displacement

why does everyone dog 305s. everyone talkes about how fast the old 302 camaros were and the had only 3 cubes smaller. is it the fact that the motor has been destroked so the powerband moves up in the rpm range? just wondering. i have a 305 to rebuild to put in my car but wondering why every one hates them. can i destroke a 350 to 302 or would it cost too much?

The reason the 305 gets dogged is its poor bore to stroke ratio. The 350 and 302 had large 4in bores which allowed large valves and increased port flow. The 305 has rather small 3.736in bores that shroud the valves and decrease port flow. This means that the 305 with the small bore and long stroke makes good low end power but gets weak in the upper rpms.

The reason the 302 was such a terror was that it was the opposite, down low it didnt make alot of power, but once you wound it up it had low piston speeds, great port flow, and could rev to 8000rpms.

As far as making a modern day 302, the main problem youll run into is finding a crankshaft. To my knowledge there are three possible methods.

one, find an old (pre 1987) block with a 4in bore, then find an old 302 (good luck) or 283 crankshaft and then get the nessesary connecting rods and pistons to fit.

Two, get a post 87 block with a 4in bore, and the crankshaft out of a 4.3L LT1 engine that can be found in 94-96 B-body sedans and wagons.

Three, call up scat or another name brand manufacturer and have a custom crankshaft made for your application and use whatever block you have laying around.

good thing i didnt waste my money building the 305:icon16:

well dont get me wrong, you can definatly mod up the 305, and to be honest, it will probly be a very strong daily driver, just dont expect to be banging 5000rpm shift points and running at top speeds on the highway. Remember that any mods you do to the 305 short of pistons will transferr directly to a 350 or other small block. this includes intake, headers, and so on and so forth. So if you dont have the money right now for a 350, you can mod the 305, and transferr everything to a 350 later. Also, check out chevrolet high performance magazines web page, they built a project 305 with vortec heads and TBI that made over 330hp, so there is hope for your 305. Its just that its going to be at a lower rpm range than would be possible with the more performance related brethren.

What about the Chevy 327? Wasn't that a pretty strong motor? How does it compare to the 305 and 350 bore and stroke wise?

cid = bore x stroke
283 = 3.736(?) x 3.00
302 = 4.00 x 3.00
305 = 3.736 x 3.48
327 = 4.00 x 3.25
350 = 4.00 x 3.48
383 = 4.030 x 3.75
400 = 4.125 x 3.75

that pretty much covers the most popular displacements. The only one im not entirely sure of is the bore on the 283, if im wrong someone call me on it. i dont really have time to check it myself.

cid = bore x stroke
283 = 3.736(?) x 3.00
302 = 4.00 x 3.00
305 = 3.736 x 3.48
327 = 4.00 x 3.25
350 = 4.00 x 3.48
383 = 4.030 x 3.75
400 = 4.125 x 3.75

that pretty much covers the most popular displacements. The only one im not entirely sure of is the bore on the 283, if im wrong someone call me on it. i dont really have time to check it myself.

it's crazy how the little bit of percentage in the bore can make so much of a difference. 89 any idea how much it would cost to get the 305 bored to a 350?

cant do it, the 305 although very similar to the 350 block, has different water passages. If you were to bore a 305 out to a 4.00 inch bore you would hit water jackets in the block and ruin it. If you want the 4.00 bore, you have to get a 350 block.

What determines the RPMs at which the engine will produce the most power? And what determines piston speed and how high the engine can rev without damage?

wow, complicated question, there are alot of variables, head design, cam profile, journal sizes, bore to stroke ratio, displacement, naturally asperated vs forced induction, exhaust design, intake runner length. so without giving a class on engine design lets do a simplified version based on what weve been talking about.

