IroczFan

Okay i have a 350 from a 1970 impala my original plan was to tear the motor down which is happening this week and possible take it to the machine shop as well this week, i want to turn it into a 383 with the kit from eagle i know i have to bore it .30 over and hone it what else would i need to have them do? the plan is to use the stock head for now but get them redone until i can afford some Dart or AFR heads and then go with a mild cam. or should i just go with the 355 and get it bored and honed, but i still wanna go with new pistons connecting rods ect.. so would it just make more sense to go the 383 route insted? let me know what you guys think the motor should be tore down by tuesday night also the goal is with stock heads around 350hp+

vetteoz

iTrader: (13)

Cubes= Hp
Can you afford $170 for a new crankshaft?
That is the main cost difference between a 350 and a 383 IF doing a full rebuild
(Allow a little extra shop labor for clearancing the bottom of the bores for stroker crank )

No you don't .
The extra cubes comes from the increased stroke of the stroker crank.
Bore can be stock size , 30 /40 or 60 over
(new 383 pistons required of course )

As soon as you bore out a engine you need new pistons regardless

84transamdude

They sell specail rods for a stroker don't they believe i bought them for my 383. think they are scat forged rods.

vetteoz

iTrader: (13)

NO
.Common to go to forged rods when making more power in any engine
They sell upgraded HD rods of different lengths you can use for any SBC; not just a 383 build

Different rods are not a requirement of building a 383; only special 383 pistons needed

84transamdude

I meant so he doesnt have to spend extra money for them to grind the block to clear the rods

IroczFan

money isnt really a huge issue when it comes to the crank im just not gonna go all out on the heads right away to cut costs, i wanna do the bottem end right now so i wont have to pull the motor in a few years. sorry i about some of my mistakes im 18 and this is my first engine build and i just wanna learn as much as i can before i start putting money into it

IroczFan

i wanna get the 383 kit from egale for $740 im not sure if the special rods for clerance come in it other wise ill have to have the machince shop make some room

vetteoz

iTrader: (13)

Educate yourself
http://www.chevymania.com/tech/383.htm

http://www.chevytalk.org/fusionbb/sh...hp?tid/131229/

1983Chimaera

You need to look at more than just the machine work and parts costs for the engine. Ask yourself some basic questions; What is the car going to be used for? Street? Strip? Both? What induction system are you going to run? Is it large enough to feed a 383? Have you upgraded your exhaust to allow a 383 to breathe? Are you going to add subframe connectors to counteract the increased torque the 383 will impart to the unibody? Is your driveshaft in good condition, are the U-joints in good shape or will they fail with the extra torque?
A lot of people completely miss these thoughts when they plan a build, set themselves up for headaches and end up spending far more than they would have had it been properly planned out from the start. Do your research first, GM High Performance, Super Chevy, Car Craft, and Hot Rod have all done numerous 383 builds, and reviewed most of the kits out there and the budget (junkyard) options available. The articles are free online, and pretty detailed as far as the overall project and build. I suggest looking at their findings, where they had issues, their solutions, as well as their costs before deciding on which direction you want to go in. They also frequently have dyno results for their builds so you can get an idea of what kind of performance you can expect. Whichever route you choose, I wish you luck!

vetteoz

iTrader: (13)

As already noted ;
just aftermarket rods with cap crews for ANY engine; not just strokers

A stock style rod with the thru bolt has a less cam lobe clearance than the aftermarket rods with cap screws and the cap screw rod clears the oil pan rail area better also
but in most cases still some grinding of the block for clearance is required

IroczFan

You bring up some good points, the car will mostly be street but alittle track time as well the intake will be carb i already have a 650 Holly for it i still need a intake manifold for it. Exhaust isnt really upgraded was playing on having a true dual set up on it after the motor goes in i already have headers for it. I am guessing i will need u joints but i will figure that out today.

morgsie

iTrader: (1)

Uh, this is wrong. You need a bore of 4.030" and stroke of 3.75" to get a "383". Do the math... A stock 350 bore (4.000") with a 383 crank (3.75" stroke) should work out to 377 CID. To get a "383" you need to bore 0.030" over. Full stop.

