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Discussion Starter #1 (Edited)
This is just the opinion of someone that has been around for awhile, listen, or don't it's your choice.

There are 2 big topics that seem to be brought up over and over. "Top Swap" and "Next mod."

Top Swap:
Just some quick advice from someone that has been around for a long time, and seen a lot of builds: If you are wanting to take a NA engine, and do the "top swap" you are better off staying as close to stock as you can. I have heard of too many people do a build with the NA bottom end, and destroy everything. The compression ratio for the NA engine is higher, and the components are weaker. There is a reason GM used 2 different bottom ends for the 2 different engines. The NA engine was not made to be boosted. Keeping that in mind, it can be done, but should not be more than just a swap, and tune. In other words, when you start talking cam/rockers etc, you need to think about that bottom end. In my opinion, it will be way better/reliable/faster to just do an entire l67 swap. That may just be my opinion, but again I have been around the 3800 community since it started, practically. I have seen a lot.
http://www.3800pro.com/forum/superchargers/37981-top-swap-not-top-swap.html

Next mod:
I have read what to do next probably 100 times. It is a very good question. There are a few things you need to figure out yourself before you can ask this question:
How fast do you want to be?
Your budget?
Your skill level?
Streetable or no?
You need to figure all this out before you think about modding.
Warning: Modding is addicting, once you start you will not want to stop. You need to set a limit from the start. Unless you have more money than you know what to do with. In that case give some to me.:icon_lol:
The #1 most important rule to follow: Do it right the first time so you dont have to do it again later.
Something to remember: Cheap/Fast/Reliable---- Pick only 2.
 

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Top Swap

Ok I read your post and agree with you but the question I have is what about swapping the other way? Can I swap the heads from a N/A to the l62 so that I can maintain the intake set up and then run a Turbo or is there a major difference in design?
 

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Ok I read your post and agree with you but the question I have is what about swapping the other way? Can I swap the heads from a N/A to the l62 so that I can maintain the intake set up and then run a Turbo or is there a major difference in design?
if your going to swap on a n/a top end which btw is very do-able basically its a top swap just the other way around but back to what I was going to say the l36 or series III n/a top end is what you'll want as it has a metal upper intake manifold. the plastic series II upper intakes like to go KA-BOOM under boost.
 

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Ok I read your post and agree with you but the question I have is what about swapping the other way? Can I swap the heads from a N/A to the l62 so that I can maintain the intake set up and then run a Turbo or is there a major difference in design?
I like this question, but I do think it's deserving of it's own thread, not the "sticky" (although a reference would be nice to the sticky).
 

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exhaust intake and leave it alone. These cars just don't do ish on the street. No traction. I had all the torque in the world but couldn't put half of it down.

BTW torque and grip is what destroys everything. HP isn't the killer.
 

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exhaust intake and leave it alone. These cars just don't do ish on the street. No traction. I had all the torque in the world but couldn't put half of it down.

BTW torque and grip is what destroys everything. HP isn't the killer.
and to help out Brandon's statement for the people who can't put 2 and 2 together. being that these cars are supercharged they tend to be torque monsters.its fun for showing off tho lol.
 

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I'll be really interested to see how my wifes top swap holds up.
I don't plan many mods really,and keeping boost stock (though the coated rotors/SC should add a little boost).
I think the only non factory parts i'm using are injectors,headers and springs.
Everything else is straight from my own playbook.
I'm counting on coatings to help quite a bit in both power and reliabilty.
If i'm not happy with power levels i've got plenty of easy upgrades on the shelf.
 

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OK so what I'm looking for is a 3800 like I have in my 97 camaro. So with this top swap would I come out cheaper or would it be better to just build one with new pistons? What kind of boost could I run? I want to keep it street-able plus the car I have chosen only weighs 1900 lbs. Also does anyone have a good place to get the parts that is the most for the money? I know this conversation isn't worth its own thread I'm just looking for knowledge.
 

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Depends how much money and/or skill you have really.
He say's to decide that up front,and it's the best advice I could give anyone also.
Decide your budget first or your expectations first,depending on which is more important.

New pistons would run upward of $4-600 pretty sure.
If your budget is 2k for the whole build this might not work,then again if your doing ALOT of the work yourself and choose your parts carefully based on needs then this might just be the biggest investment.

With the top swap you retain the stock N/A L36 (vin K) bottom end while using the SC L67 (vin 1) top end (heads,intake,SC and various bits for belt)
The rod length,compression height,wrist pin size and piston dome are different between it and the boosted bottom end.
The heads/chambers etc.. between the N/A and SC heads are exactly the same except for the SC heads have injector bosses. In the N/A the injectors are placed in the intake manifold.

The N/A has right at 1 full point of compression MORE than the SC engine.
The N/A is 9.4:1 while the SC engine is 8.5:1.
The difference is in the rods and pistons between the two.
The L67 parts are built for the boost and lower compression,so parts are a bit heavier duty.

