306 Questions....Benefits?

[94GTLaserRC]

Dont say something like "it's bigger", etc, but what REALLY is the difference/benefits of getting a 306. Is it stronger, more reliable?

How much power difference is there vs the 302 (assuming the bolt ons are identical)?

Why go this route vs 331 or 347 stroker?

Basically, just why would you get one?

Thanks
RC

 

[MadHandle8169]

I'm very interested in these questions, too.

 

[BlownFiveLiter]

The only benefits I can think of off hand are that since it's basically a standard 302 @ .30 over, so there's tons of parts available as a standard rebuild. Also, it's supposed to unshroud the valves, so the engine runs more efficiently since it's getting a better charge from the intake, but I don't have any personal experience to back that up, just read it somewhere once. Not sure too much on the benefit of going the 306 route vs a 331 or 347, other than you don't have to worry about rod ratios and all that "fun" stuff!

Matt

 

[WhiteDevil]

THe only thing i can really think of is its cheaper. I mean its a 302 bored .30 over may make some more torque, and since most high milage 302 will need to get bored over anyway its a good route to go. If my motor went now i dont have the money for a stroker it i would probably go with a 306 rebuild kit.

 

[Grn92LX]

The main benefit besides freshening up the engine is so you can run a GOOD piston so you can fit a killer camshaft and not have clearence problems. Its also cheaper for people not looking to go crazy with a new engine, but still needing a rebuild. You can reuse the stock crank/rods and use a good piston. You can also increase or decrese your compression depending on piston.

 

[BlackVert]

since the stroke is shorter than a 331 or a 347, you have less rotational inertia, which means that it should be able to rev faster. if you combine that with lightweight crank, rods and pistons, you should be able to rev higher too (with the right heads and cam) and also see better throttle response. now throw some boost into the mix and you have a car that can really snap your head back.

that is where i hope to go eventually ...

 

[4Jenna]

Fresh motor (pick c/r and bearings)..only gain

 

[94MustangGT5.0]

The only reason I can see to have your block bored .030 over to a 306 is to freshen a tired block. I don't think anyone bores there perfectly good block just to pick up an additional 4 cubic inches, that isn't exactly economical. The reason people don't go to the 331 or 347 or any other stroked combination is because it requirs a new crank shaft, connecting rods, etc., which means MONEY! A good crank such as Eagle for a 331 or 347 stroker is $1,000 or more. Also, 306 just means .030 over which is pretty basic when doing a rebuild, but you can go .040 over and be at a different cubic inch (not sure, I would assume around 308) which also means you have more cubic inches to your stroker option, making it a 333 and 349 or something like that, don't quote me on those numbers. If you have the money, do the stroker upgrade. The only other set back is that they are notorious for oil leaks, but every setup is a little different and you may not experience this. Hope that helps.

 

[94GTLaserRC]

Sounds pretty straight forward to me. I guess if I wanted to keep the blower and not fork out the extra $$ for a 331, I could do the 306 with AFR heads and a Custom cam?

Just looking into some other options.
Thanks for the replies.
RC

 

[bayellowstang]

Sounds pretty straight forward to me. I guess if I wanted to keep the blower and not fork out the extra $$ for a 331, I could do the 306 with AFR heads and a Custom cam?

Just looking into some other options.
Thanks for the replies.
RC

I went with a 327 stroker. It was fresh block no overbore. I did it just because I wanted to run the AFR 185 heads and they are to big for a daily driven 302-306.

I have no oil leaks yet. It only has 7k miles on it though.

If you are gonna run a S/C and AFR's you might wanna get new rods crank and all that good stuff anyways. I don't know how long I would trust all those stock parts under my pretty afr's.

 

[Killercanary]

Rob, as was mentioned a lot comes down to cost because in addition to the rotating assembly (rods, crank, pistons) you will normally need a new balancer and flywheel because its normally easier to balance the rotating assembly to a 28oz imbalance over the stock 50. A balancer and flywheel add a good bit of $ to the rebuild cost.

Also, in a situation like mine a step up to a stroker would require larger heads, injectors, intake, cam, etc. I "could" put my stuff on a 331/347 but it'd be FAR from maximized and I've have a "so what" combo. What I mean is the times I run now are respectable for a 302, but if I went and added a 331/347 to my car and only ran a 11.9 at 114 it wouldn't be all that impressive. If I would ever go the stroker route it better trap a MINIMUM of 117-118mph in my car for me to even concider it, and that won't happen with what I have. You on the other hand have nothing more than an intake so if I was in your shoes I'd DEFINITELY go straight to a 331/347 if you are going to stay NA and get rid of the blower, and get the heads and cam needed for the cubes.

