New engine rod knock...........
 

Put about 5 hours on newly rebuilt 2000 gen VI 7.4l MPI and decided to run it wide open ........ Well, after about 90seconds at full throttle, 4300RPM, 50mph, 24P props, slowed back to normal cruise at 30mph and heard that rythmic rapping sound. Oil pressure 40psi, water temp 175, everything normal and engine running perfectly...............

I suspect some kind of detonation pounded a rod bearing. possibly a lean condition? Engine starts and runs perfectly but has the knock during a no load condition. Idling you can't tell anything wrong. Engine will be pulled next week and hope to get by with a rod bearing change.

Machine work done by experienced shop but there was some changes made and I wonder if this resulted in a lean condition? Stock engine 310HP

Changes: New small chamber Vortec iron heads that were ported and large 2.19/1.81 valves installed. 454 magnum hyd roller cam used .510/.540 lift with dual springs. K+N filter and newly cleaned/flowed fuel injectors.

Motor ran perfect and had tremendous torque at 3,000rpm. would these changes be enough to cause a lean condition? Of course I need to find the problem but I will read the plugs and check the fuel filter/ water seperator for contamination. Any ideas or anybody ever had a similar problem?? TIA TBF

Did you have the ECM recalibrated for the mods?????

Before you get too carried away cut open the oil filter to make sure its a bearing.

+2

+2 !?!??!?!?!?!

With the amount of work you did......you should have reprogrammed the ECM.......unlike automobiles, these have no adaptive learning/compensation for mods.

Did you replace the oil cooler or have it professionally flushed????

Thanks fellas... I have not checked the oil filter but will tomorrow. I did check the dipstick and saw no reflective particles and oil looked perfectly new. If this is not a flattened bearing what else could it be? It certainly does not sound valvetrain related at all......... Can somebody recommened a place to reflash my ecm?? Thanks.... TBF

Mark Boos at Precision Marine. Look him up and give him a call. He is awesome to work with.

Odds are you went lean and burnt a piston. You may have damaged your rod berrings. You will not know for sure untill you get it back apart. Did you upgrade your oiling system?

If you are really lucky maybe its a loose flywheel. coupler or even ujoint in the drive..... Just a little optimism for you. Cut the oil filter open and let us know what you find.

Scuffed piston slappin.

definately not piston slap..... its the sickening, deep sound of rod knock............. Motor was rebuilt with all good stuff.. forged pistons were used so they are most likely fine. Stock oiling system used as this is not a high rpm engine... 4300rpm max.... I will contact Mark at precision and see about an ECM reflash. I will pull the engine next week and report back what I find.... thanks... TBF

You should not be proping your boat for 4300 RPM, more like 5000+ RPM. You could be loading up the engine that is not good either. With the forged pistons you probably took out the tops of the rod berrings. You definatlly need a bigger oil cooler. Was this originally a marine block? You need to make sure the valve has been removed from the center of the filter pad and either a plug or 30psi valve installed in the side.
Another quesion, how old was the fuel?

I can't believe you made all those changes without touching the ECM, or your builder let you do that. He obviously has no idea on how to handle EFI marine engines. I agree with these guys also on the rpms, you should never setup a marine engine for 4300 rpms, you are over loading it. The 454 magnum cam is designed for 4600-5000 rpms. You should be running about a 21" prop

MMMMM.... Max rpm with original 310HP engine and 22P props was 4300rpm.... same as new engine with 24P props and about 5 more MPH.
I believe this is within the specs outlined for this engine from mercruiser........................................ .................................................. .................................................. ....................... This boat is a cruiser, not a performance boat so top end really is of no concern. 51MPH is plenty for this boat and top end is not really a concern as this engine was built for cruising at 31MPH @ 2900rpm @ 11GPH............................................. ........................
A 21" prop would have me turning 3500RPM at a 30MPH cruise and that is not where I need to be.... also fuel flow would be much higher...... is that smart?

