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engine sizes

This is a discussion on engine sizes within the Firebird / WS6 forums, part of the Vehicle Specific category; Ok I have some questions about motor sizes. For instance what's the difference in a 346 and a 347? 408 ...

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    The red dragon bpopham22's Avatar
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    engine sizes

    Ok I have some questions about motor sizes. For instance what's the difference in a 346 and a 347? 408 and a 402,and a 383 stroker,what makes it a stroker? I want to know because I want to start a motor build for a procharged car. I want a motor pushing around 600 to the wheels on 10 lbs of boost. Forged internals are a must, I know,any info is gladly appreciated. I was thinking of a hybrid of Mr. Lous TA and Packys combined. Not a drag car,but a street machine from hell.

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    They are all referred to in cubic inches. A stroker motor is one where the length of the stroke, being piston TDC to BDC, is increased by offset grinding the rod journals on the crank (applicable only in some engines) to achieve a longer stroke, or by utilizing an aftermarket crank with longer throws. Stroker motors are supposed to produce more torque than stock stroke engines, and also have a larger displacement. They effectively compress a larger volume of air -- and fuel -- which ideally means more power.

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    Moderator 35th-ANV-SS's Avatar
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    Just for reference, there are people running meth without forged internals on a 346ci motor putting those numbers to the ground.

    You can easily achieve those goals with just a stock LS1 block and forged pistons/connecting rods.

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    The red dragon bpopham22's Avatar
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    Lol I know its cubic inches guys sorry I should have been more precise. I mean what are the differences in a 402 and a 408.....bore size? What's the difference in a 346 that's forged and a 347 that's forged. Say I want to build a forged motor that was a 450 rwhp beast,and run NA for a year until I could afford the procharger. I know less compression is good for boost,but that's not the case with NA motors. Is there a setup that works well for both? Also yes 35th I've read some of frost's post about 600+HP cars on stock internals as well I was just curious if there was a benefit to a larger motor like a 402 vs a 346.

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    Moderator 35th-ANV-SS's Avatar
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    402 has an aluminum block - LS2

    408 has an iron block so it's stronger. Downfall is it adds more weight.
    Last edited by 35th-ANV-SS; 03-15-2011 at 08:33 PM.

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    The red dragon bpopham22's Avatar
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    Ok and an ls2 is basically an ls6 with a larger bore right? So are the 2 interchangeable? Are the cam specs different? Since it has more displacement it would show larger gains over an ls1 right?

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    The other thing to keep in mind about an actual stroker is the fact that its not as strong. I know this is going to get alot of people ranting about how that its capable of the abuse you plan on throwing at it and blah blah blah. But it just isn't, plain and simple, yes you can throw power adders at a stroker and perhaps be totally fine. But the simple truth is a stoker with a power adder compared to a non-stroked engine has a higher probability of failure. At the very least you're putting that much more strain on already strained components such as rings primarily.

    For your plans you should be able to yield 600rwhp with a 402 or 408 at 10lbs depending on your top end.

    Personally I would take the 402 LS2 since its plenty strong to take 600rwhp and will save you the weight. Plus its a perfectly squared rotating assembly. The 408 will save you some cash and give you some extra insurance but not necessary. Plus it weighs more, also with that much power going into it and heat with boost it won't shed heat aswell as the LS2 would. 383 could potentially net you that power but it would likely take more then 10lbs and a really good top-end.

    Alot of this really depends on what FI unit you're planning on getting and which top end you're putting on top of this thing. Those are going to matter almost as much as your displacement. Obviously if you buy the very best you can get away with less displacement where as if you want to do it on a budget you'll need more engine.

    Hope this helps.

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    The red dragon bpopham22's Avatar
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    Yea I was thinking of a forged 402 shortblock from tx speed and some afr heads. I'm going to start buying the pieces this summer.

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    Quote Originally Posted by bpopham22 View Post
    Ok and an ls2 is basically an ls6 with a larger bore right? So are the 2 interchangeable? Are the cam specs different? Since it has more displacement it would show larger gains over an ls1 right?
    The ls2 is kind of an oddball engine, it uses ls1/ls6 style cathedral heads but it is a gen IV block like an ls3. If your building a stroker from scratch none of the following matters but it if you asking about direct swapping capabilities it does. The ls2 has the cam sensor in a different location than a ls1/6 and therefore uses a different style camshaft so those will not interchange also the ls2 uses a different reluctor wheel on the crank after 06 so you would need to buy a reluctor converter box to make it work with an fbody pcm. The ls2 and ls6 are very similiar engines though power wise because the ls6 has a larger cam than an ls2. The ls2 makes a little more power under the curve but its not something anyone would notice driving one or the other ideally if you put the same size cam in both motors the ls2 would make more power simply because of the displacement. As other people stated I would do an ls2 aluminum block its lighter and will handle 10lbs of boost just fine if you plan on going with crazy boost later on I would suggest the iron block.

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    I know the iron block is stouter, but just for reference, there are people running well into the 8's with a 300 shot on a LS2 with no issues.

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    The red dragon bpopham22's Avatar
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    Ok well what about this forged 347 I've been seeing online? What's the difference between that and regular ls1? Is it a smaller form of a stroker?

