Recently there has been some confusion as to the actual displacement of what is commonly refered to as a 426 stroker. I'm posting this to explain why some engines that are refered to as 426's may actually be 423, 420 or 418's depending on block condition, sonic testing data or builders preferance. Almost 2 years ago I started development toward designing what I intended to be the worlds first 426 CI 6.1 based hemi stroker engine. At this point in time you couldn't just pickup the phone and order a compstar or K1 stroker crank, or rotating assembly. If you wanted to do a 6.1 stroker and make 426 CI you first had to actually stroke a 6.1 crank by welding material to the top of the journal and then offset grinding it to the desired stroke. In this case it was 4.056" stroke to make a 426. You can also do a billet crank but those have a couple of months in lead time and run about $2500. It also takes a decent bit of engineering to figure out what rod length, wrist pin size and piston type to use in order to clear the crank counterweights and toner ring on the stock crank. Not like it is now where you just order a kit ready to go. But after allot of mockup and calculations 3-4 months later I had all the parts custom ordered and ready to go together. Well, it seems that Indy Cylinder head was working on the same thing at the same time and actually beat me to the punch by a couple of weeks but cool, it's the 2nd 426 in existence. The bore and stroke specs for that engine was 4.090" bore by 4.056" stroke which the displacement = 426.3 That was the one and only "actual" 426 CI engine that I've ever built the other 20 or so 6.1 based 4.050 stroke engines were all 418 or 420. I did this for good reason. After sonic checking more 6.1 blocks I determined that many of the 6.1 blocks won't handle a 4.090" or 0.035" over bore without making the cylinder walls too thin. Since the stock bore 6.1 block already has pretty thin bores for a performance engine I started minimizing the bore size of the subsequent 6.1 based strokers that I build. Since I custom order all the pistons for my builds to the particular specs for that build I can call out about any bore size I want but on a used 6.1 block I normally bore them 0.009" over or 4.064". The reasoning its enough to clean up most used blocks and get the bores straight and with a 4.065 ring it allows me to file fit the rings to the block to set the ring gap for the particular application. A 4.064 bore on a 4.05" stroke crank will yeild 420.3 CI engine. Not a full 426 CI but yet a better engine because theres more material in the bores. So do 418's, 420's or 424's commonly get refered to as 426's? you bet they do. I think most people reading my posts have seen me refer to 420's and 418 because I don't try to hide the fact. Will I occasoinally refer to a 418 or 420 as a 426 stroker? sure, and I'm not the exception. If you call up Callies and order a 426 stroker kit you can get a "426" stroker kit with 4.065", 4.08 or 4.09" bore pistons but they are all part of what is marketed as a 426 kit. Yet none of them are actually are they are 420, 424 and the 4.09 bore is actually a dimunitave 425.67 CI. Hey, does that mean the only actual 426 in existence until the 4.08 stroke K1 crank came out is Redfoxe's because he has a 4.056" stroke crank? All the other 4.090" bore engines are 425's. Well, that would be a pretty lame claim quibeling over 0.33 CI but it's not much less lame accusing someone of deception over 5.7 CI. If you order a 426 engine thats built by Indy you may get a 420, 424 or 425 and you really don't know unless you ask. Are they trying to decieve anyone? No. If you check out their marketing info do they call them 426's yeh, and so does everyone else. Does this mean I won't build an actual 426, no but I'd want to sonic check the block and would probablly advise against it. Another thing to consider is the stock gasket is only 4.08" in diameter
great post stu, very articulate and informative, thank you for your hard work on these engines, you keep building 'em and we'll keep driving the hell outta them! Steve
FWIW: Indy cylinder heads built the first "426" strokers from stock 6.1L Hemis. They too realized the cylinder walls would be too thin, and most of their engines maxed out at 4.08, or 423 C.I. People want to call them "426 Hemi's" because of the historical significance. In reality, most of the engines don't hit 426 real cubic inches, no matter who the vendor is. And to be honest, I wouldn't want one actually bored out all the way to 426 because of the cylinder wall issue. But I wouldn't put a "423 Hemi" badge on my car either. It would say "426." Stu is no different than anyone else.
good intel, never knew any of that because im an idiot. had no idea that there were 420s and 425s runnin around the place.
Our 300 has a 423 in it. Thats the smart way to do it. A 418-420 is even better if you ask me. Very well said Stu.
