mnstrlt1

Hey everyone... i might have the opportunity to purchase a 383 or 396 ready to go. I will be getting it for literally a fourth of what the original owner spent on assembling it... here is the problem, they are both primarily developed for NA application!

the 383 will make something like 430rwhp, but it's got 11.4:1 compression.

the 396 makes something in the 410-420rwhp with dished 16cc pistons. Another bonus here is that it will be equipped with a FAST ecu. However, the owner is currently debating parting ways with this one.

here is what I was thinking, purchase the engine drop it into my car, play with it until i decide what direction I will be going in later on. This also depends on what the aftermarket will have available for us as there are several LT-x based products being developed.

Do you guys thing it's okay to ram 5-7psi on top of that 11.4:1 combo? any thoughts on projected power potential?

mn_vette

11.4 is too high of a compression ratio to run boost on unless you are running race gas.

What kind of compression is the 396 running?

Have these engines been run before? If not doing a piston swap on the 383 will be very easy. If they have been run then its not as nice but still not too bad since the engine is out of the car already.

You also have to think about the cam inside these engines. If it is a big NA cam then it won't be the best for a supercharged engine. You'll most likely want to swap that out as well.

BrianCunningham

on the piston swap & the cam.

mnstrlt1

i don't want to crack the block because it would defeat the purpose. The cam's are "streetable" hot-cams. Probably not "ideal" for a blower. The pistons at 11.4:1 are obviously too high for "decent" boost, but I can't imagine that even 3-5 psi wouldn't "work". Both engines have been run. the 383 has less than 1,000 miles on it. the 396 I am not terribly concerned with because the seller is not certain on the deal.

To change out the cam and pistons, i would still clean the block, replace the bearings, check the cylinders, and obviously have to re-assemble. At that point, i would just rebuild my existing engine to the preferred specs... know what I mean?

At this point i'm running a stock Lt-1 anyway. Obviously, the cam isn't "ideal" for boost either. Nor is the 10+ compression ratio.

for example, possible justification:
I am just comparing this setup to an S2000... high compression NA, with cam profiles that are not intended for boost either. Although several are currently running with vortech's, comptech's, and turbos on stock engines.

to clarify, I just want to know if it's "do-able", and can be run that way for say... 6 months to 18 months. Until i get the heads I "want", and the pistons/cam that I want.

so would you do it if you had the opportunity, or just pass and stick with the stock Lt-1?

simple green

Just a thought, but some methanol injection might allow you to run a little boost, and will still be a complement when you get the right pistons. I wouldn't go over 5psi though.

mn_vette

If it were me and I wanted an engine that would handle high boost here's what I would do.

Figure the cost of pulling your engine, tearing it down, doing the machine work, cost of new parts.

Now figure the cost of the new engine, new pistons($700), new cam($250), New head gaskets($70), and a timing chain cover gasket ($8). You do not need to change anything else, you should be able to reuse the oil pan and intake manifold gaskets, if not add $40 to that budget.

There is absolutely no reason to change out the bearings at 1000 miles, you can reuse the piston rings even if you want to, but a quick ball honing might be nice.

I understand that it would not be nice to rip down an engine that has been run so little, but its better than blowing up an engine that is practically brand new.

The advantage of having a spare engine is that you can do all the work on the one that you have on the bench while still driving the car around, then when you get bored one weekend swap the engines and be back in business with very little down time for the car.

I guess my point is to figure out which plan will get you to your end goal cheaper. If the guy is really selling this engine for about 1/4 of what he has put into it then I couldn't see how you could do it cheaper with rebuilding your block. If you are serious about upgrading in the future I would get the engine and then take some time and swap out the parts. You should not need any kind of machining, just a nice 3M gasket removal bit.


Oh, and just because something works on one engine does not mean that it will work with another totally different setup. Look at the pontiac solstice GXP, it runs 10.5 or 11:1 compression and is turbocharged to 15psi from the factory. Would I ever try this on my engine....NO!

simple green

well put.

On another note, don't most factory turbo'd engines have oil sprayed under the piston crowns to keep them cool?

BrianCunningham

I know diesel do.

Something to think about doing.

mnstrlt1

mazda and honda has some engines that also have oil squirters...

I guess you're right about swapping the pistons and cam, but the heads are stock with LE3 port work.... "if" i decide to build an engine to my own specs, i would end up using different heads (Trick flow, dart, AFR). that is why I am trying to work with what I've got at this point. YOu know how these things go, "if" i crack the block, i'll end up doing several other mods "since i am already there"... (snowball effect). After all, it's "still" another $1000-1200 to get the proper components on top of the price that I'll end up paying for the engine anyway.

I totally agree that "not all engines are equal", but 3-5psi "should" be do-able.

Baldturbofreak

I was rocking 7-9psi on 11.1-1 with the LT4hotcam.
Spray tons O'meth!

mnstrlt1

aaaaahhhhaaa!!! finally, someone with boost on high compression.

it's got the LE3 head port work and the LE3 complementing cam. Probably similar cam profile.

****edit****

BTF- what kind of power did you make?

neat

What's the dynamic compression ratio?

AKS Racing

For several years I ran 8-9 psi on 11.4:1 with A2A that made just over 570WHP. The key is that the tune has to be spot on.

Bruce

And ask him how long did it last before it went BOOM. He start out as a 190 AFR heads and Hot cam, roller rockers upgrade with 11:1 c/r on the stock 350ci and later he strap on the turbo and the motor got trash and rebuild to 383ci which is what he got now.

mnstrlt1

bruce- i agree, it might not last long depending on how much boost you intend to run. keep in mind, i am only looking to get 3-5psi out of it. This will be with a dyno tune regardless.

AKS Racing ran much more boost then I intend to. Plus the boost delivery is different from a turbo to a centrifugal... it's not going to see 3-5psi until it gets to redline (wont be often). I firmly believe this will last longer than some may think if tuned properly and driven modestly.

mn_vette

if you are only planning on running a few psi and not seeing redline very often then why not just run the engine N/A and build up your other block for boost?

If you are going to run it just make sure that you get that tune perfect. And doing a dyno tune once won't do it. If the weather changes you'll want to recheck the dyno tune.

Definately don't forget the meth injection and check the tank level AT LEAST once every fillup, if not a few times in between if you do hard driving.

AKS Racing

I agree with the above comments that it will not last long. Mine ran several years with the very high compression, along with many trips to the drags. I did not run xxOH, but I did run a very over-sized four (4) core Spearco IC. I also spent a lot of time working on the tune, that part is key.

How much longer it would have lasted in this configuration, who knows?

But... when I built the next combo, I dropped SCR to 9.5:1. That tells you that I clearly believed I was on borrowed time. My current engine in that car runs just shy of 9.4:1 SCR.
Aaron

mnstrlt1

thanks again for the advice everyone!

TheCorvetteKid

Be careful. Boost is like a drug. Once it gets under your skin, you'll want more.

mnstrlt1

lol, i would agree with you, but it's a matter of self control. I think I have expressed this quite well. thanks!