Engine longevity and ignition/induction types?

[kennythewelder]

How about block material? I'd heard the 87+ 1pc RMS blocks were a harder material that caused less bore wear?

IDK for sure, but I do know in time, that processes of metal composition have improved tremendously. The metal today is better quality than it was in the 1970s for example. The biggest problem with all of this, is those bean counters who say, if we cut this or replace that, we can save the company millions. It's not about turning out a quality product, it's about making money. But hey, what do I know, I'm just a dumb ass welder who works in a machine shop.

 

[kennythewelder]

I don't understand "5000", "1000", "3000" and "1000".

Do you mean 0.005 (five thousandths of an inch) max, 0.001 to 0.003 preferred, with some jobs calling for max 0.001?

Automotive crankshafts, cylinder bores, connecting rod big-ends, and block main saddles are routinely cut/honed/polished to better than 0.0005 (called "Half-a-Thou", as in "half a thousandth of an inch", or (less accuratly) "Five tenths" meaning five ten-thousandths.) I can hold runout on valve faces to 0.001 pretty easy, and as good as 0.0002 to 0.0005 sometimes; although I'm still dial-indicating every one unlike a "real" shop that dial-indicates one every now and then. The used valves I ground for my Lumina came off my valve grinder with LESS runout than the brand-new "famous name" aftermarket valves I bought to replace a couple of damaged valves. (I stuck the new valves in the grinder and then dial-indicated them as if I were going to cut them. When I saw that I could do better than they did, I took a "cleanup cut" on 'em.)

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Also forgive my 1000-5000 explanation. It's the same thing as 0.001 - 0.005 ect. I have been thinking in tape measure terms for over 40 years. We got a hand drawn print in the other day it had feet and inches on it, so the first thing I did was to convert everything into inches. EG 5' 4" = 64 inches, ect. Carpenters think in feet and inches, welders think in inches, and fractions, and machinist think in decimals of an inch.

 

[Schurkey]

Back in the '60s and '70s--and likely the '30s, '40s, '50s; but I wasn't there to see it--Chevy and Ford had the crappiest, softest, easily-worn iron alloy. Pontiac, Olds, Buick, and Cadillac fans rightly brag-up the iron alloy (although they usually claim, incorrectly, that the difference is "nickel" added to the iron to make it harder.

But it was fairly obvious that SOMETHING was different, because a hundred-thousand-mile P, O, B, C engine generally had significantly less bore wear than the typical Chevy, or Ford small-block at the same mileage.

For awhile, Chevy had a specific part number for a 4" bore small-block that had additional tin in the iron alloy.

Ford has it's own problems with iron castings--inclusions, voids, etc. Hateful to sonic-test a Ford small-block, discover it has good cylinder wall thickness...and then when it's bored, pinholes into the water jacket pop up after the block sits overnight. The iron either corroded from the water jacket side into the piston area; or the iron was never there to begin with--there was a chunk of slag instead.

I don't know about Chrysler or AMC. I don't remember either having the bore-wear issues that Chevy and Ford small-blocks had. But I didn't work on many, either.

We got a hand drawn print in the other day it had feet and inches on it, so the first thing I did was to convert everything into inches. EG 5' 4" = 64 inches, ect. Carpenters think in feet and inches, welders think in inches, and fractions, and machinist think in decimals of an inch.

Yes, true. At least they didn't mix feet, inches and furlongs. Or feet, inches, and millimeters.

I hate the metric system.

 

[kennythewelder]

Back in the '60s and '70s--and likely the '30s, '40s, '50s; but I wasn't there to see it--Chevy and Ford had the crappiest, softest, easily-worn iron alloy. Pontiac, Olds, Buick, and Cadillac fans rightly brag-up the iron alloy (although they usually claim, incorrectly, that the difference is "nickel" added to the iron to make it harder.

But it was fairly obvious that SOMETHING was different, because a hundred-thousand-mile P, O, B, C engine generally had significantly less bore wear than the typical Chevy, or Ford small-block at the same mileage.

