302, 331, 347, or 351... that is the question

Topic: 302, 331, 347, or 351... that is the question (Read 4922 times) previous topic - next topic

302, 331, 347, or 351... that is the question

Reply #15 – January 04, 2009, 09:09:22 AM

The choice between the 331/347 will vary depending on who you ask. You will hear, as some have posted, the oil ring issues with the 347. This is true when the initial 347 kits were available. This is not the case now. The costs for the 347 is the same for the 331. You just get MORE power with the larger displacement.

The ultimate decision is yours. Determine what your goal is for the car and go from there. Someone has already given a link to SBFTech. You should go there and read on the (non)issues of the two different engines. This is a no bullsh*t site that gives straightfoward answers to legitimate questions.

Good luck and keep us informed on what you decide!

302, 331, 347, or 351... that is the question

Reply #16 – January 04, 2009, 09:15:01 AM

Thank ya much

302, 331, 347, or 351... that is the question

Reply #17 – January 04, 2009, 11:33:26 PM

Quote from: rancheronut;249955

so every one knows that will cause your 347 to BURN OIL.

Mikey

that was an issue, not anymore. that is why any 347 purchased today does not really add up to 347 but a little less. Your only major disadvantage to any stroker kit is rod angle wearing down the center area of your cylinders due to the larger main to rod journal distance.
engineers have not figured out a work around on this one yet, ive often thought if this ever became in issue, a man could always sleeve his block,,problem solved. The "347" has more rod angle but generates more cubes. The 331 splits the difference between 302 and 347 making the best of both world but yet it still has an effect on your cylinder walls as far as rod angle is concerned. EIther way, I think the 347 is probably the best option but be rational on the build and dont &uck it up or you just ate a stroker kit.

Rod angle is a pretty interesting read and opens your eyes to the science of a single stroke. Chevy's 302 would out stroke a ford 302 well into the rpm's you could only dream about. Now go and find out why.

302, 331, 347, or 351... that is the question

Reply #18 – January 05, 2009, 11:54:33 PM

Quote

Rod angle is a pretty interesting read and opens your eyes to the science of a single stroke. Chevy's 302 would out stroke a ford 302 well into the rpm's you could only dream about. Now go and find out why.

im going to assume longer rods and taller block?

302, 331, 347, or 351... that is the question

Reply #19 – January 06, 2009, 01:14:32 AM

Quote from: shame302;250420

im going to assume longer rods and taller block?

no special block, same size stock chevy 302.

Rod angle wear is what happens when you install a stroker kit.

the main bearing center line ratio to the rod bearing center line is greater than stock.

when any given rod journal comes around from bottom dead center (lets call this 6 o'clock) and moves to the 9 o'clock point, the rod angle with respect to the piston is at its greatest obtuse measurement. The crank is still going to send the piston up but within that area spanning the middle of each bore, there is excessive friction on the wall. Most of this reason is due to the reduced height of the piston so with a shorter piston, and at max rod angle, the wear is going to happen and it can not be helped.

This is why the 331 splits the difference between both worlds. Just a little bit of rod angle and a little bit more cubes.

rod angle is like when you want to jump in your snow boots real fast but your in a hurry and slightly off target. Said boot bends and you twist your ankle:D

The illustration below is exagerated but you should get the point.

The advantages to stroking in my opinion out weigh stock strokes but my two favorites are increased dwell and a more rapid air / fuel suction.

The increased dwell on a stroker allows the piston to hover longer in the TDC or BDC position. On the combustion stroke, the piston hangs out longer on TDC while the spark plug lights up and fires your fuel. The piston being up in the TDC range longer is like a ticking time bomb because all that fuel is still igniting. Once that piston starts going down, it creates more power,, all this because of a longer dwell.

The increasted stroke also pulls in a higher velosity of fuel and air (making more air/fuel options possible now) which complements the increased dwell characteristic.

Its a give and take though,, matter of opinion.

I suppose the only way around getting rid of rod angle wear is to have a flexible connecting rod (lol)

302, 331, 347, or 351... that is the question

Reply #20 – January 06, 2009, 01:29:12 AM

I can see why the idiot was banned again. Already fighting with people and spending mucho $$ without having a plan to pay back those who were wronged. Dumbass.

BTW, there are slightly shorter rod (5.31 versus 5.4) kits from Probe that keep the piston pin a little lower and allow more room for the ring pack. A nice tight well built 347 can easily last 100k miles - which is likey longer than the attention span of the average enthusiast who can't keep things the same for very long.

OTOH, it really does come down to deck height and the correspondingly short piston required for such a short deck and long stroke. I think the biggest issue with the 347 is piston stability (rocking) causing ring sealing issues. Oil burning is the worst. Most 347's that don't burn oil from the git-go were built tight enough to keep the piston stable. A good tight non oil burner will likely last a long time before skirt/cylinder wear become a major issue.

302, 331, 347, or 351... that is the question

Reply #21 – January 06, 2009, 07:41:42 AM

I too can see why he was banned again.
Plus he was becoming a post w and filling the board with garbage.

302, 331, 347, or 351... that is the question

Reply #22 – January 06, 2009, 01:55:07 PM

Yeah, he's gone. This thread has become, like him, redundant.