SBC Rebuilding for Modern, Low-Weight Oil Usage?

[woody b]

I drove my Suburban out to the dyno shop last week, and it got 13.4 MPG.

I'll be going out to the dyno shop again in 2 weeks, and I'm gonna get 16 MPG this time ( %20 increase ),...cause I'm going to Mobil 1 synthetic.

Randy[/
His theory only works on 1995 corollas
Tom

I'm going to try a different test on my 2015 Silverado. I usually get 19 mpg driving to work. (with 0w20 oil). I'll get my neighbor to haul it (and me) to work on his roll back, and see how much better I get.

[allencr267]

BS, sure, but he knows what he seen, an anecdote.
New tire gauge and/or tires? Any snake oils/texron?

[Mattax]

Jeff, If you're satisfied with your results - for your own purposes - that's OK - there is lots of testing we shade trees do that is useful for ourselves because we have a sense of the situation. (Although sometimes we are kidding ourselves too, so the nay sayer have a point even if you bristle at the bluntness.)

Here's some things to consider.
Fuel - in most parts of the country, fuel changes with seasons. So even with a feedback looped EFI, winter fuel mpg is generally not as good.
Terrain and idling - The milage in both my vehicles goes in the toilet when traffic is standstill. The hot rod fuel consumption I think of like a boat motor - time running. Mountain sideroads vs interstates makes a difference too, down to around 12+ mpg instead of 14+.

With respect to oil, its worth looking at the actual viscosity at the operational oil temperature. SAE Grade only specifies a range of acceptable viscosity. To get closer to the actual without sending the oil out for analysis, go to the manufacturers spec sheets. Then punch the spec numbers into Richard Widman's viscosity graphing page.

David R gives some examples in Oil Wt for Auburn

[GARY C]

There are documented test that show fuel savings with oil in controlled testing that is one of the reasons we have thinner oils but just like power gains they are small.
One of the things I noticed after spending a year following the fuel saving forums and buying a scan gauge is that without realizing it once you add or do something to your vehicle looking for fuel saving your driving habit changes to a more conservative approach and your new mod or device looks like it saves fuel..If you keep track over time your fuel economy goes back to what it was before because your normal driving habit returns. You can easily increase or decrease fuel mileage by 2+ miles per gallon on driving habit alone.

[BigBlockMopar]

Just stumbled upon this topic.
Like to share my findings with a mid 80's 318ci I have in my '73 Dodge Dart. Low compression flattappet smogmotor with just 8.6:1cr. Burns some oil through the valveseals and PCV system.

When I bought this car, not knowing the engine's history, I started out driving it with conventional oil 10w40. Oil pressures were relatively high, even at a 550rpm idle in Drive; 70 cold, around 50 warm. Perhaps someone installed a high pressure or high volume in it once.

After about a year I decided to go thinner with the oil. So oneday I drove the 20 minutes to my garage and replaced the oil with a 5w30 semi-synthetic Kendall. At the end of the day I drove home, and almost home I noticed the engine temp was reading lower than normal, at 140°F now. Engine has a 160°F thermostat for LPG fuel and usually runs at 150-160°F idle/driving and 170°F in heavy traffic).
Confirmed this the next day; Engine temps again were noticably lower, roughly 15°F lower.
During the following days I also noticed after cold morning starts, the engine felt like it had been warmed up already and noticed a little more torque during accelerating.

Driving for a while with this oil, I decided to replenish with 5w20, as the oilpressures had only dropped about 5-10 psi along the range.
After that change, oil pressure slowly got down another 5-10 psi over time.
Just for fun I decided to try out going another step and go with a 0w20 synthetic oil, which I'm still using this day.

Currently oil pressures are around 30+ psi at idle in Drive and 50-60 driving.
Drops to 25+ (550rpm in Drive) when coming from longer trip or a highway drive.

This engine will be replaced fairly soon and I can't wait to have a look at the bearings.

[gmc406]

bigblockmopar, wouldn’t it be wise to replace your thermostat? If you’re running 20* lower than the thermostat rating, it must be stuck. No reason why that engine shouldn’t be running at 160*, regardless of the engine oil.

Just my thoughts.

[BigBlockMopar]

I tested and replaced the thermostat a couple of times over the years.
This engine doesn't work hard and it's radiator and fanshroud are well upto the task of keeping the temp in check. As the engine's fuel is Propane, I always like to keep it's operating temp (and LPG vaporizer temp) a little lower.

I did install a 180F stat later on after I noticed the engine running much cooler with the thinner/synthetic oil. This was during wintertime so the little extra cabin heat was needed.
Also, which is mainly the reason this engine will be swapped soon, its core-plugs are rusted thin and I don't want the cooling system to build too much pressure, hence the lower stat temp and 7 (?) lbs radiator cap I installed.

[pamotorman]

tires make a difference my son has a chevy cruze eco with a 1.4 turbo engine and when he replaced the OEM tires with a standard type tire not the high dollar special high MPG tire that came on the car he he lost 3 to 4 MPG on trips

[randy331]

Thats funny cause my current daily driver is a 2001 Corolla and I use exclusively Walmart oil

I thought you used oil drained out of engines just broke in on the dyno in that car ??

