picklenjim

Scuffed piston slappin.

tpabayflyer

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

jeffswav

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?

rexcramer1

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

tpabayflyer

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

ezstriper

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...

ballon78

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.

tpabayflyer

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

rexcramer1

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.

Young Performance

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