cprgmr

Finally picked up a '94 LT1 doner motor. Which would you build? :)

Ray383

427. http://www.theengineshop.com/sbkits3.shtml

Ramrod92

Ray, I'm pretty sure his LT1 block willn't handle a 4.125 inch bore or a 4 inch crank. A 3.875 crank with .030 bore (4.030) yields 395.4 (called a 396), a .040 bore will give you 397.4 cubic inchs, .050 - 399.6, and .060 - 401.3. If you could bore an LT1 block to .125 with a 3.875 crank, you would only have 414.3. :cheers:

J Z06

If I could do it over again...for certain I'd have spent the extra 3K and done a 420(500 hp 562 foot pounds). I still wonder why I didn't do it at the time. :confused:

vader86

I'm planning on a 383. Although if i hit the lottery, id put in an aluminum 427 :D .

Trizney

Ramrod92,

I am trying to learn more on engines, specifically on the info you have written here. Where would someone go to learn this, and are there also math calculations/formulas that one needs to know to get this information? Thanks.

antenna

Why go for more than the 383? The few extra cubes gained by going to the limit on bore isn't going to be worth much. You don't need the cubes to make power.
If you go too far you will be risking the whole engine for little gain. If you want to take a risk to gain power, make the compression higher.

LD85

I think TPIS did a 409 LT1 thats what my choice would be.

CorvetteZ51Racer

When you start going to a 0.060" overbore, you're getting VERY thin cylinder walls which, when used in a performance engine, can and will oilcan and shift and move around. Keep in mind that the 350 (Gen 1 and 2) blocks are NOT siamesed cylinder blocks. There is a GOOD reason why folks building large CID small block Gen 1's step up to the 4.125" bore block. It's not because it's easier, but rather because it's a stronger, safer motor because you're not stretching the limits of the cylinder wall thickness and throwing in cranks that require extensive modification to fit in the motor. If you're looking for a reliable stroker motor that will last a while, go with the 383. The extra cubes you'll get from the 396 or 401 are not worth the GREAT reduction in engine durability on the LT1 architecture.

Half Fast

It depends if you need a forged crank or not. If you need the forged crank then the 396 is about the same money as a 383. If you go with a cast crank it's only available for 383 combinations.

Ramrod92

Trey, to figure displacement, just use some of that new math stuff. You calculate the area of the bore which is Pi (that magic number 3.14159) times the radius (half the diameter) squared. You take the results from this calculation and multiply it times the stroke of the crank. This gives you the cubic inchs of one cylinder. Multiply that by how many cylinders you have to get the total displacement for the engine. I believe the numbers for the L98 are 4.000 bore and 3.48 on the crank. Using these numbers (3.14159 x 2x2 x 3.48 x 8) = 349.8 which is rounded off to 350. You can check out the locale library for books on engine rebuilding.
. :cheers:

jburnett

On an LT based motor (GENII SBC) you can't go over 4.060 bore. And even the .060" is risky on most blocks; we like to see at least .275" of material minimum on the thrust side of the cylinder. That said you can always do a short-fill of Hard-Blok; I ran a 396" sbc for two years on the street in the Arkansas heat with it and didn't have any cooling problems (of course I've got a big damn radiator and a killer cooling system). I've built and run everything from 383's to 450" small blocks; for a streetable combination on an LT1 however, it's very hard to beat the 383 or the 396. The biggest problem you start to run into with the 396 and bigger motors (like the 401's and 409 LT's some companies build) is the rod/stroke ratio. When you get under 1.5:1 r/s you start getting into some problems. The engines tend to be more detonation sensitive because there is less dwell at TDC for the combustion process, and you get more thrust side loading which leads to increased cylinder wear. Other issues pertaining to the longer strokes is that when you lengthen the stroke the wrist pin in the piston has to move upwards to compensate for that...3.875" stroke and 6" rods (hell, even a 3.75" with 6" rods) and you're going to be getting the pin bores up into the oil control lands; that leads to increased oil consumption. The 6" rod 383 combination is a good compromise, you'll still get the pin bores up into the oil rings, but it isn't as bad as would be expected with an even longer stroke. Drop it down a touch to a 5.85" rod and you're golden... And you still have a fairly "manageable" r/s ratio of 1.56:1.

I like the 396" combos a lot, they're very nice and produce excellent torque and hp with the right heads and cam. But, for what you're trying to do I would probably just stick with the 383...
-Jeb Burnett
PS- A couple of engine "math" equations: Displacement = bore x bore x stroke x .7854 x #ofcyl.
HP per cylinder head flow = headflow cfm x .257 x #ofcyl. (This is a rough calculation for n/a engines.)


[Modified by jburnett, 5:43 PM 4/8/2003]

loiq

I'd go with the 383. Anything more is just for bragging fuel. Build the 383 right and you'll have plenty of power on tap.

Just my .02. :seeya

1996man

i have been contemplating this as well..... i heard that there arnt as many parts available for the 396 is this troo? i am looking to build forged NA stroker out of a LT block that will at least hang with the 600rwhp supra in our group and hopefully beat him if i squeeze the juice. if that equation is correct then i would already have over 600 fwhp if i had heads that flowed 300cfm and a cam to back it up. if i could get a little bit more out of the heads then somehow plant the power it should be possible but then again im not sure what displacement to use
i had been plannign on 396. i am basically just planning on duplicating HOOVERs engine. i think most of you know that is the lt1 on the boards running 10.64 naturally aspirated.

cprgmr

Great replies guys! Keep 'em coming! :)

pwrful c4

I would go with a 383 anything more would leave the walls to thin. :steering:

marlon88

I wish that someday soon my mini ram that I bought will find it`s place on the 427 kit from the theengineshop.com that is stated above this thread with some killer heads and cam combo and a 150shot of nitrous !!! hope that the engine combo I am dreaming about will be very :cool: what U people think ??

Red Rocket

Happy with my 396 LT-1. MTI is top notch. :yesnod:

oldace84

I'd build a 383.....long lasting and strong........but since I have an '84.....must figure out what to do with the CrossFire....Think I will just rework the system.......Oh yea......
tony
:flag

hookedup

Easy to remember V8 displacement formula:

bore X bore X stroke X 6.2832 = CID

Dave :D