im in the process of building a 383 for my '69....this car will be a daily driver but also a weekend warrior. now my question is this....i know that a 6 inch rod will make more torque than a 5.7 inch rod, but is it worth the extra cash outlay for a street car? thanks for any help!!!
graemlins/beers.gif -jd

do you want the wrist pin in the oil ring land? if not go with the 5.7 rod

If your gonna buy new rods and pistons anyways, go 6"! Like Smokey Yunick said...cram as big of rod as you can in the engine!

Originally posted by 19Nova72:
If your gonna buy new rods and pistons anyways, go 6"! Like Smokey Yunick said...cram as big of rod as you can in the engine! Also makes internal balancing a bunch easier with the 6 " rod crank

If it is a driver and weekend warrior, save youself the head aches (and cost)of the additional block clearancing and put a 5.565 (stock 400) rod in it. You will only need the longer rods if you are planning to turn that puppy over 6500 RPMS, and if your doing that you better not skimp on other parts and machine work!

Also just use a stock GM 400 crank and have the main journals turned to 2.45". The stock crank is made of nodular iron and I would trust them over any after market cast crank. There are plenty available.

Hmmmmmmm.....hard choice there. I put 6" rods in my 383...very nice, ultra smooth to 6500rpm, nice wide powerband. My brother used 5.7" rods, also runs well, not as free revving though. My dad's 383 also has 5.7" rods. Doesn't like revving much. My engine and my brother's share a bottom end to every detail except rod length. I used 6" rods and he used 5.7". But we used the same pistons, rings, crank, balancers, everything save for the length of the rod. In the low revs(i.e. under 4000) you really don't notice a difference in driving. Over 4000 the long rods really seem to smooth things out and rev nicely. You can definetaly tell the difference in cranking on the starter. The long rod engine draws a lot less amps.

Those are some observations, take them as good and bad. One real problem with 6" rods is cost. My poor block looked like swiss cheese by the time everything fit. A 5.7" rod engine requires much less machine work, roughly $200 dollars worth at the local shop.

I'd be thinking like this if I where to do these again:
5.565" rod 383- Don't bother, build a 355.
5.7" stock rod 383- Not bad, good truck motor, no revving over 5500rpm. Nice and cheap, a great combo.
5.7" aftermarket rod 383- Very nice 6000rpm easy 6500rpm if you like that sort of thing, and bullet proof if revved under 6000rpm all its life.
6" aftermarket rod 383- Best of the best. Run it love it. But, be ready to pay for it. 6500rpm is no prob with forged aftermarket rods. Low wear on pistons and cylinder walls. Easier to internal balance if you need to also. Very nice, more than any street motor needs- but never more than any street motor can use.

Actually,
Smokey didn't like a 6" rod in a 3.75 stroke motor.

I would probably opt for a 5.7 in a 383.
I really don't care for putting the pin in the oil ring.

Also can be some issues with too high pin placement and piston stability at high rpm.

Doubt it is anything a street motor would ever see.

I also think the 5.565 rod is way underrated. Obviously not the best rod/stroke ratio but it worked fine in stock 400 SBC's for 100,000's of thousands of miles.
I'm not convinced it really adds that much stress to the cylinders.
Also the short rod theoretically would make more low rpm power. That is everything in a true street motor.

Radracer,

But we used the same pistons, rings, crank, balancers, everything save for the length of the rod.

How did you use the same pistons on different length rods?

jakeshoe i like what you say. i have built and drag raced three diffent motors with 5.56 rods with good bolts and no problems.i dont think there is very much difference between the 5.56or 5.7 rod as for as performance up to 6500 rpms i have tryed both.the 6 inch rod motors do seem to run better at the track but are alot more costly to build

I believe smokey didnt like the piston in the oil ring groove and the small top land just because he hadn't done enuff testing or had enuff experience with it yet, I think many having proven that it works just fine, at least with todays technology.

A 6" 350 cost the same as a 5.7" rod 350. Don't know about a 383. One thing I like about a 6" rod is the lighter pistons. This eases the load on the rods considerable and the engine will rev quicker. Another thing is the better mechanical advantage the long rod gives. Due to the increased dwell at TDC, the crank will rotate farther around before the piston starts down. Giving a better crank angle at the start of the power stroke.

