Valve Clearance ??
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Forum Name: Shops, Barns, Varmints, and Trucks
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=172731
Printed Date: 29 Apr 2024 at 2:09am
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Topic: Valve Clearance ??
Posted By: FREEDGUY
Subject: Valve Clearance ??
Date Posted: 11 Jul 2020 at 6:51pm
I have a close friend that bought an Audi 4 cylinder engine car(I don't know the year) that broke it's timing chain and incurred MAJOR valve train damage  . He insinuated that in the "old days", there was such a thing as "high interference/low interference" heads??? He just can not understand why an engineer would design an engine with NO room for a "chain" malfunction 
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Replies:
Posted By: Alberta Phil
Date Posted: 11 Jul 2020 at 8:14pm
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Quite a common thing with today's engines. Many have the cam or cams driven by a timing belt which is supposed to be replaced at a certain mileage. Failure to do so will sometimes result in a broken belt and if it's an "interference" type engine, much damage can result!! I don't get that type of "engineering " either. |
Posted By: PaulB
Date Posted: 12 Jul 2020 at 7:29am
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[QUOTE=FREEDGUY]
I have a close friend that bought an Audi 4 cylinder engine car(I don't know the year) that broke it's timing chain and incurred MAJOR valve train damage . He insinuated that in the "old days", there was such a thing as "high interference/low interference" heads??? He just can not understand why an engineer would design an engine with NO room for a "chain" malfunction [/QUOTE It's known as "Planned Obsolescence" Engineers plan for things to break to boost sales of new vehicles and repair parts and to justify their existence designing the wheel over and over again. Luckily The engineers at Allis Chalmers were not of that mindset, however Henry Ford has been quoted that everything should not last any longer than the warranty. When everyone was making Jeeps for WWII he wanted ever single part that left any of his factories to have the "FORD" logo imprinted onto them so he could not be charged for replacing something that some other place made. ------------- If it was fun to pull in LOW gear, I could have a John Deere. If you can't make it GO... make it SHINY |
Posted By: DrAllis
Date Posted: 12 Jul 2020 at 7:53am
| Not any different than some older technology V-8's that have a timing chain and fiber camshaft gear wearing out. I have seen bent valves from that happening. |
Posted By: plummerscarin
Date Posted: 12 Jul 2020 at 3:01pm
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Luckily The engineers at Allis Chalmers were not of that mindset I discovered the hard that at least the 170 is an interference engine. |
Posted By: DMiller
Date Posted: 12 Jul 2020 at 3:21pm
| Only engines that were truly Non Interference and Not designed for that reason, flatheads. Any diesel engine breaks a cam drive or a valve hangs in a guide looking at severe damage. |
Posted By: FREEDGUY
Date Posted: 12 Jul 2020 at 4:48pm
My friend did say that "only" the exhaust valves got bent (8), but he replaced ALL 16. Why would only the exhaust valves get damaged  ??
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Posted By: DMiller
Date Posted: 12 Jul 2020 at 5:15pm
| Engines tend to be on Down stroke for Intake, Up stroke for exhaust, belt breaks, gear fails and most times the intakes are already closed/closing. Not much momentum on a cam to keep it rotating. |
Posted By: FREEDGUY
Date Posted: 12 Jul 2020 at 5:41pm
Thanks DMiller 
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Posted By: jaybmiller
Date Posted: 12 Jul 2020 at 5:49pm
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Why do 'engineers' design stuff like interfernece engines ?? Because they get paid to AND THEY don't ever have to work on them ( or PAY to have them fixed) !! We could (should ?) have a forum devoted to 'engineered booboos', 'cept it'd take up ALL the space on Darrin's harddrive !! ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: FREEDGUY
Date Posted: 12 Jul 2020 at 6:03pm
 , my friend said that the engineer that came up with the "IN TANK" fuel pump should have been castrated on the "drawing" board LOL !!! |
jaybmiller wrote:Posted By: LeonR2013
Date Posted: 12 Jul 2020 at 8:25pm
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Dave you're right about messing things up when you break a valve. Broke one on a 855 Cummins. Got the head, turbo, two inj. one piston and liner. Made a terrible racket. Leon |
Posted By: Tbone95
Date Posted: 13 Jul 2020 at 7:24am
| Hmmm.....I'm no engine guru. But aren't there some very sound thermodynamic reasons for the "interference" design? Such as, to get the air/fuel charge at the correct compression, if there were more room at the top, there would have to be more air/fuel there to be at the same pressure. Then some things like air/fuel mixing efficiency in a larger volume. Seems a lot of interweaved little issues there. |
Posted By: FREEDGUY
Date Posted: 13 Jul 2020 at 6:15pm
I was afraid that the "efficiency" (exhaust/pollution) might be a factor
. This guy is used to big block truck/racing engines that could survive "minimal" $$$ damage when/if a timing chain/belt broke . Seriously, 4 valves/cylinder ?? This particular Audi does have 1 turbo though,maybe that's the need for that many valves ?? |
Posted By: LouSWPA
Date Posted: 13 Jul 2020 at 6:26pm
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ya beat me to it TBone, many, many times in my life I have said not nice things about the engineer who did this or that, but the reality is his job is not an easy job! There are a multitude of variables with just about any engineering task, cost, performance, appearance, longevity, size, weight, available materials, and, of course, marketing's wishes, to name a few. Yes, that engine could have been designed so that should the timing belt fail there would be no damage, but, at what cost somewhere else? performance? weight? complexity? initial production cost? ------------- I am still confident of this; I will see the goodness of the Lord in the land of the living. Wait for the Lord; be strong and take heart and wait for the Lord. Ps 27 |
Posted By: steve(ill)
Date Posted: 13 Jul 2020 at 10:04pm
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Yea, i have a 125 cubic inch Allis motor that weights about 300 pounds and puts out 20 HP..... using that same spec, you could build a 400 cubic inch truck engine with NO interference fit that put out a GOOD 75 HP !!! ------------- Like them all, but love the "B"s. |
Posted By: Tbone95
Date Posted: 14 Jul 2020 at 8:13am
More valves = more/easier breathing = more performance and efficiency. And yes, more "small" valves are better than just "bigger" ones. |
Posted By: FREEDGUY
Date Posted: 14 Jul 2020 at 7:09pm
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Thanks Tbone . I happen to run an '05 5.4 Ford F250, can I assume that the "TRITON" refers to multiple valves/cylinder? I bought it used and knew nothing(at THAT time) about that engine but have been learning more about it .
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Posted By: DMiller
Date Posted: 14 Jul 2020 at 7:16pm
| Cams are problematic, cylinder heads on the earlier 5.4s were a disaster where plugs seized hard in the head threads, required special tooling to retrieve and ended with a Plug change to another type. Do NOT ignore engine odd noises that start out minor then grow as the timing chain tensioners were also a issue. Pre 2004 were only 2 Valve, after 04 three valve, Triton has nothing to do with that configuration, Just a Name. |