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ChadS
02-04-2005 20:15:58
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Re: How much airflow is too much? in reply to REDEYE, 02-04-2005 16:21:50
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Redeye, I've had alot of M-450's on the dyno, from the earliest model M, right up to the late 450. Ever notice how the 281 has its own sound to it? I mean, ideling, it dont sound like no M! I have one in the shop right now that is getting the engine redone, up to 306, with a stroker. All I can say really about the 450,(281) is that is a sleeper. Stock, these were very strong engines, the strongest for the entire history of the engine style. The later IH 4 cyl, from 1954, up to 1957 had alot of internal casting changes to improve the HP and torque, as well as being somewhat efficient to run. They had the science right, but HMMM,,,, wasnt efficient to run as for fuel economy, so they ran a low compression ratio. That made them a bit better on the fuel. Lower compressed engines dont need as much fuel. They can breathe all the can handle, or all the cyl design can draw into the cyl. The ports on them were much more straight through VS the old M heads, and they found out that the old M cam would not run right with the new head design, so they added a cam to match the head. then the power seemed to come alive on them. The intake manifold was bigger, as well as the venturi, and the carb throat size up as well. The basic 450 had flat top pistons, and if it was lucky, it had 125 psi of compression, but at 281 ci, with all the upgrades, from the factory, not anything I did, just dyno it. it was strong, the one that is in the shop is at 63 hp, and it will lug the needle down on the dyno farther and longer than any M would, at 150 psi and the old head and cam, and 4 inch bore high compression pistons was only 55!! My opinion if a 450 head can flow more than what it has, Absolutly! Im not a scientist here, but Id say the volumetric efficency kida blows when the compression is way down on them and not even close to the potential they were designed to be. The different ratio rockers? To me, it is a way to gain a bit more lift, but if you have no compression to compesate the changes, it does nothing!!! in order for an engine to require a different cam grind, is when it is lacking something preventing improvenmet, like a big cam, in a low compression engine, thats like running a 7 inch stroker in a M or 450 and have only 175 psi of compression. Your backing up if you dont have the factors to warrant such a change. You mentioned that you gasket matched your head, well it did not do much, sure it gave it more flow, but the compression did not increase. These engines need compression to gain. The science is already there, the set up is very very good in the C-281. Just give it some compression, and turn a monster loose! Just remember, 63 hp, 281 cubes, 125 psi of compression. wonder what it would be, if it was, say, 185, 190, 200 even? Tell you what,, ask someone who has a C-281 450, that is running an LP head and it is running right, find out what they get for HP if they have dynoed it. What do you want to know about a 450? Im tearing it down next week to install the stroker! ChadS
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