I am looking for some input here from experienced engine builders to see if anybody else has encountered a similar problem. I have built many performance, automotive engines, carbed, and fuel injected as well and I have an LM-1 that I can install to see exactly if I am running rich or lean. I am of the understanding that the factory engines were set up rather rich and my mods, in my opinion, were not enough to induce detonation to the point it would hammer the rod bearings flat...... This engine ran perfectly with no indication at all of detonation or any other abnormality.... sucks to be me..... TBF

Even if you ran it lean would not kill a rod bearing that quick...if thats the issue you have other problems...why did you go thru engine ? had one time that was just rebuilt...they just did not clean the block passages...killed it in 30 mins...

i have a larger , oil cooler, made by hardin that i used for last year, mint was on brandnew motor if your interested. its the biggest that you can fit in the front of the mpi, thats what i had. kept temp down alot.

Engine was rebuilt due to water ingestion from bad manifolds..... Blocked hot tanked twice as my machinist said these marine blocks just continue to leech out rust really bad.... motor was bored over .030 and forged pistons used on re-assembly. Stock crank/rods were good with all clearances checked. Machinist assembled short block and it was balanced as well. I installed new vortec small chamber heads with the 2.19/1.88 big valves and did some bowl blending and a little chamber de-shrouding as well. Injectors were cleaned and flowed so they were basically new.

As far as the oil cooler, I am using the original and have had no issues with it. Oil pressure is great and engine runs right at 175 on the temp......... One thing I forgot to mention was that I could not find one of the caps for the valve cover so the PCV system was not hooked up properly as the crankase was venting to outside air. Motor should be pulled by the end of the week so I will report back with my findings.... thanks in advance for the input... TBF

Engine rpm range is determined by the cam and heads, and as stated above the 454 Mag cam is designed for 4600-5000 rpm. Go ahead and drive around below your max hp rating if you want and lug the engine, its your money. You do not have a stock 310 hp engine anymore, not even close.

Your computer is just guessing at how much air flow is coming and going.

The engine is not even close to a 310 anymore. With the larger cam, better heads, etc. you will need to prop the engine for a good 5000 rpm. What it used to turn for rpm is irrelevant. It's not a 310 anymore. Just because you prop it for 5000 rpm doesn't mean you have to actually run it there. Yes it will bring your cruise rpm up, but that's ok. It's not neccessarily going to increase fuel flow since the engine won't be under as much load at any given rpm.
I would pretty much bet anything that with the mods you made and lugging the engine that bad, it detonated itself to death. You can not make that many changes without programming. As a matter of fact, you can't even make one of those changes ( cam, heads, porting, etc) without programming. I promise you the calibration is out in left field. I program a ton of Mefi ecm's and it is amazing how a little change in setup will really throw the cal off.
I do tuning on the Mefi's as well as Mark. What I won't do is tune it through the mail. You made enough changes where it either needs to be tuned on a dyno or in the boat. The only way to tune through the mail is if you get a data logging software (like Rinda) ,along with a wide band, and tune from the data you collect. It's still possible to take several tries at it. You take a chance of damaging the engine again as you are collecting data. It also depends on the data you collect. The tune will only be as good as the data. For these reasons, I won't do it through the mail. I either have to have the engine or be with it in the boat.
Let me know if I can help.
Eddie

I think the reason Mark's name gets mentioned every time someone asks about reprogramming is because he knows his chit! The same reason everyone reccomends RMbuilder for cams and valvetrain. Mark can tune through the mail, and although it could be optomized in the boat if you give him the correct information it will run flawlessly.

