giff

Looking for some feedback on this subject! I'm a GM guy all the way (original owner 91 formula, 305 tpi, 5 spd) but would like to here from some of you more experienced guys why, technically speaking, the 302 seems to much more readily make gobs of torque/horsepower compared to gm's 305?

As I read thru hundreds of posts on this site I see alot of money being spent to make a TPI 305 go from high 14's/low 15's to maybe low 14's. While the 302's seem to be capable of producing mid to low 13's with comparable upgrades - i.e. intakes, runners, headers, 3" exhaust etc.

Is the slightly larger bore of the 302 and maybe better breathing (heads) the answer ?

Giffman

RB83L69

Intake tract.

The best FI system the 305 has ever had was TPI, which is inferior in terms of flow to the 302's. Back in the carb days, they weren't too much different; the L69 was faster than the carbed 302s of the day.

305sbc

iTrader: (3)

Depends on how you're comparing them. Stock for stock in the same car?

What would happen if you put log manifolds and single exhaust on a 302, mated it to an automatic transmission & 2.73 gears, then added 250 lbs of weight to equal the condition that the GM 305 cars came in?

Then you'd have to use identical lift & duration numbers on a roller camshaft to make it even more equal.

By the time you are done equalling the playing field you wouldn't find much difference. The 302 does have a TON more parts out there for it to upgrade and take advantage of the wider bore.

giff

Even when you take into consideration that mustangs are about 200-300 lbs lighter they still seem to run stronger. They come stock, if memory serves me right, with a 3.08 or a 3.23 rear end - so , my 3.43 ought to make the extra weight a wash.

I'm considering going with headers, 3" exhaust, siamesed intake runners and upgraded intake. My thought being to simply let it breath. Or are the flow rate of the heads the real issue?

Giffman

bes217

I thought that the 302 also has an almost ideal bore/stroke ratio.

ChevTech84

Why do the current generation LS1 engines kill the current generation 4.6 engines? They were intended to perform, the 305 was the best thing GM could offer that would go slower than the lo-po 350's that were in the Corvette in the 80's. Can you make a TPI setup go fast, yes. Is it expensive, yes.

Vader

The larger bore allows for larger valves. The shorter stroke makes it soemwhat more rev-friendly, but also shortens the dwell at TDC and BDT, killing emissions ability (which is what killed the engine). The LS1 has a longer stroke on a smaller bore, which does wonders for both torque and peak power when properly balanced.

The Ford 281 is just too small to make any serious power and respectable torque without some sort of boost. The larger displacement LS1 actually gets better mileage in an equal platform, and makes superior torque and HP.

iroc22

Well from what I have heard, the Ford MPFI intake starved the outside cylinders while the TPI intake did a much better job at distributing the air amoung the cylinders better.

It's just what I have heard.

RB83L69

It may do that; but it also flows a whole lot more, and doesn't de-tune the engine's operation above 4500 RPM deliberately.

The comment about weight is right on the money too. Ultimately you're comparing cars as a package, not just the motors; that 300 pounds is nearly 10% of total weight, which is huge.

robertg

iTrader: (2)

assuming equal power between the two cars, the one weighing 300 lbs less would run approximately .3 (3 tenths of a second) quicker in the quarter mile as opposed to the heavier car. this is assuming driving conditons are equal, etc.

is that a correct line of thinking? 100 lbs of weight reduction equals 1 tenth?

bes217

Yes that is a common rough estimate. It is not exact and can depend on traction and other factors as well.

1PTR315

The 302 has about 15 HP less frictional loss at 5000rpm's due to slower piston speed. The lighter wieght goes a long way towards traction also. Small bore big stoke engines don't pull air through the long tune port fuel manifold as efficiently. With the same peak HP the 302 has more total HP under the entire power curve.

88IROC350TPI

Its all in the bore/stroke of the 302 vs the 305. The fact is the 302 is superior no if ands or buts... time to throw on my flame jacket.

88Camaro350

The 302 has a wide aftermarket. But not as big as the chevy small block market.

The earlier 302s weren't much better than the early 305s. However the 86-up 302 HO with EFI were nice. The EFI is still very restrictive. The ports are small like TPI ports. Still seems to flow better.

Oh..and if you got an automatic in your foxbody mustang more than likely you will also get 2.73 gears. 2 buddies have auto foxs and they have 2.73s. Dads 95 GT auto has 3.23s thought. He still cant beat me with my 2.73s... and I don't even get traction

Gumby

Funny you say that. I had a chart showing that info and which engines were the best and it was the 60* 2.8 but the 302 may be close.

Matt

1991tealRSt-topGuy

wow last 2.8 i saw running 11's was..............never lol

88Camaro350

Depends on the length of the course

One good thing about the 86-92 302's is they came with forged internals stock. One bad thing is the blocks will literally split in two if lots of power is made.

