Help! Engine Malfunction - Need Advice

[Kim Petersen]

I could use some of the high-powered expertise from fellow members on the board to help diagnose a problem that led to my engine failing this weekend at a high performance driver's event at Sebring.

The engine is a Keith Craft 427w with an all-aluminum block and TWM fuel injection with FAST FXI software. It has less than 2,000 miles on it, 98% of which have been street miles.

Leading up to the failure, I had been experiencing what seemed like the rev limiter kicking in at strange times, usually in 1st and 3rd gears at around 4000 rpm. At other times, this symptom disappeared. This had been going on for a couple of weeks. The engine had been dynoed only four weeks earlier without any apparent problems.

On Saturday, as I was pulling through a relatively low-speed chicane, I experienced several loud backfires (and a driver behind me said he saw bursts of flames exit my exhaust) and a loss of power. I coasted to the side of the track and the engine sputtered and died. The motor will turn over with the starter depressed, but it won't start. Instead it issues forth with explosive backfire.

Interestingly, when this car was being test driven for Car & Driver magazine, a similar problem occurred. On that occasion the culprit was a gear in the distributor that broke into pieces. Upon inspection it turns out the gear was made of some non-metallic substance. Dennis Olthoff replaced it with a metal gear and we figured all was well. This means that on the only two occasions where the engine has had a load put on it, there has been a failure leading to the engine shutting down.

The car is at my brother's house, and we haven't yet started tearing into it. Some questions: Does this sound like the distributor again? Could a faulty gear, perhaps with a tooth broken off, have been responsible for the sensation that the rev limiter was kicking in (under certain torque loads, for example)? If it is the distributor, what with this having happened twice, could it be that the shaft within the distributor is overheating and causing the gear to seize and break? Or could the source of the problem be a faulty cam shaft?

In a couple of days we'll have the distributor out and check if the shaft turns, In the meantime, any thoughts in advance of trying to sort this out would be greatly appreciated. I'd be especially interested if anyone else has had a similar problem. I'm facing having to transport the car several hundred miles to Olthoff Racing unless there might be some easier-to-fix remedy.

Thanks guys!

Kim

 

[chuck smith]

it definitly sounds like a distributor problem and I would check the gear first thing. Your first gear sounds like a comp cams composite and I assume the next one was a bronze gear, both of which are designed to fail before the cam gear does, however in your case there must be an explanation as to why they failed so soon. A high volume oil pump can put stress on the gear, as can faulty alignment on the dist shaft. The rev limiter problem is also hard to explain, but I would guess that to be purely electrical. tough break. Have you spoken with Craft? Those guys have a good rep for solving their own issues and taking care of the customer. chuck

 

[Jac Mac]

One other reason for gear failure can be to many RPM on cold startup with the oil pump being able to create more flow than the relief can handle. This is a localised overpressure that wont show on the gauge and as it it is a 'dry' start the gear will have very little oil film protection. You only have to do this once to start a stress mark on the gear's, from then on its all downhill.
That doesnt explain the sensation of the revlimiter kicking in at an earlier date.
The flames out the exhaust immediately after the supposed gear failure would be the now retarded spark firing while the exhaust valve is open.

 

[Dutton]

Kim,

Chuck's absolutely right - call Keith. Their reputation for customer service was the deciding factor for me when I ordered my 331 from them, and I'd be absolutely shocked if he didn't drop what he was doing to get his team involved and provide a solution.

Keep us posted.

T.

 

[Frank]

Dist gear roll pin sheared was the first thing that popped into my head.

 

[Randy V]

That doesnt explain the sensation of the revlimiter kicking in at an earlier date..

My hypothesis;

Depends on the distributor and the temp of the oil...

Odd that the heavier oil will dampen the movement (chatter) of a worn gear interface.. Once warmed up, the worn interface and the chatter could cause instances of acceleration / twisting in the distributor shaft that could then cause the centrifugal counterweights in the advance mechanism to reproduce that chatter..

I've actually got video of the tachometer (needle jumping wildly all over the dial) and sounds of the engine breaking up like a rev-limiter while this happens in a racecar..

 

[Paul Thompson 'Hooligan']

Hi Kim

re the tacho jumping about and showing a rev-limit condition - I've seen this on Motec injected setups when there is a problem with the timing signals, ref/sync. These are derived often from a toothed wheel on the front pulley and for sequential injection, from a cam position sensor that is usually derived from the distributor. It is quite possible that both signals are derived from the distributor and clearly if the gear is failing, chattering or giving an poor signal then the fuelling and spark timing will be all over the place, hence the popping, banging, flames and rev-limit condition.

Considering the previous failure of the gear and as others have suggested, I'd look there first as that may be the root cause of ALL the ignition/fuelling issues.

Keep us posted...

Edit: - One last thing - does the FXi have any error / data logging? - have a look see there too..

 

[Jack Houpe]

Kim, we have the same engine and induction except I do not use a distributor for ignition. I would check the crank trigger also, if it gets out of time you will have similar problems to the distributor drive gear issue. I use a composite gear on my distributor drive shaft, they recommended it or bronze. Don't forget to check the crank trigger.

 

[Kim Petersen]

Well guys, my brother just pulled the distributor and found that half the teeth from the distributor drive gear are missing. This prompts a couple of questions:

1. This has now happened twice. Why would a fiber gear and later a steel gear break-up inside the distributor?
2. Does this discovery mandate a total engine tear down?