Everyone is telling you the same thing. If you put it back together the same way you will just blow it up over and over. Its your money :lolhit:

My first guess would be you had a tight bearing or two. Did you have oil temp gages? If not you should add them. The LM1 would be a very good idea. You'll need to set up a spot in the exhaust for it while you have it apart. Going from memory, the 365hp mag engine which is what your cam is for, had a recommended rpm range of 44-4800rpm. So 4300rpm would not be that far off and would not cause a rod bearing to fail. It is good practice though to alway prop for being able to hit the high end of the recommended range at wot. Cruiser or not, makes no difference.

Vortech heads are detonation prone. They have smaller chambers which results in a higher compression ratio and they have a sharp point in the combution chamber between the valves. If it were my engine, I'd use a die grinder and lay that point back a bit. Just enough to smooth it into a nice rounded shape. Can't remove it completely, it's required to create mixture swirl in the chamber. Good luck.

Yes, I am intimately aware of the design of the vortec heads...... I did indeed remove the sharp edges and did some very minor deshrouding as the 2.19 intake is larger than stock. Also, there is a cast in "wing" just beneath the intake valve that must be for swirl so I don't think my porting and installation of the larger valves was worth that much power. I figure my C/R was right at 9-1 and the flat top pistons were zero decked. Using a .045" thick head gasket, I have good quench and resistance to detonation. These are small port heads and probably would run out of breath at anything much more than 4,500RPM. The plan here was to build the motor for torque and it has it in spades.

Obviously this combo failed so when it gets rebuilt, It will get tuned and A/F ratio and egt will all be monitored so as to avoid another failure. I will contact some of the previous posters that offered help and figure out a game plan and the best way to get this combo tuned. I will post back when I pull the pan and see how bad the carnage is........ TBF

I don't think the heads had anything to do with what happened..I think your engine screwed up...sounds like spun a rod bearing..if so what you did have nothing to do with that unless it was running so rich with fuel diluted the oil and killed a bearing....clearance, crank, something was wrong there ! or unless you hooked up oil cooler lines reversed and killed it that way...

If you run it lean, have bad fuel, run too much timing, or lug your engine you can take out the tops of the rod berrings pretty quick. Also if the oiling system was not upgraded from the beer can size oil cooler, that could do it too.

Without recalibrating the ECM with all the changes that were made to increase airflow this engine would have been running WWWAAAAYYYYY lean, which means detonation. That coupled with the heavy load most likely killed the bearings, though a tight bearing is still possible.

Either way I think he is on the right track to getting her straightened out

Yes...... My seat of the pants guage tells me detonation was the problem and I bet running lean was the issue. I bet the top half of the rod bearings are hammered flat so I might get lucky and change them out if there is no debris in the pan. Now comes the question of how to reflash the 2000 L-29 engine ECU? My Harley has a power commander I just installed and there are a ton of maps available for all different combos..... It works like a charm! I would think I am not too far away from the stock 454 mag tune but I need to put this thing on a dyno and make sure I don't run lean again...........

FWIW, I did check the fuel and not a drop of water or contamination. Fuel was 89 octane no ethanol. Old fuel was drained and filled to top with fresh gas so no issues there. Timing was right at spec per my installer but i will double check to see how much initial there is now. I have not heard about the oil cooler issues but I am using the stock unit and it was cleaned and looks to be of sufficient size to provide good flow with no restrictions? I always had good oil pressure and no overheating issues.............................

The only way to be sure this is tuned correctly is using a dyno or on the boat with a laptop or some kind of scantool. I will research this and make damn sure all parameters are perfect. It will probably run better and fster as well! Thanks for the help and steering this newcomer in the right direction..
TBF

Sounds like you are getting on the right track, if you spun berrings you will want to tear it down and hot tank it. Then pitch the oil cooler, a 2"x18" would work well.
The vortec heads like a little less timing, from what you are used to. I have heard in the range of 32 deg total.
I once ran some E10 fuel through a fresh rebuild and took out my rod berrings. Thats why I through that out there, it may not apply to you.
I have a aftermarket Holley MPI system with wideband O2. I can program the PCM on the fly with a laptop. If you could have a bung welded in your exhaust that would be a good idea. I have the EMI exhaust and I have a bung welded in the risers.
There are a lot of guys on here that can help you with the Merc PCM. I would take there advise on the programing.
Let us know what you find with the engine.

