is this a stable modification for a 1987 monte carlo SS?

Question

my friend brought up this idea for me to do to my 1987 monte SS big block 350

boar it over 30, so it will be a 380
add a 4 barrel
add 2 superchargers
and set up a dual carborator system

he suggests that it will make the car more powerful, and add to its top speed and acceleration

i'm wondering if this is true, and what will it do to the gas milage? and if there are any downsides to this?

just to add a few details in response to some of the answers, on the note of the reference to the big block and boaring it out 30 to make it a 380, these are all quotes from the same person who refered me to the other mods, don't know much about cars myself.

if anybody can throw in on some tips of how to give the car the highest top speed and best acceleration it can get, please be my guest, this is going to be my racing car, i drive a corolla to work and stuff.

oh yeah, and that cool lookin thing that sticks up out of the hood, after you get the hood cut to support it, i tought that was a 4 barrel, and if its not, what is it and whats it do?

Answer 1

2 superchargers? Planning on splitting the intake? 350 is too small to handle that kinda air. used two holly 1350 cfm 3 bbl carbs on a chevy 427, and it would stall when I pressed the gas. Dropped back to two 1150 cfm 3 bbl carbs and set up the linkage to be progressive and it worked better. Sounds to me like your friend knows the words, but not what they mean. 2 carbs will work, but two blowers would be a nightmare to synchronise, not to mention install. Besides with all that boost, the lower end would probably be trash in a couple days (less if you race it). Also, the .030" overbore would be so insignificant that the only reason for it would be to clean up a damaged block. Want to Bore it? bore it out into the water jacket and wet sleave it at .125" or more oversize.

Answer 2

My turn, my turn. LOL. Let's first clear up some misconceptions your, "friend", gave you...m'kay? First off, 0.030" overbore is not going to add that much displacement. 30 over will work out to about 355 cubic inches, not 380. Second, the 350 is not a big block, rather it is a small block. Pontiac, Buick, and Oldsmobiles had a big-block 350 in the early seventies. This is the smallest displacement big block that I know of, and they are extremely rare. These were a, "sleeved down", 394 inch GM big-blocks, and shared only the displacement with the small block Chevy. But really, this is the only source of confusion, and it is native to the SBC, because of this weirdo power-plant. The further we get away from its production date, the less people remember that there actually is such a thing as a big-block 350. They are just outrageously rare.

383 cubic inch, small-block, GM v-8's are usually the product of a bore, AND, stroke modification. This displacement is achieved when you put the connecting rods, and crankshaft from a 400 ci SBC into the .060 over SBC 350.

Two superchargers? Boy, you do want some performance enhancement, don't you? LOL

Twin superchargers don't exist my man. At least none that are going to do you any good. Now there are twin-TURBO setups out there, but they are a pretty difficult set up. And the reasons that you use twin turbos are different than why you only use one supercharger. There are rare instances where turbo-lag is countered by the addition of a supercharger, and both are present. But again, very rare. One blower will provide you with an almost infinite amount of added compression. Which is what its job is. In many cases this added pressure is adjustable even. Only need one. I'm pretty sure you are just thinking of a Turbo set-up and don't know it.

Where do you live? I ask because if you live in a large city, you'll likely have to have the car emission tested in order to register it. There was no 350 available for that car, that year. It came standard with either the 231 inch V-6, or a 305 in V-8. So putting a 350 in it is going to mean special registration depending on where you live.

That is a pretty kool body style, fairly light and rigid, and capable of handling quite a bit of power under the hood. With that said, compared to an older Monty, it can't even stand in its shadow. Be very careful getting a whole bunch more power under there. I should mention that any significant output gains with the power-plant must be addressed also with the transmission, and rear end. Much more than 50 b.h.p. over stock out-put and you are going to have to replace the tranny and rear-end on your project with better stuff.

Ever hear the term, "Crate motor"? That's gear-head nomenclature for a new motor. You can buy the whole engine you are describing here, much cheaper than you could assemble it yourself. A high perf crate motor will run you about $2K, and I guarantee you, that you will be very pleased with the 250-300 horse that will make. Put a stage 2 B&M shift kit in that TH tranny, and dig up a 10 or 12 bolt rear end off of a junker somewhere. And smoke the, "Fast and the Furious", crowd like they deserve!

Recipe for a good bracket racing build on that Monty:

New, high-performance 350 SBC= $3000 to your front door.
New electrics=$1000
Built TH350, or R700 transmision=$2500.
Built rear-end=$1000.

