School me on 331's and 347's

[Freakingstang]

I'm building a new motor for the 89.  I want something stout, that will live on the street and track.  It may end up Blown before it is all said and done.

It will be a forged bottom end.  It will be between 9:1 and 10:1

This will be an injected motor with Stage 3 Roush 200 heads.  intake is undecided. 
Drivetrain will be a t-5 (more than likely a G-force) and 4.11's with 31 splines out back.  It has to live to 7200 rpm.

Top secret grind cam...hehehehehe

Now  I know that 347's aren't street friendly, as the piston pin height is either too close, or is in the oil ring landings.  I'm straying away from the 347 for longevity and not so much oil comsumption.

Is a 327 the same 3.25 stroke with a 5.315 rod and a STD  bore?  And a 331 is the same with a .030 over bore? please correct me if I am wrong.

Should I stick with the .912 pin or the bigger 9.27 pin? what are the advantages/disadvantages?

who makes the better kits out there.  I'm seeing some of the kits from TMD for 699.00 and ranging up to 1499.99?  I know you get what you pay for...

Has anyone heard of Mahle Pistons?  How about the D.S.S. pistons?


Any thoughts/comments are aprreciated.  Steve, if you're out there...What are you going to be running?

[speedfreak87]

I'd say, since you're going to be driving it on the street... I'd go with the 331 for better reliability...  that's all the input I can give ya.

[quake101]

From what I hear the 347 burns oil and isn't as reliable as a 331.

[Aussie XAXB]

The reliability issue with the 347 stems from the radical rod ratio putting a lot of sideload on the piston in the bore, and with a stubby piston that effect is amplified.

Yup, 327 is standard bore, 331 is with .030 over, which I would recommend just so that you know your cylinders are perfect.

My engine is not going to be living in the extremes that your's will so mine is going to be somewhat different and lighter construction. That being said......

The crank is an Eagle nodgular iron (cast steel) crank. The journals on it are smallblock chevy size, 2.100" instead of smallblock Ford 2.123". I am told that the rod journals will also be wider than the typical Ford rods though I have not verified that. I am using SCAT 5.400" I-beam rods since I don't plan on supercharging. If you are going to supercharge you may want to consider H-beams.

The pistons are KB 725 fordged aluminum pistons. I went with forged because there is a disclaimer on the KB site that says not to use a torque cam with compression over 9:1. I AM using a torque cam and shooting for 10:1 compression, so I didn't want any problems.  The piston is actually lighter than their hypereutectic ones but the pin is heavier.

The pistons I got do have the oil ring land intersected by the pin bore. KB includes a ring with their pistons to place in the bottom of the land so that the oil rings don't have to bridge that gap. This way there is support for them across the piston pin bores. I also have Speed-Pro plasma molly rings.

As for your question about the difference in pin size, my opinion as a Toolmaker is that .015" on the diameter is not going to make a difference. I would not let those diameters be a concern or consideration in choosing pistons, unless you know you are going to be supercharging it and you find pins with a much more significant difference in size. Now if you want to go with the .015" smaller pin to reduce weight, that may be a consideration. But for strength on a non-blown engine I would not worry.

I have not heard anything about those pistons, but I have heard of magazines doing this build-up with Probe Industries pistons. Also the oil ring groove is not cut into by the pin bore with these pistons.

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



Here's a couple links to kits and prices.

http://www.flatlanderracing.com/strokerford-302331.html

http://www.rpmmachine.com/ford-302-331-stroker.shtml

http://www.speedomotive.com/FORD%20STROKER%20CRANK%20KITS.htm


SCAT and Eagle seem to be very popular with these kits. Of course you can get any of several different cranks materialwise as well. I am very happy with my eagle crank. The machining on it is excellent. The only issue I have right now is I only have .005" endplay and I could use a minimum of .010". I'll probably have to do something with the bearing to remedy that. The journals are polished beautifully though.


Let me know if I can answer anymore questions.

Steve

[TireSmoke]

i dont think that 347's have nearly as many issues these days as you would imagine.

Honestly...if you are looking to go with a nice all forged bottom end I dont see any reason why you wouldnt want a 351 based block

Well...one thing to keep in mind...strokers are not real rpm friendly so its advantageous to go with the shorter stroke of a 351...and get more cubes.  Hell...if you really want to spin the sucker destroke the 351 and throw on some monster heads/intake

[BetterDays]

Honestly...if you are looking to go with a nice all forged bottom end I dont see any reason why you wouldnt want a 351 based block

Well...one thing to keep in mind...strokers are not real rpm friendly so its advantageous to go with the shorter stroke of a 351...and get more cubes.  Hell...if you really want to spin the sucker destroke the 351 and throw on some monster heads/intake

Yes....  393 is nice...  408...  427... 440....