Randy

[Newold1]

My advise is to set up with a straight mainline a good balance job with ring package and bore finishes optimized and clearances set up for lets say 5-30w synthetic Mobil One and try and keep the torque required to keep the complete short block when turned over by a torque wrench in the 12-18lb/ft.Keep ring tensions to a workable minimum for street driving and if lower tension rings can be used effectively that will also lower pumping losses.
Then also try and keep the oil and windage in the rotating area of the bottom end to a minimum. Remember oil hitting the surfaces of the crank, bores, rods as well as staying on those parts creates pumping losses and that effects overall engine efficiency. Don't go crazy with high volume high pressure oil pump system. Moderate volume at basic oil pressure are all that's needed here. Keep the engine cooling system sized and operating at as constant as possible temperature between 180 -190 degrees F. Compression can be your friend so don't lose what's available when using aluminum heads, today's ethanol laced fuel and a well calibrated EFI system with knock control.Camshaft design will be huge and critically important. Use an expert cam designer for your combo. In this use I think hydraulic roller camshaft is the best choice and don't go crazy with spring types and pressures.
The biggest and most important savings will come from the best possible careful tune in the EFI system and ECM. Definitely use two wide band O2 sensors in the exhaust system and use a good digital air/fuel ratio gauge or ECM data logging to help tune and keep the engine using the lowest possible fuel volume in all operating conditions and modes. Tire choices not sticky or over sized for maximum mileage will work as well as ideal tire pressures, alignment and balance. A good set of tri-y headers will help a little and good exhaust sizing and mufflers will help also. An automatic with ECM controlled lockup will aid in mileage and drive ability.

Obviously a lot to consider and do but if you want to make this the best result, it takes a lot more than just oil and internals!

Thought you might have it all figured did you not, now I really loaded you up!

Have fun and best of success!

[Geoff2]

Also important to to use oil for your climate. The Netherlands is a cold climate. Today, in Sydney, it got to 47*C. Highest temp since 1939. Summer days regularly get to 35-low 40s. In winter, coastal & suburbs close to the city rarely get below 1*c.
There is no way I would use 0-10 or 5-20 oil in my V8 engines. These old engines had large bearings & large clearances.
If thin is better, why not use 5-20 in the rear axle & save some HP?

[pdq67]

thinner oil has milage benefits.

You can document this fact in direct line with EPA standards put on the OEM. Brian with BnD automotive sent me that data several years back, if I can dig it up I will post it

Mileage benefits and power benefits. Those are exactly what I'm after and the reason for asking my original question of what is required to properly support low-weight oil usage in an SBC.


Per my long previous post, I'm looking to modernize my old GEN1 SBC L82 to get as many benefits as possible from modern parts and know-how; I'd like an SBC rebuilt to look as much as possible like an LS motor while still being an SBC. Yes, I understand this is a way more expensive way to get there, yes I understand I'm putting way more money than I'll ever get out of the car if I ever sell it, and yes I understand that there's nothing remotely resembling an LS motor intake for an SBC motor (that probably saddens me the most); but it's my build and I want as LS-like of a gen1 SBC as possible, down to trigger wheel ignition, although I haven't talked myself into coil packs, yet...

Now what do I need to do to get these benefits and be able to run thin, low viscosity oil in my SBC safely?


Adam

Adam,

Probably way out of your project price range, but Bill Mitchell sells Gen 1 SBC blocks that can mount LS- heads!

As for mileage, the bigger the engine, (read B&S'd here), the less mileage it will make. Now this can be crutched by like running a smaller cam and such but at the expense of overall power production. As for oil viscosity, have your machinist put your lower end on it's lower end tolerances and use the rings you want to and roll on.

One last point is to run as high a CR as you can burning the gasoline that you want to pay for! Seems to me that with your car not being driven as a DD then set it at 13.5 to almost 14 to 1 CR and burn E85! Best of both worlds IF you can readily buy E85? We produce ethanol here in the Mid West so buying it isn't a problem.

pdq67

[ptuomov]

There’s a long LS7 article that explains what they went thru to get the rod bearings to work.

More generally, a car factory goes thru a lot of computer time and physical testing to produce a rod-bearing-journal system that works well with bimetal aluminum-steel bearings. They like those bimetal bearings because they last forever in various adverse conditions as long as they don’t see too much load. The rods are made just strong enough to not deform more than they safely can under those loads. The bearing clearances are small and oil thin to save fuel. It all works great.

Now, suppose we hotrod the engine by increasing rpm. The increased rpm now deforms the rod big end more. The stock bearing sticks from the sides, burns and spins. To cure that, one needs a larger bearing clearance (and eccentricity) and thicker oil. The larger bearing clearance (holding the journal diameter constant) now creates a much larger pressure gradient in the bearing surface — that’s just a consequence of the geometry. The ability of the bearing to carry load goes down due to larger clearance, while the load has increased because of the higher rpms. Consequently, the bearing now “wipes out” in that the material shifts in the top layer until deformation and failure.

At this point, the choice is to either design and install a stronger and lighter rod and/or lighter piston such that the rod big end deforms less at the new redline rpm and move back to smaller bearing clearances for the bimetal aluminum-steel bearings. This is the car factory solution.

Or, alternatively, sticking with the existing rods and larger bearing clearances while switching to bearings that have a much harder surface layer that can hold the higher load caused by the larger clearances (and higher rpms) without wiping out. This with high viscosity oil is the hot rodder solution.