Idle wear

[BrocLuno]

This issue is 99% related to 1980's and some 1990's Chevy V8's with known soft cams. Not Ford, Dodge or other.

Also high performance after market cams with off-shore lifters and/or higher than need be valve spring pressures.

Does not apply to most vehicles ...

 

[440Magnum]

Originally Posted By: BrocLuno
OK, here's the deal. If you have an older USA V-8 with a push rod valve train, the only oil that the cam lobes see is from sling off the crankshaft. There is no oil "pumped" to the lobes. This is a hold-over from the old splash oiling days.


I'm gonna stop you right there, because that's dead wrong, at least for a whole lot of V8 engines. Any V8 with hydraulic tappets has a large oil feed to each lifter. In most 60s v8s, the side of the lifter actually encroaches a semicircle into the main oil gallery on each side of the engine. True, MOST of that oil is contained by the tighness of fit of the lifter in its bore, but all the bleed-by goes straight down onto the cam lobe of each lifter. Furthermore, some engines have notches in the lower lifter bore specifically to increase oil flow to the cam.

Secondly, in most 50s and 60s V8 engines (unlike inline engines) all the oil return from the cylinder heads is funneled down the inside of the block "V" where it drains through slots in the block casting and directly on top of the cam. In the engines I'm most familiar with (Mopar) the cam just about drowns in oil BEFORE you even consider the spray off the crankshaft.

Here's a picture of a Chrysler B/RB block (1958-1980 production run in various forms- this is a 440 RB block from 67-78). EVERY drop of oil that is pumped up to the cylinder heads thru the casting bosses coming off #4 cam bearing drains back into the valley thru the passages around the pushrods, pools around the lifters, and drains back through the 4 large slots above the cam, as does all the oil that pushes out of the upper lifter bores. You can see that the slots are narrower than the cam diameter, so all that oil HAS to hit the cam lobes.

 

[Oldmoparguy1]

The whole issue is bogus. AFAIK, all pushrod and many OHC engines use roller lifters/followers. I believe that this is because of gov mandated levels of AW's like ZDDP. Correct me if I'm wrong.

 

[BrocLuno]

You can't stop me by showing a Chrysler product. I just said it was related to Chevies that do not share the same exact topology as your example. Some motors do not come with lifters that bleed enough oil and are a decent tight fit so ain't much coming out that way ...

That's why on new cam break-ins for Chebies, they require 15~20 minutes at 2,000 RPM and varied somewhat. That's to ensure enough sling oil gets to the lobes. All replacement cams I have bought for the last 20 years all require this.

I said it's not a problem for the other OEMs. Jeez, SBF's will idle for 20 years w/o issue. But that's not "all motors" and since we don't know what the OP was driving, I assumed worst case, 1988 350 Chebie ...

 

[440Magnum]

I really don't think its even an issue for a SBC, unless it was made in that period in the 70s/80s when they had cams and blocks made out of iron about as hard as taffy.

Mopar and Ford slider cams are also supposed to be broken in at >2000 RPM for 20 minutes, but my understanding is that is to maintain a good hydro wedge with the oil on the cam, not JUST to get more oil to the cam in the first place. That first half-hour or so of break-in of a new cam and lifters is an extra-sensitive period.

 

[BrocLuno]

Agreed 100% But the Chebies lost cams over various engine mileages. Some went early, some not until 40K or so. So it was really spotty...

In any case hydro wedge requires sufficient oil supply. You'll note that none of these engines sit in a car flat (longitudinally) so that the return into the valley is always biased toward the rear galleries. That return flow is not even or reliable (car sitting in traffic on a hill for instance).

The only reliable source of cam/lobe oil is sling off the crank. And that's not much at idle. If you've built a clearanced rod motor and you are running an HV pump, it's somewhat better ...

But as we have both stated in earlier posts - the most reliable source is to take it from the lifter bores via notch or some other means (EDM Solids, for instance) and that's what I do for my Hi-Po motors. But, that is not what Chevrolet did, part of the problem which started this whole rumor and concept in the first place.

More bad Chebies out there than BB Chryslers sold ... SBF's never had the issue.

As far as the post about rollers being predominate, that is only since the 2000's. The aging fleet of push-rod flat lifter motors took many years to come down as newer roller tech was gaining share. I have two of each in my back yard - so it's 50/50 for me.

