331 or 347

[martfr2]

I need your advise on what engine to go with, I call CHP you guys where right those guys know their stuff. Now that I have the info don't know which engine to go with 331 or 347? Do you guys know of any major problems from these?? Its going into a 94 cobra with AFR185, TFS intake, Magnaflow exhaust. I also want to slap a blower on this thing, not sure if there is a huge difference these two setups.
Thanks for your help in advance,


-Shooter in So.Cal

 

[final5-0]

What did they say when you asked them

Grady

 

[Yobi1Kanobi]

the general census here it 331 with SC and 347 NA

 

[mojopony]

Some 347's had some oil control problems because the wrist pin bores actually intersected part of the oil control ring grooves in the pistons. I don't know if newer kits are better in this area, but that would be the only thing to deter me from opting for more cubes. Is the rod ratio better with a 331? I'm by no means an expert with windsor strokers.

 

[Yobi1Kanobi]

the oil consumption prob has been fixed for a while first off, the oil prob was cause by low friction oil control rings that where installed in the early kits, they use standard tension rings now so most all new kits from reputable companies dont burn oil. And the CHP pistons dont interject the oil ring just in case anyhow. I have Kieth Black Forged pistons in my kit,

 

[BlackVert]

my engine builder told me that the main concern is that the increased angle of the rods in a 347 causes the bores and rings to wear unevenly, which shortens the life of the engine. it seems to me though, that even if it cuts the life in half (from 100,000 miles to 50,000 miles), you still have more than a few years of fun with it before having to rebuild it again, depending of course on how much you drive it.

 

[Yobi1Kanobi]

my engine builder told me that the main concern is that the increased angle of the rods in a 347 causes the bores and rings to wear unevenly, which shortens the life of the engine. it seems to me though, that even if it cuts the life in half (from 100,000 miles to 50,000 miles), you still have more than a few years of fun with it before having to rebuild it again, depending of course on how much you drive it.

I dont think the Rod angles are that dramatic that would cause that much of a difference. But what do I know I say for the same money you might as well take the free cubes..

 

[5spd GT]

Increased piston speed is more the issue than rod ratio. Yes, the 347 has a slightly steeper rod ratio than a 331.

Proper machining (Piston-wall clearance), and using a good oil support ring with a dimple alleviates much of any extra oil blow-by issues.

Piston skirt design is a big deal for engine longevity and oil control. The 1.175" piston (5.315" rod 347 or 331), has a slightly longer skirt.

 

[BlownFiveLiter]

To add to what 5spd GT said, using the 5.315" rod with the 347, versus the 5.4" rod is what solves the oil consumption issue that they used to suffer. Using the 5.4" rod, the wrist pin intersects the oil ring and the piston skirt is shorter, so it can rock in the bore more.

 

[juiced_94gt]

I LOVE my CHP 331

 

[Black95GTS]

All I'm going to say is... if your builder makes an engine that has oil consumption problems on a 347, it won't matter what rod you use; that builder doesn't build very well.

Knowing that you are using the stock block, and supercharging, I'd go with the 331 here. But I don't think you could go wrong with either. It depends on your tune and how high you turn the boost up.

Adam

 

[Killercanary]

Although I don't like telling you to go elsewhere, you should do a search on 331 versu 347 on http://www.hardcore50.com I would NOT post a new thread on this subject though as its been beaten to death so many times you'll surely get flamed for it. All the information you need is out there to help with your decision. I'd almost ALWAYS go for the larger cubes. There are very few instances where I'd choose a 331 over a 347, but there are a few.

 

[BlownFiveLiter]

I'd choose a 331 if I wanted to rev to the sky. Otherwise, 347. Also, I'd go over to the Fox side to search on this topic, versus going over to hardcore. There's a ton of info over there without even having to leave the site. If you can't find the answer you're looking for there, then I'd check out hardcore.

 

[final5-0]

Well

I've been waiting for the original poster to tell us what CHP had to say

I agree
This subject has been hashed out over and over on many sites

I love this place cause of the peeps on it :Word:
but
Hardcore has peeps who make their living building and racing motors

Most of us here do our thing with Stangs as a hobby for enjoyment

In no way am I saying we don't have knowledgeable peeps here

I'm saying more have done it ... and ... done it over and over on Hardcore
sooooo
The exposure and experience is more vast with those peeps

Like Paul ... I'd say 347 in most applications
but
The 331 could be a fit in a few of them ... one might run across

Grady

 

[BlownFiveLiter]

Grady, are you forgetting about Rick 91GT? He's built several engines for people here on StangNet. I bet he's got some knowledge

 

[5spd GT]

The only thing to keep in mind about Hardcore, is they have very little care for a car that may seek a 100,000 miles.

Much of their engine life is based upon 'a season' or years (which does not mean mileage).

There are some good engine builders over there, but just keep in mind their hobby and living.

The fact of the matter is, you can go with a 347 and not have any worries about "extra" oil consumption.

After all, a 347 is a 347 for most intended purposes.

The solution:

A 1.175" compression height piston with matching 5.315" rod. You still get the 3.4" stroke, and you still get the wrist pin OUT of oil ring land. The difference in side loading on the thrust side is very very minute.

If staying N/A, I would go with a 3.4" stroke.

A stock block, stroked crank, and boost is not something I would suggest, whether 3.25" or 3.40" stroke. The block will likely go before the piston crown anyways.

High boost and high nitrous use typically should be seen to have as much ringland as possible within the given parameters of the engine.

Now, an aftermarket block, stroked crank, and boost is fine.

 

[94-302-vert]

For me. I will either go 331 or 306 because I put 14-19k miles on a year. (14k averge with a 19k high one year). For me longetivity is #1. If it is a toy and power is #1 then 347 all the way...

 

[VibrantRedGT]

the oil consumption prob has been fixed for a while first off, the oil prob was cause by low friction oil control rings that where installed in the early kits, they use standard tension rings now so most all new kits from reputable companies dont burn oil. And the CHP pistons dont interject the oil ring just in case anyhow. I have Kieth Black Forged pistons in my kit,

This is true. The 347 issue of several years ago has been fixed.

The CHP 347 is stout. Couldn't be happier.

 

[5spd GT]

It has been 'fixed', if you use proper parts and a reknowned engine builder/machinist.

Your typical engine builder may not have 'fixed' it yet...

 

[final5-0]

Grady, are you forgetting about Rick 91GT? He's built several engines for people here on StangNet. I bet he's got some knowledge

No

I was not forgetting or calling attention to ... ANYBODY

Yes there are a lot of racers who focus on the strip on Hardcore
just as David said

I do feel you see more of ... hear say ... as being
thought of ... as fact ... here and places such as
the Corral than over on Hardcore.

Again ... this place and the peeps here are great
sooooo
I was not trying to point out anything negative about our site

I was trying to say it kinda has a different focus ... if you will

Grady