IroczFan

thats what i thought that it needs to be bored over, even in the kit it says there .30 over pistons

dfarr67

iTrader: (2)

I considered this myself,a few comments:
- If the 383 is so good why didn`t GM offer it until recently as a crate, the 350 was very long lived.
- For myself this is more cubes to feed.
- Talked to a popular engine builder-racer and what they found for the extra expense, difference they expected at the end of the track was dissappointing.

vetteoz

iTrader: (13)

A stroker is a stroker
Guys don't set out to build a 383 ; it is just the most common end result because they have to bore their old blocks a min of 30 over (4.030 ) to clean them up.
If the block had mint bores they could use a 4.00" 383 pistons to get 377 and keep the thicker cylinder wall ( preferred )
If they went to 60 over they would have a 388
Big deal
As I noted above the major increase in capacity comes from the increased stroke ,in the case of a 383; 27ci vs only 6ci from the 30 over bore increase

1983Chimaera

I might also suggest finding a different starting point than the 1970 Impala block, unless it is a high performance casting. Many of the 350's from that era are full-on "smog" motors, making a meager 150 hp or so and less than desirable for a performance starting point. The heads frequently had 76cc combustion chambers, and had dismal airflow characteristics. I've seen a few of these motors first hand, and they are boat anchors at best. Also might want to check if your heads are the older style of exhaust bolt pattern, which won't work with more modern manifolds or headers. I don't usually suggest someone spend money on a different block when they already have one in hand, but if you do have a smog block, it would still make more economic sense in the long run to invest in a better one than to try to wring performance out of it (assuming you have access to a you-pull-it junkyard nearby). I would use an '87 up roller block with 4-bolt mains, a one piece rear main seal, and allow use of roller camshafts for more longevity from reduced valvetrain friction. There are also adapters for using the older style 2-piece rear main seal crankshafts in the one piece blocks, I have one on my roller 327. If buying a longblock, I suggest either swirl port truck heads or vortechs if junkyard sourced, or RHS Vortechs if buying new aftermarket. The RHS vortech heads are an improved casting with thicker decks for crack prevention, 170cc intake runners, have both the vortech and traditional intake bolt holes, and are already machined for increased valve lift and larger springs, saving much on machine work. Or you could go with Scoggin-Dickey vortechs, which as well as having the same features as the RHS versions, are available also in 190cc and 220cc intake runner versions and with or without 2.02 and 1.6 valves. Look up Kendrick Performance for Chevy small block and cylinder head casting numbers, they are pretty much the same as the old Mortech lists (which I still have printouts of!). Again, do your homework, and plan your build before you start spending or tearing into anything.

T/Aperformance

GM didn't offer the 383 because it wasn't in there line up for production cars.
It was the hot rodders that came up with the 383. Someone had a 400 crank that more than likely spun a bearing and they turned it down to fit the mains of a 350. And becouse the 350 four bolt main was stonger than the 400's it became a good fit. And it made great power. I've built a few and love the performance.
This person on the right track.
Build a good foundation for your engine. Upgrade the uper end as you can afford. As a matter of fact. a good 383. with 10 to1 compresion and a set of mild ported vortect head with a decent cam will gain you around 450 hp.

Orr89RocZ

iTrader: (20)

383 flat top piston kit plus stock iron heads = race gas only motor assuming 64cc chambers

If you build now with dished pistons + stock iron head, you have a very handicapped motor that cant breathe right but once upgraded to aftermarket aluminums, now you have too little compression.

SO you need to decide how you want to do this.... If 350hp is all you need at the motor, a rebuild mild cammed 355 will do that. If 350 hp at the tires is what you want, a 355 can also do that but its easier to do it with a 383 and get more torque while your at it.

five7kid

iTrader: (14)

Pretty much irrelevant, since it's the pistons and heads that determine compression, and add in the cam and exhaust to determine power. The block itself has NOTHING to do with any of that.

1970 was the last "pre-smog" year, for what that's worth. The 2bbl versions had low power, but the typical 4bbl version had 300 HP.

Still, the 1970 heads will be what limits you more than anything, as a good set of heads will make more power on a 350 than a 383 will make with stock heads, all other things being equal.

Oh, 1970 heads didn't have hardened exhaust valves or seats for unleaded gas. Something to consider before putting any money into them. By the time you got them up to snuff, you could have gotten a good set of Vortec heads (that will make more power on a 350 than the 1970 factory heads will make on a 383, all other things being equal...).

