Cylinder #6 solutions inline 6 heat issues

[Garage5]

So I don't know if this is the right section for this question or discussion, but since this section seems to have the most hands on guys I figured why not. I've tried searching and found nothing of substance where this topic was directed towards Cylinder #6 preventative ideas.

I recently had a rather extensive race motor fail at cylinder #6, I've had quite a few other failures at cylinder 6 in the past. I remember I had two head gasket issues 1 on an s52 and 1 on an s54 both fail at the division between cylinder 5 & 6. I had countless issues over the years with coils that seem to hover around cylinder #6. Most m5x family motor seems to have VC leaks back behind the back of the motor yet once again near cylinder #6.

I know its an inline motor, so obviously the last one in line will be the one that gets the least amount of air, so i'll have more heat. I was told it also gets the least amount of oil pressure/coolant (don't quote, just something i was told)

It gets the bulk of the exhaust heat as well. All this being said. What ideas have been done or can we come up with to protect our track/race cars from carnage or engine failures (specially at #6)??

-Factory heat shields being intact
-Exhaust wrapping the pipes/headers
-High Temp heat reflective tape

[olemiss540]

So I don't know if this is the right section for this question or discussion, but since this section seems to have the most hands on guys I figured why not. I've tried searching and found nothing of substance where this topic was directed towards Cylinder #6 preventative ideas.

I recently had a rather extensive race motor fail at cylinder #6, I've had quite a few other failures at cylinder 6 in the past. I remember I had two head gasket issues 1 on an s52 and 1 on an s54 both fail at the division between cylinder 5 & 6. I had countless issues over the years with coils that seem to hover around cylinder #6. Most m5x family motor seems to have VC leaks back behind the back of the motor yet once again near cylinder #6.

I know its an inline motor, so obviously the last one in line will be the one that gets the least amount of air, so i'll have more heat. I was told it also gets the least amount of oil pressure/coolant (don't quote, just something i was told)

It gets the bulk of the exhaust heat as well. All this being said. What ideas have been done or can we come up with to protect our track/race cars from carnage or engine failures (specially at #6)??

-Factory heat shields being intact
-Exhaust wrapping the pipes/headers
-High Temp heat reflective tape

Hood venting helps tremendously as well as oil cooling.

[Garage5]

Hood venting helps tremendously as well as oil cooling.

I have dual oil coolers as of 6 months ago. Hood venting has been on my mind at times, i think its something that will end up on the car before the next time it sees the track.

Any other ideas? or info fellas?

[TheJuggernaut]

Can you provide more details on the failure? I've heard some speculation that these engines have flow issues on the upper rear corner of the block/head joint. If that's true, running the coolant pre-pressurized and a higher pressure rad-cap would help the flow through the system (as well as raise the boiling point and possibly shift the point of any local boiling from stagnant flow)

[Garage5]

Can you provide more details on the failure? I've heard some speculation that these engines have flow issues on the upper rear corner of the block/head joint. If that's true, running the coolant pre-pressurized and a higher pressure rad-cap would help the flow through the system (as well as raise the boiling point and possibly shift the point of any local boiling from stagnant flow)

Sure. Built s52, no expense spared. Spent most of its life being shifted around 6800 rpms (sole driver). Been running for about 18 months. Maybe 1000 highway miles between shops and storage locations (dealer tag). Handful of races and about 15 track days. Changed a few things and wanted to a retune.

Both intake valves let loose around 5500-6000 rpms right at the head on the dyno, motor shut itself down. This was was a hot summer day, had ample fans. 8-9th pull of the day. Should have been the final pull.

The carnage is bad I'll try to post some pictures later today. The head is thrashed pushed both exhaust valves into the seats. Cylinder number 6 has two ample sized cracks, I'd suspect aftermath. Both intake valves broke pretty cleanly right at the stem.

No, broken springs or retainers. No, damage to any other cylinder, so I'd rule out a timing issue.

Dual oil coolers
S54 oil pump and pan
Aluminum radiator with fan, on a temp switch with functional power switch (it was on)
Upgraded water pump
Low temp thermostat
Alum housing
All ducting and paneling in place
No hood venting but the hood was opened
Fresh oil change
BMW coolant

I'd like to say I covered all the basics plus some.

[TheJuggernaut]

When you say no expense spared, does that include aftermarket valves, such as Supertech? The OE valves are two-piece and are known to separate under sustained high performance conditions, especially exhaust.

[TXBDan]

Did you have a water temp gauge or logger during the failure? What was the actual temp? I don't think overheating would cause a valve train failure.

[Mr. M3]

Since you said you have upgraded valve springs and since both intake valves hit the piston at the same time on cylinder 6, I can almost guarantee your intake cam was set up incorrectly with too tight of a piston to valve clearance for hydraulic lifers. Nothing to do with temperature.

[pbonsalb]

Could meth injection help. If so, should it be direct port (each runner) rather than just a single pre throttle body nozzle? If the issue is heat related detonation, it might help. If so, tuning that cylinder differently could also help.

[dcvee]

Since you said you have upgraded valve springs and since both intake valves hit the piston at the same time on cylinder 6, I can almost guarantee your intake cam was set up incorrectly with too tight of a piston to valve clearance for hydraulic lifers. Nothing to do with temperature.

x2

You're searching for a ghost. Sure, cylinder 6 gets hotter. But not hot enough to cause the failure of any properly working collection of components. It's just the weakest link...something has to be. I'd look for other issues or combinations of issues like above.

Don

[Garage5]

One piece performance valves.

