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Myth: Modern engines have tighter clearances?
#177465
12/28/08 09:10 PM
12/28/08 09:10 PM
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Joined: Jan 2003
Posts: 17,841
S.E. Michigan
ZIPPY
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I actually went through this months ago but I've been meaning to discuss it here to see what folks thought. Engine is a 2004 5.7L Hemi for a buddy's car. First 5.7 I ever worked with. It was knocking when he got it, looked like it was run out of oil and then ran hard, lost two rod bearings. Tore it down and decided to just use the block/replace everything else in the bottom end. He bought a brand new crankshaft, rods, pistons, rings, and all the bearings from Mopar. Prices were surprisingly cheap for the mundane stock stuff like that. Anyway I spent some time checking it out... Clearances: Mains: .0028 to .003" across all 8 Rods: .002 to .0025 across all 8 Piston to wall .0012 to .0015 across all 8, normal for a cast or hyper piston, always has been Checked the service manual, everything was in spec per Chrysler. So...being that the clearances are basically the same as a V8 from the sixties, what's up with the myth "Modern engines are built tighter"? It's really no different from my 1968 318 2 barrel in that dept.  + or - tolerances may be slightly tighter on the machining end, which I guess I'm on the receiving end of... but recommended final clearances appear to be pretty much the same as always. Thoughts?
Rich H.
Esse Quam Videri
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Re: Myth: Modern engines have tighter clearances?
[Re: ZIPPY]
#177467
12/28/08 09:22 PM
12/28/08 09:22 PM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
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Those clearances were even looser than old specs. 60's spec's. .0005-.0015 rod and main in my book (/6, 318-440). Hemi's were fit looser though.  I still fit mine at .0015-.002 at the loosest.
Clean it, if it's Dirty. Oil it, if it Squeaks.
But: Don't fix it, if it Works!
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Re: Myth: Modern engines have tighter clearances?
[Re: BergmanAutoCraft]
#177469
12/28/08 09:48 PM
12/28/08 09:48 PM
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Joined: Feb 2003
Posts: 10,201
Someplace you aren't
SomeCarGuy
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Quote:
Its fuel injected, so no fuel washing past the rings and into the oil. Thats the biggest difference, and the reason why new EFI motors seem to last forever if they are taken care of.
Ding ding ding
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Re: Myth: Modern engines have tighter clearances?
[Re: Jim_Lusk]
#177472
12/28/08 11:07 PM
12/28/08 11:07 PM
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Joined: Nov 2008
Posts: 173
Tucson AZ
2cudabuck
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Having a degree from UTI but not even close to the years of knowledge on this board, I can offer my .02. Fuel injection and volumetric effeciency is key. Modern materials, ie more consistant expansion/contraction rates, less or no contaminants in little or no blowby, VERY effecient PCV etc systems make for an engine that contains each element of it's performance in it's allocated place, with little cross contamination. This allows for for tight tolerances that LAST. The same tolerances are generally required for an engine to function, but deteriorate quickly if cross contaminated or improperly maintained.
Buck
67 273 Dart GT
69 RT 440 Charger (SWEET!)
70 318 Cuda
74 Cuda Packin a 426 roller Hemi
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Re: Myth: Modern engines have tighter clearances?
[Re: 2cudabuck]
#177473
12/28/08 11:56 PM
12/28/08 11:56 PM
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Joined: May 2004
Posts: 12,385
Taxes & Virus's R-US, NY
Dragula
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I had worked at GM for the last 7 years, and part of my job was setting up the final bore and final production hones as well as write the specs for them and monitor capability. I can tell you the crank bore tolerences were no worse than +/- 0.012mm, with most our lines running around +/-0.008mm and run-out was only allowed 0.025mm from front bore to the rear bore max.
Cylinder bores were only allowed +/-0.011mm and a max of +/-0.008 on the thrust wall and cylindricity of 0.013mm max and max taper of 0.007mm. And just in case you don't think it can be held, it can be, and it can be done day after day, week after week, etc. The machines use in-line feed back to constantly hold size.
