Talk:Iron Duke engine

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Intake manifold on passenger side?[edit]

My Pontiac Astre had an Iron Duke, and I seem to remember that its intake manifold was on the left (driver's) side. Anyone concur? -—Preceding unsigned comment added by (talkcontribs)

Yes, the intake is on the driver's side (opposite side from the 140). And you can always spot one easily in the H body cars as the dipstick is on the passenger side. — Preceding unsigned comment added by 2607:FCC8:A2C0:E700:E0FE:4445:3ED4:26D4 (talk) 13:56, 8 December 2015 (UTC)

Origin of the 'Iron Duke' moniker[edit]

Does anyone know how the engine got the name "The Iron Duke"?--King V (talk) 06:23, 24 December 2007 (UTC)

Because it has all the technological innovation, efficiency, and reliability of a 150-year-old steam engine? (Wow, a 2.5 litre engine from the 80s/early 90s that develops 90hp or less, and is recommended to keep under 70mph to avoid wearing out the timing mechanism... only in the American auto industry, eh! *breezes past at 80 in a more powerful, reliable european/japanese design with half the displacement*) —Preceding unsigned comment added by (talk) 02:10, 3 April 2008 (UTC)
Actually, despite its simplicity, it's a very reliable motor that gets good gas mileage. Considering what Japan and Europe was providing us with in 1977, you really can't knock it. Though in the later years Japan/Europe came out with newer designs, GM kept this older design around, essentially because it was a reliable motor that was reasonably well suited to the size and weight of the cars they were putting it in. The origin of the Iron Duke name dates back to 1977 when it was first introduced. —Preceding unsigned comment added by (talk) 22:27, 19 June 2009 (UTC)
180.56's comparison to the performance of more complicated engines misses the point. It's low powered because it's a true economy engine - simple, cheap and reliable. Conventional non-interference 2v/cylinder pushrod design, all iron, easy to service, and parts are cheap. The displacement gives it good torque, but it doesn't rev enough to compare with the horsepower of high-revving OHC, aluminum, 16-valve hotrod motors that they put in so-called "economy" cars today. Those modern designs still get good mileage but they fail to be as economical as the iron duke in any other respect.

As far as the origin of the name "Iron Duke", I'm not sure but I've read of it being advertised by that name in promotional displays back in the 70's. On a related note, I disagree with the article referring to the 1984 engine as a "Tech 4". I can't find any examples of that graphic being used that year. The earliest use of the name "Tech 4" that I've seen is a commercial for a 1985 Chevrolet Blazer, which was Chevy's first year using this engine on that vehicle. The name might be Chevy's invention for 85 marketing. From the cars I've seen and pictures online, this name didn't appear on Pontiacs until 1986, probably because they had to recycle Chevy's air cleaner housing. —Preceding unsigned comment added by (talk) 03:17, 12 August 2010 (UTC)


Where is this engine ever referred to as 2500? I've never seen that anywhere. --Sable232 02:44, 28 November 2006 (UTC)

I've never heard any such reference myself.--King V (talk) 06:21, 24 December 2007 (UTC)
Only in the Oldsmobile Omega ES2500 of 1981 or 82 vintage.—Preceding unsigned comment added by (talk) 22:28, 19 June 2009 (UTC)
It is called 2500 because it is a 2.5 liter engine. Mine is 39 years old and runs like a champ with great gas mileage 32 mpg. — Preceding unsigned comment added by 2607:FCC8:A2C0:E700:E0FE:4445:3ED4:26D4 (talk) 13:53, 8 December 2015 (UTC)

Is the 151in3 Iron Duke/Tech4 a derivative of the Pontiac V-8?[edit]

It was widely said at the time that the 151in3 Iron Duke pushrod 4-cylinder used in a variety of smaller GM cars of the '70s and '80s was "half of a Pontiac 301". Is the Iron Duke/Tech4 engine a variant or descendant of the 195in3 Pontiac 4-cylinder mentioned in the Pontiac V-8 Wikipedia article? If not, what's the relationship between the Iron Duke and the Pontiac V-8? Even if the answer is "none", this tale was common enough in the day (both heard in bull sessions and written in car magazines) that mentioning the association would be a worthwile inclusion in this article. Darwinianphysicist (talk) 21:05, 14 June 2008 (UTC)