I think I will be spending the extra money and just buying fuel on the water... no ethanol is just a better idea in my book. I am towing my boat to the launch today and getting it on the trailer. I will bring it over to the boatyard on thursday and get the engine pulled. I read another thread about tuning and think the best idea is to actually do it on the boat.... The dyno will probably use headers and I want to tune with my new osco manifolds with water etc... I wonder how much the tuning software is and even if available for for the 1998-2000 L29 engines..... anybody got some used stuff for sale??? TBF

I've been watching this thread and reading it for over a week now and I can say as an engine builder that some of the important points put forward in answer by some good OSO'ers and builders have pretty much covered the probable answers pretty well. Just a few points though. First a open raw cooling system marine performance engine should be operating in this horsepower range with about a 160 degree temperature, not 175 degrees! This was probably the first indicator the engine was to lean and was prone to detonation.
Second, when rebuilding marine higher performance engines I think its also a good idea to upgrade the stock oil system on most BBC's with a good HD/HV oil pump like the Melling 10778 series. The GM type oil system relief valves must be in place and changed to the higher pressure 30 psi units that will assure enough volume of oil is flowing to the cooler and filters without bypassing.
Remember both water and oil remove heat from an engine and determine the overall operating temperatures of the engine and oil. Unless you were actually measuring your oil temps, I suspect at those previously mentioned LUGGING rpms under load were much higher than you suspect.
Combustion chamber surface temperatures in the head and top of the piston can be raised in any engine under load from either timing, lean burn, or poor engine cooling to a point where detonation will occur no matter the cylinder head, piston, spark plug, compression ratio, etc., etc.
I would also consider on your rebuild to get those top rpms up with proper propping to at least 4800-5000 rpms to make sure the engine is not being lugged under high engine loads.
I would also recommend to many moderate marine engine performance users like yourself to consider the new "alumina" series rod and main brearings now available from most of the major bearing suppliers. We have found along with many others in the industry now that these bearings can take higher loadings in marine engines, not distort or pound out as easily as the older tri-metal babbit types and actually give better life to the engine and the crankshaft surfaces, especially on today's nitride treated crankshafts.
Hope these suggestions and thoughts help in your second go.

Best Regards,
Ray @ Raylar

Thank you so much Ray.... I will get the Alumina bearings for my rebuild. I have the boat out of the water now and will have the engine pulled next week. I have to agree with your post as I did smell a bit of burning initially with the fresh engine that appeared to be hi temp paint flaking off the bottom of the osco manifolds..... Sounds like it was getting toasty..... I think I have the Hi volume oil pump now but will double check..... I think the thermo is a 170* degree unit as it always ran right around 170-175 when up to temperature.

This motor was originally an L-29 310HP gen VI engine that I believe has knock sensors installed in the system. I guess they were not effective in pulling timing out for me? We shall see what the post mortem shows at the end of the week.... TBF

The fuel injected motors typically use a 160 deg therm. When I am running on plane I usually see 150 deg on the gage, at idle around 160-170. The only thing I have different is I use a crossover with bypass system. Check and see what temp therm you are using. I am trying a high flow this year.

Thanks for all the help on this thread... just finished the autopsy and number 6 spun and scored the crank journal so engine is coming apart....... about half the other rods showed signs of flattening and the upper bearing shells had lost their crush. I would say detonation was the culprit. Probe forged pistons all look good if not new. Had a little bit of copper in the bottom of the pan but the whole lower end looks excellent with no debris....................... depressing..................

