Recent thread on a 241 got me thinking-I know there's alot of Hemi tech here, but not sure about a specific link on structural strength. Maybe someone can point me in the right direction.. I've heard the early hemis can be built tough, but just how tough is tough? ***uming the standard tricks of main girdles, and forged internals, just how much power can the "standard" upgrades take.- talking street engine so no alloy rods/filled blocks. Imagine a blower/turbo build with 10-25lbs of boost... today's engine blocks are taking 1200hp without much prep- what's the limit for the baby hemis, midsizes, and even 392s? I'd love a baby hemi and lots of boost if i can avoid alloy rods/block filler. I think all the hemis are bad***, and boost can certainly make up for cubes... rick.
Rick. This was a filled 354. I can't tell you how much they will take. But I can tell you what they WON'T take! Lippy
Why do you need more than 10 psi on a street motor? Hemis are plenty strong for street use and if you are using a 241 you need to be realistic on what HP you want out of it for the street. If I was building a 241 for a rod I would expect 225 hp to be enough for what I was going to use it for. If you want more HP then step up to a larger motor.
The first thing you notice about the 241/270 Dodges is how much thinner the rods are. Not a problem with street horsepower.
Kind of a strange question considering your avatar! Street HP, how much do you need? What is the weight of the vehicle? What kind of trans, rear and suspension are you planning on to handle all this power? What kind of brakes will stop this monster? When you answer all those questions, ask how much maintenance are you willing to do, if you plan on taking it to the strip, and if you can afford all this or is it just a dream? If you sink 15-20K into a reliable blown hemi, http://www.hemiengineparts.com/ another 2K in a rear, another 3-7K in a trans, and at least another 2K in brakes and 2K in suspension, plus an exhaust, a cooling system and fuel system that can support it, you are at 25-30K easy. You haven't bought a car, frame, wheels, tires, paint, interior, and all the little stuff to make it street legal. Also remember that if you use an original block, it's got a lot of years on it and you will want to make sure it doesn't come apart. Better to get a new block with that kind of investment, plus have added strength. http://www.jalopyjournal.com/forum/showthread.php?t=523801 If that seems like overkill, maybe you should reconsider 10-25 pounds of boost and 1200 HP on the street. 5-10 pounds is fairly normal for a street blown motor. Above that, you have to decrease compression and timing OR run race gas. Sometimes both. If you have access to street E85, that helps.
Chrysler V8 was about the strongest of the early V8s. Don Garlits big speed secret for years was what he did NOT do to his motors. Stock bore, stock stroke, stock crankshaft and head castings, blower and nitro gave him a reliable and repeatable 1000HP which was all the tires of the day would take. Olds V8 was as strong but not as powerful because they did not have hemi heads. Another thing I noticed in reading hop up articles dating from the 50s to the 90s. Every one said the early hemis were very well made and accurately machined. You could check all the dimensions but remedial machine work or "blueprinting" was seldom necessary, they were "blueprinted" from the factory. Having said that, the newest early Hemi is now over 50 years old. I would not ask one to boogie the way they did in the old days, any more than I would expect Cher to. If you really want big HP numbers why not consider a more modern engine?
Good points from both of you. The reason i was kicking it around is that i've been playing with quite a few street cars with modern efi and forced induction- 750-1250hp, loaded, leather, moonroof, etc. and wanted to know what the reliable limit of the other Hemis is. I've found that the older big trans- 727s, T400s, etc. take brutal power probably because they are old and weren't shaved down to the last inch like things are designed today (finite ****ysis, etc). they over built them. I was wondering if the older Hemis had a bit more m*** in their *** than was needed just like the old trans did... This was brought on by people trying to get me to toss my 415 inch LA mopar out of the Falcon g***er and put in a turbo LS1 for maybe 900-1100, (it's cheap and pretty easy) BUT i was thinking that if i do change, i want a more vintage mill not less... rick
Early Chrysler blocks were the weakest part. Your avatar pic should speak volumes about your question. I was hoping there would be a new premium version with the release of the Adams & Lajoie(?) casting that was supposedly to have occurred earlier this year, but I've not found anything about it since the press release last year. Tom S. in Tn.
If you hop in your time machine and trudge back to about 1968 you will find 392 going head-to-head with the 426 cars. IIRC they were in the 2000 hp range with the can 'tipped'. All of the Chrysler engines were overbuilt simply because that was the order from the top. "Make 'em last 100,000 miles" was the requirement and a pretty tall order considering the quality of the oil in the 50's. No, the blocks are not deep skirted like some, but a 392 block weighs at just under 200lbs. No exactly a light weight. Cranks? A 392 crank weighs right a 80lb. Heads? about 70lb each. All of that iron must be good for something. Lastly, big dyno numbers cost big dollars (and even more as inflation destroys the value). If you want to build a streetable blown 392 (or other) you are staring at $20k unless you get real lucky finding the right parts and do most of the work yourself. .
How much hp do you really need for a street car? I mean honestly and really, not I just want as much as possible because that just doesn't make any sense on a street car, especially what is suppose to be an older, traditional type car as we would expect on this site. Once you are above 400-500hp on a street motor, is it really that much different than 700-1000hp (let alone a ridiculous waste at 1500-2000hp) besides how much money you have wasted on something that isn't really usable? Unless you are the type that just wants to throw your money down a hole so you can go around honestly telling people you have a 1500hp motor, why even bother with this question?
Every motor is blueprinted, it's only a question to what extent. As for those LS guys, they can have it. There's no doubt you can make decent power with one, but that's more of a street machine engine.
The main webs of all the early hemi blocks are weak. The cylinders on a 392 aren't thick so with any serious power, they crack. I have no exp. in testing the wall thickness on a 241. I ran a 241 in a 27t roadster years ago. They don't make much power without alot of work.
The webs are perfectly fine until you get into the 2000hp range and the side of the 'vehicle' says AA/FA or AA/TF or similar. A blown street package is unlikely to ever have web issues. And a 392 is best at std bore and then slowly creeps into danger-land at 0.060 but cylinders can be sleeved. On fuel cars (back in the old days) the cracked cylinders were often the result of too much lead in the mag. .
We ran a 272 Dodge Hemi in an injected B/Fuel roadster. It had Don's boxed rods, main cap straps, forged alum. pistons, and flat tappet Shnieder cam. Block, crank, and most everything except Ported heads. Ran Five Years (7.97 @ 180) without major problems on Nito.
Funny, I have an old race block 392 that has a 4.125" bore. No block fill, no water jackets showing, and nothing broken. It was run at that bore, not sure for how long, but it was run (and probably raced) like that. That's a .125" overbore. As far as hp out of a 241, I'd say a solid NA street engine would be in the ~250 hp range. No reason that any of the old hemi's can't make 1 hp per cube NA with with the right set up (up the compression, cam, etc.). And you could still get more if you want to get a little wilder with the cam and compression, but you'll start sacrificing driveability. 25 lbs of boost on a street car is just nutty, it would be hard to make it a good driver on the street at that level. The weakest part of the Dodge hemi's were the cranks, they didn't run balancers from the factory and had a tendency to crack as a result. Running a balancer and opening up and chamfering the oil p***ages makes them last longer.
Another factor is the age/ condition of these blocks. I'm in the 1000hp street car area and have had nothing but issues till the block finaly cracked this year. I'm starting over with a better block this time.
The little dodge had some crank issues but that was because of the lack of a damper. They have more journal overlap than a small journal 327. As for wall thickness I bored a 241 to use standard 259 pistons and one cylinder had so much rust damage I had to sleeve it. That cylinder went .200 over for the sleeve and I never went to water.
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