Originally posted by onovakind67:
Radracer,

But we used the same pistons, rings, crank, balancers, everything save for the length of the rod.

How did you use the same pistons on different length rods? True, not the same part number. The same KB style hypereutectic piston. Floating pin and same ring widths, just different compression heights to accomodate the different length rods. Sorry about that. And since I know why you asked the question, no, i'm not stupid. tongue.gif

If you use cap screw style rods, you shouldn't have to do much grinding at all for clearance.
I put lunati 6" rods in my 383. Spent about 1 min with a die grinder for clearance. Well over an hour to check each rod for block and cam clearance though.
5.85 rods get the pin out of the land I believe. But I haven't seen any cheap 5.85 rods. Scat 4340 6" cap screw rods are about 250$ I think.

I ran the stock 5.556 rods and dished trw pistions in my 406 It ran a best of 10.50 at 130 turned 6900 in the lights. Put flat tops and 5.7 rods in it ran the same times.

I ran the stock 5.556 rods and dished trw pistions in my 406 It ran a best of 10.50 at 130 turned 6900 in the lights. Put flat tops and 5.7 rods in it ran the same times.

Amen Brother!

Also lets break it down in Cost per HP!

Short rod motor:
Used parts, proven combo all parts will fall together;
Stock GM 5.565 rods set......... $50.00
Stock GM 400 crank turned....... $125.00
Stock 350 +.030 forged pistons.. $125.00
No clearancing needed........... $000.00

Total: ......................... $275.00

Long Rod Motor;
you will not find good used parts so the cost will have to be for new parts. Plus the prices will be for parts that really are only good to 6500 RPMs anyway, you can double that if your going to turn 8000rpms!
Scat 6" rods (cap screw)..........$279.00
Scat Cast steel 9000 crank....... $299.00
Custom forged pistons............ $550.00
Block clearancing labor...........$300.00
(and additional clearance checks)
Total:...........................$1428.00

Short rod HP= 470 with good cam and heads

Long rod HP = 470.5 with good heads (and it is still only a 6500 rpm motor!)

You do the math on the HP per dollar!

A 383 or 400 with a 5.7 rod has very close to the same ratio as a stock 454. I don't see the big deal about internally or externally ballanced either. As long as it is ballanced who cares how you get there.

I shift my 400 at 6500 sometimes 7000 if i'm not paying attention. Very smooth, 5.7 rods, externally ballanced.

Why would 6" rods require more block clearancing? The big end is the same, and the slight angle difference won't make that much difference. :confused:

Lonnie

Originally posted by Pat Kelley:
A 6" 350 cost the same as a 5.7" rod 350. Don't know about a 383. One thing I like about a 6" rod is the lighter pistons. This eases the load on the rods considerable and the engine will rev quicker. Another thing is the better mechanical advantage the long rod gives. Due to the increased dwell at TDC, the crank will rotate farther around before the piston starts down. Giving a better crank angle at the start of the power stroke. Both rods spend the same amount of time at TDC.
Rick Draganowski has an interesting study on the effects of rod length. Some excerpts:

Because of the mechanical advantage provided by the toggling effect of the rod the shorter rods act as if they were in a longer stroke engine at the top of the stroke. This effect would make the short rod engine rev faster from 2000 to 4000 rpm and the circle track people claim that acceleration out of the turns is significantly improved with the shorter rod. In all other factors the longer rod comes out superior...

Dwell Time

This measurement is of the number of crankshaft degrees the piston is within 0.250 inches of top dead center. It is the subject of much conjecture and controversy in the automotive literature.
This table is for a 3.75" stroke used in a 400 0r 383 small block Chevy engine.
Infinite rod---59.853 degrees
6.0" rod------52.397 degrees
5.7" rod------52.071 degrees
5.565" rod---51.915 degrees

Percentage difference in dwell time between the 6.0" rod and the 5.7" rod is 0.626%.
Percentage difference in dwell time between the 5.7" rod and the 5.565" rod is 0.3%.
Percentage difference in dwell time between the 6.0" rod and the 5.565" rod is 0.928%. (Still less than 1 percent)


According to my calculator, at 30° ATDC, a 6" rod has the piston .3249" down in the hole, while the 5.7" rod has the piston .3288" in the hole, a difference of .0039". This is probably outside the end-to-end deck tolerance of most motors. At this point the shorter rod has a rod/bore angle of 9.47°, giving it better leverage on the crank than the 8.99° the 6" rod has achieved.

