Bore x Stroke vs Harshness on oil

[Jaymus]

Do you think bore and stroke affect the wear on oil?

Let's take a Ford 302 and 351w for example.

302 = 4" bore x 3" stroke
351w = 4" bore x 3.50" stroke

Would a longer stroke put less lug on the engine and be easier on the oil with all other things being equal? I know not all things are equal between the 302 and 351w, but was just an example.

My wife's eclipse has a 3.405" bore and 3.94" stroke (WHAT A STROKE). I know the engine design (SOHC and all other factors) may have a lot to do with it, but from UOA's I've seen, these engines massage the oil instead of beat on it.

Just a question I have wondered. Does bore x stroke affect how hard an engine is on oil in any way, shape or form?

 

[expat]

You would also have to consider connecting rod length.
The longer the Con rod the less side thrust in the piston.

 

[CBR.worm]

And piston skirt length, shape.

 

[expat]

RPM and mean piston speed.
Also a large diameter piston will put a greater cooling requirement on the oil.

 

[Ben99GT]

Ford 5.4 - 3.552" bore x 4.165" stroke, 1.60:1 rod to stroke ratio - UOAs no better or worse than the 4.6. Longevity no better or worse than the 4.6.

Ford 4.6 - 3.552" bore x 3.543" stroke, 1.67:1 rod to stroke ratio.

 

[SteveSRT8]

usually long stroke makes more torque. If you get extreme you can affect longevity.

But the Ford Modulars are notable in that regard. Of course the redline is awfully low on the new all aluminum GT500 because of it, but it is still a great long lived motor,

 

[aquariuscsm]

I would also think that long-term high rpm would be hard on an oil. For example,a huge V8 cruising 70mph at 1500 rpm imo would be much easier on an oil than my car,which has a 3.0 liter V6 that spins a lil over 3000 rpm at 70mph.

 

[Ben99GT]

The GT500 has the same redline as the '05 - '09 Mustang GT, 150 rpm within the 6.1 Hemi's redline.

 

[mechtech2]

I don't think this is a consideration.
With engines of the same size and cylinder configuration, actual power produced would be the comparing factor for oil being beat up.

 

[Doug Hillary]

Hi,
Jaymus - Long stroke high torque engines of the past produced many undesirable side effects. These resulted in bearing issues and crankshaft and manual gearbox failures (vibration related) amongst other things

The use of high reving multivalve engines resulted in the JASO (Japanese) lubricant standards

Modern engines benefit from very advanced design,test,production and engine management facilities so few problems occur in real terms. As you can see - they did in the past!

 

[Michael_P]

I would think the oil passages / galleries and their relation to how close all the engine heat is has a greater impact on oil life. Passage size and proximity to the bulk of the engine heat does play a role in whether it is a sludger or not.

 

[ARCOgraphite]

The Subaru 2.5L prob has one of the most oversquare B/S in a 4cyl and it seems to do ok in the UOA wear dept (other than piston slap) It thinks it is: 99.5mm/79mm; That equates to a shorty 1.5" throw crank!

 

[mechtech2]

The Chevy 302 was more oversquare than that at 4X3.

 

[440Magnum]

I don't think the ratio matters- but bigger bore engines are (IMO) a bit harder on oil. More blow-by, more consumption, higher piston center temperatures, etc. all come into play with bores much over 4" compared to bores less than 3.5"

But other design features probably matter even more than bore size. I don't know exactly what the cause is, but (just as an example) many of the Nissan oil analyses on here seem to show that Nissan engines are harder on oil, in general, than most other manufacturers. That's nothing against Nissan, some of these same engines always earn high marks for low NVH, power to weight, and overall performance.

 

[SteveSRT8]

yep, that 302 was a real revver.

I shifted mine at 7800 if I thought I was losing!

And easy Ben, we all like the new GT500. And it finally can perform as advertised. But I run my 6.1 at a 6600 rev limit.

Just read another test on the 5.0, a ragtop. Ran another 13.2!

 

[440Magnum]

Originally Posted By: ARCOgraphite
The Subaru 2.5L prob has one of the most oversquare B/S in a 4cyl and it seems to do ok in the UOA wear dept (other than piston slap) It thinks it is: 99.5mm/79mm; That equates to a shorty 1.5" throw crank!


Again, I think the bigger effect on oil correlates to overall bore SIZE rather than ratio of bore to stroke. And as Mechtech2 pointed out, both the Ford 302 and Chevy 302 (the original LT-1) are more oversquare than the Subie at 4" by 3" in both cases. And I don't remember right off the top of my head, but I think if you look up the Buick 455 you'll see a pretty impressive amount of oversquareness. Conversely if you look up the Olds 455 you'll find an undersquare big-block with an amazingly long stroke at 4.25"(would have made a better heavy truck engine than the 454 did, IMO). The Mopar 400 big-block from the mid 70s (its a bored 383)is also extremely oversquare at 4.34" by 3.375".

If nothing else, the large quench areas in big-bore engines that make them generate high emissions also make them generate a lot of oil contaminants, and (by the way) those contaminants are concentrated in the upper ring land area- right where they're most likely to get pushed into the oil.

 

[440Magnum]

Originally Posted By: SteveSRT8
yep, that 302 was a real revver.

I shifted mine at 7800 if I thought I was losing!

And easy Ben, we all like the new GT500. And it finally can perform as advertised. But I run my 6.1 at a 6600 rev limit.

Just read another test on the 5.0, a ragtop. Ran another 13.2!


Saw and heard my first "Coyote" 5.0 in person this Sunday. Schwing! That's how a Mustang should sound (and perform!) But I still prefer the low chest thump of the 6.1 among all the current big 3 performance v8s. Yes, I'm a Mopar homer. So sue me. ;-)

 

[Steve S]

I Would agree with the rod lentht/thrust angle. The valve train is the highest stressing thing in an engine that the oil sees.

 

[Steve S]

Originally Posted By: 440Magnum
Originally Posted By: ARCOgraphite
The Subaru 2.5L prob has one of the most oversquare B/S in a 4cyl and it seems to do ok in the UOA wear dept (other than piston slap) It thinks it is: 99.5mm/79mm; That equates to a shorty 1.5" throw crank!


Again, I think the bigger effect on oil correlates to overall bore SIZE rather than ratio of bore to stroke. And as Mechtech2 pointed out, both the Ford 302 and Chevy 302 (the original LT-1) are more oversquare than the Subie at 4" by 3" in both cases. And I don't remember right off the top of my head, but I think if you look up the Buick 455 you'll see a pretty impressive amount of oversquareness. Conversely if you look up the Olds 455 you'll find an undersquare big-block with an amazingly long stroke at 4.25"(would have made a better heavy truck engine than the 454 did, IMO). The Mopar 400 big-block from the mid 70s (its a bored 383)is also extremely oversquare at 4.34" by 3.375".

If nothing else, the large quench areas in big-bore engines that make them generate high emissions also make them generate a lot of oil contaminants, and (by the way) those contaminants are concentrated in the upper ring land area- right where they're most likely to get pushed into the oil.
Big block V8 anything

 

[Ben99GT]

Originally Posted By: SteveSRT8
And easy Ben, we all like the new GT500. And it finally can perform as advertised. But I run my 6.1 at a 6600 rev limit.


FPV GT (Boss 315) has a 6500 rpm rev limiter
GT500 6250 rpm rev limiter
Ford GT 6600 rpm rev limiter