Hulk0202

I know about the added stress on the cylinder walls, but does anyone have any examples to give of it causing a problem. Id like to weigh my options. ive never built an engine. Im not worried about building it, just clearancing the block. I always hear the technical info., but I want REAL LIFE info.. Thanks guys.

AlkyIROC

When I had a 383 it had the short 400 rods. I was running high 11's at 117 mph.

They built 383's like that for years before stroker pistons became available and cheaper. There's nothing wrong with a short rod stroker. It's easier and cheaper to build.

94-6spd

It is definitely better to go with the 5.7 rods. I have talked to www.speedomotive.com about this before. The dyno pulls are always better with the longer rods. They sell a budget 383 stroker kit with the short rods but the guy said that if you really want performance to get the longer 5.7's.

The short rod strokers can be used in a truck or tow vehicle with good luck but if you really want it to rev faster and higher go with 5.7's.

ctandc

The short rods are FINE. The main reason for all the "experts" using the 5.7" rod is cylinder side-loading, and it being easier to rev a long rod engine.....It's a stroker for ***'s sake, use the massive low-end torque it will have naturally, keep the revs below 6000 RPM and use the cash you save for something more worthwhile.......Like BALANCING.....even if you're using an externally balanced crank, have the balancer pistons,rods,crank,flywheel ( or flexplate for auto) balanced as a rotating assembly.....WELL WORTH the extra $150-200 you'll spend.

I've seen TONS of real life dyno pulls on short rod and long rod strokers, and I've NEVER SEEN the long rods make any more power worth mentioning, when ALL OTHER components are the same.

As for Speedomotive, OF COURSE they'll push the more expensive long rod kit, they are in business to make money after all...

Have the rods checked, get 'em resized if needed, and use ARP bolts.......


HTH
Chris

Ward

iTrader: (1)

Well, as a general rule of thumb, a shorter rod will give you more side loading, due to the increased angle at which it will be, in relation to the cylinder wall. Also, a shorter rod will lower your compression unless you make the combustion chamber smaller by decking the block, milling the heads, or getting heads with smaller chambers. I would keep the 5.7 rods on a 383,because the longer crank throw will already increase side loading, as well as increase your compression.

jcb999

Most street combinations will not show a hp or torque increase because of the limited rpm. Piston selection and rod options (weight mostly) are much better with 5.7 rods. But, you also have rod bolt clearance probs.

Look at what pistons you want to use.. there might not be a 5.565 version.

Dragula

short rods work fine but :
short rods=more side loading
short rods=slightly less torque but who cares, its a stroker
short rods=less rpm potential so just keep it under 6000
short rods=no real price advantage over buying 5.7" unless you already have them from a 400.
If you are buying new, then buy 5.7" or 6".
If you have some already from a 400, then just use those and spend the extra money somewhere else

76L88

I have been running a short rod stroker (that someone else built) for a couple years now. It had 5000 miles on it when I picked it up and probably 15000 now. I rev it past 6500 RPM all the time. I was told it was put together "race loose" (extra ring gap, bearing clearance, high volume/pressure oil pump) but I don't like it because I get lots of blow-by and oil pressure out the valve covers. It actually blows out those K&N push-in type breathers at 6500. However I do have all paperwork from the builder and it was balanced, plus I noticed a big difference above 5500 RPM when I put on one of those $329 Fluidamper balancers. I definately recommend that, especially for a stroker.

Polecat

If your worried about rod clearance, and want to use a standar cam, not the smaller diameter one, get some 5.7" rods from Speed-O-Motive. The acome already re-sized and ground for clearance. Then all you'll have to do is do the block, which is a 20 minute job at best.

gmgod

The longer rod will let the piston dwell around TDC longer and give a better combution process.

Apeiron

That's why you get pistons to match the rod length.

Hulk0202

Will using the 5.565 rods help any with the clearance issues. Im a little worried about workingf the block. Ive never seen it done first hand. Does anyone have any or know where I can get real photos of where and how much? I have a bunch of articles with crappyu diagrams, but I'd like top see the real thing if possible. Thanks for all the ionfo. so far. Im definently getting closer to my decision Thanks again!

ctandc

Some very good points made...

The best one being this...

IF you ALREADY have a good set of 5.565" rods, KEEP 'EM and spend the $$$ somewhere else.

