tpabayflyer

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

Raylar

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

tpabayflyer

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

jeffswav

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.

tpabayflyer

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

Budman II

iTrader: (1)

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.

tpabayflyer

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

ur2slow

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.

tpabayflyer

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

tpabayflyer

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