BTW - I was always a fan of BB Chryslers. Great motors. Just never had too many calls to build one ... Hard to argue with the HP/Weight ratio of an SBC with aluminum heads. intake, water pump, etc... Same for BBC's when you want over 460 inches, and strokes up to 500 ci+ are cheap enough ...

 

[Shannow]

Re idling and cam wear.

The reason that we play silly games with revs, and additives when we rebuild engines is that the materials are "fresh", and don't yet have the zinc/moly/phosphate/sulfide glassy tribofilms on them.

The parts are new, and are operating essentially in point contact, until they wear in a little.

Holding the revs gets plenty of oil to splash around, cooling the contact point, providing some hydrodynamic lubrication (not heaps on cam contacts), and carrying away microscopic wear particles.

WRT the OP's premise, on a run in engine, the tribofilms are there, functioning, and are very low friction/wear surfaces compared to new. They operate in mixed/boundary lubrication, and last many thousands of km without special treatment.

If you have a properly run in engine, there is nothing to be gained by raising the revs to protect the cam.

(If you've got a nutz custom combo, YMMV).

 

[BrocLuno]

Like Nutz Custom Combos ...

Just like BITOG'rs trying to out guess the petro chemists who dream up oil formulations, custom combos are an way of life

 

[Garak]

Originally Posted By: Oldmoparguy1
I believe that this is because of gov mandated levels of AW's like ZDDP.

Was there also a friction related advantage, as in fuel economy?

 

[turtlevette]

Originally Posted By: Shannow
Re idling and cam wear.

The reason that we play silly games with revs, and additives when we rebuild engines is that the materials are "fresh", and don't yet have the zinc/moly/phosphate/sulfide glassy tribofilms on them.

The parts are new, and are operating essentially in point contact, until they wear in a little.

Holding the revs gets plenty of oil to splash around, cooling the contact point, providing some hydrodynamic lubrication (not heaps on cam contacts), and carrying away microscopic wear particles.

WRT the OP's premise, on a run in engine, the tribofilms are there, functioning, and are very low friction/wear surfaces compared to new. They operate in mixed/boundary lubrication, and last many thousands of km without special treatment.

If you have a properly run in engine, there is nothing to be gained by raising the revs to protect the cam.

(If you've got a nutz custom combo, YMMV).


I don't think raising the revs protects the cam. It creates a faster sliding friction which generates more heat which activates the zddp at that specific contact point. You want initial wear to occur to mate the surfaces. But not too much wear, so the zddp limits it.

In hydrodynamic mode the cam would never break in.

Many cams have a coating applied from the manufacture to provide a controlled break in.

People tend to criticise the small block, but its the best design for its time. It would compete with the newer ls series with a 12 degree head.

 

[440Magnum]

Originally Posted By: BrocLuno

As far as the post about rollers being predominate, that is only since the 2000's.


Well.. again ONLY Chevy. Ford and Chrysler didn't build a flat-tappet V8 after about 1985/86 (I think Dodge Truck 360s stayed slider a little longer than the 318, not sure about the Ford 460- but the 318 and 302 definitely went roller around 85).

Originally Posted By: BrocLuno
BTW - I was always a fan of BB Chryslers. Great motors. Just never had too many calls to build one ... Hard to argue with the HP/Weight ratio of an SBC with aluminum heads. intake, water pump, etc... Same for BBC's when you want over 460 inches, and strokes up to 500 ci+ are cheap enough ...


I obviously love the B/RB engines myself, but you're right they were never in as much demand. Ironically, they're probably cheaper to build in some sizes/combinations NOW, nearly 40 years after end of production, than ever because of the aftermarket support.

Chevy power has always been cheaper than anyone else, and you certainly CAN build a fantastic Chevy-based engine (I drool over some of the things Mercury Marine does with them). But right out-of-the-box, the first-gen SBC and the Rat motors were bottom-of-the-heap compared to every other choice, IMO. They were after all, GM's "affordable" line of engines and cars The SBC was actually engineered really well, but (as alluded to earlier) not always given the best materials and QC. I'm not sure the engineers ever quite finished the BBC, though.

My personal favorite GM v8s are the post-Nailhead Buicks and the Olds, even though in many ways they're opposites. The Buicks were kings of light-weight power- a Buick 455 weighed in about the same (or less) than a Chevy 350, and had the best rod/stroke ratio of any GM v8 including any Chevy bigger than the 327- actually they were comparable to a Mopar in that regard. Olds would have made the best choice for heavy-duty truck engines- absolute torque monsters with huge bearing surfaces, stout cranks and conrods, and plenty of cooling. Yet the only HD application they ever really got was the (still highly collectible) GM FWD motorhome with the Toronado drivetrain. Both Olds and Buicks got built with better iron (higher nickel percentage) than many Chevy blocks did.