Years ago, the sizes and tolerences were not this tight, but to meet the ever increasing demand for 100k warrenties, and not go broke in the process (on second thought, I guess they did go broke), all the specs were tightened over the years. If your measuring in thousandths, your already oversize....
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Re: Myth: Modern engines have tighter clearances?
[Re: DennisH ]
#177479
12/29/08 12:38 PM
12/29/08 12:38 PM
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Joined: Nov 2003
Posts: 3,577
Long Island, NY USA
BergmanAutoCraft
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Quote:
You may have guessed-no degree here. Tell me more about the reason that the new 5.7 Hemi calls for 5-20 instead of the 10-40 recommended by the builder of my 440. Is it the tolerances? Is this why the make-up of the synthetic can clean/loosen buildup that can lead to a leak?
Is it the passage ways themselves that are too tight for the 40 weight?
The MDS plunger is basically an oil restricter that is designed to be used with light weight oil.
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Re: Myth: Modern engines have tighter clearances?
[Re: stubbs300 ]
#177481
12/29/08 03:50 PM
12/29/08 03:50 PM
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Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
B G Racing
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I left out an important word after micro.Parts are micro polished to reduce friction.The tolerences are closer with the types and quality of lubercations(synthetics) and cleaner blends also also reduce friction.Mirror like cylinder wall finishes and ring styles and materials have greatly improved engine life.Many of the import and commercial engines are warrantied for 100Ks miles some thing unheard of in years past.Actually we have some 600 hp Cummins diesals in our tracter trialer fleet(lowboy heavey haulers)that came with 500,000 mile warranty.engine building techonology has change,when I first started playing with cars 30/40K miles you were ready for rings,bearings, and valve job.We have many pieces of heavy equipment(dozer,excavators,etc)with over 10,000 hrs on them.One excavator(Kebelco)has 18,000 hrs with only in frame overhaul.Needless to say we have a good maintaince program. 
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Re: Myth: Modern engines have tighter clearances?
[Re: B G Racing]
#177482
12/29/08 05:59 PM
12/29/08 05:59 PM
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Joined: Jan 2003
Posts: 17,841
S.E. Michigan
ZIPPY
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I guess my point was, just because machining + or - tolerances are closer, and finishes are better and smoother, really does not mean the clearances are any tighter. They aren't, at least not in the case of
that 5.7.
Relative to another comment above...at one time in the '90s it was fine to run the 2.0 Neon engine on 10w30 oil. If you took your car to the dealer, odds are good that's what they would pour in. Come 2005, and you absolutely can not run anything but 5w20 per the pwner's manual. Look up the clearances for both engines, and guess what...they have not changed over time either. I'd think if there were going to be any big changes they would show up in little 4 cylinder engines first, but even that doesn't seem to be true.
It's just something to discuss and throw around, I'm not trying to prove anything but I think the myth is funny. Tolerances may be tighter, I don't doubt that, but the desired end result is pretty much the same as always.
At the OEM level, it's not uncommon to scrap a few hundred engine blocks because the bores are oversize by like two microns. MICRONS. Pieces that could have went 150,000 miles without an issue. Sounds a bit wasteful just for the sake of maintaining tight tolerances, doesn't it?
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Re: Myth: Modern engines have tighter clearances?
[Re: DennisH ]
#177484
12/29/08 08:30 PM
12/29/08 08:30 PM
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Joined: Apr 2007
Posts: 2,826
NY usa
540challenger
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I never broke the motor done or check specs but my brother had a 2001 ford focus. That was the start of the 5w-20 thing for ford if i remember right. At the time it was hard to find a full synth. oil in 5w-20. So i changed over to 5w-30 no problems then next oil change i went with a 5w-50 and had a knock.  Switch right back to the 5w-30 kock went away.
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Re: Myth: Modern engines have tighter clearances?
[Re: 360view]
#177486
12/30/08 12:30 PM
12/30/08 12:30 PM
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Anonymous
Unregistered
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Anonymous
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A few more numbers that I happen to have access to right here.
