Problems with rebuilt engine


We had the 360 engine in a ?71 Ford F100 rebuilt and stroked to a 390. It has taken a year and three engine failures, and still is having problems. Currently, it has burned 1.75 quarts of motor oil in 130 miles. Oil is seeping out of three of the spark plugs. There appears to be trace amounts of motor oil collecting in the coolant overflow tank (this was a big problem during the first failure).

This is the problem in a nutshell, but the history is long and complicated. We have almost $4000 (including a $350 towing bill) invested and an engine that still doesn?t work. Any suggestions?


Throw in the towel and drop a 460 in there.
Without details I have no idea what is causing the problems but oil oozing out of the spark plug holes means a ring problem.

In a nutshell, sometimes piston/ring problems can occur when stroking a motor as the rod angle changes due the longer crank journal throw.
There were some problems along this line when people first started stroking 302 Fords and making 347s out of them. The 331 stroker was fine, the 347 was not, and all because of rod angle, piston ring placement, etc.

No idea if this is the problem or not; just posting a hypothetical.


Your discription sounds like warped heads. That is usually how oil gets into the water or water into the oil.


Cut your losses, buy a modern truck with a modular fuel injected engine. You have already spent enough to buy one.


Thanks for the quick replies. Taking the loss and getting a new vehicle are not options, for many reasons.

It seems to me that for money paid, a working engine is expected. We know about the ring problems. How many miles of driving should it take to get them to seat?

As for the warped heads and the rod angle, wouldn’t that be the shop’s responsibility? That’s what we paid them for.


Yes, checking cylinder heads for warpage and surfacing them if necessary should be part of a proper overhaul.
I do not know if rod angle plays a part in this problem or not as I’m not familiar with any quirks on a stroked 360; only pointing out a possibility.

The piston rings should fully seat within 10-20 miles. There are a number of reasons for rings not seating; improperly bored and honed cylinders, excessive piston/cylinder wall and ring end gap, rings installed upside down or possibly damaged during installation, etc.
Usually if you have oil being pumped into the combustion chamber this points to an oil wiper ring problem rather than the top compression rings.
A cylinder leak down test could be performed to check ring condition, but it may be a waste of time actually.

From the multiple problems it sounds like the job was just not done right rather than it being a stroker crank/rod angle problem.
You could possibly have recourse in a small claims court, but the shop may have an out here.
They could claim that the engine is a “stroker”, therefore it’s a performance engine and no guarantee is given or implied, the warranty is up when it goes out the door.

Hope some of this helps anyway and wished I could be of more help. With engine in hand and a partial teardown I could probably figure out what went wrong pretty quickly.


Very informative for me, thank you. If you haven’t guessed, Jeff’s Secretary (me, his wife) knows little about cars, and Jeff himself knows little about computers.

I have one more question…

Why wouldn’t a stroker/performance engine have any guarantee or warranty? If that is what we paid them to do, shouldn’t we have an engine that works?


Get a lawyer. You’ve spent too much money and way to long playing with these guys. Have the lawyer send them a letter spelling out EXACTLY what the problems are and that they are to fix them at their expense. Also in the letter give them a time frame when you expect the work to be done.


The simple reason a warranty is usually not given on a performance or modified engine is that the shop would reasonably assume the engine is going to be hammered hard; either on the street or at the drag strip.
This is a valid point of view from a shop perspective.

A friend of mine got into racing years ago at the local track. He would build an engine during the week and never failed to blow it up within 5 laps of the green flag.

You may have a case here, but I’m not a lawyer and don’t know the million details behind the problem.
If any receipts state no warranty on a modified engine or if that disclaimer is posted at the shop you probably don’t have a case even if the rebuild was improperly done.

It’s a tough call and it may involve talking to a lawyer. Wished I could be of more help, but good luck on this.


A question. How did you get to 390 from 360? Was a stroker crank put it? Was the increase done by boring the cylinders alone?

Give us a little more information


A quick look at one of my manuals shows the 360 was basically a de-stroked 390 so I guess they put a 390 crank back into the 360 block?

This should rule out a rod angle theory unless there is a difference in the piston construction. Maybe the 390 crank requires 390 pistons, which would mean bore to fit as there is a slight difference in the bore diameters.

(Just so the OP will know what I mean by rod angle it works like this. The crankshaft stroke is lengthened and this means the rod travels further outside the cylinder centerline. This has the effect of exerting more pressure sideways against the piston, and therefore, against the cylinder wall and rings.)

Definitely an unusual deal here. I’m not knocking the OP on this but I don’t understand going through all of that expense, and now major headaches, to perk up a smog 360 engine when a 429 or 460 can be easily found and will generate a lot more power even as is.
Pretty tough deal here; hope it works out for them. :frowning:


They put in a 390 crank

The 360 rod measures 6.540" from center to center. The 390 rod measures 6.488".

In the beginning, we asked the machinist if we needed to use 390 rods. He said, “No, that he could get the 360 rods to work.” We think he said he’d have to do some machine work in order to not have to use 390 rods.

The machine shop has maintained that excess unburned fuel is causing the rings to not seat. After failure number one, the carburetor was sent out to be rebuilt and vacuum advance replaced on the distributor. After failure number two, they sent the carburetor out to be rejetted. The problem remains, and we haven’t contacted them about failure number three yet…we want to explore all our options first.

Can we simply ask for our money back and start over with a new shop? There are several factors not detailed here that have made us lose confidence in the integrity of the shop.


Without having all of those items piled on the table in front of me for examination I can’t speak with too much authority on what affects what. There’s too many questions about the rod length, piston type, piston compression height, etc.

Yes, it is possible that if you have a problem with too much fuel entering the combustion chambers due to a faulty carburetor, excessive fuel pressure, etc. the rings may not seat.
Generally if you have one this bad the engine will be running very badly, belching black smoke, and fouling spark plugs very quickly.

A compression test could be easily performed and that should answer the ring question with no doubts. If the cylinder pressures seem low, apply a squirt of oil into the cylinder and retest. If the reading takes a significant jump upwards the rings are shot.

You may have a very hard time (near impossible probably) getting money back on this.
You can ask or if push comes to shove you can take them to court, but it’s going to be very iffy.
JMHO anyway, and good luck on this.


One thing did come to mind. If the people that built the engine also installed it and ran it long enough that a carb or fuel pressure problem ruined the rings then it’s possible you have a case against them.

Running excessively rich for a short time should not hurt anything, but if the vehicle was actually operated like that for several days then raw fuel could damage the rings and cylinder walls by washing the oil down.
If an engine is running this rich the lower end can also be ruined. Raw fuel contaminates the engine oil and this will in turn wash out crankshaft and cam bearings, cam lobes, lifter faces, etc.


When you make the wrong rods work, you end up finding out that they don’t. The top of the pistons may have been damaged when they smacked the head. Usually it costs too much money to sue. You can represent yourself, but you will need a legal theory instead of a mechanical one. With the long rods, you didn’t quite reach 390 cubic inches either. From the oil consumption, it does sound like the ring lands have crushed into the rings. The engine has to be taken apart again.


The machine shop has maintained that excess unburned fuel is causing the rings to not seat

A carb that’s running too rich can RUIN an engine. It’s called cylinder wash. Unburned gas washes down the cylinder walls and removes any oil that’s there. The piston ends up running up and down on a non oiled cylinder wall…That is NOT good.