goto a 331 or a 347

Pinebluffracer · Feb 7, 2006

I am in the process of rebuilding my '89 302 and wondered if a 331 stroker kit or a 347 stroker kit worked best. I would imagine the 347 makes more power, but are there any other concerns, extra things I will need for the project as opposed to keeping it a 302-306? I'm sure the kit comes with crank, rods, pistons, bearings and rings but are there any things to think about? I might need pistons anyways and the 302 crank might need turned as it stands.

Tonys96Cobra · Feb 7, 2006

You didnt say money was a problem, so go with the 347, it will make more power regardless of your other accessories, for the most part.

90mustangGT · Feb 7, 2006

We don't need another 331 vs. 347 thread. Either one will really help. What are your current mods such as what heads, intake, and exaust? I started out and was going to build a 306, even bought one but I will never use it. Then I decided to do a 347, even bought the rotating assembly, just to decide since I was this far, to go ahead and break the bank and do even more cubes.

Cubes opens doors for larger heads, cam's and intakes, which leads to more power, which also leads to more cost. The cost of a stroker kit will be comparable to having your stock crank turned and everythign prepped, and then new pistons, a stroker will cost about the same. The only thing is that with a stroker, you'll need a 28oz inbalance balancer and flywheel/flexplate.

Jack's95gt · Feb 7, 2006

I did a 342 with new standard bore SVO block. That's the same as a 347 with a 30 over bore. You have to notch the bottom of the cylinders for the connecting rod clearances with the 347. That no big deal at all. Just measure and gring away with a die grinder. I also had my crankshaft balanced for a 50 oz imbalance. It runs just fine with it. They really got to remove plenty of metal from the counter balance weights to get to the 50 oz. The 11 extra cubes is good for some extra torque.

304billet · Feb 7, 2006

I would just rebuild the 306, add on SRP, Ross flat top 9:1 pistons, stock crank and rods, AFR 185 heads, Comp cam XE282HR w/ a 114LC and a RPM ll or Systemax ll intake port matched. Then throw on a S-trim blower and 12 lbs of boost and hit close to 500rwhp, the max of a stock 302 roller block. Way more fun and more power than either a 331/347. I have been there and done that with the 347. I wish I would have just did what I suggested to u with the 306.

There r NA 306's w/ 11:1 comp and the above hitting 385rwhp.

Pinebluffracer · Feb 7, 2006

Heads: Trick Flow, roller 1.6 rockers, full kit
Exhaust: stock manifold, new H pipe, flowmaster cback
intake: GT40

Pinebluffracer · Feb 7, 2006

Can the tranny handle all the added power a 347 can deliver? I have no Idea what tranny I have. It is a '89 LX.

sunil6784 · Feb 7, 2006

auto or manual ?

Pinebluffracer · Feb 7, 2006

It is a manual 5-speed..

sunil6784 · Feb 7, 2006

All depends on how gentle you are with it...your combo isn't TOO radical, but be prepared that your tranny might go out.

Also, you might want to go with a not so grabby clutch. I've heard the SPEC clutches do a number on your driveline.

1991vert · Feb 7, 2006

i just bought my 347 stroker kit. forged "0" balanced eagle crank, forged dished probe pistons, and forged connecting rods.

go big or go home going in a dart block with a paxton novi2000 blower, custom cam, and AFR185's.

i say go for the extra cubes or u will prolly regret it down the road

86mustang5.oh · Feb 7, 2006

not tryin to steal anything but when you do a 347 dont they eat up more oil from the rings??????? thats what i heard cuz of the wrist pin.

1991vert · Feb 7, 2006

internet myth. oiling problems, for the most part have been solved. if ur machine shop does a good job (or the installer) installing it, you shouldn't have a problem.

sunil6784 · Feb 7, 2006

I dont htink its a myth. I talked to a lot of of engine builders and they all said the same thing. More wear on the cylinder walls = oil getting burnt up. Probably won't happen right away but over time.

Pinebluffracer · Feb 7, 2006

OH OK... something i didn't really ocnsider.. I did pick up a Street/strip center force clutch.
I never thought of it until earlier today, but the tranny could be a weak link here. ouch...

... What about the Puter?? and injectors?
I really want to spend conservatively.

5spd GT · Feb 7, 2006

It isn't a major concern or anything but the steeper rod ratio of the 347 compared to the 331 does cause more wear. It shows up more so over several, several thousand miles though.

331 if you plan on boost later (but I would upgrade the block anyways).

90mustangGT · Feb 8, 2006

... and a 331 probally causes more wear than a 306. I say because it's the same price, and you are basically getting 16 free cubes, why not go 347. I am sure some engine builder did a 347 and did a crappy job and the engine drank oil, when the customer asked why he probally told them about the wrist pin intersection and that is probally how the myth started. It seems that most high performance engines do consume a little oil. I don't see what the big deal is.

Rick 91GT · Feb 8, 2006

The 347 burning more oil is a myth. Does the 347 wear the cylinders more? A little there is more side loading but by the time it happens you'll need a new motor anyways. You can put 100,000 miles on a stroker and not see the wear. If your worried about the pin ring intersection then use a 5.315" rod and a 1.175" piston (same as a 327/331).

THEY WILL NOT BURN OR CONSUME MORE OIL IF PROPERLY ASSEMBLED AND MACHINED.

Straight from a builder....

David your parts will be on your door step anyday....

5spd GT · Feb 8, 2006

Rick 91GT said:
David your parts will be on your door step anyday....

Excellent

nmcgrawj · Feb 8, 2006

You'd be surprised how many "engine builders" who have all the equipment to build a motor and machine the block, who still cant bore a straight cylinder or file a ring correctly. The myths come from guys who cant do it right. Rick put up the facts. Any motor that isnt built right will burn oil and stop running very quickly. The bigger the stroke, the less room you have to fawk it up.

And David, im dying to know....did u decide on a stroker or how u're gonna rebuild your motor?

goto a 331 or a 347

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