Vintage Mustang Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
1,242 Posts
Discussion Starter #1
do i need merley a stroker kit, or is there a certain overbore i need to go at? I thought it was .030, but i can't remember. There are some really good kits on ehay, and if i got one of those, i want to make sure my engine isn't already bored out past what i need or something.....TIA
 

·
Registered
Joined
·
5,066 Posts
IIRC, the kits are 4.030 pistons, which assume a .030 overbored block to put them in. You need a block that will clean up at .030. If it wont, you can get another block or find a kit with .040 pistons if you want (if you feel you have to keep your original block), im sure its more expensive.

You are wise to check the bores of your current motor first to make sure its usable at .030. I checked 3 blocks before I found one that cleaned up at .030 for my 347. Or you can buy a new block from Summit or something, and use std pistons. That would make it a 342, not a 347.
 

·
Premium Member
Joined
·
11,703 Posts
347 requires a .030 over-bore and notches in the sides of the block to clear the rods.
342 is the 347 w/out the .030

331 uses a slightly shorter stroke w/the .030 over-bore
327 is the 331 w/out the .030 over-bore
 

·
Registered
Joined
·
14,601 Posts
Okay...a bit of a stupid question...and I think I know the answer anyway...but:

What's the major advantage to a stroker kit over say, a warmed up 302? Is the extra cubes/HP the big win? Are we talking a significant increase in torque? Both?
Seems like I could build a very snappy 302 approching 400hp much cheaper than a stroker...am I just over simplifying this?

It would be cool to see performance numbers for a 302 vs. 347 with a similar build. ::
 

·
Premium Member
Joined
·
3,637 Posts
.040 Over kits aren't that much more expensive (makes it 348.68 C.I.D.). If your block has been punched to .030 previously, and the cylinders don't show much wear, then you can probably hone it to .040 (have a shop inspect it & mic it before doing any work, or ordering any kits). Anything over .040 on a Stroker is flirting with disaster.

Main bearings are another thing you need to think about as many of the cranks out there have been turned .010 under and your block might need to be line honed/bored.
Again, have a shop inspect the block and determine if its usable for your application BEFORE ordering any kits.

Ken
 

·
Premium Member
Joined
·
11,703 Posts
The major advantage is the stroke. It provides both more cubes for HP and more leverage for torque.

Think of the "arms" of the crank as levers. When you lengthen the stroke you lengthen the levers, which means the same downforce creates more leverage and therefor torque.

There are downsides to too much stroke though. On the 347/342 the pistons have to be really short and come so far out the bottom of the bore on the downstroke that they have a tendancy to get canted in the bore. They don't move much, but enough so that longevity is impacted.

On some 347/342 kits the wrist pin is actually set into the oil groove in an effort to maintain the piston length. The added length is good, but the placement of the pin is not. The added length does not really help the canting issue either, since that happens at the bottom of the stroke, when the skirts are hanging out the bottom of the cylinder.

Then theres the skirt-to-crank clearance issues...

I prefer the 331/327. It does not give up much in the stroke department (1/4" IIRC), but it resolves the wrist-pin issue, the canting issue and the longevity issue.
 

·
Registered
Joined
·
14,601 Posts
Thanks Kent, that's pretty much what I thought. Good info on the 331 though...wasn't aware of that.

Seems like these kits are really popular despite any lifespan issues...what kind of gains are we talking about? I know that were not exactly talking apples to apples here...but, I'm thinking the "seat of the pants" factor has to be pretty good with the added torque for people to go to all the trouble, machining, etc.

I've never really built a motor from the ground up...done heads,intakes, etc. Is the extra machining that big of a deal? You generally have to do alot of that when rebuilding a motor anyway. I'm just wondering if when all things are said and done, and I'm looking for ~400 FW HP, a good crate motor would be the way to go? ::
 

·
Premium Member
Joined
·
11,703 Posts
Ya know... I just am not sure about some of the numbers I see in magazines and such.

400HP from a well built 302 is not unrealistic. Heck, according to my engine guy, 500HP from the 327 we are building now is realistic.

So... what can you do with a 347? Use 400 as your base HP number and work up from there. All it takes is money ;)

My now dead 302 was putting out near 400hp, normally aspirated. My goal with the 327 is 450, but my engine guy said he may have problems keeping it that low ::

If you do a 347 "right" 500hp should be fairly easy. Torque would be close to that number as well.
 

·
Premium Member
Joined
·
3,637 Posts
Brian,

Depends on the $$$$ you want to spend. My 347 Stroker is probably really close to 400 FWHP, but have not been able to dyno it yet. I'm only using "Worked" Stock Heads (Ported w/1.90/1.60 valves) and wanted mine more for Torque and streetability so I went with comp cams 281h hyd roller cam & lifters for a power range of 2500 - 5500 RPM's.

Now, had I gone solid roller and a 292h or better cam with some 185 or 205 AFR's, and Victor Jr. intake, Holly or Demon 750 carb, I'd be in the high 400's or very close to 500.