With the 305, its small bore, long stroke ratio will give it very high piston speeds for a given displacement, this will create high port velocities in the heads with small valves dictated by the small bore. At low rpms this works to better pack and evacuate the cylenders, however as speed increases, there is less and less time to fill and evacuate the cylenders and those small valves, with those high piston speeds will choke the engine, and it wont be able to fill the cylenders proporly meaning less power at higher rpms. Youll also notice the cam in the 305 engines are rather on the small side, which further aids in creating a cork in the airflow into the engine. Creating very high low rpm port velocities, but cutting off airflow at high speeds.

Now the 302 was a rev happy motor, with its large bore and short stroke the piston speeds were very low, the piston didnt move much from tdc to bdc, the larger bore alows larger valves which remove the cork in the system we are plagued with in the 305. The combination of larger freer flowing ports and low piston speeds allow the 302 to rev up to 8000rpms and still make power. The cam for these engines has generous lift and durration to allow the cylenders to fill. However what youll notice is that due to low rpm port velosities and bad turbulance, you will suffer some low end power losses, not unlike the blackbird these engines were designed to be running fast, and didnt like running slow.

Ok, thanks for the in depth description. I probably sound like a Noob asking a question like that but I was curious. This is why our mods ROCK around here, cause they know their shit.

i wonder what the ideal bore/stroke and bottem end would be for 500hp and to pull most of the torque around 2000 to 6000 rpms. i want to spank ls1s easily in my thirdgen. i can put money into the car as is i dont drive it much. i weighted it yesterday at the scales at the junkyard. it cost me 5.00 my car weights 2,978 pounds. how much lighter is it than a 4th gen

89, you were right about how the 305 pretty much falls flat around 90, but i was wondering if work is put into the motor can it accelerate to speeds over 90 decently(bad choice of words). It still has pull, just you don't feel it as much. Say when people run the 1/4mile and get trap speeds over 100, can the 305 be made capable of doing so? Also, since you said it will have great low end power, does that mean excellent 0-60 times?

So how did GM work up the LS2 and the LS7? Those engines are hugedisplacement but are still SB. I know the stoke on them is crazy long but how did they bore the 6.0L LS2 out to 7.0L for the LS7?

TX Chevy, '89 IROC made a good point of why the 305 motor is lack
luster. Another point is the milder cam lift and more restrictive heads as compared to L98 heads. At my shop, we only have a few 305's come through every blue moon. What we like to do with them is increase bore,
put compression around 10.65:1, run Wiseco forged pistons, little better heads, and a custom cam w/ 1.6 rockers, last but not least a N.O.S nitrous kit in which we convert to wet system and allows a 75-150 horsepower boost, great for high rpms. The destroke to 302 crap is just impractical and too expensive.

TX chevy - the ideal bore stroke ratio is a tricky deal, and you are looking at a very wide powerband to be making power in. I would say your looking to make a high winding engine to compete with the LS1, for that i would suggest a large bore short stroke. a very popular one that still gives good displacement is to use a 400 block with a 4.125in bore, and a 350 crank with main cap spacers. this gives you an extreamly high winding 372cid small block that should still have decent low end power. The powerband is also going to be decided by what camshaft you use, your heads, and intake choice you make. But that shortblock would be a great starting point. to answer the question on weight, a fourth gen camaro weighs in around 3500-3600lbs from the factory.

Link85x - the mods i listed above would extend the power peak to allow better high speed acceleration. The key mods to do to accomplish this would be the cam, heads, exhuaust and intake. and yes, the lower powerband would make for good acceleration times, 0-60 for instance.