GM 6.0, 2007, used in 1 ton van. 300hp, 360 ft-lb
rods.0008-.0021
mains .0008-.0025
piston to bore .0009clearance to .0012 interference (coated skirts)
This is from the factory service manual
Look like pretty normal V8 specs to me, definitely not tighter.
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Re: Myth: Modern engines have tighter clearances?
[Re: ZIPPY]
#177487
12/30/08 01:21 PM
12/30/08 01:21 PM
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Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
B G Racing
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Quote:
I guess my point was, just because machining + or - tolerances are closer, and finishes are better and smoother, really does not mean the clearances are any tighter. They aren't, at least not in the case of
that 5.7.
Relative to another comment above...at one time in the '90s it was fine to run the 2.0 Neon engine on 10w30 oil. If you took your car to the dealer, odds are good that's what they would pour in. Come 2005, and you absolutely can not run anything but 5w20 per the pwner's manual. Look up the clearances for both engines, and guess what...they have not changed over time either. I'd think if there were going to be any big changes they would show up in little 4 cylinder engines first, but even that doesn't seem to be true.
It's just something to discuss and throw around, I'm not trying to prove anything but I think the myth is funny. Tolerances may be tighter, I don't doubt that, but the desired end result is pretty much the same as always.
At the OEM level, it's not uncommon to scrap a few hundred engine blocks because the bores are oversize by like two microns. MICRONS. Pieces that could have went 150,000 miles without an issue. Sounds a bit wasteful just for the sake of maintaining tight tolerances, doesn't it?
 I did some research on the big commercial and industrial engines,and did find the clearences to be tighter and the allowable runout of componants held to near perfect tolerances.Most tolarences were held to .0000 on runout and clearences usually held to
.000 were .0008 to .0005 on a Volvo engine. 
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Re: Myth: Modern engines have tighter clearances?
#177488
12/30/08 02:38 PM
12/30/08 02:38 PM
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Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
1_WILD_RT
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Quote:
A few more numbers that I happen to have access to right here.
GM 6.0, 2007, used in 1 ton van. 300hp, 360 ft-lb
rods.0008-.0021
mains .0008-.0025
piston to bore .0009clearance to .0012 interference ( coated skirts)
This is from the factory service manual
Look like pretty normal V8 specs to me, definitely not tighter.
Go back & re-read the high lighted spec...Pay particular attention to the word interference... I don't recall any muscle car vintage engines with an interferenca fit spec for thew pistons..But it's been the norm in modern enginges since the mid 90's...
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Re: Myth: Modern engines have tighter clearances?
[Re: 1_WILD_RT]
#177489
12/30/08 05:05 PM
12/30/08 05:05 PM
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Anonymous
Unregistered
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Anonymous
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Note what is in parenthesis--coated skirts.
The coating is using up the clearance and into interference, and the extra wears of almost immediately. I think they even had a separate spec for clearance once pistons had been run.
You could never run an uncoated piston with interference, it would gall instantly.
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Re: Myth: Modern engines have tighter clearances?
[Re: 1_WILD_RT]
#177492
12/30/08 07:12 PM
12/30/08 07:12 PM
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Joined: Jan 2003
Posts: 9,872
Weddington, N.C.
Streetwize
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I'm not sure blueprint clearances are tighter but generally operating (at temperature) clearences are. So in that respect I'd be a little surprised if build tolerences are that much tighter. If you notice a lot of newer motors are pretty noisy (the GM LS motors especially) when they're cold. Plus add the fact that most motors run 5W and some even 0W oils so somethings got to be up. Most motors these days run at 192 degrees and some over 200. The main benefit of modern motors is the fuel injection which minimizes fuel wash and greatly enhance bore and ring longevity. I suspect coatings are more for protecting internal parts under extreme (hot or cold) start conditions than any real MPG savings, the gains at cruising speeds would be relatively infintesimal(sp?) compared to the bang for the buck gains of optimizing fuel mapping at cruising speeds
Last edited by Streetwize; 12/30/08 07:32 PM.
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Also they were working toward having main bearing fasteners & head bolts all extended to the central mass area of the engine rather than just through the main caps/cylinder heads..Main Bearing Girdles are also common on newer engines...