation for building race engines.
Thanks very much for your guidance on this!

 

[Chryco Psycho]

Yes you can just blow through the lines .
A boroscope can allow you to look into the cylinder through the spark plug hole .

 

[74stroker]

Thanks. I appreciate it!

 

[74stroker]

There are 3 lines running out of the top of the charcoal canister. One is plugged with a rubber cap. The middle line that runs from the canister to the tank is blocked. The third line runs to the carb and appears to be open.
The unvented gas cap was replaced by a new vented one. The people who built the engine will not look at it until July.
Compression (dry) test below (May 2022 at top), June 1, 2023 at bottom. Passenger side exhaust was burning oil after 30 mile drive on highway at ~ 60 mph. Plugs show oil in no. 6 which lad the lowest compression, but not that much lower than the rest of the cylinders. Again, car has only about 200 miles since they rebuilt engine, mostly short trips of 3-6 miles.
I will try and get a camera to see inside the cylinder--any suggestions as to a good model to purchase?