If you don't match the blower, the boost, and the driving habits to the longblock, the fuel, and the application, then you will shorten the engine life 100000%.

If you clearly understand the variables and come thru with a good setup and keep an eye and ear on all of the other controllable factors, and nothing weird happens, then you will see somewhere between 35% and 75% of the original engine service between rebuilds. Failures will be more dramatic though.

mc

I was speaking from personal experience and you are exactly right,my 540 which I run 10-12 psi boost gets rebuilt every 125 hours or so. I find a few parts that are just starting to get tired every time to the point where I'm glad I took it apart. I ran 6-8 psi of boost on a almost stock 502 mpi (it had merlin heads and pistons with std rings,not the metric ones) for 3 years/175 hours. It was leaking from every gasket by the time I tore it down,rocker fulcrum balls were galled blue,one pushrod tip was ate off,timing chain was pitted on the rollers,ring seal had went from less then 10% leak down at 100 hours to 40-60 %,it was leaking and burning about 2 quarts of oil every hour of run time. I never try to go past 125 hours any more,Smitty

A side note on the 502-the last long ride I took it on before tearing it down I held it at wot for 25 minutes which probably didn't do it any favors but it was already very tired,Smitty

Can you still run 87oct with a charger or do you need higher oct?

I run 9 lbs of boost on my motors. They are 454 Mag MPI's that have Edelbrock aluminum heads & the stock rotating assembly, less the camshaft.
2 seasons on them & still going strong......when they go.

It depends on the operator and the application as much as the motor and supercharger. If you set your application up for 8psi, but only ran it there for a total of 30 seconds over 1000 hours of engine life, then it would last a signifant time, but run it at 8psi, 5400rpm at all times, well then it's not going to live the same.

Low compression motors are more tolerable to power increases and typically will last longer. A broken in motor can also have its benefits, as the rings, bearings, etc. are already broken in. The SC causes increased temps so a brand new motor can sometimes have issues if you let it build up enough heat too fast.

So, to answer the question, it's nearly impossible to really know with all the varying varibles. But, in a general sense, for a reasonable boater, I would say 10-15% lower life. For someone that really runs hard, or a boat that requires near full power at all times, then life can drop 40-50%.

A stock 330hp carb engine should make it near 500 hours in most applications with 5-6psi of intercooled boost and setup properly.

This is of course on stock engines, not modified, as modified can be built to last as long as a stock motor.

Thanks,
Dustin

You can build a motor for that, but you can't run a motor thats already rated for 87 octane, with boost, and 87 octane. You would have to run such low boost that the power to operate sc, pumping losses, etc. will negate any real noticable gain. If you took a stock motor and did head work, and or lowered compression, went to aluminum heads, then you could get away with 87 octane and a reasonable power gain. But it's not easy, 87 "knocks" when you just look at it wrong

This is interesting..! WOW...!

How on earth did some of you come up with the % figures that the motor will last so long at X or Y # PSI/BOOST Pressure...?

Have you guys actually sat down and calculated that even if you double the power, the ACTUAL pressure load spike of the increased air and fuel in the cylinder will not exceed 20% over the baseline?

Physics... Burning gas pressure is only part of the issue, heat and a few other variables make up the rest... One variable, is that the pressure will also be affected by crank angle after TDC...

The stock engine can last just as long, if the supercharger system is designed properly. BOOST is increased pressure, and is inversely proportional to flow. So, just because you have more (PSI) does NOT mean you have more airflow. It is definitely possible to have two identical supercharged systems that if calibrated differently, the one with the lower (PSI) can outflow, and produce more power than the one with the higher PSI reading. Air mass + fuel mass when mixed and ignited makes power... Increased Flow = increased mass = increase in charge density (all other things being equal)

Many of the manufacturers want you to believe otherwise, and buy the marketing that they are selling.. Do a little research, it will pay off in spades.

One of the most important things is to control charge Density... The intercooling will play a very important part here, and can pay off in spades. The heat from supercharging in relation to the ambient air temperature comes from compressing the air.... Enemy of charge density is heat...!

The lake water, or ocean water is your heat reservoir... You are in a boat guys, it works a bit differently than in a car.. We boaters are capable of getting much higher efficiencies from the lakes and oceans than the car guys do on the track and roads etc..

Anyway, to answer the original question of durability, the correct answer is it depends on a few things:

1. Condition of engine
2. Supercharger system design in relation to use and desired power
3. User's expectations
4. Proper build using proper design from 2 above

Lotsa variables, but it's not difficult to figure out.

Don't go by the PSI thing, it is a misnomer, and is incorrect, that more PSI means more power.. Not true.. The only thing that more PSI means is more HEAT.. HEAT = DETONATION...! That is what kills head gaskets... The pressure spike from the detonating....!

So, for all the carbed SC's, without knock control, they will have to run richer to compensate. Then you will hear that this is to run the motor cooler due to the vaporizing effect of the fuel, and rich is safe.. Rich mixture is only a waste of fuel because of LACK of PROPER DESIGN and BUILD...

Well, if it was EFI, and controlled properly, you could use less fuel, make more power, and have knock control to keep the motor safer. Then, if you sized the intercooler correctly, you could get some more power... If the head is prepared properly, and all the burrs and sharp edges removed, you could make even more power, as there would be less hot spots in the chamber to promote detonation..

Now I'm gonna give away the farm about building a better SC motor. Well, not really, cuz there are a few more things, and they require a bit of patience to verify. I did not even get into flow inefficiencies and pressure loss calculations in the system.

Good thing is, no one will take me seriously, cause I don't spend a few Mil $$ on marketing, and I am not a "premiere engine builder"...!

What is neat, is I did not invent the science, but get to use it for free.. Oh, Whipple, Procharger, Vortech, BDS, GMC, Holley and other manufacturers also did not invent the science...!

By the way, revving a motor to 7K vs 5K is more stressful on the assembley than the 2X power produced by supercharging.. Oh, and the motor builder (Merc., GM., Etc.) tells you that you should not rev the motor past 5,500 Rpm for their warranty, nothing else.. It's called rotational inertia stresses... Highest load on the assembley is at TDC when the piston wants to go through the top of the cylinder, but the con rod says...hey, hold it just a sec.......... This force increases at a non linear rate with increased RPM's......

Anyway, Being a regular guy tinkering in his garage is great..!!!!!

Get a properly designed system, and you will be fine if your motor is in good physical shape, and you do not abuse the engine after supercharging it..

My 2 cents.. Hope it helps..!

R

Amen brother!! It is all in the physics.

Thank you

My answer is based on personal experience from running a supercharged application for the last 8 years,502 for 3 years and 3 different combinations of my 540 for past 5 years,current one is making 1050 hp on pump gas. I seen your theory on making big power from a m-1 on your motor but I'm not convinced its going to meet your goals,how long before you go to the dyno? Smitty