331 vs 347 Stroker

[BoureeOne]

I have decided to stroke my 302. I would love to get feedback from those who have done this. What are the pros and cons of going 331 or 347? What kit did you get, what cam, intake, carb, trans, etc. How do you like the drivability? My plans are a weekend driver. No offroad. I have an NV3550. I read a story where a very reputable builder out in Cali built a strong reliable 331 stroker using the stock heads. Has anyone done this? I have the edelbrock performer intake and edelbrock 500 carb, are these an ok choice for a stroker?

Thanks for your feedback.

Scott

 

[joshnjulie1]

In my opinion, I would just switch to a 351W. Money wise may not be that big of a difference. You stroke your 302 to a 331 and you have one shot left if something goes wrong. Stroke it to a 347 and soemthing goes wrong, you'll wish you swapped it out with a 351. you can get more torque and HP out of a virgin 351W than you can that 302. I have always found going up in engine size is the safer more reliable route. Just my opinion though. Good luck with whatever you decide.

 

[BoureeOne]

I knew this would happen, but did not think it would be the first comment. And thank you for your comment and opinion. But, I am going to stroke my 302. I am not debating between stroking and 351.

Thanks
Scott

 

[Broncobowsher]

I would use a 289 crank.
Or get a 351W.


And I have experience building and running a 330" stroker.

There is a stroker thread where feedback about people running strokers put all the info in one place. http://classicbroncos.com/forums/showthread.php?t=196925. So your answer should be there, if it exists.

 

[BoureeOne]

I have subscribed to that thread and read it. Lots of good info there. Right now I am looking for more opinions and experiences, then I will crunch some numbers and specs. I have so much stuff for the 302 already. Carb, intake, Mallory Unilite, Headers, etc. I also have a really good machine shop close by that is run by a guy that is a dream to work with. He is all about you coming and watching and learning. I am leaning towards the 331 for reliability issues. But I would still like to here the opinions of guys on here. I also think I have a slight positive in the fact that I have a Mexican 302.

Thanks
Scott

 

[red hot71]

I think horespower and RPMs is the big question to ask.

If you're looking at about 5000RPM and 300-330HP then the 347 would be the way to go because of the torque. But if 6000+RPM and 350-400HP is what you're thinking then the 331 makes sence because of the so called piston pin problem that some think is a issue with the 347. But a 331 will work just as good in lower RPM appl.

I think the so called oil consumpsion problem in the 347 comes from poor machine work, questionable parts, assembley and high RPMs. It sounds like you're on the right tract by getting a good machine shop to to do work.

 

[bigcountry]

i would go 347 for the torque at lower rpm. I am building a 348 which is just a 40 over piston. It will have trick flow 170 heads, edelbrock air gap intake, and an eagle stroker kit with SRP forged pistons at around 10:1 compression. It should be in the 350 - 400 hp range.

 

[BoureeOne]

Do you guys think either or both of these need to be changed?

Performer Intake

Edelbrock 500CFM Carb


I think I could get by with them if I go 331

Thoughts?????

 

[bad 68]

carb and headers will work for ether a 302 or 351 block. Ok I'll stop. Ok, your going to have to budget in a gear swap to make the high revving 302 pull like a 351. Now I'll stop.
Ok, you realize one reason the 351 makes good torque in the midrange is due to it's taller deck hight and the straiter push of the long connecting rod on the crankshaft instead of the sideways push of a short rod on a stroker crank 331?

 

[1966bronco392]

Both engines like and need rpm to really shine.If your stuck with the 302 just build a 306 you will be just as happy,and your drivability won't suffer.

 

[73azbronco]

If your choice is 327/331 or 347, always go bigger.

Per the Eagle specialty products website, the rod length is only an issue at high rpm, as in 10,000rpm.

As far as driveablility between 306 and 347, there should be a marked improvemenet for a bronco as long as you get the right cam and induction system wired. Screw those up and you might as well keep the smaller motor. Even at low rpm a stroker makes more power than stock, think about it, stroke is stroke, cubic inches is cubic inches, more is always better.

Look, I like 351's, stroked 351s even better. But the reality, you can do some amazing things with a properly prepped 302 stroked to 347 and not add 150lbs of metal by dropping in a 351.

150lbs is no big deal you say? I'll use aluminum heads you say? Fine, so will I in my stroked 302 saving even more weight, and the reality is, who wants a 12 year old kid sitting on the hood while you try to climb?