 

[BrocLuno]

I agree with 99% of this. Buick and Olds made great motors. I also love the big Caddy's. But, customer and resale says Chebie ...

The roller deal started in the 1980's for USA built engines, but with an average vehicle lifespan of 13 years USA-wide, it took a long time to get the numbers up. I'm guessing it hit crossover around 2000.

Ford trucks (number One selling vehicle) did not get roller cams until the mid-1990's. I have to assume that was the same for other OEM's...

 

[440Magnum]

Originally Posted By: BrocLuno

Ford trucks (number One selling vehicle) did not get roller cams until the mid-1990's. I have to assume that was the same for other OEM's...


Chrysler was definitely all-roller before 1990 when all the trucks went TBI. And the Magnums (1992 on) were roller. The OHC 2.2/2.5 4-bangers and Jeep 2.5/4.0 never went roller though.]

As for Ford, wasn't the 5.0 for the Mustang (and maybe the Panther cars) rollerized in '85? I could have sworn that only the truck SBC stayed slider past 1990, but maybe not.

 

[turtlevette]

Originally Posted By: 440Magnum
Both Olds and Buicks got built with better iron (higher nickel percentage) than many Chevy blocks did.



Is there any documented proof of that? I've heard that a few times

Softer means less prone to cracks, no? I've never heard that cylinder wear was any worse with Chevy's.

 

[BrocLuno]

There is some evidence from foundry specs. This actually started with Hudson who got blocks cast with crazy nickle content. They are so hard, many machine shops will not try to bore one. The flathead seldom need exhaust port inserts, even on modern fuels ... ...

But, this is OEM insider data and not easy to come by. You can discuss with your local high performance machine shop. They can tell you how many cutter bits they go through with different blocks.

Nickel does not make it more brittle necessarily. Nickel is a constituent of stainless steel, and that is often pretty malleable. It's all bout the whole alloy formula, just like oil. It does seem to add to rigidity

The wear is mostly related to ring metal. Some rings can really do a job on a cylinder wall. I like to let the rings go away, and keep the block straight, so I mostly use Hastings iron rings. Mahle thin packs if spinning big R's. It's also about the silicone content in the piston metal ... Wear is not so much a block metal phenomena.

The easiest to crack are low alloy iron blocks. I swear most will break just looking at water and the sky on a winters day

 

[440Magnum]

Originally Posted By: turtlevette
Originally Posted By: 440Magnum
Both Olds and Buicks got built with better iron (higher nickel percentage) than many Chevy blocks did.



Is there any documented proof of that? I've heard that a few times

Softer means less prone to cracks, no? I've never heard that cylinder wear was any worse with Chevy's.



As Broc said, its mostly found in interviews, writings, conversations, etc. with former engineers at the car companies. Chrysler engineering bunch in the 50s/60s was pretty proud of the low-wear properties of their block alloys, for example, so you can find a number of references to it.

And in this case "soft" doesn't mean "ductile" or "malleable," it just means "not as wear-resistant." So the higher-dose nickel blocks aren't more brittle at all, but they do resist wear better and generally have a higher Rockwell hardness.

Anecdotal observations of torn-down engines over decades tend to back up the rumors about metallurgy- Chevy engines of a certain period were well-known for having a lot less honing crosshatch left combined with bigger ridges at a given mileage than their Olds, Ford, Buick, & Mopar counterparts. Some of it might be the awful rod ratio that the SBCs above 327 CID have, which puts a lot more lateral frictional force on the piston/cylinder interface. Some of it might just be because SBCs are so numerous that abused examples seem more common than all Ford and Mopar smallblocks combined. But the odd engine from other manufacturers with simliar rod-ratio numbers (ironically, the "indestructible" 225 Slant-6 is an example, as are most Olds engines) didn't show the same kinds of wear... at least on a broad and anecdotal average.

So its a largely unsubstantiated claim, but its backed up by two independent sources (one 'insider' and one not), so I think its pretty widely accepted these days. I mean nobody goes out saying, "I really want to find a 1977 or 78 Chevy 350 core block to be the foundation of my next ultimate engine build."

FWIW, none of this really applies to the Gen-III and Gen IV GM v8s, they're a whole different kettle of fish.