306 vs. 302

[sodaking663rd]

I'm not a mechanic and correct me if I'm wrong about any of this but please enlighten me why a 306 stroker engine is that much more powerful than a 302. I understand that 306's probably have better components since it is built for power. Thanks!

 

[grey5.0beast]

A 306 is just a bored out 302 by .030, making little to no power over a 302. The reason for doing this is to clean up the cylinder walls. Take a 302 with the same combo as a 306 and they would make very little power differneces.

 

[srothfuss]

yup, greybeard said it just right... There is no noticable power increase between 302 and 306 cubic inches [using the same top assembly]

 

[sodaking663rd]

interesting! thanks for the info.

 

[Tonys96Cobra]

Well, the main difference is that one is 4 bigger than the other one.

 

[poneypower89]

the only reason you have the impression that 306s make more power is for this reason:

Generally the only reason someone has a 306 is because the rebuilt their engine. Now, usually anyone who can rebuild an engine is an enthusiates... and when they DO rebuild the rebuild with better parts.. IE better heads, cam intake.. and therefore... the end result is more power

Generally... the proportion of stock setups in 302s is much much greater than the proportion of stock setups in 306s.


But, if EVERYTHING is same except one is a 302 and one is a 306.. the difference is minute and not worth mentioning.





306 is NOT a stroke.. the stroke is still stock.. its just an overbore in the cylinder wall. 327, 331, 347 <--- these are stroker sizes and DO make more power in general.

 

[BlownFiveLiter]

The 306 may make slightly more power than the 302, but the difference will be negligible. Some people say it makes more power because the larger bore unshrouds the valves.

 

[8950HO]

Those extra 4 cubic inches of displacement is all it takes to pin you in your seat under hard acceleration .

 

[Coupe5oh]

306 is NOT a stroke.. the stroke is still stock.. its just an overbore in the cylinder wall. 327, 331, 347 <--- these are stroker sizes and DO make more power in general.

Very true.

And you forgot the 342
which is a standard bore 302, but with a larger stroke.... sodaking fyi..
Late

 

[Foxfan88]

i hate when people think a 306 is something to brag about.

I have a friend who seems to think there is a noticable difference from a 302 to a 306, its 4 CI, hardly nothing at all...

 

[FastDriver]

Unshrouding the valves is worth like 50 hp, man.

BTW the 327 and the 331 have the same stroke. The 342 and the 347 have the same stroke. With an aftermarket siamese bore block, you can run more bore and can make some other interesting numbers like a 347 with the same stroke as a 331 etc...

Check out the July hotrod for every spec you'd need to make an 816 hp 374 c.i. SBF. It's a 302 block with a 4.125" bore and a 3.5" stroke. Fun stuff.

Chris

 

[grey5.0beast]

I read that in one of the old mm and ffs. But I think the biggest you can go on a stock block is somewhere in th360 c.i. range, much past that and the cylinder walls get too thin.

 

[85_SS_302_Coupe]

You guys are missing a very important aspect that seperates the two, and why your typcial 306 WILL make more power than a 302.....they usually have aftermarket pistons, which usually have more compression and are lighter. Granted, this isn't going to be huge, but it's enough to notice it. Compression alone can boost power enough to feel it over stock.

 

[Foxfan88]

yeah but take 2 engines that are exactly the same... and the 4ci wont make a difference.

say if u rebuilt and engine and just got it bored .030 over and got a cheap flat top piston like stock but in a .030 oversize, that being the only change, i doubt you could feel a difference...