No engine is perfect. Except maybe the new 572. :hail:

Fredless

The mustangs are also true-dual from the factory. If you post on this site, what should I do to make my car faster...I bet around 60% of the members say EXHAUST.

These cars have terrible manifolds and a 2.25" exhaust (at least on the L03's). Its easy to make the decent flowing mustang exhaust even better and cheap.

Wasn't the 302 designed to at least Compete with the 350? I think they did a great job with that motor. Another member on this site said (or somewhere around it) "If you have a foxbody mustang and it doesn't run 12's, its a turd. If you have an F-body that runs 12's, its FAST."

Ken Ruether

It is true that the blocks will split in half but it takes a lot of power to do it.

There are guys on Corral.net that are making big power on stock short blocks with good heads and a power adder.

Jeff Bellman made 499 ft lbs of rear wheel torque with the small Kenne Bell blower on a stock short block, stock cam, and performer heads.

There are guys making 800 hp on stock short block with twin turbos aftermarket cam and heads.

I don't know if it's a curse or a blessing, but to me, all three of the big auto makers have cars I'd love and cars I'd hate to own. I'm only loyal to performance, no matter who built it.

I've owned a lot of cars made by all of the different makers. I had a stock 79 vette once that was only 1 1/2 seconds faster in the 1/4 than a VW Camper bus and about 1 1/2 seconds slower than a V6 74 Capri

Take care.
Ken

Quick_Trans_Am

iTrader: (2)

He's not saying the 2.8 is quick, he's saying that it has an ideal bore/stroke ratio. If you have a bigger engine with a more ideal bore/stroke ratio, like the LS1 or something to that effect, you're going to be optimizing its performance potential.

Nixon1

I agree in that I think the 302 was designed to compete with the 350 on some level. Not to say to beat it, because it won't, but to hold its own. Top model to top model.

I can vouch for the power of the 302. I've got plenty of buddies with 302's or 306's running 12's and faster. One friend of mine just ran high 10's on nitrous with slicks, and his only suspension mods being drag springs and no front sway bar. No traction bars, no control arms, nothing. Even without the nitrous, with the slicks on, he can spin the backs to about 80 mph on the street.

Oh and also, to vouch for how tough these suckers are... This old man at the shop where my engine was put together, we call him Old Man Dave.....he's got a stock block, stock bottom end primered Mustang running a 350 shot of nitrous with no problems yet. I think he ran somewhere in the low 11's.

And as far as my car goes.. It did 14.5 at 95 mph with a badly bent connecting rod and an assload of blowby. Can't beat it. :lala:

Though I'd still rather have a 350!

iroc22

Yeah I knew of a few around here that did that actually with their 302's, I might even have a pic on my comp of one....

88Camaro350

fox bodies do seem to be pretty fast. Not stock thought. Stock they are OK but it takes modding to get into 12's just like any other car. Like a mustang with exhaust and intake mods isnt gonna run 12's. You gotta upgrade heads and camshafts just like our cars. The only advantage they have is slightly less weight, better FI, and a better rearend...

Gumby

Ditto

It just has the best [ideal bore/stroke ratio] with a possiable 14000 rpm.

Can it do that, no. but by the numbers it can, if you could get the parts.
Not sure where but this site had every engine listed with the "ideal bore/stroke ratio" and the highest possiable rpm by the numbers and some other really cool info.


It was a very informative chart. Wish I could find it.

SSC

What the 302 better then the 305? Better go buy a 302 then just so I can upgrade to a 351w when I find out its not.

In fairly equal platforms like trucks, where the weight is very close, rear gear ratios, and transmission ratios are close theres no comparison. THe 305 will make much more power all around and be better on fuel. The only good engine actually I'll say superior was the 300-I6.

Gumby

Ok I was wrong, the 151 4 cyl is the best but the 2.8 is right behind it.

THe page use to be here.
http://users.erols.com/srweiss/tablersr.htm

buts its broken. I was talkig to an enigne builder about a 2.8 over ICQ a long itme agoa nd he was explaining them numbers.


" the bore/stroke = 1.0937 so the 2.8 has higher rpm then the 3.4"

"but the 2.8 has advantages no other motor has for rpm's"

"i think u could get away with a cam and nevermind the 3.4 and all that hassle, that engine should be good for 8000 rpm or so"

"u could stroke the 2.8 and end up with a normal engine"

"it just has such a short stroke being stock for the size of its rods"

"but thts good for such a small engine"

"The short stroke allows high RPM without destructive piston speed (7100 RPM = 4000 ft./min., the accepted "safe" limit for piston stress). The large bore permits big valves (2.14" intake, 1.81" exhaust).
"

It was a very long good conversation that went into V8 of every brand and some detailed math.