When I'm done painting, I'd be happy to let you feel for yourself ::
 

·
Registered
Joined
·
14,601 Posts
Cool, thanks Ken...I'd never ask to drive someone's car...but since you offered! ;)

My little 289 seems pretty solid...I often wonder if a cam and new heads would do the job...for a while anyway. http://www.pcmc.cc/forum/images/smiles/burnout.gif
 

·
Registered
Joined
·
1,633 Posts
the 347 uses a 3.40 inch stroke while the 331 uses 3.25. Both use .030 overbore to achieve these dispalacement #'s. stock bores with the same stroker setups achieve 342 and 327. You shouldnt need to notch the bottom of your bores for the 331. Kent is right on the hp thing, I was shocked!!! My 331 with AFR 185 heads is estimated to make around 475 hp and 420 ft lbs. Thats pretty empressive. Now I just need to finish the car so I can try it out. LOL
 

·
Premium Member
Joined
·
3,637 Posts
Drive?........... Did I say Drive? ::

Uh, I only said you could "Feel" it when the paint is done :: :p

Seriuously though I think we can work something out ;)
BTW, the thought of a little cam & head upgrade will only lead you to the dark side my friend :: Remeber all you've got is that T5 ::

Ken
 

·
Registered
Joined
·
14,601 Posts
Drive?........... Did I say Drive? ::

Uh, I only said you could "Feel" it when the paint is done :: :p
HeHeHe...ya like how I slipped that one in there? ::

BTW, the thought of a little cam & head upgrade will only lead you to the dark side my friend Remeber all you've got is that T5
Are you thinking the T5 would take a crap even with a little cam/head work? After reading the article you sent me...my thought was that "as long as my T5 was in good wroking order", 400hp should be fine. ::
 

·
Premium Member
Joined
·
3,637 Posts
Just giving you a hard time..... First it's heads & cam, then it's a stroke kit, then once you have all that power, you'll want to get rough with it, next thing you know, that T5's allover the road ::

I'm sure it will be fine with a mild build, but NO POWER SHIFTING, or it's toast!
 

·
Registered
Joined
·
5,066 Posts
to build on what kktell explained in most excellent terms, the big difference between your hypothetical comparison is WHERE in the torque/RPM curve those 400-500 horses arrive. Yes a built 302 will go 400 HP but you will be up there in the RPMS to find it, and the torque is up there also. A 347, making the EXACT same HP, will bring in the torque MUCH sooner in the RPM range; that makes it a much more street-friendly motor, with much less wear on the motor itself. The leverage advantage of a stroker at lower RPMSs has it all over the stock stroke in my opinion.

Additionally, as with any displacement issue, the smaller the CID, the more money you will throw at it to get the same HP figure. Bigger motors are cheaper and work less to accomplish the same thing, all else being equal (a disadvantage is slightly poorer fuel mileage). A 331/347, properly built, will give you the power of a stout 351 or better with the weight/size advantage of the 302 (the smallest-dimension American small block V8 made).

AFAIK, the oil-ring issues and crank angle issues of the early stroker kits have been engineered out, now that the kits are in mass production and use specifically-made pistons and cranks. Early kits used different rods from diff manus (Chrysler 318 and 2.3 Pinto rods were especially popular)bolted to turned-down Cleveland cranks and the like which did cause oil-burning probs and piston side-loading issues. Almost all kits now keep the piston pin out of the oil ring.

whoa! I just noticed....I talk too much..tell me to shut up next time, willya? ::
 

·
Registered
Joined
·
14,601 Posts
Just giving you a hard time..... First it's heads & cam, then it's a stroke kit, then once you have all that power, you'll want to get rough with it, next thing you know, that T5's allover the road ::
I hear that...I should probably make sure I can afford what I'm doing to the car right now before I get all excited about engine tweaks! ::

...but NO POWER SHIFTING, or it's toast!
NO POWER SHIFTING?!?!?!? Ah, crud...I guess I don't get to drive your car after paint's done! :( :: ;) ::
 

·
Registered
Joined
·
1,242 Posts
Discussion Starter #17
Wow. See, this is why i love the VMF. I ask a question, get some very good answers, but people just keep coming in with more explanations and tips. Thanks a ton guys. You're all great. :: :: :: ;)
 

·
Registered
Joined
·
1,242 Posts
Discussion Starter #19
http://www.parenthoodplace.com/ubb/graemlins/blowup.gif I hate it when people hijack threads! It makes me wanna http://dc.dizolv.net/ubb/graemlins/puke.gif

Nah, just kidding. When it happens, the results are usually better than intended. I quite like it sometimes. ::
 

·
Registered
Joined
·
1,215 Posts
All of the above info is correct. Here are some numbers I changed around on my current combo for the visual people, according to desktop dyno. This assumes your engine is running 100%, no alternator, no water pump, no fan, no drivetrain nothing to steal power this is just flywheel numbers.
My warmed up 306(.030 over 302) is making peak 424 HP at 6500 RPM and peak 377 ft lbs of torque at 5000 RPM. When I alter just the stroke to 3.4 changing my total displacement to 347 ci, it is now peak 434 HP at 6000 RPM and peak 413 ft lbs of torque at 4500 RPM or 414 ar 5000. 10HP and 40 ft lbs of torque doesnt sound like much to most people since that's all they look at is the peak numbers. After the drivetrain and other power robbers you might see and feel 6 HP and 25 or 30 ft lbs at the rear wheels. What most people miss out on though is the curves, a stroked engine as mentioned earlier provides more power and torque at lower RPMs basically letting the engine run better without working as hard, more efficicently. Here are some pictures they are kinda big so just click the links, but it shows the noticeable increase in low end and mid range torque and power. notice how much quicker the curves 'peak' than before, mostly torque but the power actually comes a little earlier too. This also doesn't take into account the usual added compression when 'stroking' due to 'high performance' pistons rather than whatever was in before, most stroker kits are about 10 or 10.5:1 and most stock or stock replacement pistons are about 9:1 so there is a little something extra that I didn't add into the graphs.
BEFORE

AFTER

EDIT: I guess I DID change the compression in the graphs, from my current est. 9:1 to the advertised 10.3:1 of the stroker kit I'm looking at, that esplains the HP peak increase.
 
1 - 20 of 22 Posts
Top