331 0r 347
 

Well fellas, I need some help in my decision to upgade my 302. Does anyone have opinions on either of these builds ( 331 or 347) positives and negatives. Also what size carb would you reccomend and also are GT40 heads ok for the build..

Thanks for all of you help
Happy Easter

I went with a 342, new block, can't beat more inches

Why a 342?

a 342 is a stroked 302 standard bore

What your really talking here is the 3.25" stroke or 3.40" stroke. If you like to rev the motor out & the sound it makes @ upper RPM then go 3.25". If you want more low down punch go with 3.40". There are lots of other mech reasons too- like rod ratio, cyl wall pressure etc.

Me, I would go with the 3.25" it 'sounds' nicer and isnt quite so 'harsh' on longer trips.---

Here are the options that you have and what I feel is the best for each application. The 302 block has a fairly short cylinder which with the strokers pulls the piston out of the bottom of the cylinder causing more rock and wear. The 3.250 stroke is a better combination for longevity and street use. It does not pull the piston out of the cylinder as far at bottom dead center and it also has a longer piston with a better compression height and rod ratio. The 347 with the 3.400 stroke pulls the piston out more at bottom dead center and the rings and piston do not live as long as the shorter stroke package. If it is not going to get many miles over its life time and you are worried more about power they are fine but will need rebuilt sooner and may us a little more oil. This has nothing to do with the pin going into the oil rin because both the 331 and 347 have this do many SBC combinations.
We do a lot of the Dart Sportsman blocks with a 4.125 bore and a 3.250 stroke that also yeilds 347C.I. and this is the best way to go but the block is more money. These are just some of the things we have found out over the last 20 years of building these. You take what you have and try to build the best combination possible for the application. Good luck, Keith Craft

I've never worn out a street 331.

I've also never worn out a street 347.

The 347 will normally have more torque....but with that head you're probably looking somewhere around 330 to 350 H/P.

Personally, I'd take the 347 but everyone has their preference. I do sell 50 347 kits for every 331.

Whatever that means.......

I put a Ford Racing 347 stroker in my BDR Cobra. Best decision I ever made. Lots of torque and RPM's. Ford claims 450 HP and I believe it. Idle decent and with a 700 CFM Holley, no problems.

I did a 326-327 4.00 bore 3.25 stroke --very nice motor , and almost no oil consumption.

Beware of stoker pistons that intersect the oil ring with the wrist pin. --Steve

I had my 289 stroked to 331 resulting in 390 HP and 370 ft-lbs torque. Plenty for me.

The issue with pistons that have the oil control ring intersect the wrist pins hole is blown way out of proportion. The problem is engine assemblers putting together engines and not using proper techniques when installing oil control ring. A professional engine builder knows what to do, you must use a ring support under the oil control ring. This provides support to the oil control ring where the piston material is missing for the raised wrist pin. Also this support ring should be dimpled to ensure that the oil control ring doesn't rotate and the ends end up in the wrist pin area. I have had two motors that used the 3.40" stroke with no oil consumption issues. Just my opinion...Mac

From all the dyno test I have seen on the GT40 heads and the flow data, they are a poor choice for a stroker. The heads don't flow good enough for a 302 let alone a stroker. Look on Keith's web site at heads. For just a little more money you can buy much better heads.

If it is in the budget, the 4.125" bore block that Keith suggested would be a great engine.

Why would you beware of those?

Are you an engine builder?

Not being a smart ass...though I'm prone to it..........:3DSMILE:

I don't like perforated oil ring lands.
And I am an engine builder these days... :O

They are an added variable in the ring stack in terms of an extra piece, with it's dimensional variance and quirky installation tolerance/deformation stack up (due to a clamp load around the groove ID) in an area where other dimensions are measured in tenths. They are a necessary evil in certain builds - but I consider them as something to avoid if other options are possible.

In terms of performance the cubic inches will pretty much always win any street contest.
In terms of oil consumption a couple items are noteworthy. First is that everybody has a different tolerance for oil usage. One guy won't ever notice if he uses a quart every few thousand miles 'cuz he changes it every month during the summer. The next guy will get upset if he sees the stick down a half quart between annual changes. Just because you don't see blue smoke does not mean that you're not using oil...

I tend to think that teh 5.4 rod deal is a fashion statement with no benefit. A shorter rod would keep the oil ring clear and have no downside. Mark has made pistons and shorter rods with the market result being that darn near nobody cared. They all read magazines that extoll the virtues of a longer rod with no quantifiable benefit.

Mark,

No I am not but really tried to educate myself before buying my 2nd stroker. I had the first (347) torn down after a valve spring retainer broke and piston to valve contact. I took it to a local reputable builder, he actually built my 347 10 yrs earlier. He showed me how he set up the ring support to control oil. Mac

Thanks for all the great info, My next question , Can you really tell the diff erance between the two motors, and What type of heads would you use on a 331? I am looking for a good street motor.

You guys have been very helpful, and thanks for the great responses

Phil

Keith, do you guys do just the short block?

Thanks

Phil

There's a minor difference in H/P and a noticeable increase in torque (all else being equal).

In case Keith doesn't check in...not just short blocks. Keith can do complete engines to suit any application from pure street to Pro Stock. He's known for both his quality and his honesty.....and can do a nice dyno'd crate motor that you're certain to be happy with.