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    Quote Originally Posted by bpopham22 View Post
    Ok well what about this forged 347 I've been seeing online? What's the difference between that and regular ls1? Is it a smaller form of a stroker?
    nope same block with forged internals

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    Not being mean or anything, but if you're asking these kinds of questions, I would suggest letting an engine builder assemble your motor and install it.

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    Quote Originally Posted by bpopham22 View Post
    Ok well what about this forged 347 I've been seeing online? What's the difference between that and regular ls1? Is it a smaller form of a stroker?

    A 347ci is a stock LS1/6 block with a hone job to clean it up and some forged pistons with file to fit rings. That is all. It uses the same size crank but gains an inch of displacement from the hone job.
    Last edited by Packy; 03-17-2011 at 04:24 PM.

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    Quote Originally Posted by bpopham22 View Post
    Yea I was thinking of a forged 402 shortblock from tx speed and some afr heads. I'm going to start buying the pieces this summer.
    Just make sure you go with a D1SC, 8 rib set-up, and an Aster bracket for it. You will need it to keep that 402 fed with air.

    You can also look into a 370 or 390ci. Both are great for boost!
    Last edited by Packy; 03-17-2011 at 12:11 PM.

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    The red dragon bpopham22's Avatar
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    Oh no I don't plan on doing it myself,I might try and bolt the heads up. When I say engine build its more like buy the parts and pay someone to do the hard shit...assembly/install. And Ty packy for clearing that up about the 347.

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    I'm looking at dropping an LS3-based 416 ( 4.07" bore x 4.00" stroke) motor into my 2000 Formula hardtop ... Kooks SS long-tubes ... Mufflex 98402C-DT exhaust with cats ... 4L80E w/ Yank 3400 converter ... Strange S60 with either 3.54 or 3.74 and TrueTrac.

    The camshaft will be an "offshoot" of the Lingenfelter GT-11 cam, with the specs "bumped up" to be appropriate for a 416 cid motor, since the GT-11 is basically designed for smaller displacements.

    I am shooting for a "sleeper" approach with a smooth idle and a broad, flat torque curve.

    A very "nasty surprise" . . . LOL !

    Dave

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    ^^ That works!

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    Senior Member redbird555's Avatar
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    Quote Originally Posted by ez2cdave View Post
    I'm looking at dropping an LS3-based 416 ( 4.07" bore x 4.00" stroke) motor into my 2000 Formula hardtop ... Kooks SS long-tubes ... Mufflex 98402C-DT exhaust with cats ... 4L80E w/ Yank 3400 converter ... Strange S60 with either 3.54 or 3.74 and TrueTrac.

    The camshaft will be an "offshoot" of the Lingenfelter GT-11 cam, with the specs "bumped up" to be appropriate for a 416 cid motor, since the GT-11 is basically designed for smaller displacements.

    I am shooting for a "sleeper" approach with a smooth idle and a broad, flat torque curve.

    A very "nasty surprise" . . . LOL !

    Dave
    Sounds like a nasty combo man only thing I would suggest is give Geoff at EPS or Patrick G on tech a call and tell them exactly what your buildign and want and they will spec you a cam. They have been dong it many years and with great results. Only reason I'm saying to do that is I assume you will be using square port heads on the ls3 and the gt-11 cam was mainly made for cathedral port heads. It is a well known fact today that the two types of heads prefer different specs to make power the cathedral port heads seem to do well with moderate lift and a tight split on duration while the l92 type heads seem to like more of a wide split and a little higher lift. Either way that engine will be a beast but having someone like geoff or pat spec you a cam is 20 bucks well spent given their reputation.

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    Quote Originally Posted by redbird555 View Post
    Sounds like a nasty combo man only thing I would suggest is give Geoff at EPS or Patrick G on tech a call and tell them exactly what your buildign and want and they will spec you a cam. They have been dong it many years and with great results. Only reason I'm saying to do that is I assume you will be using square port heads on the ls3 and the gt-11 cam was mainly made for cathedral port heads. It is a well known fact today that the two types of heads prefer different specs to make power the cathedral port heads seem to do well with moderate lift and a tight split on duration while the l92 type heads seem to like more of a wide split and a little higher lift. Either way that engine will be a beast but having someone like geoff or pat spec you a cam is 20 bucks well spent given their reputation.
    Thank you, Sir !

    I will definitely contact Patrick Guerra for getting my cam spec'd . . . Heads will be CNC'd LS3 / L92.

    For comparison, the specs on the LINGENFELTER GT-11 are:

    CAM SPECS:
    Intake Exhaust
    Valve adjustment: HYD HYD
    Lobe lift (inches): 0.370 0.378
    Valve lift (inches): 0.629 0.643 with 1.7 rocker ratio
    Valve lift (inches): 0.666 0.680 with 1.8 rocker ratio
    Duration @ 0.006": 265 281
    Duration @ 0.050": 215 231
    Lobe Separation Angle (LSA): 118.0
    Degrees of advance: 0.0
    Valve timing @ 0.050" tappet lift: Opening Closing
    Intake: -10.5 BTDC 45.5 ABDC
    Overlap angle: -13.0
    Exhaust: 53.5 BBDC -2.5 ATDC
    Specs are with cam installed at: 118.0 ICL 118.0 ECL
    Recommended installation angle: 118 (intake center line angle)

    Thanks,
    Dave

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