So basically your just supercharging your N/A motor that wasn't built for boost.
The higher compression makes it more susceptible to detonation,which can destroy an engine in seconds.
Detonation happens,with todays crappy fuels especially.
The N/A motor isn't built to withstand as much as the SC motor is which is more prone to it because of the boost.
So basically your raising compression and adding boost,which makes the SC motor MORE prone to boost with LESS protection to withstand it.

There are ways to combat it. Crappy fuels can be offset a bit by higher octane gas. Keeping boost at reasonable levels as well as knowing the limits of your mechanical components.
You could have pistons coated significantly cheaper than buying (about $25apeice?) in general it will allow you to bump at least 1pt in compression all things staying equal.
If you lower the engine operating temp you could run more timing for more power with less susceptibility for detonation also.

Just remember,the most expensive pistons will still fail if everything else is not as it should be.

My personal preference for parts is from forum members,or junkyard depending what i'm looking for. Alot of factory parts can be had cheap and used for upgrades (LS6 springs/MAF/TB,L32 valves,Cobra injectors).
If your going to have machine work done,factor in the cost.
Best thing you can do for any engine is balancing the rotating assembly and set up all the clearance's correct.
Same with cleaning the head up a bit for better flow,if your equipped you can do it at home.
That stuff costs a good bit to have done,and even the stuff for doing heads yourself can run $100 pretty easy and HOURS of work.
Factor that stuff in.

Step 1
Decide what you want/need from the vehicle
Step 2
Decide how much you can realistically spend
Step 3
Multiply by 2
Step 4
Build plan/list for what you will need to do to attain goal(time goal is nice too)
Assign parts of the given budget to parts.

This will be different depending on what you found in step 1.
Some people have 5 grand and just want a fun reliable car and won't ever see a track.
They might just buy a takeout long block L67 and raise boost,and do some headers.
If you've got 5 grand and looking to race then there's a much different plan of actions.
Also whether it's streetable or not makes a different in parts choices. I have friends that just buy all the "go fast" stuff for their car as well as biggest cam etc..
And it runs like crap on the street,but great for 1/4 mile in a straight line.
4k stalls suck on the street,big cams with low stalls suck on the street.
Decide what you need,and build a plan for it.
THEN ask questions based on how you can get there.
You can pick a horsepower number,and then simply build the engine for it. Engine's are just math,Ideal Gas Law is your friend.
You need X amount of air for X amount of fuel to be capable of X amount of HP.
You build the engine to flow the air,the fuel system to flow the corresponding fuel so you can percieve X amount of hp. with corrections for engine efficiency etc..
From there it's all about keeping it together,remember horsepower is simply a function of torque.
In the end it's all numbers,just have fun :)


Sorry for the long post,woke to baby crying and can't sleep.
 

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OK I get where you are going with that but the conversation I started was doing the top swap in reverse so the info I need is on the strength of the supercharged bottom end what can it handle. As far as my skill level I am very able and will be doing all the work myself I'm just looking for advise on parts, what I can do and what I cant. I fix vehicles for a living now just never really modded one. and don't worry about the long post I am taking in your words. Can you please go into that formula in a little more detail for me I knew there was one out there just couldn't find anyone to explain it to me. Also I would like to know more about the do it yourself head work. Thanks so much for the advise.
 

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The L67 bottom end with NA topend should handle boost just fine.
I've seen where people suggest not using the plastic upper,but to date i've never seen one blown apart from boost either.
The amount of boost it would take to blow one apart more than likely puts it in that category of "why the hell so much boost and stock upper anyway".

As for formula,basically gasoline has X amount of energy/potential.
To realize that energy it needs to be converted from chemical to mechanical energy.
Engines do this in the form of combustion,for combustion you need fuel,oxygen and heat.
The fuel contains the needed energy,air the oxygen and spark/timing handle the heat.
If you want to build for X amount of HP,first find out how many CFM of air is required to support that much HP.
Your TB,intake,heads,cam,valves,etc all need to be capable of this CFM flow.
Of course,the amount these components flow is also relative to the RPM of the engine.
So when calculating your HP needs,you need to know what rpm you want it at.
This is where street/track preference will be important.
If airflow will support it,HP will climb as rpm rises.
Hence the reason for high stalls etc..
They wish to take off higher in the rpm range,to reach a higher hp/torque range quicker. The cam is spec'ed to flow at these higher rpms for that reason.
Because of no velocity under that lift spec,it flows like crap till it reaches the range it's spec'd for.

Hopefully brian or Aj will come in here with some formulas.
I'm on my phone currently,but when I get on a computer i'll post up some of the formulas for various stuff.
I'll see if I can find the build math for the 3.1 Mclaren turbo motor i've built for one of my fiero's.
Built for 350hp and still mostly stock motor(205hp).
If you don't use math while building an engine,your doing it wrong.
Doesn't mean it won't work,just means it won't work to potential and your guessing at what you'll get.
Desktop dyno works because of this math.
A great app if you have an Iphone is Idrag.
It's got fuel and airflow calcs,static/dyn compression calcs,everything you need.
 
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