Are these spherical 904s and 727s or are they flat?
AJ's Opinion; what size SBM do I need
- Thread starter AJ/FormS
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Are these spherical 904s and 727s or are they flat?
diymirage
HP@idle > hondaHP@redline
the pan is flat, the bell is spherical, that is pretty obvious, the only real questionable parts are the planetary gears
rmchrgr
Skate And Destroy
Ok, back to engine talk. If you go with the conventional wisdom that a 4" bore is the nominal size for a "small block" performance platform (I do) then the 318 falls short.
For comparison, whether 2bbl or 4bbl, both the 302 and 327 were designed around a 4" bore. Besides the increase in up swept volume, one would realize the other key benefit of the larger bore is reduced valve shrouding. With either of those ancient Brand-X choices you wouldn't have to deal with that negative aspect of the architecture before you even start like you would with a 318. Heck even the 289 had a 4" bore too. '65-66 K code would wipe up the floor with any 318.
Not sure why some of you guys get stuck in this mindset that 318s are worth pursuing, especially over a 360. They were never designed as or meant to be performance engines, just basic motivation across multiple platforms. In reality they were under powered, gas guzzling boat anchors for their entire 30 some-odd year run. When you look at the design of the LA 318 from a purely factual/logical/scientific viewpoint, you'd be hard pressed to justify building one up because the basic architecture isn't there to support it. How many 318 combos running in NHRA Stock or Super Stock? Not too many. If it was favorable you'd better believe there would be lots of them out there. Both were and are still readily available cheap so if you have to chose between one or the other, the 360 is the logical choice. Last 360 short block I bought was maybe $100. If you want to build one for your own amusement and have the means to do it, knock yourself out and prove me wrong.
The 360 wasn't a world beater either in stock form because it was never produced with any real compression. But, as a build platform, it's got the magical 4" bore and can swallow a 4.25" stroke even though it's basically the same externally as the 318.
Same story with the 383 vs. 400. 383 was a pedestrian big block with a relatively small bore that found it's way into millions of cars. It was replaced by the 400 which over the course of it's run was mostly a lo-po torquer/dog in factory stock form. it is generally thought of as the go-to for big power low-deck strokers. Why? because of the 400's 4.342" bore which is the largest bore of any muscle-era Chrysler production engine. Don't see many guys building 383s because for the same money you can build a 400 based combo that nets more cubes and the potential to make way more power. Same block externally.
For comparison, whether 2bbl or 4bbl, both the 302 and 327 were designed around a 4" bore. Besides the increase in up swept volume, one would realize the other key benefit of the larger bore is reduced valve shrouding. With either of those ancient Brand-X choices you wouldn't have to deal with that negative aspect of the architecture before you even start like you would with a 318. Heck even the 289 had a 4" bore too. '65-66 K code would wipe up the floor with any 318.
Not sure why some of you guys get stuck in this mindset that 318s are worth pursuing, especially over a 360. They were never designed as or meant to be performance engines, just basic motivation across multiple platforms. In reality they were under powered, gas guzzling boat anchors for their entire 30 some-odd year run. When you look at the design of the LA 318 from a purely factual/logical/scientific viewpoint, you'd be hard pressed to justify building one up because the basic architecture isn't there to support it. How many 318 combos running in NHRA Stock or Super Stock? Not too many. If it was favorable you'd better believe there would be lots of them out there. Both were and are still readily available cheap so if you have to chose between one or the other, the 360 is the logical choice. Last 360 short block I bought was maybe $100. If you want to build one for your own amusement and have the means to do it, knock yourself out and prove me wrong.
The 360 wasn't a world beater either in stock form because it was never produced with any real compression. But, as a build platform, it's got the magical 4" bore and can swallow a 4.25" stroke even though it's basically the same externally as the 318.
Same story with the 383 vs. 400. 383 was a pedestrian big block with a relatively small bore that found it's way into millions of cars. It was replaced by the 400 which over the course of it's run was mostly a lo-po torquer/dog in factory stock form. it is generally thought of as the go-to for big power low-deck strokers. Why? because of the 400's 4.342" bore which is the largest bore of any muscle-era Chrysler production engine. Don't see many guys building 383s because for the same money you can build a 400 based combo that nets more cubes and the potential to make way more power. Same block externally.
Find where I said a 318 is worth PURSUING. Didn't say that. I wouldn't run out and buy a 360 if I already HAD a 318. That 318 would get built. As for bore size, sure, more is good. Not necessarily better for "everything" under the sun, but more is good. I obviously don't care much for bore size since the bore in my engine is 3.445".
383 small bore ? 4.25 bore same size as a 427 Chevy oh and a 426 Hemi.
It would be best not to compare a 383 Magnum to a 318. lol
It would be best not to compare a 383 Magnum to a 318. lol
I love '64 Fairlanes, and I love 289's !!!!!!!! Although '66 Fairlanes are my favorite, the '64's have a special place with me, and my child hood !!
rmchrgr
Skate And Destroy
It's small compared to a 400. Not comparing a 383 to a 318 but just saying that if you have the choice to build an engine that's externally the same but one has a larger bore, you do that.
I drive a 383 Magnum all the time in my '68 Coronet, it's nothing to write home about. Has headers, dual exhaust, "RoadRunner" cam, Performer intake, 452 heads... meh.
5.8
I said all weight and gearing be equal... in other words, a 5.2 in a Duster could and should be just as exciting as a 5.0 in a fox body.
I always said a 383 is a grown up 340... Big bore, short stroke
Plus with so many 3.75" cranks out there a 431 should be a no brainer and a decent size over a 408.
No one on here is arguing that a 318 is a superior stating point over a 340/360 Just if one of our members wants to do a 318 instead of a 340/360/408 and understands the short comings then people should help with that goal instead of the "go 360/408" cause of xyz routine.