Ok, so why did chevy go to 6" rods in late models?.

I didn't do it for more Hp. Just increased durability. And I got a 1750 or so bob weight.
Try finding a stock 400 crank in some areas.
I've seen forged pistons for $400 for a 6" rod.
I've never seen forged 350 pistons for $125 Hypers yes.
I don't know where you get the 6500 rpm.

I'm using 6" rods in my 383 simply because they were available at the same price as 5.7" rods of the same strength with no extra cost.

The difference is minimal, sure, but still significant for people who spend time worrying about windage, ring friction, etc.

Every little factor adds up.

I didn't do it for more Hp. Just increased durability.

First off, where do you get the idea that putting the pin in the ring land will give you durability?

Try finding a stock 400 crank in some areas.

I buy them all the time off eBay

I've seen forged pistons for $400 for a 6" rod.

Ok, the difference is now $1053.00 + headaches, Still not worth it to me for the same motor!

I've never seen forged 350 pistons for $125 Hypers yes.

I buy them (used) on eBay for that all the time. here is a link to a brand new set for $180.00 on ebay. eBay.com (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33623&item=2425281413)

JD, I would sugest you jump on these right away. only two hours left!

I don't know where you get the 6500 rpm.

The parts for either motor that I priced out will not hold up to 8000 rpm thrashings, I would not spend much time over 6500 rpms unless you go with a Forged steel crank add another $300.00, file fit molly rings, add $75.00 H series bearings add 50.00, additional cost of internal balancing add $50.00-$200.00 for possible heavy metal.

I'm using 6" rods in my 383 simply because they were available at the same price as 5.7" rods of the same strength with no extra cost.

Ok, list your combo including converter, rear gear and tire size, how much you paid for parts in question and how many RPMs you turn!

The difference is minimal, sure, but still significant for people who spend time worrying about windage, ring friction, etc.

Ring friction huh? post your ring friction and how you measured it :D

Every little factor adds up.

Don't you mean every little dollar adds up ;)

I often wonder why the anti-6" rod guys are so virulent in their objections to using these. It's just a rod. In my case (355ci), the rods (Eagle SIR bushed) were the same price as 5.7 bushed or press fit ($219, what I paid for reconditioned 5.7 stock rods in the past). The Wiseco forged pistons were the same price ($419 including 1/16" moly rings). The pistons weigh 416 grams, somewhat less than the 5.7" pistons. The rods weigh 582 grams (3 grams lighter than the 5.7 factory rods I had before) with very minimal balance pads (something you can't say about factory rods). Throw in a Scat cast crank and you have a decent rotating assembly for just over $800. I shift at 7000 on every pass. Perhaps the engine would perform the same or better with 5.7 rods, I don't know. I have 6 inchers and I'm happy with them. If the pin impinges on the oil ring, well, that excellent oiling for the pin.

I often wonder why the anti-6" rod guys are so virulent in their objections to using these.

I am definitely not an "Anti 6" rod guy", they are perfectly fine on a high revving internal balanced 350 with the shorter stroke turning higher RPMS! The 3.48 stroke crank has much less rotating mass and pin is not as high in the ring land. ;)

The 383 Stroker is a totally different, and there is no way wiseco forged pistons with those rods will internal balance on a scat 3.75 stroke cast crank without plenty of heavy metal! Then what's the point, you might as well buy a real crank like lunati or callies.

My point is that for a street strip ride save your money, not have the headaches and build the low cost short rod motor. Especially if you’re going to buy less-than mediocre parts such as a scat cast crank, and Eagle Sir rods. graemlins/waving.gif

Originally posted by gatewayracer:
I often wonder why the anti-6" rod guys are so virulent in their objections to using these.

I am definitely not an "Anti 6" rod guy", they are perfectly fine on a high revving internal balanced 350 with the shorter stroke turning higher RPMS! The 3.48 stroke crank has much less rotating mass and pin is not as high in the ring land. ;)

The 383 Stroker is a totally different, and there is no way wiseco forged pistons with those rods will internal balance on a scat 3.75 stroke cast crank without plenty of heavy metal! Then what's the point, you might as well buy a real crank like lunati or callies.