Matt

bigals87z28

Ok

302 had a better bore... bore is where the power is.. not stroking a small bore engine.
Take example, Chevy 302 vs Chevy 350. The 302 and 350 can both make the same power, but torque will be greater with a 350 due to stroke. And yes, the 302 was a chevy engine first before ford made one. The EFI 5.0 is a marginaly better set up then TPI. They have a very limiting intake, hence the many aftermarket ones they make. The 5.0 would be nothing if it didnt have a HUGE aftermarket... just look at the 305. small (micro) aftermarket.

SBC 302 > SBF 302.

88Camaro350

So your stating that the aftermarket for small block chevy's is micro? 305 has just as much of a aftermarket as ford does. Small block chevy parts are almost generic. Now with a lt1 intake you may be able to get a 305 tpi running with a efi 302. lt1 intake will definetly flow better than a stock TPI setup. 400$ plus fuel lines ect is what youd pay for a edelbrock EFI manifold.

I still wouldn't go about building up a 305 personally. I tried it once...didn't have the greatest results.

bigals87z28

How many 305 heads do you know?
How many pages of stuff do you see just for the 5.0/4.6 mustangs in summit?
Yes, small block stuff is interchangeable, but to get the size of aftermarket support like the ford 302? Only engine bigger then that is the SBC with bores bigger then 4inch.

SSC

All the support is for a 350, true because a 350 drop is the most common modifaction done when replacing a 305. As far as heads there use to be quite a few places making good quialiy 305 heads, they stoped because GM phased out the 305. Actually the 416's common on 305 3rdgens are good enough for making power especially when transplanted to a 350 so they gave us a freebe.

Spectre

The 302 was designed sinse it had to compete in a displacement
race.. wasnt it?

five7kid

iTrader: (14)

I'm trying to justify leaving this thread open.

I'm not getting very far...

giff

ok. It seems the larger bore, slightly better breathing and free-er rev'ing capibilities of the 302 are the answer.

Could I expect to knock 5 to 7 tenths off qtr miles times by letting my 305 breath? (after market runners/manifold/headers/3" exhaust) OR will the limited flow ofthe stock heads negate any gains I might see from these parts ?

Giff

bigals87z28

basicly, you have the horrid cam, crappy heads, and chitty intake to get over. Just look at 5spd version 305's and how much faster they are then 305 auto's (tpi im talking about). The 305's got the larger l98 cam and look how many 305 5spds are running mid 14's... and thats with a factory cam!! Im doing a head, cam, intake change this winter... Ill let everyone know about the performance when i get done. Im aiming for low 14's to high 13's with good traction and good prom tuning.... which i have yet to start to do.

Vader

Hello! (Tap - tap - tap) Anyone in there?


That's why the LS1, with a smaller bore, longer stroke, and better flowing heads makes more power than the older design 4" bore 350s (which had four more cubic inches). The 305 can be similarly treated, and make more usable power than a larger bore, shorter stroke engine. The trick is in getting larger valves in the chambers. There's plenty of room in the heads for adequate ports, upstream of the intake valves. 1.94" valves can be squeezed in with some work, and undercut stems will help the flow that much more. A little radius on the front margin/face of the intakes will also help edge flow around the tight chambers. The biggest question posed by 305 drivers might be "Is it worth the trouble, when 350s and larger engines are a bolt-in replacement?" Ford 302 owners don't have that kind of option, since there are not nearly as many 351s floating around.

OutLaw305

what size (in cc's) did the stock 305's come with. I am looking to put a new set of heads on my 92 lo3 and am stuck at a wall with tryin to figure out what are the largest i am allowed to go.

Chris89GTA

iTrader: (2)

Here is a pic of a 302 I found on Corral not too long ago. Just a little N20 put to it. Think the guy was only pushing 550 rwhp though.

Gumby

Wow, just a little work and that will never run again.

Geese.

I guess if it came down to it, one allways could build a chevy 302.

wouldnt an old 289 or what ever that v8 was in the old C20 trucks be build able into the famous 302.

I know the old chevy 302 was a 7000 rpm all day long motor stock. BUt it had solid lifters.

Matt

iroc22

Yeah the Trans Am series had a 305 ci limit.

iroc22

Stock is 58cc but there really isnt a true limit on how large you are allowed to go. The larger the combustion chamber size, the lower your compression ratio will be.

gruveb

I'd say it is...if you shop smart. I have a set of used ported Torquer 305 heads, a Comp Cams XE 262, used Weiand intake, rebuilt edelbrock 600 carb, a set of used SLP headers and 3" cat, and a Hooker catback, a used Jacob's pro-street ignition system.........all for about 1100 bucks. I've not been to the track yet, but others with similar set ups are well into the 13's....which is respectable for a daily driver. I couldn't touch a 350 with similar mods for that much dough.....not unless I already owned a 350 block.

jasonbennett

a ford 302 is a STROKED 289. the chevy 302 was a stroked 283. the reason that they put out more power than a 305 is the rod length/bore ratio, just like what happens when you stroke a 350 or 400. if you put 6 inch rods in a 350 then you will get more power output than the stock length. same when stroking. when you add 6 inch rods to a stroke you get more power as apposed to the 5.7 rods. it allows for more piston travel at lower speeds

AJ_92RS

You're right about the Ford 302 being a stroked 289 (2.87" to 3"), but a 302 is a DE-stroked 327. It used the 283 crank.

