I currently have a stock 92 lt1 vette. I just pulled the engine due to a failed head and main gasket. Easier to replace everything anyway. I am wanting to build a stroker motor and I am debating the 396 vs 383. What are the streetabilty and reliability differences between the sizes? What is the range of rearwheel horsepower I can expect (Hard to estimate I know)? With the 396 will I be constantly tearing the engine down due to failing parts? I am planing on using forged internals (SRP Pistons and Eagle crank and rods). Addtitionally I am having CNC Cylinder heads do their magic on the heads. Thanks in advance for the replys. :auto:

 

Either displacement engine can be realiable but it depends on the parts selected. If you are thinking about going with something other than a OEM oil pump go with a high pressure rather than high volume. A high volume pump can pump even a large capacity pan dry with extended high revs (track, driving event, etc.)

Depending on cam / head / value choice choice, you can see about 400rwhp/400rwtq out of the 396 with 10.5:1 compression (92 octane gas). It also passes emissions if that is a concern.

 

I am in the same boat. Just pulled my motor last night and disassembled it. Looking into the 396 and 383.

 

The difference is cost. 396 requires more machining and you'll only have forged cranks to choose from. If price were no object I'd go with a 396. You will need good heads, larger injectors, less restrictive exhaust etc. to support that much increase in displacement. The wilder you go the more you'll need to upgrade the driveline, cooling system, fuel system etc. Set a budget and plan accordingly. You will also always have unexpected costs. You might want to look into purchasing a complete short block from a builder that specializes in LT1/4's. Some machine shops don't take the attention to detail that these motors need. Good luck! :chevy

 

Are you considering any power adders? Supercharger, or nitrous?

Jim

 

I am not considering any power adders for the motor. I currently have EM Headers and corsa exhaust to bolt on, so I think I am good on the exhaust side. The cam I am looking at is a 222/230. Will I need to change out the oil pan to clear the stoker crank? Thanks for the advice in reagards to the oil pump. Please keep the suggestions coming. :auto:

 

396. :chevy

 

Like the others have said it's going to boil down to cost. You can get a 383 crank that is cast, which is much cheaper. It's also a lot weaker, I wouldn't trust it in a forced induction or heavy nitrous application. The 396 is only available in forged which is a lot more expensive.

The thing is the price difference between a forged 383 crank and a forged 396 crank is very small. If you've got the budget to go forged, might as well go with the 396.

 

If you are going to use the Eagle H beam rods. You will need a new oil pan for rod clearance. I am using Morroso oil pan for my blown 383LT1 I don't know the part # because my motor was built by a tuner, during assembling process they found that the stock oil pan are not clear the rod.

Bruce

 

What nobody has asked yet (and is the first question the Late Mr. Lingenfelter would ask) is:

What do you expect to do with it?
1. race? What speeds? (Solo2, < 100mph, > 100mph, drag?) (If so, plan on more radiator, more brakes, etc.)
2. Pass Emissions? (If so, know your cam timing)
3. Live a good long while? (If so, overdesign now)
4. Cost a certain amount of money?
5. Is this a stepping stone to more power later? (If so, overdesign now)

You want to maximise the power output for the area the motor will spend the most time...A 396 with 4.10 gears (according to your sig) may very well be traction limited through the first three gears. Cool, but not fast unless you also budget drag slicks.

Here's what _I_ decided when I started my project:

1. Being a convertible will limit my car's ultimate usability on a track - it won't be competitive, and it's aerodynamically unfun above 140.
2. it will spend 99.99% of its time on the street.
3. I wanted to look over at the contender, see that they've got street tires, and know that they may have more power, but I can lay it down better.
4. Being a convertible, if it turns faster than 14s, I can't drag race it without it getting booted off the track. (It turns mid 13's in it's not yet done state of tune in Denver...it's a mid 12's car at sealevel)
5. I had to budget exhaust and a WHOLE NEW INTAKE to make the levels I wanted. (What's a LT-1 intake capabile of supporting?)
6. You cannot tweak one or two parts and expect the best gains. You built a stout motor, and you'll have to address cooling, fuel delivery, programming, etc. (You're one step ahead with the 6-speed, I'm still putting power through a weaker rear-end) And it'll allll have to be budgeted for.
7. Take your budget...now double it....now plan on conveniently 'loseing' all of your NAPA recipts.
8. Don't go cheap, it'll biteya in the azz later.

 

RocketSled thanks for the advice. To answer your questions:

I would like to have a car that is streetable, but still take it to the track.
I am not worried about it passing emissions :D

I agree with your comments about strong parts. The parts I purchase will be all forged. As of now, I think I am looking at 10 grand to make this thing happen.

What are the rearwheel horsepower differences between the two setups. Is there more of a chance of cracking the block with the 396? With a 383 will the cooling and fuel systems need to be upgraded?

 

How bout maintenance? There's an upper limit to power output with a roller valvetrain (ooh, THAT'S another question or two: Hydraulic or solid lifters?)