My point is that for a street strip ride save your money, not have the headaches and build the low cost short rod motor. Especially if you’re going to buy less-than mediocre parts such as a scat cast crank, and Eagle Sir rods. graemlins/waving.gif Wow, someone has there panties in a bunch. I have to ask, forgive me, but why are Scat cranks and Eagle SIR rods "less-than mediocre parts?" They seem to work pretty well to me. My 383 is external balance with a plate under the flywheel and the same parts you mention. It was close to being internal balance but would have required a little heavy metal and I didn't want to pay for it. With forged pistons it probably would have been internal balanced. It has not had a problem revving to 6500. Should I be expecting it to blow up for some reason? You know, a lot of people bitch about the pin in the ring land on a 6" rod 3.75" stroke motor, but mine is, and it smokes less than almost any other motor I know. *shrug* Weird.

I've never seen forged 350 pistons for $125 Hypers yes.

I buy them (used) on eBay for that all the time. here is a link to a brand new set for $180.00 on ebay.Do you know how much TRW pistons weigh? Over 550 grams.

Ok, list your combo including converter, rear gear and tire size, how much you paid for parts in question and how many RPMs you turn!
Don't you mean every little dollar adds up
Since we're talking about engines I'll stick to that for now. My usable RPM range is from idle to 6000.

I have no idea what relevance the trans, converter, gear, and tires have to this discussion, but I'll mention them later.

Here's what I have so far:

010 block, clearanced, bored, & decked: $475
Cast 3.75" crank: $160
Scat 6" Rods: $240
Dished hyper pistons: $230
Ext. balance damper: $50
Ext. balance flexplate: $50
Rings: $100
Balance job: $125
Rod & Main Bearings: $50
Oil pan: $65
Oil pump & pickup: $30

Total $1575 for the complete balanced shortblock with all new parts. I'm still building this engine.

The heads are GM Vortec. I paid $400 for the heads and Performer RPM Vortec Intake. The heads are all set up with screw-in studs, guideplates, and springs for up to .650 lift. The springs will be changed depending on cam choice.

Let's round it up to $2000 at this point and say I spend another $350 on a Crane solid cam, pushrods & lifters and $150 on gaskets and fasteners. That brings us to ~$2500 for the complete engine, from intake to oil pan.

Just so everyone is clear on this, I do not race. This is not a 1/4-mile car. This is a street car with highway performance as my primary concern. And I have a lot of fun driving this car every day of the week.

It's performing very well now with the solid cammed 357, 700R4, 26.5" tires and 3.55 gears. It should perform even better with the 383 and 3.08 gears.

Ring friction huh? post your ring friction and how you measured it OK, so maybe "ring friction" was a silly thing to say. I've been reading Vizard a lot lately. Just one of the things he mentions from time to time.

The bottom line here is that there's more than one way to skin a cat. I'll do it my way and you do it your way. Meanwhile we can continue to discuss the pros and cons (as we see it) like gentlemen.

Some might say "let's agree to disagree", but I don't think it applies here. It's as silly as me agreeing or disagreeing with your choice of plumbing fixtures in your home.

Add me to the stupid people list :rolleyes: I also went with 6 inch eagle Hbeams , scat cast crank and hyper dished pistons. It also came in at around $800.00 for the rotating assembly. One specific reason we chose that route; allows for an internal balance without mallory. I also like the stealthyness of the small balancer.
C.J., Pat don't know why you guys are bothering to defend yourselves. I read this last night and I'm thinking troll.

I have nothing against 6" rods, they work just fine. I just think they are picked for the wrong reasons, and the geometrical difference between the 5.7" and 6" rod is less than perceived. The real reason to use a longer rod is to lose weight off the rotating assembly. The geometry of a longer rod is more suitable at high rpm's, you can run a lighter piston, you can internally balance the motor, you can run a lighter damper and flywheel.
Gere Stahl defines a short-rod motor as one whose rod/stroke ratio is less than 1.8, meaning you would have to have a 6.76" rod in your 383 to join the 'long rod' club. Some interesting reading:

http://www.stahlheaders.com/Lit_Rod%20Length.htm

im running a 5.7 H rod and flat top srp pistons. internaly balanced (NO MALLORY) and a scat steel crank. all seems fine to me. stayed together at 6500.

