Small block horsepower question
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Small block horsepower question

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    Senior Member carreradude's Avatar
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    Default Small block horsepower question

    How much horsepower can a 2 bolt small block N/A deal safely withstand? I am gonna be building a motor for the street. It will be a 383 stroker deal. Probly max rpm of 6500 and shooting for 500 horse or so. I haven't started any parts chaseing yet. I was just wondering in case the truck I have has a 2 bolt block in it. Have yet to yank the pan and peek inside. It is a 1974 Chevy stepside 2WD.

    Thanks for any feedback!!

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    Some guy obnoxious001's Avatar
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    Quote Originally Posted by carreradude View Post
    How much horsepower can a 2 bolt small block N/A deal safely withstand? I am gonna be building a motor for the street. It will be a 383 stroker deal. Probly max rpm of 6500 and shooting for 500 horse or so. I haven't started any parts chaseing yet. I was just wondering in case the truck I have has a 2 bolt block in it. Have yet to yank the pan and peek inside. It is a 1974 Chevy stepside 2WD.

    Thanks for any feedback!!
    I think as plentiful and cheap as 4 bolt 350 blocks are, it might make sense to buy one. I am not saying a 2 bolt won't handle the power ( I built a 2 bolt 496 that makes close to 600 HP, but big block main bolts are 1/2" instead of 7/16"), but if you are building something nice, you might just as well find a 4 bolt?

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    gn7
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    Quote Originally Posted by obnoxious001 View Post
    I think as plentiful and cheap as 4 bolt 350 blocks are, it might make sense to buy one. I am not saying a 2 bolt won't handle the power ( I built a 2 bolt 496 that makes close to 600 HP, but big block main bolts are 1/2" instead of 7/16"), but if you are building something nice, you might just as well find a 4 bolt?
    Not only are BBC bolts larger, but the cap is considerably larger as well, and it has the same clamping area as a 4 bolt cap. The SBC cap is whimpy compared to a 400 cap, which like the BBC, has the same clamping area for both 2 and 4 bolt blocks.

    This is a 400 block. Notice the center caps flare out compared to the straight down sides of the front and rear.Look at the surface area at the cap/block interface compared to the front cap! BBCs do the same thing on the 2 bolt, on all 5 caps.


    The strength of the small block is not just HP. RPM and stroke are the main culprits. And a 3.75 stroke spinning 6500 in a 2 bolt is risky business. Forget the HP, its the RPM/stroke.

    By the way, 500HP at 6500 from 383 ci? Good luck!



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    Last edited by gn7; 12-10-2012 at 07:04 PM.

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    Senior Member carreradude's Avatar
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    Thanks for the answers!! I too have a 496 2 bolt in my boat. I totally get the cap size thing. I will be on the hunt for a 4 bolt if there isn't one in the truck now. Won't know until I pull it. GN, Is 500 ponies possible at 6500?? I knocked a front main out of a 383 stroker a long time ago. Over reved it when I lost traction. Didn't have a rev limiter back then. It also was the "short" rod 383 with 350 pistons. Won't run that combo ever again. will be using either the 5.7 or the 6 inch rod. I had a 6inch rod 406 small block that ran like hell to 7000 rpm. Pushed a 3800lb car to 11.33 in the quarter.

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    Quote Originally Posted by carreradude View Post
    Thanks for the answers!! I too have a 496 2 bolt in my boat. I totally get the cap size thing. I will be on the hunt for a 4 bolt if there isn't one in the truck now. Won't know until I pull it. GN, Is 500 ponies possible at 6500?? I knocked a front main out of a 383 stroker a long time ago. Over reved it when I lost traction. Didn't have a rev limiter back then. It also was the "short" rod 383 with 350 pistons. Won't run that combo ever again. will be using either the 5.7 or the 6 inch rod. I had a 6inch rod 406 small block that ran like hell to 7000 rpm. Pushed a 3800lb car to 11.33 in the quarter.
    You didn't stipulate that it needed to be a pump gas engine or compression ratio, so of course it's possible.

    If you plan to do it safely on pump gas, you are looking at just over 1.3 HP/ cubic inch,, not super easy to do.

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    gn7
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    Quote Originally Posted by carreradude View Post
    Thanks for the answers!! I too have a 496 2 bolt in my boat. I totally get the cap size thing. I will be on the hunt for a 4 bolt if there isn't one in the truck now. Won't know until I pull it. GN, Is 500 ponies possible at 6500?? I knocked a front main out of a 383 stroker a long time ago. Over reved it when I lost traction. Didn't have a rev limiter back then. It also was the "short" rod 383 with 350 pistons. Won't run that combo ever again. will be using either the 5.7 or the 6 inch rod. I had a 6inch rod 406 small block that ran like hell to 7000 rpm. Pushed a 3800lb car to 11.33 in the quarter.
    I am not a fan of the 383, never have been. I have no doubt the 406 ran good. I would much rather run a 406 than a 383. The 383 has its place, and they hugely popular as street engines due the low end torque compared to a 350. It was an easy build, like building a 454 or 496 from a 427.

