306 or 331??

[1fastsn95]

ok I spun a rod bearing in my 87. Sooooo, a rebuild is in order. Obviously I want to have the block machined and bored 30 over. From summit, a 331 kit is only about 300-400 more bucks than a 306 kit. No replacement for displacement right?? But Im still gonna run my stock heads and Cobra intake for now. Is my factory Speed Density gonna cooperate with me on this? Wha other issues might I run across? or should I just go with the 306? Thanks guys!!

 

[1fastsn95]

one more thing...will I have to notch the block to clear the rods for a 331 like you do for a 347??

 

[68keyblr]

I'm in a very similar position. I'm building a 331 with P heads and cobra intake. I currently have a Speed Density computer and a stock throttle body.

I paid $1,500 for a 331 short block with forged rods & pistons, ARP rod bolts, etc.

I went 331 because I wanted to make more power with a less radical cam and get decent gas mileage for my daily driver.

I bought a short block because I wanted to take my time to machine my old block and buld up a wicked supercharged EFI for my '68.

I believe you do have to notch the block for a 331 as well.

Good luck

 

[Grn92LX]

347

 

[slappy9090]

347

 

[jammer84_03]

i would go 331.... 347 are great except for the ring land. no replacement for displacement!!!!!

 

[Grn92LX]

i would go 331.... 347 are great except for the ring land. no replacement for displacement!!!!!

huh? lol

 

[jammer84_03]

i threw the 347 in the middle...but his original q of the 306 or 331.... i was saying no replacemnt for displacement to that...

as for the 347 i personally wont do one becuase of the ringing issues with the wrist pin. personally when i get the new boss block, im just going to get the stroker crank and bore the crap out of the block to get the desired 347. will last alot longer without the typical issues associated with the 347. especially since my car is a daily driver (at least 100 on it everyday) and i would wear out the bore extremely quickly on the 347

 

[Grn92LX]

You're a "tad bit" incorrect. But I won't get into it

 

[ninety15.0]

Oil consumption problems due to the aforementioned "ring placement" is no longer an issue with 347's.

 

[86nu]

spend the money on a 351, get a junk yard block, gotta machien it anyway you go, can use the same heads, get a lower manifold and an oil pan and headers and boom, a nice upgrade that will lend itself to more mods later on down the road

I personally dont know why people keep dickin around with 5.0's when they pop, when for just a little bit of money can drop in a 351

 

[5spd GT]

If you go 347, get the 3.4" with a 5.315" rod. The 5.4" rod has the oil control ring intersect with the wrist pin boss. It will not go as long as a 5.315" rod combo.

Want some real info, instead of bias, on 331 vs. 347 strokers. Check out these links:

Check out the piston comparison they show in the first link, 7th picture down That is why you do not want to go with a 5.4" rod and a 3.4" stroke if you want daily driver longevity.

A 331 allows you to run both the 5.4" rod and 5.315" rod, so you can avoid the 'intersection.'

http://www.mustangandfords.com/techarticles/5197_331ci_stroker_engine/

http://www.fordmuscle.com/archives/2003/09/stroker/

http://www.strokerengine.com/RodStroke.html

Remember, getting the stroker will also need you to go with a new balancer/flywheel, unless you want to 'pay' for extra balancing.

 

[Grn92LX]

The 5.4" rod 347 stuff is fine. If you want real info from people who do this for a living, try www.hardcore50.com or www.*******.com Or if you get lucky, maybe Rick 91GT on here will respond. He built my stroker and knows his stuff. I personally run the 5.315" rod combo but much prefer the 5.4" rod. The 5.4" ultralight rod I wanted was on a long backorder so he could not get it for me quickly so he called me and asked if I minded switching to the 5.315". I didn't want to, but didn't want to wait extra longer.

Another builder I contacted, before i knew Rick built engines, had a 363" 5.4" rod stroker with over 185k miles no issues.

Try and listen to those in the game with first hand ford stroker experience rather than those who talk about it and post internet links.

Edit, sbf(no space)tech dot com is the site, dont know why stangnet wont let it work?

 

[2000xp8]

another vote for the 347.
No point in doing a 306, 331, or 351.

 

[5spd GT]

I have talked to more than a few very well known engine builders, that build NHRA engines.

The 5.4" rod provides a very slight dwelling time at BDC and TDC, and is typically reserved for track or strip/street cars. If you want to start having blow-by before the 5.315" rod runners, get the 5.4" rod

Then again, you can always go with the 331 and have 100% piece of mind from all of this hub-bub

But back to the original question, if you can afford the balancer/flywheel, go 331

 

[5spd GT]

another vote for the 347.
No point in doing a 306, 331, or 351.

If your on a budget, is there something wrong with a 306?

If your going for HIGH boost, what is wrong with the 331?

If you are planning on stroking the 351 later, what is wrong with a 351?

 

[2000xp8]

If your on a budget, is there something wrong with a 306?

If your going for HIGH boost, what is wrong with the 331?

If you are planning on stroking the 351 later, what is wrong with a 351?

Me personally, i'd rather just spend the money on a drop in JY engine with maf than put a dime into a 306 that's going to get stock parts back on it.
$500, and no real labor to put it in.

331 costs almost the same as a 347

351 is heavy and will make little to no more power than a 347, and you'll need 351 swap parts.

 

[5spd GT]

Me personally, i'd rather just spend the money on a drop in JY engine with maf than put a dime into a 306 that's going to get stock parts back on it.
$500, and no real labor to put it in.

331 costs almost the same as a 347

351 is heavy and will make little to no more power than a 347, and you'll need 351 swap parts.

Atleast you have good reasons for your choice and not 'bias'

I personally did a 306, because I was on a budget and at the time was looking for max longevity out of it. Now I could care less, I have another stang to drive

 

[86nu]

351 is heavy and will make little to no more power than a 347, and you'll need 351 swap parts.

80 lbs, all you need are headers, oil pan, lower intake and a dizzy.

use stock 5.0 mounts, convertables prefered, but stocks work.

If you are building a motor then half of these parts should be on the list anyways.

Look at where the power occurs, and the curves, peak numbes may be similar, but under the curve is where the moneyshot is

 

[2000xp8]

Atleast you have good reasons for your choice and not 'bias'

I personally did a 306, because I was on a budget and at the time was looking for max longevity out of it. Now I could care less, I have another stang to drive

I could understand the 306 for a car that's getting h/c/i, but paying for all new gaskets and seals, just to put stock parts back on, just doesn't make sense to me.

I realize not everyone has h/c/i money lying around, that's why i say in this case, get a complete maf engine from the JY, comp and all.

Head bolts, hg's, and the rest of the parts are going to add up quicky.

86nu, i've seen a bunch of 347 combos run 10.50-11.0 NA, in a street car, a 351 isn't going to do much better, if any.