I'm in a delema like this right now as I have to rebuild my shortblock and I REALLY want to add cubes to it since it's going back to being 99.9% a street cruiser and the added cubes/torque would make for a car that is even more fun to drive on the street.

 

[BlueOvalStangGT]

If I were to build a 306 now, what does it take to make it a 342 later? Just a different crank?

 

[Killercanary]

If I were to build a 306 now, what does it take to make it a 342 later? Just a different crank?

Nope, everything needs replaced except the block. New pistons (the compression height is smaller due to the increased stroke), new rods (longer than stock), and a new crank (with more stroke than stock).

 

[WhiteDevil]

Also a 342 is a stroker crank and rods but the stock bore of a 302, if you bore it .30 over for a 306 then when u stroke it it will be a 347.

 

[YEAHLOH95]

i had a 306 in my mazda pickup it ran really good for all it was ,i will be adding cubes some day and more than likely it will have a longer stroke to go along with it.

 

[Joes95GT]

I'd go for the 347 over the 306 if you are starting over like you would be doing.

Since you don't have a set of aftermarket heads, you'd need to buy a pair anyway. It's not like you could re-use your E7's. That would be a waste.

You'd have to get your crank and rods checked to see if you could re-use them or if they would have to get turned. For the prices of cast cranks these days, it would probably work out to be somewhat comparable in price (maybe $200 more for a new crank).

You would have to buy new pistons either way. The rods would have to be checked. Yada, yada.

Plus, since you got the Escort, you can get a little more wild with the car now. More cubes = .

Joe

 

[lietuvis91]

I don't know about 347, the horror stories I read about it blowing head gaskets cuz the compression gets too hight and oil leaks makes me think a 331 is a better choice. Plus the 347 supposedly isn't very streetable for some reason. For all around stability and reliability 331 seems to be a better choice. That's what I'm going to go with one's my 302 is toast!

HEY YEAHLOH95:
are you making 455hp on the stock block & stock internals???

 

[bjl95mustang]

I don't know about 347, the horror stories I read about it blowing head gaskets cuz the compression gets too hight and oil leaks makes me think a 331 is a better choice. Plus the 347 supposedly isn't very streetable for some reason. For all around stability and reliability 331 seems to be a better choice. That's what I'm going to go with one's my 302 is toast!

HEY YEAHLOH95:
are you making 455hp on the stock block & stock internals???

Don't always go by what your hear. If someone got a too high Cr with a 347 then they didn't check it right when they were building it. The 347 oil problem was the oil ring on the piston or something like that but I think CHP fixed that. I haven't looked at the 331 to 347 too much but when I was looking at 351 strokers reliability it came down to which one was built better. If I got a 393, 408 or 418 the cost was the same so I opted for the 418.

 

[sociopath5.0]

The only other set back is that they are notorious for oil leaks, but every setup is a little different and you may not experience this. Hope that helps.

It really depends on the skirt design of the piston. If the piston pin bore does not intersect the ring groove, you should have no oil leaks, provided evrything else is in order. My Mahle pistons are engineered this way, many aftermarket pistons included in stroker kits do not.

 

[WhiteDevil]

I don't know about 347, the horror stories I read about it blowing head gaskets cuz the compression gets too hight and oil leaks makes me think a 331 is a better choice. Plus the 347 supposedly isn't very streetable for some reason. For all around stability and reliability 331 seems to be a better choice. That's what I'm going to go with one's my 302 is toast!

All those 347 things are just old myths. Those oiling problems were back in the day it was where the wrist pin intersected with the piston rings, that design flaw has long been fixed. And as for "streetablitiy" that has nothing to do with the C.I. of a shortblock block, it has to do with the H/C/I used and the tune that is on the car. Also the compression of the motor has nothing to do with the C.I. of the motor you can have a 347 with 8.5:1 compression if you wanted that. You could have a wild 302 combo that isnt streetable and a mild 347 combo that behaves like stock. There is really nothing better in a 331 over a 347 unless having 16 less C.I. is a good thing