1983Chimaera

Actually the older blocks still had undesirable features themselves, such as the location of the dipstick tube on some of them. It was placed on the driver side of the block, and is impossible to fit with later manifolds or headers. As for dates, Mortech lists 70-76 for the smog era blocks, the important thing to check is the date code on the block itself, as well as the tag info on the front passenger side corner of the block, just below the head. This will tell you manufacture date, location, intended application, etc.
From a build standpoint it is likely more economical to start fresh with a later model 4-bolt roller block than to throw money into a smog block, especially if it can be sourced with better heads in the junkyard. Take casting number lists and mix n match the block and heads and purchase as a longblock assembly. Or, purchase as a complete engine and add an intake (performance 4BBL ones are occasionally in the yards), valve covers, harness, starter, distributor, accessories, carb, and brackets. This would be an excellent way to source a lot of the basic parts needed as opposed to buying them individually, and also a chance to upgrade to a later style serpentine belt arrangement. The TPI serpentine setup is virtually identical to that used on the 4.3L setup, and is readily available in most junkyards. Pick and choose from the yard and piece together the parts that you want. The "complete engine" doesn't necessary have to be pulled intact from one vehicle. Mix n match! As for the block, yes, with the 383 only the block itself will be retained, but the '87 up still offers advantages over the older casting. If going the 355 route, all that will be needed is pistons. Either way a roller valvetrain and 1 piece rear main seal is gained.

five7kid

iTrader: (14)

Mortec is helpful, but hardly the final word.

The 1970 passenger car 4bbl 350's had 10.25:1 CR, which is hardly "smog era". Of course, the following year, when CR did start to drop, they used many blocks cast in 1970.

It could be argued that going to the JY and getting a '96-'99 light truck 350 would be a better starting point for a build. But, the "given" was the 1970 350 block. It could also be argued that the JY Vortec 350 longblock would require as much work (read:$'s) to get ready as the 1970 350 with Vortec heads would, although with the L31 longblock you would have the advantage of roller lifters and one-piece RMS (as well as generally better casting quality and machining than they did in the 70's).

IroczFan

id love to get a 96-99 truck 350 but i dont have huge funds for this motor build, i really wanna get this done and pull my oil leaker 305 out

Orr89RocZ

iTrader: (20)

In any event, 355 or 383, just dont use the stock heads. Vortecs are best bet for cheap option that do make decent power but with a 383 you still need to watch compression. Need a dish piston with that stroke and iron heads for sure.

1983Chimaera

Let's back up then. Post EVERY identifying mark or code you can find on your 1970 block and heads. The block casting number, the date code, the codes on the front passenger side below the head, and the cylinder head casting numbers. This way we can determine exactly which engine you have, and whether the heads are worth putting money into or better off sold for scrap.
For the record, I never said to use a Vortec block, only Vortec heads. Any '87 up one piece seal roller block will work, a 4-bolt truck block being ideal. My roller one piece seal 4-bolt came out of a '91 Suburban.

IroczFan

well guys i got some bad news its a 2 Bolt!!

NagleMac

iTrader: (1)

Nothing wrong with a 2 bolt, it should be fine for your build, I picked up a 350 for a 95 truck that's at the machine shop right now, it's not a roller but has the provisions for the setup, just needs to be drilled and tapped, it's also a 2 bolt even tho I was told it was four but it should be ok at a maximum of 425hp and 460tq if I can make it too that

evilemokid94

iTrader: (6)

where are you guys getting your kits at? i just picked up a 96 350 vortec, or L31 and im wanting to make it a 383 so i need to figure out where i can get the crank and rod kit.

NagleMac

iTrader: (1)

Jegs/summit will work, if you're getting a pre-balanced one, scat is much better than eagle

evilemokid94

iTrader: (6)

i looked them up on summit but didnt get any results?

NagleMac

iTrader: (1)

Go to google and type in "scat 383 rotating assemblies"

IroczFan

i will try to get all the numbers i can off the block this week

InfernalVortex

iTrader: (4)

Does anyone have any actual PROOF that aluminum heads need or can handle more compression than iron heads? I've seen experiments that seem to indicate there's no difference. That the only advantage to aluminum is weight and how easy it is to machine and port.

vetteoz

iTrader: (13)

http://www.carcraft.com/techarticles...t/viewall.html
http://www.chevyhiperformance.com/te...ads/index.html


"It's important to note that cast iron heads can actually deliver more power than comparable aluminum heads because cast iron can retain heat as opposed to aluminum, which dissipates the heat. The more heat in a combustion chamber means a higher potential for power.