And using 6" rods doesn't allow for more piston travel at lower speeds. Stroke allows more piston travel, not rod length.

Increasing rod length gives better rod angularity and also increases dwell time at TDC (as Vader pointed out). The drawback is it also increases dwell time at BDC.

It also increases piston speed because the added time the piston spends at TDC and BDC has to be accounted for somehow.

Air_Adam

Bore = Horsepower
Stroke = Torque

The 302, as far as performance goes, is far superior to the 305. The 305 was never designed to go fast, it was designed to pass emitions. The 302 was designed to go fast, and that goes for both the Ford and Chevy 302s.

The reason the 302 is better than the 305 is because (all else being equal) the 305 can't feed itself at high rpms like the 302 can.

The 305 has a small bore and small valves, and a pretty long stroke, so at high rpms, it can't fill the cylinder nearly as well as the 302, which has a big bore, big valves and a fairly short stroke.

Basically, the 302 can breathe, the 305 cannot. That is why the 302 is better, for high rpms anyway.

The longer stroke of the 305 will give it more low end torque than a 302 can make.

But for high performance use (like drag racing or auto cross) the 302 is superior.

Jasonbenett:

The 302 Chevy was not a stroked 283. A 283 has a 3 7/8" bore. The 302 has a 4" bore. Both have the same stroke.

The Chevy 302 was a 327 block with a 283 crank in '67, then it was a 350 block (large journal) with its own 3" stroke crank for '68 and '69.

You are right about the Ford though.

bigals87z28

No, Chevy did a very popular swap by putting in the 283's crank into a 327's(350) block making a hi-hp motor and alow it to rev for SCCA racing regulations. Chevy should have went 302 instead of 305. OH well, hind sight is 20/20.

jasonbennett

pardon, i got my blocks mixed up on the chevy 302, won't happen again

1PTR315

Long rod ratio does not increase maximum piston speed. The math is really complicated, but the maximum piston speed at 90* and minimum piston speed TDC and BDC do not change. Also piston speed at 45* is the same. The piston acceleration is slower to 30* with a longer rod. The acceleration from 30* to 60* is quicker. At 60* the piston is moving faster with a longer rod. by 90* they are both the same (short or long rod ratio). This reverses itselsf on slow down to BDC. What this does is put less piston travel at low valve lift and more piston travel at higher valve lift in the intake cycle. more time at hidher velocity helps to breath the engine at higher rpm's. The long rod does not change low rpm performance much because the volumetric efficiency is low anyway. Longer rod ratio does dwell the piston at TDC longer. This keeps the chamber much smaller during the entire fuel burn. It makes the burn more efficient, less prone to detonation because the burn is not trying to chase fuel that is moving down the bore, and lets the crank move farther so there is more leverage on the crank at peak cylinder pressure. There is also the benifit of less side load on the cylinder wall. The only real drawback to long rods is that they put the wrist pin closer to the piston top. Cooling and oiling MUST be good to keep the pins from overheating. Also due to this the ring package gets problematic. Pin hieghts of less than 1.00'' are tough to unworkable for a street or endurance engine. The ring lands and ring spacings start to cause problems. This leaves maximum rod lenght of 6.00 on a 350 which doesn't have very much effect on rod ratio but will show a little. To get a substantial benifit 1.9-1 rod ratio is needed and in a small block that limits crank stroke to 3.25''. If anyone wants to have some fun, a 327 crank in a400 block makes a 350'' engine. I've seen thie engine built and with flat top pistons and 56cc chambers makes 11-1 compression and runs on 87 octane at 36* total advance. Check out AFR's web site-articles-the 350 chevy chevy should have built.

8Mike9

Just some info on the Chevy 302...this wasn't some "whizbang" engineer at GM who designed it...back in the early 60's...maybe even in the late 50's as well, what HotRodders found out was that the 283 could take a .120 or .125 overbore..I don't recall the exact displacement...something like 301.something, that rounded up to a 302CI engine.

My personal opinion is that years later GM just followed what the common man was doing to thier block for all the previous years.

bigals87z28

hummm sounds familar..

ahh there it is. hehehe just bustin ya ***** bud.

ME Leigh

Thats true the original 302 was a 1/8" or .125 over bored 283. Later though GM build blocks with the 4.0" bore so.....