I could go on the /6 section and go all day long and tell them they be better off with even a 273 over a /6 build but it's obvious thats not what they want. unless their going on about a super unrealistic goals like 500hp na destroked 170 daily driver
Plus people make it sound a lot harder and more expensive to make power out of 318 than it is, sure pistons are more but other than that everything else is the same. a 10.5:1 zero decked 323-328 with speedmaster, eddy, trickflow etc... and a 275-285 cam etc.. is gonna make power and needed a little more gear and stall over a similar 340, and most just want a 4bbl headers and RV cam on a stock longblock and turns into 50 pages how it can't be done cause of xyz, even though 318willrun has already built and video documented the results.
I could go on the /6 section and go all day long and tell them they be better off with even a 273 over a /6 build but it's obvious thats not what they want. unless their going on about a super unrealistic goals like 500hp na destroked 170 daily driver
Plus people make it sound a lot harder and more expensive to make power out of 318 than it is, sure pistons are more but other than that everything else is the same. a 10.5:1 zero decked 323-328 with speedmaster, eddy, trickflow etc... and a 275-285 cam etc.. is gonna make power and needed a little more gear and stall over a similar 340, and most just want a 4bbl headers and RV cam on a stock longblock and turns into 50 pages how it can't be done cause of xyz, even though 318willrun has already built and video documented the results.
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You have missed the point and thinking this backwards.
Let me explain…..
Many here don’t have the money to go out and repurchase an engine, have space for another engine, the means to easily get ride of the “Boat Anchor” spare engine or just simply want to build the 318 they have in the car. Be it a full rebuild for stock, mildly hopped up or hard runner.
I don’t know if you yourself have ever been limited to such a degree where doing much of anything else besides dealing with what you have within the means you have limits you to the engine at hand. The one in the car.
If your seeking help and your limited in one or more of the above or just simply wanted to do the engine you have, in this case the 318, why would you not help that person with what THEY want to do?
I believe that no one here is stating what you seem to believe above.
I cleaned up the thread. Keep it on topic and keep the insults to yourselves.
Not according to someone here……
The question serious.
Good question!
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Just the point I'd like to make about the bore of the 383 being so small. It's 4 and 1/4 in as in 4.250 which is the same as a 427 Chevy and a 426 wedge or 426 Hemi. I don't see where 4 and 1/4 in is a small-bore.
400 replaced the 383 in 72 when everybody went smog. They lowered the compression they decammed them they devalved them. Any good 69 Roadrunner would outrun a 72 or 73 Roadrunner with the 400.
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The 396 is 4.094. Weird, but that's what it is. But I agree. I don't see anything with a bore 4" and over being as "small".
33IMP
Well-Known Member
396 chevy bore is 4.094. 427 chevy is 4.25 . Supposedly there are a few 396 blocks that can go .130 over. I havent found one.
And, a 383 mopar, with a .060 overbore and a 4.25 crank, is the exact same bore and stroke as the highly regarded 496" bbc.
Chevy changed the 396 bore in 1970 to 4.125 going .030 over. Lotsa urban myth stories like someone set the boring bar .030 over by accident and several thousand blocks went through before it was caught....blah blah blah....but the reason for it was strictly financial. The all new small block 400 debuted in 1970 and the engineers decided to jack the bore on the 396 up to 4.125 so they could use the same ring pack as the 400. They continued to market it as the 396 in cars, but 400 in trucks. Poor thing never was marketed for what it really was, a 402.
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rmchrgr
Skate And Destroy
OK, well that didn't really come out right, 4.25" is not a small bore. Mopar did have some comparatively large bores - 400 is 4.342" which is big, maybe that was my logic for saying the 383 bore was small? I dunno. Funny too because I'm actually building the 438" stroker below with my friend based on a .060" over 383 block. Bore is 4.310" so getting into 400 territory.
My point is the 383 is sorta equivalent to the 318 in status. There are millions of them out there but no one really wants 'em because the 400 makes a better combo, all things being equal. It's the same logic as the 318 vs. 360 argument - the blocks have the same external dimensions but the one with the bigger bore will generally make more power in an average build.
My point is the 383 is sorta equivalent to the 318 in status. There are millions of them out there but no one really wants 'em because the 400 makes a better combo, all things being equal. It's the same logic as the 318 vs. 360 argument - the blocks have the same external dimensions but the one with the bigger bore will generally make more power in an average build.
33IMP
Well-Known Member
Everything is relative. 383 4.25 bore is bigger than the Pontiac and Olds 455s, smaller than the buick. 429/460 bore is 4.360, and can go quite a bit bigger. Aftermarket blocks for chevy,ford, and mopar can easily go 4.5, and quite a bit more. I just dont think bore size is the be-all/end-all of whether an engine works, or doesnt.
I'm not buying that the 383 is to the Big Blocks what the 318 is to the small blocks.
Back in the fifties or sixties you could get a 383 with two four barrels on it. And I have yet to see a roadrunner with a two barrel from the factory. I know you could get a 383 2 Barrel in the charger but I believe you can get a 318 in a charger also. I'm talking early 70s late sixties.
383 is no dog or boat anchor.
I would say the 350 big block or the 361 would be comprable to the 318 in status.
Back in the fifties or sixties you could get a 383 with two four barrels on it. And I have yet to see a roadrunner with a two barrel from the factory. I know you could get a 383 2 Barrel in the charger but I believe you can get a 318 in a charger also. I'm talking early 70s late sixties.
383 is no dog or boat anchor.
I would say the 350 big block or the 361 would be comprable to the 318 in status.
Those 383 dual quad motors you speak of in the early 60s were Stock Eliminator champions.
That's lookin real nice!
Because the performance wedge engines of the mid 60's hadn't been developed yet.
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