However, The lighter weight of aluminum pays big dividends in performance, so the bottom line that cars equipped with aluminum heads can accelerate comparably, even with less HP ".

InfernalVortex

iTrader: (4)

Unsubstantiated voodoo claims about how different materials retain heat, with vague assumptions about whether or not that's a good thing. Just speculation. Definitely established and commonly held to be true, but that doesn't hold much water with me. I've been in this hobby long enough to learn that there's WAY too much unsubstantiated nonsense blowing around. I take everything people hold to be "established truth" with a grain of salt.

Not aimed at you or in response to you, vetteoz, but Im about to go on a tirade against superstitions.


http://www.carcraft.com/techarticles...t/viewall.html

The implication to me is that the long-held belief that aluminum heads need or can handle more compression than iron heads just isn't true. Now that confuses the hell out of me, because that's just one of those things you learn and take it for granted. How can 10.0:1 be risky on iron heads, and yet 10.5:1 is fine for teh same engine with aluminum heads if the above article is true?

I'm starting to think it's mostly because aluminum heads have better chambers/design than the iron heads people often compare them to. People often switch from factory iron heads to aluminums. And then people switch to aluminums and lose weight off the car which also helps it go faster. And then people who are going from factory engines or even built up factory engines with spruced up factory heads, they switch to aluminum heads and a bigger cam, and the lower DCR from the bigger cam counteracts the increased SCR. I think it's a combination of all those things that lead to this being accepted gospel, and I'm not sure I would just assume I can push the limits with compression ratio with aluminums any more than I can iron.

The whole point of my tirade, is you can get dished pistons for a 383, and run 083's or vortec heads, and then save up money and install some 64cc aluminum heads and not worry about the compression ratio needs changing. If you set it up to have a decent compression ratio from the start, just get aluminum heads with 64cc chambers and go about your life. I dont think you're leaving anything on the table leaving an aluminum headed 383 at 9.5:1 to 10.0:1 compression. But even if that really does bother you, you can always have the head shaved down.

I'd love to see more real dyno evidence of either the parity or the differences between the characteristics of aluminum and iron, but every time I look at the numbers and/or the back to back comparisons, either the conditions/control aren't conclusive, or if they are, they seem to indicate there's no real difference. And the only "evidence" that aluminum as a material responds differently in the context of an engine cylinder head, is the editorialized comments in these articles...

I am not convinced having hotter metal in the combustion chamber helps any thing. People are always running their engines cooler and cooler for more power, and that DOES work with carbed cars. I am also not convinced aluminum or iron will lead to different temperatures in the combustion chamber given the same conditions. I think when you're turning 2000 to 7000 RPMs, and you've got each chamber igniting between 15 and 60 times per second, I dont think the "heat" in the surface of the chamber has any time to flow out any faster or more or less efficiently regardless of what metal the chamber is made of. All the wasted heat energy goes into the coolant anyway. and that goes through a radiator with a finite capacity. And I dont think aluminum wastes combustion energy any more or less than iron does, at least not significantly.

And to be clear, I am in no way saying aluminum heads are bad and iron heads are good, I just dont see any reason to move the goalposts when it comes to compression ratios with either of them. The OP doesnt need to feel like he cant afford to build a 383 worth building just because he cant afford aluminum heads. I think it's a great option to get some cheap, decent iron 64cc heads now if that will enable him to build a 383, and then later on when he can afford it, he can buy some aluminum heads to put on it. The same cam and heads and intake will make very close to the same horsepower regardless of displacement, but larger displacements will allow larger cams without sacrificing low end torque. So I think it behooves anyone to skimp on the heads and build a 383 bottom end if they can, and then do heads or heads and cam later on.