Any thoughts before we give Keith Craft a call? Thanks to everyone for their thoughtful – and often prescient – remarks.

Kim

 

[Pat Buckley]

Was it a steel gear or a bronze one?

Are you running a sold roller cam?

Are you running straight 50 weight oil?

Do you warm the car up carefully from cold start?

Are you running an HD oil pump?

You probably should tear it down to get those pieces out - unless you can account for every last one of them through draining the oil and some sort of flush......

 

[Peter Olliviere]

I am not an expert on the subject of the distributer gear but I did do some research when the subject came up on my engine build. For whats it worth it seems that people go with a HD oil pump for the greater oil supply or pressure it should provide or even for bragging rights, when the standard pump will do the job. But it seems that the HD pumps are causing a number of the drive gears to fail.

I went with the standard oil pump and am seeing oil pressure when warm of over 50PSI @ 2K and higher as the rpm 's go up with no problem from the drive gear.

Just my reason for not using a HD pump. Peter

 

[Jac Mac]

Half the teeth missing would raise the remote possiblity of a bent dist shaft or an incorrectly machined or out of round distributer or camshaft gear. ( as drive from cam to dist is 1/1 the same teeth mesh all the time ) My guess reading between the lines is still a cold start over rev along with the possibility of an oil of heavier than necessary spec-- if you fit in this category or allow others who do to drive your car the likelihood of repeat occurrences can only be lessened by 1.use a std vol oil pump, or fit an external belt drive pump such as Peterson ( Dont tell me you own the Company ) This would remove the cold start factor on the dizzy gear.

 

[Howard Jones]

While you are at it make sure the oil pump drive rod is the correct lenght. It's possible that the shaft is binding and causing the distributor to load up and shear off the teeth. This is a long shot but easy to correct and simple to check. You will need to check the up and down freeplay of the drive rod with the pump and distributor in place. This can be a problem with ARP and other high performance drive rods used on aftermarket pumps. Unless someone else has a easier way you will need to pull the oil pan to do this.

I don't remember the clearance for this but the stock spec should work.

 

[Randy V]

Kim - I suspect that the drive gear on the camshaft is damaged and is eating up the driven gear on the distributor.. The really bad part is that your engine has ingested that metal through the oil pump. I would, at a minimum, remove and replace the oil pump with a high quality Melling or Clevite standard volume oil pump. You can also purchase these pumps "blueprinted" by Precision Oil Pumps (you can find them on ebay).. Great bunch there.. I used to blueprint these pumps but found I was putting far too much time into them and losing my shirt.

In addition to cold start / thick oil - one of the things that will also cause additional loading on the interface is if someone has put the oil pump driveshaft in upside down. This will cause the distributor to not sit all the way down on it's seat unless it is forced down by the hold-down.

 

[John P]

The Precision Oil Pumps are a work of art, and well worth the money. For the HP model, the inside surfaces are Teflon coated, the end plate is precision fit and safety wired in, and the oil pressure is adjustable. They install a Boss 302 relief spring, and as shipped, will pump aprox 100 PSI, so the the pressure needs to be turned down a little. I just tried his website, and couldn't get it to come up, so they may be having some problems.

 

[W.C.Dilweg]

Kim, how did the issue with your motor play out w/Keith Kraft ? I only ask because I have been building a '66 Mustang Fast back w/ a C4 Corvette suspension and was considering the Keith K. 427 small block that you are currently using but could not find any warranty information on his web site unlike Roush. Could you update us on his response to the engine problem you are having and do you have to send him the car or the motor for him to examine and who pays the freight and labor ?

 

[Rick]

It appears that FE's have issue with this more than the Windsor or 289/302 small block. By design the distributor clamps to the manifold. How much impact does the variation in intake manifold or head gasket thickness and the resultant machining of each have anything to do the the correct meshing of the gears?. I would think this would be easy to overlook.(?)

Rick

 

[W.C.Dilweg]

This appears to be more of a oil pump or cam issue. My question is that Kim's on his second distributor drive gear through no fault of his own. A cam or pump can have flaws, the question is not Kieth Krafts ability to build a good motor, he has a good reputation in that regard, but more to what assistants he provides his customers when parts installed do fail. This motor clearly needs a total tear down the ensure that all the bits and pieces of gear have been removed after the problem itself as to the cause has been established and corrected.Without a written warranty on a $20,000+ motor I would be having sleepless nights.

 

[Jac Mac]

It appears that FE's have issue with this more than the Windsor or 289/302 small block. By design the distributor clamps to the manifold. How much impact does the variation in intake manifold or head gasket thickness and the resultant machining of each have anything to do the the correct meshing of the gears?. I would think this would be easy to overlook.(?)

Rick

While the dist clamp is on the manifold, the actual shoulder for dist location is in the block as per small block design. Where the dist pass's thru the intake manifold there is a compliant rubber seal and it is designed so that there is little chance of metal to metal contact at this point. The only way the manifold could effect the alignment would be if this hole was incorrectly machined or there had been major machining of cylinder head/manifold faces, both of which would make distributor fitment difficult.

 

[Rick]

JacMac:

Thanks for the heads up. My oversight. Not having put one together, visually it appeared as though the distributor was vertically registered by the manifold. Sorry:worried:

Rick