Ok, another 2 cents :D
I gotta agree with Pat, unless you are using stock rods where is the difference in price?
And with the price of new rods today why use a stock rod?
Being a machinist & engine builder I am gonna make more money on reconditioning your stock rods, it's all labor, but it is still a stock reconditioned rod with an unknown number of cycles on them & before someone gets their shorts in a knot, I know stock rods are strong & I know there are lots of engines out there with stock rods & yes I mag them & throw away the ones that show cracks.
Point is, everything fatigues eventually so why not at least start out with a part as highly stressed as a rod that has no cycle time on it??
As far as length, I have built quite a few 383's & 400's & I feel there is just no discernable difference in power between 5.7 & 6.0 but I do prefer the 6.0 & the main reason is I like to internal balance everything I can & it just makes life eaiser with the longer rod & a 6" crank.
Most 5.7 rod combos are going to be external balanced or need Tungsten to balance.
There are exceptions but the majority do, but I have never had to add Tungsten on with a 6" rod .
On the block clearancing issue, if someone is charging you an extra $200 dollars because of a 6" rod I suggest you find someone else to do your work :D
The only difference is possibly a little more grinding for the larger counterweights of the 6" rod crank & it is usually not much.
The rod clearancing is the same given the same rod type & stroke.
As for "piston stability" I respectfully disagree with Jakeshoe. The higher the pin the better the stability.
Consider the rod & piston as a lever. If you move the pin down in the piston you will have more piston or "lever" above the rod & more "piston rock" or instability not less.
We have built a bunch of both 5.7 & 6" rod 3.75 stroke engines (& a few 5.565") & having the pin in the oil ring is just not a problem.
And I believe somenone said they buy used pistons on ebay all the time for the "budget deal".
Why do you think those engine builders are selling a "perfectly good" used piston set?? Don't suppose they know something about used parts they aren't mentioning?
We do a lot of circle track stuff & we replace the pistons on a regular basis & if we have one broken piston in an engine we replace them all. And no, we don't sell them on ebay :D
The reason is if one fatigues, there is a good chance the others are ready.
As far as the HP issue, on a scale of 1-10 the difference is probably about .5 in my opinion smile.gif

And as long as I am blabbering on :D
I just gotta ask where the post by gateway racer comes from?? Especially if you’re going to buy less-than mediocre parts such as a scat cast crank, and Eagle Sir rods
As a real world example, I put a scat 3.75 stroke 9000 series cast crank in a circle track modified on alcohol that ran 3 seasons before finally breaking.
That's a pretty fair "mediocre part"
BTW, it was the customers choice to use the cast crank, not what I would recommend ;)
We have been selling & using Scat cranks & rods for about 10 years & their quality control is pretty damn good. I can not remember the last time I had a problem worth mentioning.
While I will agree that there is some Junk out there I do not feel Scat is in that class.

Mike,
I'll have to dig through my stuff here...
I remember reading somewhere that the pin if placed TOO high causes some stability problems.
Obviously like everything else there is a an ideal point it would be placed, too high or too low and it creates problems.
I cannot rememeber the entire theory behind this as it's been months or years since I read it. But basically if it is too high it changes the stability of the piston. It allos the piston to rock on the pin, where if the pin was lower, the skirt is on one side, the rings are on the other, so it is all balanced out.
Like I said earlier too, it is probably not something guys like us even need to worry about, more a NASCAR or other ultra high rpm deal. 6000 rpm is NOTHING... smile.gif
Now where did I study that at, I'll post it verbatim if I can find it.

I think the stability of the piston has less to do with the pin placement than the shorter skirts usually used on long rod pistons. A short rod piston, with the pin lower, by necessity has a longer skirt. Long rod pistons usually have much shorter skirts which allow the piston to rock more. I guess pin placement does determines the skirt length and therefore the stability of the piston after all.