IroczFan

Alright well i decided to go ahead and use this block scince i dont have a huge budget to build this motor, there are a few things ive been thinking of scince its a 2bolt does it pay to go and buy the 4bolt mains conversion and have a machince shop drill some holes for the extra bolt on each side? also the heads are 487s not the 487X ive read that they are low compression 76cc heads are these worth putting alittle money into and using or no? and what would be a good ballpark number for the compression of this motor to try and run it at with out having to only run premium gas

Orr89RocZ

iTrader: (20)

Just need to look at the thermal conductivity of the material to know that aluminum transfers heat at a much higher rate than iron does. You can extract more heat from the chamber with aluminum heads and cooler chambers mean less detonation/pre ignition prone.

http://www.engineeringtoolbox.com/th...als-d_858.html

however you are right in chamber design helps ALOT when dealing with higher compression. Most stock iron heads dont have good chambers. Most good Aluminum ones do have improved chambers

Jim85IROC

iTrader: (2)

You make power by feeding cold air into a motor, then having hot combustion. People confuse these 2 things and assume that colder is always better. Cold air is more dense, so you can pack more oxygen into the combustion chamber. Once it's in thete, you want a hot combustion chamber. The heat expands the air, building more cylinder pressure, but more importantly, it allows for more complete combustion. With a cold combustion chamber, you get much less efficient combustion, which means less power.
But, as other articles have pointed out, a few degrees difference between iron/aluminum heads isn't going to make a difference.

sofakingdom

iTrader: (1)

Lots of misconceptions and general ignorance about the aluminum/iron deal...

First off, the thing that MAKES POWER in an engine of this type, is HEAT.

Heat comes from burning the fuel. Each milecule of fuel contains a certain amount of energy (another word for "heat") locked up inside it chemically. Burning it releases the energy.

The energy makes the gases in the cylinder become hot, which increases the pressure, which pushes on the top of the piston. That's how heat is converted into mechanical force.

In the process of pushing on the piston, as the piston moves, the gas cools. The cooling of the gas is the result of the heat being taken out of the gas and turned into mechanical work.

The more heat that is released from fuel molecules (which is determined ENTIRELY by the # of them that are burned, which in turn is determined by the cyl size and how fully it is packed with fuel and oxygen) and subsequenty converted into mechanical energy, the more "power" the engine makes.

"Compression" is more than just a measure of .... compression. Much more importantly, it is also the measure of HOW MUCH THE GAS EXPANDS during its energy-conversion operation, and therefore how much of the heat that is released, gets turned into mech work. That's where the higher power output comes from when the "compression" is raised; not from anything to do with "compression" itself, but rather, a higher rate of turning heat into useful work.

Unfortunately, not nearly all the heat that is released by burnung fuel, turns into mech energy. There are a number of specific places that some of it goes; for example, a certain percentage stays in the water vapor in the exhaust (the "heat of vaporization"), a certain amount just stays in the exh gases as heat (temperature), and a certain amount "leaks" out of the cylinder and through the metal and into the cooling system. Very roughly and approximately, at full power, 1/3 of the gasoline's chemical energy becomes "useful" 1/3 goes out the exhaust, and 1/3 goes into the cooling system. This last is where the difference between aluminum and iron enter the picture.

Aluminum has MUCH higher heat conductivity than iron; meaning, ALOT more of the heat that COULD be turned into "useful" work, instead "escapes" through the metal and into the coolant. This lowers the total amount of heat in the cyl. (duh) Therefore in order to get the same amount of useful work, an engine with aluminum heads MUST have higher "compression" than an otherwise identical one with iron heads.

For some reason, most hot-rodders are fascinated by and obsessed with the idea of "fire". They tend to completely ignore all of the stuff that makes a "heat engine" ACTUALLY WORK, and instead concentrate on "fire". Fact of the matter is, the whole "burning" aspect of our engines, is almost incidental to the production of power; as long as it happens AT ALL, the results are the same, no matter what. Which is why all the gimmick plugs, multi-spark ignitions, and so on, make only a MARGINAL difference to the ACTUAL POWER OUTPUT: it's irrelevant. They might make the engine easier to "start", or improve "driveability", or whatever all esle; but as long as the fuel burns, the result is the same. This is pretty easy to grasp if you're lighting a fireplace: you get the same fire whether you light it with a match or a lighter or a MAPP gas torch. No different in an "engine".

http://en.wikipedia.org/wiki/Internal_combustion_engine
http://en.wikipedia.org/wiki/Heat_of_combustion
http://en.wikipedia.org/wiki/List_of...conductivities

In the last article, browse down through the table, and note that the heat conductivity (which is, the time rate of energy passing through a one meter thickness of material, per degree of absiolute temperature difference) of aluminum is in the range of 200 - 250; while for cast iron it's around 55. Meaning, aluminum conducts (in the case of an engine, "leaks") heat out through the castings and into the coolant, around 4 times as fast. And it's not hard to figure out, if the heat goes into the coolant, it (a) fails to help push the car around, and (b) requires a larger cooling system to control it.