The Iron Duke, was a revamped version of the Chevrolet 152, which was in the early Chevy II (Nova). The 308 was not in production for very long, and I do not believe that parts are available for the 308 due to the time elapsed and it's rarity. Al. — Preceding unsigned comment added by 2607:fcc8:a2c0:e700:e0fe:4445:3ed4:26d4 (talk) 14:02, 8 December 2015
The Iron Duke, was indeed, an offshoot of the Pontiac 301 V8. It wasn't a revamped version of the Chevy 152.
See Motor Trend of the period among others for it's engineering background. From the book "Pontiac Since 1945" : ..."The new Pontiac engines were the first from the division since the OHC6 of 1966".
"They were an inline 4 and a V8. Under project managers Tom Davis [V8] and John Sawruck [4 cyl] and chief engineer Stephen Malone, the designs shared common cylinder dimensions of 4" bore and 3" stroke, resulting in displacements of 150.8 cubic inches [2.5 liters] for the four and 301.6 [5.0 liters] for the V8".
"They also shared common pistons, piston rings, wrist pins, connecting rods and rod bearings".
"They did not have the same bore centerline spacing and thus the cylinder heads were not interchangeable".
"The valves were different, as was the portin; the V8 had crossflow porting, while the L4 had it's intake and exhaust ports on the left side".
Not a Chevy engine. Not a rehash of the Chevy II 4 cyl. — Preceding unsigned comment added by (talk) 18:36, 21 September 2018 (UTC)

Aluminium timing gear heated in oil, but not the others ?[edit]

The statement about heating the camshaft timing gear in oil to put it on the camshaft is correct for an aluminum gear (a "performance" part). But this isn't part of the directions for installing the stock "composite" plastic timing gears that I have seen.

Tashiro (talk) 13:24, 27 September 2008 (UTC)

Insidious weakness ?[edit]

I've seen one of these engines where a retainer bracket for the lifters broke. One lifter turned sideways in its bore and the roller wore the cam lobe down. When the engine was taken apart two of the other brackets were cracked. When these brackets are installed, you can see that they often rub against the lifter so much that it will not drop of its own weight (when the rocker arm is not on the push rod). The brackets are flimsy and I suspect they get hot from friction and crack.

Tashiro (talk) 13:24, 27 September 2008 (UTC)

Who knows if the engine you looked at ever had its oil changed often enough. —Preceding unsigned comment added by (talk) 22:29, 19 June 2009 (UTC)
I have 2 great running Iron Duke engines that are 38 and 39 years old. They are very reliable and I get very good gas mileage (32) mpg. Al. — Preceding unsigned comment added by 2607:FCC8:A2C0:E700:E0FE:4445:3ED4:26D4 (talk) 14:04, 8 December 2015 (UTC)

Timing mark on camshaft timing gear ?[edit]

The Chevy S10 books by Haynes and Chilton show that when the piston in cylinder 1 is at TDC on the compression stroke, the timing mark on the camshaft gear is about at 5 o'clock and matches with the mark on the crankshaft gear which is at about 11 o'clock. But I find (with both an aftermarket plastic timing gear and an aftermarket aluminum gear) that this is wrong on an Iron Duke from a 1987 S10 Sonoma. It is 180 degrees off. The mark on the camshaft gear needs to be at about 11 o'clock.

Tashiro (talk) 13:34, 27 September 2008 (UTC)

151-S/Chevrolet Opala[edit]

I'm not sure the 151cu engine in the Brazilian Chevrolet Opala was an "Iron Duke". The car's article contradicts itself whether it was or not, and if the engine came out in 1977, it wouldn't have appeared on the Opala starting in 1975. --Vossanova o< 19:11, 31 March 2011 (UTC)

1987 Iron Duke engine gallery.[edit]

I got a hold of one of these cars that was gonna be melted down. It drives ok, but gets over 30 MPG reliably. If it dies I will do a gallery of this engine if the demand is there. --Dana60Cummins (talk) 18:55, 15 August 2011 (UTC)


I do not believe that this engine is based on a V8 engine. I admit that I need to research this and do not currently have any documentation, but I always believed that it was a derivation of the the Chevrolet 153 4-cylinder engine produced from 1963 to 1970.

