Tony, I asked about the name iron duke just to make sure if it was new desing, although using the look of the old 153, or just a 153 with a different casting to accept 4" bore, like it is in Brazil. I also asked about the bolt number just to see if the iron duke still used 4 bolts aroud each cilinder bore or 5 like the SBC V8. Seems that You can put a 151 cross flow head in an early 153. A friend of mine that is very well informed about cars, numbers of production and stuff like that told me that there was a series os fiero that came out with the 181 cid engine in a effort to offer a better performance than the one obtained with the 2.8V6.
Locobreath I have some really nice pics of some Brazilian only chevy trucks, they are based on U.S. built models of course, but the shhetmetal is way too different. Where do You want me to post them??
The mexican stuff is unknown to me, but here, we have nowadays a truck called Silverado, by the way it is the same that was sold in U.S. till 1 or 2 years ago. And this truck offered 3 engines to choose, 2 diesels, one 4 cilinder that is called maxxion, in fact an old perkins 4-236 with some mods to the injection some 100 hp, a MWM 6.07, 4.2 litters displacement, turbocharged and intercooled with 170 hp, a real nice engine, faster than all the diesels 62. or 6.5 liters GM diesels and much more peasant to drive, but no auto trans, just stick five speed, and a 250 efi, 168 hp. No V6, no V8 whatsoever. Only shortbed, no extra cab, no 4 doors.
Greybeard, I also dealed a lot with boats. In fact I made it as for living, fixed boat engines for more than 16 years, now I'm living 1000 miles away from the sea and some fellows still pack their engines and send then for me to fix here. I fixed skiboats, all V8 powered. Have some pics of the boat you raced??
As to Your questions, ain't the 151 4" bore?
Here in Brazil they are all 4". Yes the 181 does not have a Cross flow head, but I can garatee You that the head flows very well.It is really based on the chevy II 153 head, but is another casting, the runner base is much higher, and it helps a lot the flow, in as much as the smaller gas activitie area in a runner is the base. Just port the upper areas and the bowl above the valve and You're done. Don't know if You're using the cast iron water cooled intake exaust manifold, if so, I see that You'd be better off with the stock one from a 181 than trying to use an earlier one for a 153, as long as there will be a mismatch in the ports.
The 4" bore is obtained with a different cast core than the one found on 153 engines, for sure the 153 is not able to be opened to 4" bore in a safe way. Like it is not wise to try to bore a 307 or later 283 to4" in order to make a 327 or 302. And if the 181 uses a 6"long rod, the block must be taller than the 153, or esle You'd need to have the piston pin into the oil ringland.
The rod is not the same as the 6" long rod of 4.3l V8 because the rod's foot is thinner in a V8 engine. Take for example a rod from a 153, it's almost the same as the one from a 265/283, but the lower part is wider on the inline, it needs to have space for the radii in both sides, in a V8 they ride side by side, so only one wide radii space in the outer side, the inner side rides against each other, so no space for a radii. That's why You should no assemble a 6" rod out of a V8 into a L4.
Darrel, the 140cid Vega engine is somethig really weird, I guess it looks like an 153 but it's very different inside. Maybe using the crank for a stroker based on the 153/151 may be a good idea, but I dunno if it fits or not. A 4" bore and 3.625 stroke ends up more or less 181. Dunno also if it is easy or expensive to get a decent 181 out of a boat in U.S. to justify the hassle of dealing with it.
Alexandre Garcia