In a typical auto engine, the majority of the heat loss from the cyl into the water jackets is through the chamber surface of the head. Only a small part is through the cyl walls of the block. Therefore, since the head DOMINATES this aspect of engine behavior, the block material matters little; but the heads are CRITICAL. Also, since the exh port in the head is usually made of the same material as the chamber, heat conduction from the exh gases throught eh exh port walls and into the coolant, FURTHER aggravates the whole cooling system requirement thing.

This is why it is not only POSSIBLE, but actually NECESSARY, to use a higher static compression ratio with aluminum heads, than cast iron.

More science and less "mythology" would do wonders for improving one's understanding of how engines work

InfernalVortex

iTrader: (4)

I dont buy it. Show statistical proof that it makes any difference whatsoever in an internal combustion engine and Im more than happy to believe it. I dont think the separation of fire and heat in this case is at all relevant. The engine is turned by expansion of the air fuel mixture. Is that triggered by heat or is it triggered by spark? Maybe in a diesel it matters.

I dont doubt that it may have some effect, but I doubt it's anything relevant and significant.

Orr89RocZ

iTrader: (20)

The explaination was given...if you dont buy it then theres nothing else to argue Spark ignites the mixture, but the rate of expansion is controlled by burn rate which is highly dependent on chamber design and temperature (and fuel type.)

Go build a low compression aluminum motor and then compare it to a higher compression version and see where it goes in power/et. If it didnt matter, we would beable to boost 11 to 1 comp aluminum motors on pump fuel. The heat in the chamber is higher with more compression. Simple physics of air compression.

Trevmust

Is the gas mileage terrible or decent? I dont know if I should go with Carburated or to buy a TPI/TBI system...

vetteoz

iTrader: (13)

Do you use the LOUD pedal alot ?
383 can be very economical if driven correctly because it makes more torque; so can run at lower revs and pull taller diff gears better suited for economy than a 350

BUT , it you hit on it ( as you will ) it will use more fuel because it makes more power than a 350 and you can't make more power without burning more fuel

Trevmust

Well it's a standard, but I'm glad it'll be better on gas when I don't feel like crunching the pedal. I plan on lightening the car a bit as well lol. What gears go you recommend? 3.73? I think imma get a 12 bolt cuz I don't plan on making crazy power.

NagleMac

iTrader: (1)

You're looking at 3.23s for better mpg, I'd only use 3.73s if it's a strip car, I'm putting 3.42s in with my 383

Orr89RocZ

iTrader: (20)

My old 383 with stealth ram injection running off the factory MAF TPI electronics actually got good mileage when just cruising around.... I'd say it was low 20's mpg capable on highway and 16-17 in town depending on how you drive it. My stock L98 was 23-24mpg highway and 17-18 in town on a good day for comparision. EFI should get better fuel economy than a carb but a carb should be capable of decent mileage. It just will take alot of work to make sure the carb tune is providing a lean mixture at cruise rpms, and a vacuum advance would help with timing at part throttle to get the most out of the car.

NagleMac

iTrader: (1)

You can get good mpg with FI or a carb, you just need to supporting parts to match and good tuning

Trevmust

Thanks for the advice guys. for a carb I was looking at a 670-770CFM street avenger with an electric choke....

NagleMac

iTrader: (1)

I'm putting a 770 on my 383, I don't think you'll be happy with a 670, unless it's strictly street use and you're only worried about had mileage, you can set the secondaries to open earlier or later depending on the spring you put in, for better mpg having them open later would be the best

Trevmust

When you set yours up can you tell me how you did it? I'm new to Carburators. Or maybe just refer me to a book?

Trevmust

btw the best gears I can find are 3.08 or 3.43/2 (depending on the website)