For awhile, Chevy had a specific part number for a 4" bore small-block that had additional tin in the iron alloy.

Ford has it's own problems with iron castings--inclusions, voids, etc. Hateful to sonic-test a Ford small-block, discover it has good cylinder wall thickness...and then when it's bored, pinholes into the water jacket pop up after the block sits overnight. The iron either corroded from the water jacket side into the piston area; or the iron was never there to begin with--there was a chunk of slag instead.

I don't know about Chrysler or AMC. I don't remember either having the bore-wear issues that Chevy and Ford small-blocks had. But I didn't work on many, either.


Yes, true. At least they didn't mix feet, inches and furlongs. Or feet, inches, and millimeters.

I hate the metric system.

That is the one thing I really hate about our trucks. Is it metric, is it SAE, you have to have a ton of tools to do anything, and that's not a problem, I have the tools, bit a lot of metric sizes are very close to SAE sizes. Then there are the torques and reverse torques that GM loves so much. Like those screws on the distributor cap on a vortec. I have a billet distributor. I pulled the distributor out and retapped those threads to accept a SAE cap head screw. Now all I need is a T handle Allen wrench to remove and replace my distributor cap. Much better, much easier.

 

[El Tigre]

Lets not forget powdered metal connecting rod w/fractured caps.
All these things together? Night/day difference to carb/HEI motors.

 

[MIHELA]

How about block material? I'd heard the 87+ 1pc RMS blocks were a harder material that caused less bore wear?

Higher nickel content is the reason the Cadillac big blocks could go 200k miles with minimal bore wear while the cars rusted out around them. I believe the TBI and Vortec blocks had a somewhat higher nickel content than earlier SBCs.

 

[L31MaxExpress]

I had an 83 305 go nearly 300K before it lost a rod bearing. Oil starvation from timing gear teeth in the oil pump pickup. I think overdrive transmissions did alot to help. The leaner calibrations and electric chokes used on the later Q-Jets helped them run for a long time. Block still had visible cross hatch in the bores at nearly 300K.

I will also say metalurgy wise the 880 Vortec blocks are the best factory castings around. Forget those junk 010 70s castings.

 

[Pinger]

That I wouldn't know. But I do have a very good understanding of machine tolerance, and the machining process. I am a welder in a machine shop. I can run an old school lathe and mill. 5000 is max tolerance for our shop, and 1000 to 3000 is preferred depending on the job. Some jobs call for rite on spec with a max of 1000. Even on a welding fab job, we don't like anything more than 1/16" out of spec and that's on big jobs only. Small welding jobs need to be spot on.

I think that in the time we are discussing here the big breakthrough was Japan mass producing microchips more abundantly and cheaply than ever before and their adoption into everything. Engine management systems as has been mentioned but also it saw an explosion in CNC machining globally the accuracy and repeatability of which was a game changer.

When carbed engines wash the oil off the bores - they also wash the fuel into the oil. The lubrication ability of oils is severely compromised by fuel dilution.

 

[Erik the Awful]

I think carburetors have nothing to do with it. It's all about the metallurgy and better tolerances. My Cadillac motor had over 300,000 miles on it when I took it to the machine shop. The bores were perfect, and that was with a Quadrajet. A friend of mine had a carbureted Datsun 720 pickup, and at 400,000 miles it blew the head gasket. We pulled the head and you could see the factory cross-hatching in the bores. Is there any evidence C2 Corvettes with fuel injected 327s have better cylinder wear characteristics?

 

[stutaeng]

I really don't know anything about block material metallurgy. But I do recall reading about the bearing materials being changed in the later engines (maybe Gen III?) Maybe also tighter tolerances? I don't know.

What's the common failure mode of an engine? Isn't it low oil pressure (from worn bearings) that eventually necessitates it be torn down, or worse, catastrophic failure?

I agree that it's not likely the ignition system type that determines the expected life of an engine.