    Can you hit 500 with a 383? No problem. At 6500? That gets a little tougher. You will REALLY need to have you manifold/heads/cam act together. You can throw a much of each at it and get there. But it won't do it at 6500.

    Torque is primarily a pruduct of cubic inches, for the most part. Really its induction. You can hit that number with you eyes closed using a blower. Simply intake AND cylinder pressure. Getting a N/A to inhale enough to make 404lbs at 6500 will be a challenge, and you still need the cylinder pressure. How do you make cylinder pressure in a N/A? COMPRESSION!
    Example. The 6.2 LS3 Vette make 424lbs torque, but at 4600. At its peak HP @ 5900, its only making 383 lb. torque. And that engine no slotch. You will have to make considerably more torque below 6500 to still be making 404 at 6500. If you make 404 as a peak @ 6500, you will have probably built a 8000 rpm engine. You cannot make the torque and HP equal each other above 5252, and you'll never make 500 at that rpm.

    So how much torque do you figure you'll have to produce around 5000 if your still making 404 at 6500? I am guessing, your need to make north of 500lbs around 5000-5500. Your in BBC territory.

    Is the HP goal too lofty, or is your RPM goal to low? Thats for you to decide. Remember, RPM stands for Ruins People's Motors.



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    Senior Member carreradude's Avatar
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    Thanks GN!! As usual, your info is awesome. My plan is either the 383 or now considering a 406. around 10.3 to 10.5 to 1 comp. aluminum heads (200cc intake) full roller deal on pump gas. Is that comp too high for the cali dino piss 91 octane? I am gonna run a tight quench to help with that. haven't nailed down a cam profile as of yet. been thinking around 245 @ 50. Doesn't really need to be 500 horse. Just would like to have it, but don't want to spin the shit out of it to get it. I want it to last for a while. So I took your "RPM" rule and will be happy with what I wind up with. Should still be a stout small block.

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    Or Seth, either one Budweiser's Avatar
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    500hp 383 is completely doable. Pump gas with a 6500 red line... still doable. Waaaay doable.

    Like GN7 said, just comes down to a well matched package.

    If you're not going to take the time and money to have the heads flowed, it's a really good idea to take advantage of a known combination. Let the big guys do the leg work and just put the puzzle together.

    Picking this outta memory, so don't take it as absolute. But, I seem to remember cracking that number with a ZZ4 (350ci) short block, and Edelbrock RPM heads, cam, EFI package. It for sure made one or two ponies over the 500 mark, right at 6500, over at Bob Lambecks place. May have been a 383, 90% sure it was 350 though. This was about ten or so years ago, don't remember if it was observed or corrected.

    Air Flow Research has touted their 383 "package", or recommended parts combination, forever too. However it claims to break the 500 mark at only 5500rpm. Here's those details.

    Engine: Chevy 383ci Hot Rod
    Heads: AFR 195cc Competition Heads
    Compression: 9.4
    Carburetor: BG Silver Claw 750 Carb w/ 75/83 Jets
    Intake manifold: Edelbrock Performer RPM
    Ignition: MSD 85551 Distributor 36° Timing
    Cam: Comp Cams 12-433-8 Hyd Roller Cam
    Exhaust: 1 3/4" Headers

    RPM Torque H.P.

    2500 439 226
    3000 454 262
    3500 487 330
    4000 520 396
    4500 518 444
    5000 503 479
    5500 480 503
    6000 443 506

    If you're going to spend the time and money to build something of this caliber, it only makes sense to do it right. Make sure it's a 4 bolt block or even machine a 2 bolt for splayed 4 bolt caps.

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    gn7
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    Budweiser, you are correct. It is doable. Its is little harder than a 406, and it will take a well thought out program. Its not going to get done with a pick and chose as you go along program. Its not alot unlike the SE deal. You can make some impressive power, WITH THE RIGHT CHOICE OF PARTS, and some will be a little pricey in the eyes of some. 500HP from 383 ci at 6500 is not a budget deal. That combo wouldn't be my choice for a boat, but I have no doubt it will make the power. I think it has a little more in it with a solid roller and a single plane manifold, but the Rs will probably break thru 6500 a little.

    Any combo that will make that power and uses a 3.75 stroke in a SBC needs a 4 bolt. Personally, if I was tracking down a block, I go with a either a converted 2 bolt 400 or even leave it as a 2 bolt 400. The the center caps on a 400 are little tougher than the 350 and have proven themselves fairly well.

    Stay far far away from the 4 bolt 400. Its a pile looking for a place to fail!