Thinking about having the crank cut and rods resized and sell the short block as it was just bored .030 and align honed as well. New osco manifolds and brand new heads with stainless big valves, new starter alt, etc.... I may just piece this thing out and get what I can and see about getting a new 380 hp 8.2l closed cooling motor..... TBF

Everything I have read on the stock magnum roller cams says that they are 224*/224* @ .050 and .483/.483 lift. Was this cam reground for more lift? Just curious.

It sounds like a probable lean condition that led to detonation to me. You only went up a couple of inches in prop size. I still don't know if I am convinced about the whole "lugging" situation at this time. Sure, the bigger prop puts more load on the engine at a given RPM, but it is the same mechanical load on the engine whether it is capable of spinning that prop up to 4400 RPM or 5400 RPM. Why aren't the high performance engines detonating too? Is it more of a function of the higher cylinder pressures combined with a part throttle lean condition that is leading to the detonation? Is it the fact that a high performance engine is jetted richer that is "protecting" them? Just curious.

Cam was stock 454 MAgnum hyd roller.. I think it was .510 intake and .540 ex lift and dur @.050 less than 230..... not too much larger than stock and ran pretty smooth for the most part. just a little more rumble at idle than stock.... Excellent cam in my opinion... I have decided to just get a set of aftermarket rods with 7/16 rod bolts. Just not worth it to resize stock ones and i am afraid they took a beating... I plan on using the the H series bearings that are grooved and have a melling HV oil pump and hardened shaft. I like the idea of the rods getting a continuous flow of oil at all times... seems like cheap insurance to me. TBF

I actually spoke to marc today at precision marine to flash my computers, I have same motors as you and did same cam, with emi exhaust, he mentioned need to switch fuel pressure regulator also because needs higher pressure for new setup to help with lean condition. Hes going to tweak computers that send them back and i will test them see how close we are, then send back after run with 02 graph.

Update:
 

Well, after 5 months and about 30 hours on the new engine all is well! My original crank was trash so I found another cast gen 6 and put it in with the H-series bearings and also new Scat rods with 7/16 bolts cap screw style. All balanced of course. HV oil pump as well and I put an adapter in the starboard riser to plug in my LM-1 so I have done some data logging real time under load. I installed an adjustable fuel pressure regulator and at 45PSI it gives me numbers that are just about perfect everywhere except idle. Runs rich about 11.7-9 AFR at 600rpm but as soon as its above 1,000 rpm it gets back to normal. WOT is 12.5 and cruise at 3,000-3,300 is 13.5 - 13.8...... I will probably get my ecm reflashed to compensate for the rich idle. I am sure that the 454HO cam is probably giving me lower vacuum than the super smooth stocker and may be part of the issue..................

Engine has excellent torque and effortlessly pulls the boat up on plane with a load of folks and does it at half throttle. It will hit 50MPH but 29GPH is not in my budget! 40MPH is 3,800rpm and 20GPH at just a bit more than half throttle but normal cruise at 30MPH is an economical 11-12 GPH.

This engine is raw water cooled and I have been using salt away after each use and the manifolds still look new inside with zero corrosion or rust. Amazing stuff and well worth the effort.

Big lesson learned here is to make sure proper tuning is done when making any performance increases over stock...... TBF

Geez, I forgot to mention the most important thing, A previous poster mentioned that he had a block that had crap in it and caused a failure.... Winner! upon disassembly, my block has had crap, rust flakes all through the cooling passages and I am sure that the internal temps were way too high due to lack of water flow around the lower part of the cylinders but the the temp probe still showed normal as it was still getting a normal cooling flow up at the manifold/thermostat area..... I spent a day day cleaning and flushing the block and was shocked at the amount of scale and rust that came out. I am so pissed at my machinist as he assembled the short block the first time and left all that crap in there.... lazy bastard............ I had the block sonic checked and even at an .030 overbore, these marine 454 blocks are super thick!

That is why I recommened using salt away for any raw water cooled engine. My next boat will be closed cooling for sure! I hope this thread can help someone in the future and learn from my mistake......... TBF