Part of my evidence to this fact is that I have a 250 L6 from a 1978 Pickup that currently has a water pump from a 1990 Chevrolet S-10 bolted on to it. The timing chain covers also look to be the same part.

(The purpose of swapping the water pump was as part of a serpentine belt conversion as the water pump will have to rotate in the opposite direction.)

The primary difference in the later L-4 from the earlier one, is the cross-flow head with the intake and exhaust on opposite sides of the head vs. the earlier reverse-flow heads with the intake and exhaust on the same side.

Here is a long quote from an on-line S-10 forum (with P breaks added by myself):

"Ok boys and girls here is a little more info on the 2.5 "Iron Duke" engine for any of you that really care.

For years and years there has been lots confusion over the difference between the "Chevrolet" 153 (3.875" bore x 3.25" stroke) and the "Pontiac" 151 (4.00" bore x 3.00" stroke). Everyone seems to want to call both of these an "Iron Duke". There has been a long going debate over whether that nickname started with the Chevy II 153 or the Pontiac 151 (2.5) engine.

I can tell you from personal experience (since I am an "old fart") that it wasn't until Pontiac started building the 151 in 1977 that it became known as the "Iron Duke". The "Stovebolt" 153 was originally built by Chevrolet between the years of 1962 and 1970 for use in the Chevy II as well as the 63-67 Chevrolet (Economaster?) van. It was for the most part a shortened 230 cu. in. Chevy six cyl. It was also produced by GM for OMC Marine from 1964 -1992 until OMC sold out.

At around that time Mercury Marine (Mercruiser) took over the use of this engine with GM building a bored and stroked (4.00" bore x 3.600" stroke) 181 cu. in. version albeit with a new better casting for the block. Both of these engines (153 and 181 [UP TO 1993]) used a non crossflow head (Intake and exhaust on the same side), a two piece rear main seal (same part # as Small Block Chevy), a Chevrolet bellhousing bolt pattern (same as Small Block, Big Block, Six cyl., and the 4.3 V6), and a Chevrolet flywheel/ring gear and starter (also the same as a Chevy V8). The 1994 and up 181 "Marine" block and crank used the "one piece" rear main seal therefore the block and crank were different. The 153 and the 181 were also used in industrial applications like forklifts as well.

In 1977 Pontiac started building their own "version" of the four cyl. engine. They obviously "based" their original design on the Chevrolet 153 but with a different bore and stroke (and with rods and pistons like those found in the 301 Pontiac V8). As I recall they, for only the first 2 1/2 years (1977 through mid year 1979 in the Monza and Astra), stayed with the Chevrolet bellhousing bolt pattern, two piece rear main seal crankshaft and the non crossflow head design as the 153 and 181.

The crankshaft in this engine would drop right in a 153 (or vice versa) as long as you used the proper rods and/or pistons. This is when the circle trackers took advantage of the larger bore of the 77-79 151 by installing the 153 crankshaft yielding 163 cu. in. (same bore and stroke of the famous 327 Chevrolet) in the 151 block. For them this was a bolt in no brainer.

Now starting mid year 1979 until 1993 the block, crank and heads were changed to accommodate a one piece rear main seal and crossflow (intake and exhaust on opposite sides [better flowing]) head. Now this part I am not 100% sure about (only about 95%), my memory tells me this is also when they changed the bellhousing to the "Small Corporate (60 degree V6 [2.8])" bellhousing bolt pattern (the same as ALL 2.5 S10s).

Because of these changes you could not anymore just "bolt in" the 153 or the 181 crankshaft in the later (79 to 93 2.5) block without a custom rear main seal adapter, a hand made flywheel and special rods/pistons. Nor could you just bolt in a 153 or 181 engine into your S10. It can be done but you would need to change the bellhousing, flywheel, clutch, hyd. clutch, and starter just to name a few. You would also need to fabricate engine mounts as the block is of a completely different casting, your accessories wouldnt bolt back on and you would still be stuck with the non crossflow head (along with several other differences to deal with).