CamarosRsweet94 - the LS2 is just the 6.0L truck engine cast in aluminum for all practical purposes. with different details. but the block is basicly the same dimentions. remember the sbc 400 was 6.55 Liters from the factory, and was just a small block. with a .030 overbore and a 4in stroke the displacement increases to 434cid or 7.1L all in a standard sized small block. The LS7 is an LS2 engine that has had the iron bore sleeves removed and replaced with thinner but siamiesed bore linings that allow a larger bore, and then a larger stroke went into it i believe. giving the 427cid or 7.0L displacement. Keep in mind there are many aftermarket kits to transform a sbc 400 into a 454cid beast, and the LS1 into i believe a 462 cid monster.

but original for around my town. every hotshot in a hot rod has a 350 i wanted to break the mold and do something fairly original a 302 in a thirdgen sounds original to me just a thought though

i just wanted something original in my thirdgen seems every kid with a hotrod has a 305 or 350 just a thought though

sorry about that replied twice kinda thinking about what i can do to and noy paying attention

and the LS1 into i believe a 462 cid monster.
That would be a mistake though. Paperthin cylinder walls on a fairly high revving motor isn't a good idea.

I just took the standard LQ9 block and added LS1 stroker parts. Makes for a 402 LS1 basicly, except iron (for strength).

well yes i agree if you were to bore out the existing sleeves, to get that displacement out of an LS1 you have to resleave the block with thinner, but much stronger sleeves. and in the case of the new LS7 motor, siamesed sleeves are used for added strength.

as far as the 302 in a third gen, i think its a great idea, thats what im doing and i think it will be a great combination of performance and economy. not to mention it will just be cool to have the 302 badges on my Z28 they way it was originally done :evillol:

I heard you get reach higher rpms with the old 302.

well yes i agree if you were to bore out the existing sleeves, to get that displacement out of an LS1 you have to resleave the block with thinner, but much stronger sleeves. and in the case of the new LS7 motor, siamesed sleeves are used for added strength.

as far as the 302 in a third gen, i think its a great idea, thats what im doing and i think it will be a great combination of performance and economy. not to mention it will just be cool to have the 302 badges on my Z28 they way it was originally done :evillol:

89, when do you think you'll be all done? I gotta see what this thing can do!!

yup, the old 302 engiens would spin up to 8000rpms.

as far as when ill get mine done... its gonna be a while. I gotta do the junkyard crawl for a bit longer. Gotta find a local pick your part that will give me just the crank and rods out of the 4.3L LT1 instead of making me buy the entire engine. Which isnt easy. And on top of that im still in school and make no money, and i have two camaros currently in differing stages of disrepair, hopefully ill make some headway on them this summer. But its probly gonna be a few years before i get that engine put together and installed.

That is where the 302 came from.... 327 block with a 283 crank.....

~John
http://www.supercarvideos.com/G92IROC

So 89, do you drive the RS? I assume the 302 is going in the iroc.

yeah the 302 is going in the IROC, the RS is a daily driver with a stock drivetrain, but the front suspension is broken so i gotta replace it so i can sell her.

yeah the 302 is going in the IROC, the RS is a daily driver with a stock drivetrain, but the front suspension is broken so i gotta replace it so i can sell her.

NNNOOOOO!!! Don't sell her! Why are you selling her? I know tryin to take care of to cars can be a biotch!! I gotta berlinetta and it just sits there and collects dust.

i have a question about the 302......i have everything i need to build the 302 except the pistons.....i've looked everywhere and cannot find pistons fitting the 4.00 bore and 3.00 stroke.....does anyone know what pistons i can use in this situation? thanks!

i have a question about the 302......i have everything i need to build the 302 except the pistons.....i've looked everywhere and cannot find pistons fitting the 4.00 bore and 3.00 stroke.....does anyone know what pistons i can use in this situation? thanks!

Couldn't you just get some forged pistons? You know what, i'll let the experts handle this, kinda outta my league.

i have a question about the 302......i have everything i need to build the 302 except the pistons.....i've looked everywhere and cannot find pistons fitting the 4.00 bore and 3.00 stroke.....does anyone know what pistons i can use in this situation? thanks!


Cheif I told you what to do in ya seperate question if you can't figure out how to calculate piston compression height(pin height) I'll help you out.