I don't agree with the P-V tapping to be honest. Why after that much time? We are assuming it was miss timed?

[Mr. M3]

One piece performance valves.

I don't agree with the P-V tapping to be honest. Why after that much time? We are assuming it was miss timed?

When you think logically which is more plausible? Have two one piece high performance valves fail at the same time without a failure of any valve retainers/springs or too tight of piston to valve clearance causing the piston to contact the valves at high rpms? Might of just been too tight of a tolerance that any buildup of carbon in the piston valve reliefs caused contact with the valve causing the damage? Or your hydraulic lifers are getting old and not doing their job. Remember hydraulic lifter setups usually require higher piston to valve clearances for added safety to prevent piston to valve contact. Might be able to get a better idea of the failure type if we say some pictures of the valves and the top of the piston. I've seen issues like this before which are usually caused by an over-rev situation usually by a miss-shift into the wrong gear or incorrect cam timing.

[Garage5]

When you think logically which is more plausible? Have two one piece high performance valves fail at the same time without a failure of any valve retainers/springs or too tight of piston to valve clearance causing the piston to contact the valves at high rpms? Might of just been too tight of a tolerance that any buildup of carbon in the piston valve reliefs caused contact with the valve causing the damage? Or your hydraulic lifers are getting old and not doing their job. Remember hydraulic lifter setups usually require higher piston to valve clearances for added safety to prevent piston to valve contact. Might be able to get a better idea of the failure type if we say some pictures of the valves and the top of the piston. I've seen issues like this before which are usually caused by an over-rev situation usually by a miss-shift into the wrong gear or incorrect cam timing.

I don't disagree with you regarding what sounds more plausible but...

I have solid lifters.

[Mr. M3]

I don't disagree with you regarding what sounds more plausible but...

I have solid lifters.

Ok still seems odd that you had piston to valve contact then only on one cylinder. Pictures would be the definitive proof. Do you happen to know what the engine builder set the cams at and what the p to v clearance was when new? That would also help.

[Press22]

After speaking with some highly regarded engine builders they told me never to block off coolant ports at the back of a inline6 motor.
Not sure if you're running the standard heater delete plug, but essentially they recommend to run a line from that back to your radiator/expansion tank.

Normally I would disregard this but these guys have 1000hp+ motors running reliably so I won't question it.

[TheJuggernaut]

I've heard rumors about the heater delete, it never made sense to me since stock it's flow that only happens via valve to a radiator (heater) but I considered adding a hose to route it back to the expansion tank. I talked to racers who run these engines and they have no issues with the plug. They also confirmed that I would have issues if I did this since I would be short-circuiting the hot coolant back into the system (expansion tank/water pump) rather than the radiator and reduce coolant flow to the upper passage of the head. Also note that the coolant flow path on an M50 family engine is not the same as M54 and S54.

[ScotcH]

After speaking with some highly regarded engine builders they told me never to block off coolant ports at the back of a inline6 motor.
Not sure if you're running the standard heater delete plug, but essentially they recommend to run a line from that back to your radiator/expansion tank.

Normally I would disregard this but these guys have 1000hp+ motors running reliably so I won't question it.

They're wrong. Every single race motor we've built has the rear port plugged. As do many others. They coolant flows through the head and block ... otherwise, it'll just circulate through the main port back to the tank without going through the engine.

[digger]

the heat that causes exhaust valves and the like to fail is usually from the tune rather than the coolant. the tune is not the same with each cylinder

there are quite a few reasons why the piston could have tagged the valves now and not earlier, the valves might have just failed or something else in the valvetrain that cause valve to drop, the evidence will be infront of you with the damaged bits

metric mechanic claim that 1 and 6 run cooler than the others as far as block temperature goes, im not sure its a simple as that but....

http://metricmechanic.com/wp-content...ance-Chart.pdf

[Garage5]

the heat that causes exhaust valves and the like to fail is usually from the tune rather than the coolant. the tune is not the same with each cylinder

there are quite a few reasons why the piston could have tagged the valves now and not earlier, the valves might have just failed or something else in the valvetrain that cause valve to drop, the evidence will be infront of you with the damaged bits

metric mechanic claim that 1 and 6 run cooler than the others as far as block temperature goes, im not sure its a simple as that but....

http://metricmechanic.com/wp-content...ance-Chart.pdf

That's good to know. Can you give me some solid evidence regarding you comment about the tune?

[NeilM]

there are quite a few reasons why the piston could have tagged the valves now and not earlier, the valves might have just failed or something else in the valvetrain that cause valve to drop, the evidence will be infront of you with the damaged bits

Someone I know who builds S50 family engines pointed out to me once that valve timing changes slightly as you go to the rear of the engine due to camshaft torsion at high rpm, resulting in cylinder #6, as the farthest away from the cam drive, being the most sensitive. Any slight cam timing issues, tired valve springs, or added lift/duration from aftermarket cams are more likely to show up first as problems with #6.

Neil

[digger]

That's good to know. Can you give me some solid evidence regarding you comment about the tune?

not sure what you specifically mean but the conditions in the combustion chamber are alot hotter than the the coolant temp, the metal parts wouldn't really flinch due to coolant temps, if the AFR or ignition timing are off you can cause the temps to rise and things can fall off a cliff so to speak and it cn happen to a single cylinder just due to natural imbalnce in mixture or there could be a delivery problem with fuel or faulty ignition parts. excessive coolant temps can bring on detonation but this doesn't sound like detonation (no pun intended). IMO the chances of both inlet valves breaking due to a fault of the valve itself is quite low