If you need to get new rods anyway, then going with the 5.7" won't cost more.

As for the side-loading issue... it's pure garbage.

HOLD ON. keep reading..

YES, shorter rods will have more "side loading" effect than longer rods in the same engine... but if this is primarily a Street engine ( rev range UNDER 7500 RPM or so ) it doesn't make a darn either way.

As for clearancing...

As far as the rods go , screw paying extra for "clearanced" rods. Use regular 5.7" rods and then use ARP rod bolts for the 4.3. The head is much lower profile, most times you won't have to clearance them at all..

As far as the block... EVERY BLOCK is different because of machining tolerances...

A way I 've used before is this...

Take the crank you're going to use and coat the thing with Vaseline. Put it in the block, hold it in with a couple of mains and bolts, and SLOWLY rotate it with the block upside down so you can watch it closely...Any spot where it makes contact or comes very close, mark it for clearancing.

Then after those parts are cleared, install the cam, piston and rod assemblies and crank.... rotate SLOWLY and check for clearance...


I normally do all the block work BEFORE I take it to the machine shop.... that way the hot tanking will get all the small shavings from clearancing....


HTH
Chris

Polecat

maybe so, but in order to use a stock dialmeter cam, it's highly recommended to pay a couple dollars more for ground rods. call SOM, bet you find it's alot cheaper than you think, plus, they already come with pressed in ARP bolts.

ctandc

Okay, maybe I didn't make it clear...

The main clearance point for a 5.7" rod in a 383 is the rod bolt area...

The Chevy 4.3 V-6 ( a 350 minus 2 cylinders ) ARP rod bolt is already clearnanced....it's lower profile...


It's not about spending money, it's about spending it in the most effective places....


Chris

Hulk0202

Damn ctandc, that's exactly th kind of straight forward info. I was looking for. Thanks for the all the help. I now feel mucho comftorable with the job at hand. Ill give you some credit when I become the first 300mph street legal 91 firebird. Thanks!

ZZ28ZZ

Bought my 383 stroker kit from Powerhouse.com.
It has 5.7 rods.

Had to grind the oil pan rails and the bottom of the cyls to clear the ARP rod bolts. Actually they didn't hit, but came REAL close.

Also had to shave a very small amount off the counterweights to clear the 1,2,7,8 piston skirts. They actually did touch.

Ground everything that was close\touching so I had >.070" clearance. Don't have the cam yet. Still need to check that.

The clearance work is actually pretty easy.
All you need is a grinder and an appropiately sized allen wrench to check the clearances.
I did mine in a couple of hours.

Hint: While clearancing, use a ground-down wrist pin that will slide into the rod. The guy at the machine shop let me borrow one for free.

300 MPH huh?
Maybe you should skip the 383 and go with a JT8 high bypass turbofan. That would get you 300+ at half throttle!

BadSS

If you're new to engine building and want the cubes, consider building a 5.565" rod 406. Super simple, no clearance issues, and while the piston for this application may be heavy, with ARP bolts, and keeping the RPM level under 6500,,, you'll have no problems. In fact, I've shot over 350 horses of nitrous to a 550HP 408 using 5.565" rods and ARP bolts on the $245 TRW pistons. I'm not saying I didn't hold my breath for the 10 second ride though. Point being the reliability of the 5.565 rod is better than most give credit.

If you're set on a 383, you're going to have to grind on the block, and if you don't have the rods already, and don't mind clearancing a few inside rod bolts (and pads) then I would go with the 5.7". The piston will be lighter, there are more high performance piston applications available, and the 5.7" rod is stonger - as others have already pointed out.

However, the performance difference between 5.565 and 5.7" (.135") is not much. If it's a carbed application the slight power band differences between the rod lengths can be cancelled with cam selection - no big deal there at all. If it's a EFI or emmissions application, the longer rod engine becomes more inviting because you can run a smaller cam and get the same or effective rpm band of a shorter rod engine running a larger cam,,, and pull more vacuum with the longer rod and smaller cam. Still, we're not talking about a lot of difference even comparing a 5.565" rod to a 6" rod.

Anyway, that's my 2 cents worth based on 20 plus years of farting around with engines and here's a couple links with some mathematics applied to rod length comparisons.

http://www.iskycams.com/techtips.html#2005
http://www.aros.net/~rbuck/rick/rodstudy.htm