Cheif I told you what to do in ya seperate question if you can't figure out how to calculate piston compression height(pin height) I'll help you out.

yep and thank you very much for your help....the compression height is 1.8 for the 302...i looked it up....on a site i found the pistons but they where .030 pistons so i would have to have it bored obviously.....but that makes a 306 CID engine kinda taking away from the 302 originality...worse comes to worse thats what i'll do...but thanks so much for your help that was a great point in the right direction!

yep and thank you very much for your help....the compression height is 1.8 for the 302...i looked it up....on a site i found the pistons but they where .030 pistons so i would have to have it bored obviously.....but that makes a 306 CID engine kinda taking away from the 302 originality...worse comes to worse thats what i'll do...but thanks so much for your help that was a great point in the right direction!


1.8..... are you sure you calculated it right.... that seems like a very large pin height.

Also if you calculated it right and can't find it in a 4" bore your not looking in the right spots.

well......this is what i saw but i think im probably wrong....thx again....i saw the compression height for a 9.0 deck was 1.8....but according to the method they have of figuring this out...

Zero-Deck = 1/2 stroke length + rod length + piston compression height.
Example 3.480 stroke, 5.700 rod, 1.550 compression height piston.
1/2 stroke = 1.740 + rod length 5.700 + compression height 1.550 = 8.990 or .035 down in the hole on a 9.025
deck block.

http://www.raceseek.com/chevy_v-8.htm

so the 302..... 2 (1/2 stroke) + 5.7 (rod length) + 1.8 (compression height) = 9.5 deck height but the compression height they gave was for a 9.0 deck sooo is the height off? i assume the height is 1.8 i looked it up somewhere but cant remember where i had..... on http://www.jepistons.com/pdf/2002-srp-chevy.pdf they have 302 pistons with the .030 bore making the engine a 306 w/ 1.8 compression height and with the 64cc a 10.4:1 compression ratio. heres some more with the .030 bore http://www.flatlanderracing.com/wisecoprotru-sb01.html and it says it has a compression height of 1.805 and 11.0:1 compression.....

this is what i had planned for but on another site http://www.beckracing.com/page17.htm they say for a 302 to use Caprice 5.94" connecting rods and any kb pison with 1.561" compression height....noting "this is not an original equipment chevy 302" but having a deck height of 9.501

so i guess either method would work.......or am i mistaken? thanks again for the help!

Ok well i just crunched a bunch of numbers for you. Using a standard SBC 5.7" rod your going to need a 1.8-2.0 pin height piston depending on deck height(9.025 or 9.020, standard SBC deck heights) and what piston to deck clearance you use.

This is not going to be an easy piston to find cause it's only has 2 real applications which is a 283 and the Chevy 302. Keith Black and others do make 1.8's 2.0's are not gonna happen off the shelf. So you'd either have to stick the slug way in the block ewww or deck the block a good chunk ewwww to get to popular pin heights to improve selection. But no fear I'm here to save you.

If I was you I would use 5.94 connecting rods like you mentioned on a stock 9.025 or 9.020 SBC. This will only raise your rod ratio from 1.9 to 1.98 which is very high making it not a great torque motor but the Chevy 302 never was. But changing to this length rod on zero deck will put you in the 1.585 pin height which will open you options up big time compared to the 1.8+ pin height you were dealing with. Also we can move it in the hole a lil more to lower it if needs be.


Now that you can narrow it down with that, you need to start calculating compresson ratio of the pistons you find for an off the shelf slugs that will give you want you want..

thanks so much!!! your help was great....thats what i'll do....the 5.94" rods becuase this engine isnt gonna go into an original 302 car anyways....its going in my 98 camaro and like you said that will make the options a lot more abundant.....thanks again!!!

well said GTstang, i ran into the same problem with my 302, my solution, because im looking for high rpms anyway and a low weight rotating assembly is to use 6.000 or 6.125in connecting rods (havent decided yet) that will allow me to run a much shorter piston that is lighter and easier to find than the 1.8in pistons.