I believe Pat's got it..I know we had problems with piston rock on one of our car lines a few years back and the fix was redesigned pistons with longer skirts.

thats why i used the 5.7 rods. the short skirt did not appeal to me in what is basicly a street car.

Ok, looks like I stirred it up pretty good!

All I am saying is that when building a 383 stroker, to be used under 6500 RPMS, you can save a bunch of coin by building it with stock used parts! And no, don't buy anything that has a crack in it!

As far a Scat cast crank goes, You won't catch me putting one in a Race engine! I've seen too many cars pulled off the track. In fact buddy I pit with got 4 runs before it cracked!

If you buy Scat go with the 4340 forged and have your machinest go over it when balancing!

Sorry if offended anyone that uses scat, not my intention.

As far as the Long vs Short rod debate, here is a link to a pretty good read.

Connecting Rod Analysis (http://victorylibrary.com/mopar/rod-tech-c.htm)

"Add me to the stupid people list"

This is not personal just a debate!

"I read this last night and I'm thinking troll."

Ok, now its personal, consider yourself added!


:D Take a chill pill, Just kidding!

Originally posted by gatewayracer:
"Add me to the stupid people list"

This is not personal just a debate!

"I read this last night and I'm thinking troll."

Ok, now its personal, consider yourself added!


:D Take a chill pill, Just kidding! It's not your message pal its your delivery... peace.
jack

"It's not your message pal its your delivery
jack"

My Delivery?

Thanks for that article, now that I know 454's are only good for limited street use, I guess I won't build one. :rolleyes: graemlins/clonk.gif

"Thanks for that article, now that I know 454's are only good for limited street use"

Ooohh! now were going to turn it into a Small block big block debate huh! tongue.gif

Actually it wasn't related to the skirt length,
not directly anyway.
Skirt length can be as long on a 6" motor as a 5.7 if not longer assuming all else is equal.

I'm not anti 6" rod either. In a 3.48 stroke motor, without a doubt, do it. It does lighten the bobweight up, this is always good.

In a stock deck 3.75 or longer stroke SBC motor, I don't feel it's necessary. And may cause some concerns that the 5.7 doesn't.

Originally posted by gatewayracer:
Ooohh! now were going to turn it into a Small block big block debate huh! tongue.gif No, that article said that all 454's with stock length rods and sbc 383's with 5.7 or shorter rods are for limited street use. I'm refering to the rod ratio chart... pretty dumb.

There is nothing wrong with running the longest rod that you want or can afford. There is also nothing wrong with running a 5.7 rod in a 383 or 400, proof being the thousands of 454's out there with the same rod ratio with long lives. Nothing to do with SB vs. BB.

Every one knows small blocks are better anyway. j/k. tongue.gif

Lonnie

"There is nothing wrong with running the longest rod that you want or can afford. There is also nothing wrong with running a 5.7 rod in a 383 or 400, proof being the thousands of 454's out there with the same rod ratio with long lives. Nothing to do with SB vs. BB.

Agree 100 % and as long as you can afford it, and since you are buying aftermarket parts, prepping the block for a stroker etc. Why not buy a 3.875" or 4" stoker crank! Ive never built one but it would be a 396 or 408 cubic inch torque monster! :D

I normally don't like to jump into these debates because it's way too easy to be misunderstood. But I think gatewayracer makes an excellent point that needs to be reinforced. How many of us on this board are regular racers running the power levels/RPM's to break properly prepped and assembled stock parts? I think most of us are hobbyists that cruise around a little on weekends and make a few trips to the track for fun each summer. I've heard just as many stories about low-end aftermarket stuff that broke as I have about stock stuff that broke. Bottom line is that aftermarket stuff has a place, but for what most of us are doing, it's probably insurance more than anything. If you can afford the insurance, great, but if you can't, don't be afraid to use stock parts. I've got a 383 in the works that will will have a stock 400 crank and stock 5.565 rods w/ARP Wavlock bolts. Maybe I'm an idiot, but if it lets go, at least I'll feel a whole lot better knowing that I didn't spend a small fortune. :D

I'll tell you this: My 357 has 10.5:1 compression and stock 5.7" rods and it sees 6500 RPM at least once a month (playing around). No failures yet.

When I rebuilt the engine, I didn't have the rods checked. I had 7 days to pull the engine and do the entire rebuild, including balancing the new Summit crank.