Now Pontiac has made several different versions of the 151 with all sorts of changes over the years which has caused lots and lots of confusion. They built "2", "5", "R", "U", "E" and "A" code engines (I may have even left out a few). The one you mainly need to stay away from for your S10 is the "U" code engine as the crank is 1 1/4" shorter and the block is different as well. The "U" engine also requires a different head gasket even though some of the head casting #s are the same (IIRC they moved one of the bolt holes).

I believe all of the others are of the correct dimensions but you need to watch out for those that dont have the front water pump machining for your S10. Some of the front wheel drive (as well as the Fiero) blocks only have a "Hole" on the drivers side to acommodate their side mounted water pump. This hole can be covered as long as the block still has provisions for the front mount pump (some do some dont) for your S10.

Many of these engines have "balance shafts" and "Gyro" type oil pump systems. Now it has also been rumored that the S10s have stronger blocks than the passenger car engines. To be honest with you I dont know for sure but what I do know is that they have different casting numbers and to play it safe I would recommend staying with an S10 block in your S10 since at least you will know everything will still "bolt on" when you are finished. If you do try a pass. car engine look to the "R" engine but make sure you do all of your homework first. Other than a Super Duty block I would recommend the later 10044311 (88-93 S10/S15/Astro/Postal Vehicle) roller cam block in your S10.

IIRC when Pontiac built their first "Indy Fiero" they used a stock Fiero (no stronger than your S10) block with a Super Duty crankshaft and head and pumped out 232 hp. This should tell you that the little 2.5 block in your S10 can handle more than you might think (they did upgrade to 1/2" head studs and maybe even 1/2" main cap bolts as well). The crankshaft (along with the rods) on the other hand are another story (maybe to be continued [its up to you!]).

I know I have left out lots of block and crank details in this but I am just getting started and I dont think you need to know everything (just too overwhelming) right now. If you really, and I mean REALLY want to know more about building up a 2.5, then you need to post some more replies or you never know I might just "Fade Away". StrokerS10" — Preceding unsigned comment added by Nyth83 (talkcontribs) 23:22, 7 April 2013 (UTC)

StrokerS10, thank you for the history lesson. I have 2 Dukes, a 1977 Hatchback Astre, and a 1979 Sunbird Safari Wagon. Both of these engines run great, and get nice gas mileage. I would like to find a period Duke for my 1976 Notchback Astre currently equipped with the Durabuilt 140. The 140 runs great, but uses a fair amount of oil (valve guides?). But all I ever see for sale are later model Dukes with fuel injection. Not sure I could deal with that upgrade. Al. — Preceding unsigned comment added by 2607:fcc8:a2c0:e700:e0fe:4445:3ed4:26d4 (talk) 14:16, 8 December 2015
Based on the 301 Pontiac V8 designed at the same time. The Iron Duke is not a variation of the Chevy II engine. Based on the statements of project engineers who worked at Pontiac who worked on both engines: Tom Davis, John Sawruck and Stephen Malone. — Preceding unsigned comment added by (talk) 18:47, 21 September 2018

Still in production?[edit]

Found this on GM Powertrain's website: It's a 3.0 L OHV all cast iron engine with the same bore as the Iron Duke 2.5. I have a hunch that this more than a coincidence. VX1NG (talk) 16:29, 19 November 2013 (UTC)

I think you are right.--Dana60Cummins (talk) 16:57, 19 November 2013 (UTC)

Requested move[edit]

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: page moved. Armbrust The Homunculus 00:27, 1 May 2014 (UTC)

GM Iron Duke enginePontiac Iron Duke engine – All General Motors literature refers to it as a Pontiac engine. --Relisted. Andrewa (talk) 03:10, 23 April 2014 (UTC) VX1NG (talk) 18:54, 15 April 2014 (UTC)

  • Oppose but relisting to allow discussion of BDD's suggested alternative. Andrewa (talk) 03:10, 23 April 2014 (UTC)
    • Support alternative of Iron Duke engine. Andrewa (talk) 03:10, 23 April 2014 (UTC)
    • Support alternative of Iron Duke engine. Thanks, Andrewa VX1NG (talk) 14:14, 23 April 2014 (UTC)
    • Support alternative of Iron Duke engine.--Dana60Cummins (talk) 15:09, 23 April 2014 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.