And thinking about 357 or maybe destroking for more RPM...  however, what about the block...  remember hearing something about stock block not liking HIGH rpm runs////

[TireSmoke]

ya...a nice block with thick webbing certianly will solve the RPM problem...well at least for the bottom end.

Another issue with running lots of rpm is the fact that you need to change spring real often.  Driving around at 7200 rpm on the street and changing your springs all the time will get real old real soon

[Jim B]

the 347 kits had a bad rap. their alot better now.
www.propowerparts.com from what ive seen are good so is dds.com thay make their own pistons i believe good kits
alot of people run their kits check them out and dont forget you can make alot of power out of the little 306
as far as rpm 7200 is a little much for reliablebility   
just my .02 worth

[90LX]

The only issue I have right now is I only have .005" endplay and I could use a minimum of .010". I'll probably have to do something with the bearing to remedy that. The journals are polished beautifully though.

That seems to be a common occurance with Eagle cranks.  My engine builder has had to sand the thrust bearings on approx 12 engines with Eagle cranks thus far, Chevy and Ford.  600 grit on a marble surface lubed with WD-40 works good.

[Freakingstang]

This is the kind of information I was hoping to hear.  Steve Thanks.  I'm sure I'll be keeping in touch with you throughout the build.

Why did you chose a 5.40 rod versus the more rod ratio friendly 5.315?

[Aussie XAXB]

I contacted Eagle about the endplay issue. The spec I was referring to, .010", is the minimum spec on a stock 1968 302. The specs are .010" - .020". HOWEVER, when I talked with the tech at Eagle he said the endplay spec on their crank is .003" - .006" . So with mine being .005" it is perfect enough.  So no issues with Eagle there.

The reason for the longer rod is leverage. You know the famous quote "Give me a lever and a place to put it and I can move the Earth". And with the 3.25 stroke the ratio is still not too radical.  Enough that I am satisfied that I will not be having any issues with it. Of course time will tell if I am right or wrong.

Theorietically in two identical engines if one has a longer rod the advantage will go to that engine for having more leverage to act on the crank.

Steve

[Aussie XAXB]

On an interesting note about rod ratios......

My engine has a ratio of 1.66 . The venerable 289, known for being a dependable screamer, has a ratio of 1.79 .

So, as Dave Williams said, ratio is not as important as it would seem. (Paraphrased)


Steve

[tmoss]

Most good builders have the 347 issues addressed and you can spin them to 7,500 rpm no problem.

Aussie - you look like the Road Warrior in your sig photo.

[speedfreak87]

Aussie - you look like the Road Warrior in your sig photo.

lol! that is the road warrior! 

[tmoss]

OK, so I'm gettin old and my eyes are bad (and Mel is really young there).

[Aussie XAXB]

AAAAAaaaaaactually...............that is Mel in the original Mad Max. He was 21 there. After he finished shooting the film he went back and finished acting school.

LOL, yeah.....a very long time ago, a very young Mel Gibson.


And I am glad you expect my car to look that good when done.     I've made some movie replicas before and I've always been a stickler about detail. My Mad Max car, for practical, real world driving purposes, will be the least accurate replica I will have built, but also the first truely functional one. Only the die hard, seriously anal fans will notice what's wrong.

Steve

[BadAndy]

Aussie, as long as your Falcon has a huge blower sticking through the hood, screw the diehard fans!!!!!!!!

[speedfreak87]

is it left or right hand drive?

[Aussie XAXB]

I'll start a thread in BBB forum, I don't want to hijack this one.   


Steve

[91Notch]

Hi guys. I had a 347 about 2 years ago and it lived about 3.5 to 4 years had a stock .030 bore block with a main gridle. With fuel injection and a 5 spd and a .625 lift soild roller and turned it 7200 rpm. When I switched to a carb setup and a C-4(tired of replacing t-5s) I turned it 7700 and have turned it 8000 rpms. Granted about 8 months after 1 to many 7700 rpm trips it developed a squeal when you cranked it.
Find out it had 3 cracks in the mains and a crack at a cam bearing that let walk, this was the squeal. Main gridle saved the bottom end. Put it in a new block and sold it, still running fine today. 347's are good motors as long as you dont go crazy with the cam. Drove mine not everyday but 3 or 4 times a week with a soild roller, granted I had to adjust valves quite a bit but oh well had a blast with that motor.