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    Quote Originally Posted by gn7 View Post

    Stay far far away from the 4 bolt 400. Its a pile looking for a place to fail!
    On the other hand, we have run one at 13-1 in a dirt modified at 7000 RPM. Always heard they were not as good but on a budget it's what we first built a few years ago,, still have the same block.

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    Quote Originally Posted by obnoxious001 View Post
    On the other hand, we have run one at 13-1 in a dirt modified at 7000 RPM. Always heard they were not as good but on a budget it's what we first built a few years ago,, still have the same block.
    I have heard the same thing, and I have seen the results of a failed block as well. Its where the outer bolts tie into the block. Its never pretty when they fail. For me its not worth the risk, but like you said, guys have run them.
    Some even claim the bolts themselves aren't the problem, but that the 3 freeze plug blocks are weaker regardless if its a 2 or 4 bolt block.
    More "info" about SBC out there then any other engine. All you have to do is shift through it all with a shit strainer



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    Quote Originally Posted by Budweiser View Post
    500hp 383 is completely doable. Pump gas with a 6500 red line... still doable. Waaaay doable.

    Like GN7 said, just comes down to a well matched package.

    If you're not going to take the time and money to have the heads flowed, it's a really good idea to take advantage of a known combination. Let the big guys do the leg work and just put the puzzle together.

    Picking this outta memory, so don't take it as absolute. But, I seem to remember cracking that number with a ZZ4 (350ci) short block, and Edelbrock RPM heads, cam, EFI package. It for sure made one or two ponies over the 500 mark, right at 6500, over at Bob Lambecks place. May have been a 383, 90% sure it was 350 though. This was about ten or so years ago, don't remember if it was observed or corrected.

    Air Flow Research has touted their 383 "package", or recommended parts combination, forever too. However it claims to break the 500 mark at only 5500rpm. Here's those details.

    Engine: Chevy 383ci Hot Rod
    Heads: AFR 195cc Competition Heads
    Compression: 9.4
    Carburetor: BG Silver Claw 750 Carb w/ 75/83 Jets
    Intake manifold: Edelbrock Performer RPM
    Ignition: MSD 85551 Distributor 36° Timing
    Cam: Comp Cams 12-433-8 Hyd Roller Cam
    Exhaust: 1 3/4" Headers

    RPM Torque H.P.

    2500 439 226
    3000 454 262
    3500 487 330
    4000 520 396
    4500 518 444
    5000 503 479
    5500 480 503
    6000 443 506

    If you're going to spend the time and money to build something of this caliber, it only makes sense to do it right. Make sure it's a 4 bolt block or even machine a 2 bolt for splayed 4 bolt caps.


    Wow! That AFR "package" motor is impressive! Only 9.4 to 1 to boot! Thanks for the info buweiser!

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    Senior Member carreradude's Avatar
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    Quote Originally Posted by gn7 View Post
    Budweiser, you are correct. It is doable. Its is little harder than a 406, and it will take a well thought out program. Its not going to get done with a pick and chose as you go along program. Its not alot unlike the SE deal. You can make some impressive power, WITH THE RIGHT CHOICE OF PARTS, and some will be a little pricey in the eyes of some. 500HP from 383 ci at 6500 is not a budget deal. That combo wouldn't be my choice for a boat, but I have no doubt it will make the power. I think it has a little more in it with a solid roller and a single plane manifold, but the Rs will probably break thru 6500 a little.

    Any combo that will make that power and uses a 3.75 stroke in a SBC needs a 4 bolt. Personally, if I was tracking down a block, I go with a either a converted 2 bolt 400 or even leave it as a 2 bolt 400. The the center caps on a 400 are little tougher than the 350 and have proven themselves fairly well.

    Stay far far away from the 4 bolt 400. Its a pile looking for a place to fail!



    Good to know about the 4 bolt 400. My old 406 was a 4 bolt. guess I got lucky with that one I am not a huge fan of the steam holes found on the small block 400's for a street deal tho. This truck will find my boat behind it when I go to the lake. Just wanted a kewl ride for weekend fun and lake trips, and an occasional visit to the Wed nite drags here in Sacramento. It has a running 350 in it now so I got the time to get good parts for it and build it rite!! Thanks GN!!

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    JMLAO But the 400 small block is a 3 freeze plug block and time has proven that a seasoned 350 block 2 or 4 bolt is much stronger! BBC 400 blocks have nothing to do with what you are trying to achieve which is very doable! Do alittle search and you will find with a good combo 355 inch sbc will make alot of low rpm (6500) power and live very well. Just ask a nascar guy back when the limits were 355 ci and they still managed to make over 800 H/P and turn over 8k! Well understood that these were not your'e out of the box 2 bolt blocks and the dry sump helped along with the valve train, A/M crank,rods and the list goes on and on! But if I were going to build long arm small block I would stick with a 6.0 rod 350 block and add crank and bore as you feel fit! Again just my dumb ass opinion! M

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