Since I've been running the solid lift cam, the thing pulls well past 6K. So sometimes I use that to get the car out into traffic. graemlins/thumbsup.gif

Do I need Scat 6" rods on my 383? No.

Do I want them? Yes.

For all youse hot rodders who want an opinion from someone who is "in the business" check:

www.iskycams.com/techinfo_index.html (http://www.iskycams.com/techinfo_index.html)

Iskendarian has been in the racket since the mid-fifties (maybe the late forties?). They have probably seen every "discovery", fad, hype, and other assorted b.s. that has come along regarding modification of USA-manufactured production V-8 automobile engines for increased output. They don't seem to advertise much anymore. Maybe they don't need to?

My $0.02

Originally posted by gatewayracer:



Also lets break it down in Cost per HP!

Short rod motor:
Used parts, proven combo all parts will fall together;
Stock GM 5.565 rods set......... $50.00
Stock GM 400 crank turned....... $125.00
Stock 350 +.030 forged pistons.. $125.00
No clearancing needed........... $000.00

Total: ......................... $275.00


You do the math on the HP per dollar! This was a great thread....I got a lot of great info from it, especially from the lnks provided. Thanks to all!

And to gatewayracer...I hope your wife balances the checkbook!! (No offense intended)

When rebuilding my "hardcore" 427 sb, I took a real engine builder's advice (as well as Tom Mobley and others on this board) and replaced the original 6" w/5.7's. There were a lot of problems with the engine in general (less than 200 miles before requiring a rebuild), but the long rods, short skirts, and wide wall-to-skirt clearance caused enough rocking to score the walls and the skirts. Had I run it as mitchell originally built it, it may have hung together for 1000-2000 miles before flying apart. Instead, we punched it out and went with 5.7's. The "427" is now a 434 - smooth operator with tall skirts and tighter clearances. Again, the rod length was not the originator of the problem, but a bad build sure did make the damage that can be done in a short time very obvious.

Best,

Wow, don't believe I missed this post until now :D I've done a lot of reasearch on the subject and wanted to clear up a few misconceptions . . .

1. A shorter rod has a greater effective stroke due to greater angularity (shorter rod has more leverage on the crank pin). The greater effective stroke creates some increase in low end TQ over the long rod.

2. The shorter rod also causes faster piston acceleration. This is kind of a double edged sword - it helps low end Volumetric Efficiency BUT higher piston acceleration rates can contribute to ring flutter at higher RPMs (like 6500+)

3. Pistons made for longer rods (shorter compression height) are much lighter than the shorter rod versions. This weight reduction on the piston more than offsets the increased weight of the longer rod. A lighter reciprocating assembly will let the engine rev faster and hold together longer over time.

4. I have personally never, ever heard of a piston failure due to oil groove spacers used on 6" rods stroker motors. I suppose if you put them in wrong (if that's even possible) you have problems, but have never heard of it happening.

There is a lot more info on the net on this subject, but my conclusion is that the shorter 5.7 (or even 5.565") rods are best suited to street engines that need to make max power below 6000 RPM. If high RPM durability and/or power is your main concern then a 6" rod is definately the way to go.

In other words . . . it depends on your application.

One thing that I haven't seen posted is that if this is to be inexpensive then the 5.65 rod is the one to use as the 5.7 rod will have interfearance with a roller cam as in hydraulic which is well spent money for the performance. I learned this the hard way.

Would you trust the stock 5.565 rod in a motor making 500 HP, assuming a top-notch rod bolt is used?

Originally posted by BPOS:
Would you trust the stock 5.565 rod in a motor making 500 HP, assuming a top-notch rod bolt is used? Not even in your motor ;)

Ouch. So I added a little safety margin. :D

ill take your 5.56 rods all day with good bolts. gateway your math may be a little off but im with you .now if you are buying rods then go with the 5.7 rod and put your money towards good light weigh pistons like wisco.the wieght is where the horsepower is.now 350 for crane cam alot of money for a name .i have used elgin cams and have had no problems 100 dollars cam and lifters, solid only for me .to my under standing elgin grinds a great deal of cams for people.i also have alot of faith in ud harolds grinds and his advise is price less to all of us