Without getting into the "it IS/is NOT an Iron Duke" debate, I would like to get some more info on the GM 2.5L motors. I realize that if I start the snipe hunt in North Jersey for one of the elusive Mercruiser 3.0 engines, I'll come up empty handed. However, I have located a few of the later models of the 2.5 line in a local yard. The problem is, they come from the FWD GM cars like the Fiero, Grand Am, and Ciera. The one that's already out of the car is from a 1990 Ciera. It's also technically a "tech IV". The engine turns freely and has 35k miles on it. I've read that these engines are not as desirable as the RWD ones from the S10s for at least two possibly legitimate and other numerous ethereal reasons. The first are the plastic gears that they used on the cam in lieu of a timing chain. When the gear goes, the cam has to come out...not fun...but what are the chances? The other had something to do with the camshaft(?) and something about not being balanced the same, causing vibration and breakage issues. Finding older "dukes" up here is like hens teeth, and finding them under $300 is even harder. That pissing and moaning aside, can anyone corroborate or dispel the rumors about the Tech IV FWD motors? Also, can you mount a manual trans to the back of it? I'd like to find a inexpensive 4 banger for my ride, so this is where I'm starting.
I have a 2.5 in my 90 S10 DD, 280k miles and still going strong, I can pull a block number off it for you and see if it crosses over to the FWD engines. Search craigslist for S10 parts, I come across them frequently
The later Iron Dukes have the small GM corporate bell housing pattern. That pattern can be found on FWD setups, and on the 60-degree V6's and I4's, such as the S10. So yes, you can get an Iron Duke / Tech-IV engine from a FWD donor, and back it up with the bell and trans from a manual S10.
From 1978-1990 the had direct acting timing gears. The one on the cam was some sort of fiber reinforced plastic crap. It needs to be replaced at or before 60k. I have never seen an aftermarket steel gear. It is a non-interference engine, so it at least wont kill the engine if it breaks. Pre-'88 models do not have a balance shaft, and tend to vibrate more. After 1990, they got a timing chain, so the cam turns the other way, which may help cut down on vibration.
Problems with the FWD 2.5 engines include. Tho they all look the same externally. There is very little parts interchangability. Depending on the VIN numbers. There are at least 7 different cyl heads. Head bolt holes in different places, length of cylinder head, bolt pattern and shapes of intake/exhaust ports. Different rocker arm/valve train, valves springs. Blocks, weak castings, at least 5 different. As mentioned, different head bolt locations. Different camshaft configurations, drive systems. Different crankshafts, some with less than 10 degrees difference in timing/counterweights. But, get them mixed and you have a nightmare. Oil pump setups. Two earlier series have bad stress cracking from coolant into lifter area. BAD piston pins/pistons. 4 different types of con rods. These engines can turn into your worst enemy if you don't have experience with them. Most of them went to the junk yards and stayed..
It appears that I spoke too soon. There is a steel / ductile iron timing set to replace the steel / fiber set. It is Cloyes p/n: 8-1018. And here is more info: http://ironduke7.tripod.com/IronDuke.htm
My '88 S10 banger stripped the timing gears at about 100K miles. I got a new set (from Florida!) and have it pulled down now. An extra engine I tore down has two stuck wrist pins. I think the old Chevy II engines were far superior. BTW, the timing gears from a 230/250 Six are direct replacements and are metal. I didn't find that out until I already had the fibre ones installed. Dang!
Which engine are you trying to interchange the timing set with, the Chevy 6 timing set only interchanges with the Chevy II 153 style 4 cylinder engines.
I had a S-10 and had to replace the engine, the only one I could get free was from a fwd car. I think we only had to weld a tab on the block for the starter, and some other minor changes to make it work.
The Chevy II/Mercruiser 4cyl engine was never referred to as the Iron Duke by the automotive press or hotrodders.
Some of the interchangeabilty issues mentioned above are the result of there being "long" and "short" versions of this engine used in different GM FWD chassis. The long version was used in the wider A, W & X bodies like Citations, Luminas and Celebrities. The shorter version was used in the narrower N bodies like the Buick Somerset and Pontiac Grand Am. They looked similar but were maybe like 1 1/2" shorter to fit in the narrower engine compartment. Valve covers and side covers don't even swap due to the different lengths and the short version even has slightly narrower timing gears to save a bit of room at the front of the engine. I'm not so sure that even the bore centers aren't different between the two designs. The '82 to maybe '85 or so Camaros and Firebirds were also offered with a 2.5. But they're not common, as you might suspect.
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