Why a 306?

Bens95cobra8594 · Oct 27, 2006

All -

I have searched but never really found an answer to this question.

I am trying to decide what to do to the engine this winter and wondered why people would bore out a 302 (5.0L) to a 306 (5.1L?)? ? ? I must be missing something because all the work of yanking an engine and boring it for 4 cubes seems counterproductive.

From what I know of strokers, they use bore and a different crank to achieve a higher total cube amnt. So why would someone only want to bore the thing to a 306? Not knocking anyone's work here but just trying to find out some information...

Thanks all.

95Vert · Oct 27, 2006

Well, when I've heard of people doing this is when they break their motor and need to repair it. They take the opportunity and bore it out. Hey 20hp/tq is 20hp/tq. You're right though, I wouldn't pull mine out and go through all the trouble just to do this, but I would consider if I need to reapair it.

Jackie Chan · Oct 27, 2006

generally it is when the internals are freshened up. i would personally just go ahead and go to a 331/347 if i were doing that though

Therian · Oct 27, 2006

generally 306s come about due to a budget rebuild because of an engine failure or heavy blow-by.

sometimes you must bore the engine slightly to accomodate piston clearances.

also it's quite a bit cheaper than buying a new crank for a 331/347

306s also have better potential to spin higher than 331/347 setups

AznStanger3v · Oct 27, 2006

i made mine a 306 shearly because of money issues and time constraints. I was in college at the time and i needed my car back. No more worry of p/v clearance. I wish it gained 20 hp/tq with it. more like 10 at most, and i might be overshooting it. It was also a chance to get forged internals as well.

HISSIN50 · Oct 27, 2006

Right-on. It's not done as a means of displacement increasing, but just to get things tight again if a hone won't cover it.

A fresh 306 vs an old 302 (with same parts, like HCI) can be kinda disappointing timeslip wise if someone was expecting times to drop.

Guero · Oct 27, 2006

yeah i only went with the 306, cuz it was the same price as a 302

Bens95cobra8594 · Oct 28, 2006

Okay, cool. Thanks for the answers!

Pokageek · Oct 28, 2006

I went 306 because I had 150k on my engine and wanted a new one but I really like the awesome sound of 5.0's.

I didn't know whether a 331/347 would sound the same as that 302 and they were a lot more money than I wanted to spend. So I went 306 with a better cam and upgraded arp rod bolts and some extras..then I added more and more to it until it runs so well n/a that I don't even want the nitrous anymore. It's fast enough at 290rwhp and that is even with cats on the car.

SeventyMach1 · Oct 28, 2006

If the walls get gouged or scratched up .... you have to bore it. And leave it at that if you're on a budget.

Since you're doing research .... I made this a year or so ago. Just a chart showing the displacement of different bores/strokes.

STROKE x BORE = C.I.

3.000 x 4.000 = 302 *

3.000 x 4.030 = 306 *

3.000 x 4.040 = 307

3.000 x 4.060 = 311

3.250 x 4.000 = 327 *

3.250 x 4.030 = 331 *

3.250 x 4.040 = 333

3.250 x 4.060 = 336

3.400 x 4.000 = 342 *

3.400 x 4.030 = 347 *

3.400 x 4.040 = 348

3.400 x 4.060 = 352

3.450 x 4.060 = 357

* = common or fairly common.

There is also a way to get a 363 c.i. out of a 302 SBF ..... but I don't know what the exact bore x stroke combo is for that.

AznStanger3v · Oct 28, 2006

SeventyMach1 said:
If the walls get gouged or scratched up .... you have to bore it. And leave it at that if you're on a budget.

Since you're doing research .... I made this a year or so ago. Just a chart showing the displacement of different bores/strokes.

STROKE x BORE = C.I.

3.000 x 4.000 = 302 *

3.000 x 4.030 = 306 *

3.000 x 4.040 = 307

3.000 x 4.060 = 311

3.250 x 4.000 = 327 *

3.250 x 4.030 = 331 *

3.250 x 4.040 = 333

3.250 x 4.060 = 336

3.400 x 4.000 = 342 *

3.400 x 4.030 = 347 *

3.400 x 4.040 = 348

3.400 x 4.060 = 352

3.450 x 4.060 = 357

* = common or fairly common.

There is also a way to get a 363 c.i. out of a 302 SBF ..... but I don't know what the exact bore x stroke combo is for that.

i *think* its something like:

Bore x Bore x Stroke x .7582(?) x 8

so find the mystery number and youll get the 363. im not in my math mode right now, but it shouldnt take you more than a couple minutes

SeventyMach1 · Oct 29, 2006

Pi (3.1416) x Bore x Stroke x # of Cylinders = C.I.

You can't really do it that way. For example, there are 2 different 327's. One uses a different stroke and is very uncommon, IIRC. So you really have more than one variable.

HISSIN50 · Oct 29, 2006

AznStanger3v said:
i *think* its something like:

Bore x Bore x Stroke x .7582(?) x 8

so find the mystery number and youll get the 363. im not in my math mode right now, but it shouldnt take you more than a couple minutes

That's racers math (I think it's .78XX though. The true value is pi/4).

Justin's conventional math: Pi(R^2) * H * number of cylinders, gets the same thing.

The Green GT · Oct 29, 2006

BIGGER IS ALWAYS BETTER

Why a 306?

Bens95cobra8594

New Member

95Vert

New Member

Jackie Chan

I didn't read this.

Therian

The Highlander

AznStanger3v

Active Member

HISSIN50

"How long does it take to get help in here?

Guero

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Bens95cobra8594

New Member

Pokageek

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SeventyMach1

Keep it lubed .... keep it straight .... and keep

AznStanger3v

Active Member

SeventyMach1

Keep it lubed .... keep it straight .... and keep

HISSIN50

"How long does it take to get help in here?

The Green GT

No 13 year olds are safe around me.

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