New front-end=$1500.
And plan on about $2500 misc. to deal with any of the 4 or 5 million little headaches this set up is going to cause.

That's about 11 or 12 thousand dollars to produce a solid, 300 horsepower car that will take the pressures of racing. I could spend that on just the engine alone, and still get beat.

Conversely. An 11 or 12 thousand dollar restoration would give you a collectors item that will eventually be worth that.

Never try to enhance the performance of an engine with any amount of mileage on it. You'll just finish killing it, and likely won't realize any actual benefit. Performance modifications START being productive when the engine is in top shape.

That thing sticking out of the hood you are talking about, is lovingly called a bug-catcher. This has nothing to do with anything, and will fit carburetors, and certain fuel injectors. Those, "butter-fly", valves are there to prevent atmosphere from gathering near the intake while the engine is idling. You'll notice they are closed in this state, and open when you put your foot in it. At a certain point you dont want atmosphere doing anything unexpected as it can cause a backfire that can destroy an engine that likely costs $150,000. They look kool as heck on a street machine but you will realize no actual effect here.

In short. You might want to cut your teeth on something a little less ambitious. The Monty would make a kool bracket racer, but its true value is as a collector piece. Before deciding to, "install a four-barrel", I'd recommend knowing what, exactly, that is.

Answer 3

1st off the 350 is a small block.. Boring it .030" over will only add 5 cid to the size (355).. It get 383 cid out of it you would need to go to a 3.75" stroke crank shaft and bore it .030" over.. That will then make a 383 stroker.

Forget the dual supercharger BS.. You don't need 2. 1 supercharger can make 600 to 1200 HP on a 350 but you need the best of everything to support that kind of power.

Best bang for the buck would be a mild 355 build up, 10:1 compression, aftermarket alum heads, single 4 bbl carb, performer RPM intake, etc.. You can get 450 HP or more from something like that.

If you want a supercharged engine, theres a couple types.. You have the roots style blowers that sticks up through the hood and carb(s) sits on top of.. For this you will need a forged crank, better rods, forged pistons, compression around 7.8:1 to 8.0:1, great fuel system, 150+ GPH fuel pump, 1/2" fuel lines, etc.

Then you have the Centrifugal type which looks a lot like a turbocharger.. It mounts in front/side of engine kinda like your power sterring pump or alt.. Then a pipe is routed up to the carb, and a sealed box or air hat replaced your carb's air filter.. The pipe hooks to that box/hat.. With this type you can go up with the compression to around 8.0:1 to 8.75:1 but you still need the best of parts like mentioned for the roots blower

Answer 4

If you are going to bore the block .030 over, you might as well get this done while the engine is apart
- ported and polished the heads
- install forged pistons
- change the cam

And you want to go with a dual 4 barrel carb setup with dual superchargers?

I do not believe this can be feasibly done and even if you were able to, it would be outrageously expensive.

I have played with a twin turbo system before but never twin superchargers.

Build the engine to be a low compression nitro beast first, then add a single turbo

Answer 5

boring a 350 .030 over does not make it a 380, you already have a 4 barrel carb, running 2 superchargers is not too realistic, it would cost quite a bit. Try a roots type supercharger under the carb, some of these are carb compliant. Also, too much horsepower will destroy the stock th200 transmission. As far as fuel mileage, a supercharger does not help.

Answer 6

Sounds like your friend has been standing to close to the exhaust again. 30 over will not give you 30 cu/in more displacement, Then a 4 barrel carb, with a dual carb setup? I gotta see that. gas milage wil be nil, and the life of the motor will drop dramatically. Get a crate motor if you want lots of power.

Answer 7

Um, this setup is ok if you want to drag race this car. If you want better horsepower with gas mileage with the money you plan on spending the kind of money on these things I would suggest an aftermarket fuel injection kit from Edelbrock or Holley and perhaps 1 supercharger. Either of these kits are electronically adjustable for horsepower or economy on demand. I think you'd be pleased.

Answer 8

to start i hope the engine mounts will handel the tourqe plus you will need a stronger tranny and a stonger suppsion. plus boring .30 over does not give you a 380 plus with the supper charger you will need a inner cooler for themplus a deeper oil pan for the extra oil for the supper charger to much money and no plus to drive something like that unles you are going to be racing it then still you have alot of working to do for that also .

Answer 9

I hope you have a lot of readily available cash. You're going to need it to accomplish those mods and purchase all the other parts to make those mods drivable, not to mention the money for gas when you get about 3MPG out of the car.

Answer 10

Go to Advance store and get a gas tank twice as big as the one that's in the car right now.