Then I'd suggest figuring out what $5000-$6000 can buy you. :p:

It's not that simple. (and I don't recall if the LT1 block is a four bolt block or not, if it is - great, if it isn't - better! Have a 4 splayed bolt kit machined to it) While more displacement, all things being equal means more torque, it also generally means more reciprocating mass. I've got a 383 that's all done at 5500 rpm with the Superram intake...it's also potentially good for 500 ft/lbs of torque (excellent for a street motor) The same motor with a miniram would make a little less torque down low, but could revv to 6500 rpm with the right parts.

Here's the hard part. My motor was dynoed last week with 290 rwhp and 378 rwtq. This is a car that is FASTER than a Z06, as fast as a Turnbo 911, and still has some power to be built. But it shows nowhere NEAR the 'hp' numbers the other two cars make. It beats them because it can develop more average power for a longer period of time.

Now, here's the meat of the problem: the car's got Forged pistons and a cast crank. It'll easily take a 250hp shot of NOS. At which point it really doesn't matter the difference in displacement. (as the Dana36 would be reduced to rubble)

All things considered tho, the number 396 just flat SOUNDS cooler. :reddevil

Fuel: To do it right, a 383 needs 30 lb/hr injectors and a healthy fuel pump, a 396 will need more.

What really chapps MY hide is. When I started this project, 383's were big....when I fired the motor up, 396/407 blocks were getting popular. Now, LS1 based blocks are making SICK NA power.

 

How do you get 396 cid out of these? Do the LT blocks have more meat than L98 blocks?

 

Paul, a stock LT1 has a bore of 4.000. Both the 383 and 396 have it bored out too 4.030. The stock crank has a stroke of 3.480. The 383 uses a crank with a 3.750 stock. The 396 uses a 3.875 stroke. To figure out the displacement of an engine you take 1/2 the bore times itself, then times PI, then times the stroke, then times the number of cylinders. The stock motor is actually 349.846, the 383 is 382.666, and the 396 is 395.421. If you were to bore it to 4.030 and use the stock crank, you'll end up with a 355 (355.114) :steering:

 

3.875" stroke crank, 4.030 bore, 5.85 rods are preferred for a thicker piston crown and ring lands.

 

i went with 383 (actually 388 with .060 overbore) because i didnt want too much of a stroke. The motor sees high rpms so we dicided not to push it too far . For most apps id say go with a 396. the more the better. :cheers:

 

As mentioned you will want to splay the mains. The 396 isn't any more likely to crack a block than a 383. You will need to upgrade the oil pan but forget about the cooling. You will probably replace the thermostats with a 160 / 180 and turn the fans on sooner when you do the chip.

You will want to radius the valves and have at least a 3 angle valve job done. 30 lb injectors work fine w a 52mm TB. $10K with everything forged is going to be real tight if someone else is doing the work. Plan it out ahead (looks like your are) and look for areas that you can scrimp on without scarifcing realiability. (Don't waste your money on a 58mm TB, you've already got the headers, etc.) Count on a good chunk of change to get it tuned properly (dyno time)

 

well it sounds like you are wanting to do this thing right if you are planning on spendingthat much money... like said earlier, if that is ur budget look at about 5-6k on parts.... that will build you a HELL of a NA motor. i would definatly go witht he 396. after all same bore just different crank then you are garunteed forged crank. i would obviously go with forged internals everywhere possible. may cost a little more but the stronger it is the more durable and dependable it is. the only problem with running that kind of power is that even if you build a strong enough motor to handle it.... other parts wont handle it always. like mentioned before if you have the ZF you have the good rear end but be prepared to upgrade the u joints pretty quick(not a huge problem or $ amount) also think about traction. the more traction you have like at the track (ie slicks) may mean better time but is also going to make it easier to break things (mostly in the drive train). i plan on making my LT4 into a 396 eventually and my budget will be about the same as yours so i definatly think you can build a motor perfect for you with that amount. good luck and keep us updated! im a sucker for 396s!

 

Your stock block is already 4 bolt. I don't know if you can convert a 4 bolt over to a 4 bolt splayed. I'm thinking you actually have to start with a 2 bolt in order to do that. Fortunately though the stock 4 bolt is very strong as it is, so long as you're not planning on shooting a huge power-adder to it you may be fine there.

For RPM remember some other important things. Although a stroker does have a longer stroke, that doesn't mean that it can't spin faster than your 350. It's very possible that you new parts with be stronger AND lighter than your factory pieces. It's also likely that it'll be balanced more precisely than your stocker.

The real limiting factor on RPM is going to be your camshaft choice and your valvetrain. With a lightweight valvetrain and heavy duty enough springs there is no reason why you can't spin 7000 RPM's easily, and you can do that with a hydraulic roller cam. If you wanted to go with a solid roller you could gain even a few more RPM's but you'll have to keep it adjusted more frequently, which can drive some people away.

Of course you also need to remember that just because you CAN spin your motor that fast doesn't mean that you need to. If you're done making power at 6500 then don't bother spinning it any faster. It's just good to have the peace of mind that it can wind up higher if you miss a shift or something. Overkill is a good thing.




[Modified by Nathan Plemons, 3:56 PM 3/28/2004]

 

Thanks for all the advice. I have chosen to go with the 396. I am going to call the guys at More Performance tomorrow to see if they can do the block work. Currently, I am going through the suspension replacing the rubber bushings with poly and cleaning the entire suspension. It looks like this will take a while, but I guess that is what a hobby is for. Once again thanks for the help.