So, lets keep this a discussion on topic of helping the guy stroke a 302.

 

[blubuckaroo]

This makes no sense to me. I've seen 347s built for torque and it work really well. Maybe the bad examples are using the wrong cam?

 

[73azbronco]

Exactly! You have to have all parts work together, putting the non stroker cam you had in a stroker is asking for well, not a stroker.

The 347 oiling issues have been solved.

 

[Outlaw Bronco]

To start i have ALWAYS been a 351w kinda guy. I have built many 500hp 30over windsor's, 800hp 408 on spray, 2600hp twin turbocharged 427 but this time I built a 347 to put in my 71 EB.

The bottom end is just cheap eagle cast crank, I-beam rods, and SRP forged pistons. I am running Brodix ST5.0 heads, Performer RPM intake, Holley 580cfm street advenger carb and a Extreme energy cam shaft. I can get the spec's but it's 1800-5800 rpm range .509 lift.

The engine has a little over 4k on it now and doesn't use a drop of oil. I have plenty of power down low even though i still have the 3 speed 3.55 gears and 30" tall tire's. I crusie at 2000-2500 rpm in my area and get 16mpg. Not the mpg i had holped for but i am sure a smaller cam would help?

The ONLY regreat i have with this engine is i stayed to the high side of my compression ratio of 10.2:1 and need to run 93 octane now, not a huge deal but 87 it just cheaper LOL. I know guys run higher CR on 87 but my cam just will not lend it's self to that.

If i can help ya any at all just PM me. Brandon.

 

[73azbronco]

Brandon, what cam or compression ratio would you run with a 347 to get it to run pump 87 octane?

 

[Outlaw Bronco]

Brandon, what cam or compression ratio would you run with a 347 to get it to run pump 87 octane?

I pesonaly would stay around 8.5-9.0:1 cr. I know this sounds very low but the gas we have now a days is very different from even just 5 years ago.

For the cam, the lobe separtation (LS) has a great effect on things as well. Most RV or mild street cams will be in the 110-112 LS range and you will need the lower CR to make things happy. Think of the LS as trapping air down at lower RPM's. 106 has lot's of over-lap and bleeds off cylinder psi at lower RPM's but comes alive at higher. A 116 is oposite, little over-lap, lot's of cyl psi and a very flat power band. Normally a 114-116 LS is used in "power adder" engines, you most likely will not see these numbers in a street cam for various reasons.

You guys will probabely think i am telling one here, but the 351w in my mustang is 11:1cr and will run off of 93 octane. The trick here is the cam is a 106 LS, very race'ie for a street car and has no bottom end TQ at all.

 

[Outlaw Bronco]

Here are the spec's on my cam! PN#31-242-3 Comp Cam. Fairly rough idle but it crusie's great and lot's of power from 2500 up. But on the flip side it's a little to large to have in a 4X4 imo for a daily driver.

.509 .512 lift

224 231 Duration

110 LS.

 

[BoureeOne]

Spoke with my engine guy today. I think I am going with the 347. I also discussed something with him that I had read about. I read a long article about a big shop out in Cali that built a stroker motor using the stock heads that had some work done to them. My engine guy said he can certainly do the same thing. So this will be my goal. I will share more as I move along. Thanks for all the input.

Scott

 

[73azbronco]

might want to reconsider stock iron heads, you can do so much with aluminum that you can't with iron, one big thing is comp ratio, with aluminum, that pulls the heat out of the charge and essentially allows you to run a higher CR for given engine. Saves you 50-75lbs is another. Saves you rework costs as Edelbrock or AFR's will cost you what the machine shop will charge you.

 

[KyleQ]

You would be better off putting aluminum heads on a 302 rather than stroking a 302 and leaving the factory junk, I mean heads, on there...

I'm a 351W guy too, displacement is where it is at, people stroke 302's because they rev super fast so they can make power up top. It doesn't mean you can build it for torque, but stroking a 302 is a RPM/speed sort of deal. Don't EVEN go with the weight bullshit, this is an EB - 150lbs up front isn't going to change anything.

Off the soap box though, roller 302 with some 165 series heads and a nice roller camshaft will get what you are after. Whatever you do, don't stroke your motor and leave the factory heads. The old Ford heads are pretty much junk from the factory, try and push them even harder and you are wasting your time. If anything find a nice set of E7's or GT40's for <$300 and put them on your stroker, that will allow you to eek a little more power out of it.