what I have is a standard bore 350, high nickel-Tin block, , I have some standard size ''new in box'' flat top TRW sealed power 4.00'' forged alluminum pistons I mean 30 yrs old, I cant remember what the skirt to block clearance was on old forged piston but do remember that it was way more than cast pistons of the day, loose enough to hear piston slap untill warmed up to operateing temp, and at one time I think they where some of the best pistons that money could buy and this old block probly would have been bored if I had the money, So I really need the extra clearance that is called for when using old fashioned forged pistons,
Sounds like a gift horse, but heres the bad part. they are 327 pistons, so the only way I can use them is to use 5.565 sbc400 rods, all things considered I'm stumped, I have studied and studied till im blue in the face on rod length ratio's and side loading, dwell time tdc and bdc, and from what I read from some pros that seem to have knowledge say that you cant actually feel any differance in the drivers seat, on a 383 w/ 5.56 rods and 383 W/5.7 rods, and then theres a multitude saying longer rods and even longer rods, some guys saying the differance is real in theroy but still very small. And then others claim that the guys saying they are so much better are full BS that was feed to them by nerd with calculators, and not from actual real life experiance,

Back in the day 5.56'' rods in 383 was the best a poor boy could get, and they had a longer stroke than my 350-3.48'' crank, and a few racers still use them to avoid clearance issues and I think in some 406's nowdays, SBF's where running shorter rods with a reputation for long life engines.
I only have 50 bucks in these pistons, but not any rod options that I have found so far other than stock 400 rods that I can polish & install ARP bolts, so will the strength I gain with the "OLD SCHOOL" forged pistons be lost by rod-stroke ratio as opposed too some cheaper cast pistons with the 5.7 rods. the 383's running 5.7 rods are less than 1/4''longer rod and on top of that have a 1/4'' longer stroke, I wonder the stroke to rod length ratio comparing 383 3.75 stroke W/5.7' rods versus, a 3.48 stroke using 5.565 rods? I would like the short block solid enough to handle 6800RPM's & 500HP, which is probly all I can get from my tricked out GM 906 vortec's with all the other goodies. I do know it sure sounds good to me, " 350 crankshaft, 327 pistons and 400sbc rods, I guess I could call it a stroked 327, so is it forged TRW forged pistons & 5.56 rods? or cheap cast pistons and 5.7 rods?

 

For only 400 HP, either should be fine. Whichever's cheaper, I'd say.

 

Thanks Ape for the vote of confidence, but I am hope to get the formula for figuring the ratio or atleast someone will figure it for me, with the 5.56 rod would it not be less side load than a 383 with the 5.7 rods??

 

Other way around, the longer rod has a lower rod angle and therefore less side loading.

Really though, it's not going to make a lick of difference on a 400 HP street engine.

 

Chances are, if you've been doing research, you've come across this article from one of David Vizard's books.
I've scanned it so you can have a look.

 

Also some interesting info in this link.
It supports what Aperion has to say.
http://www.speedtalk.com/forum/viewtopic.php?t=406

 

Another vote here for whatever works out easiest/cheapest for you.
You or your engine will never know the difference in that 0.14" of rod length.

 

Ultimate horsepower notwithstanding, the real drawback in this application is the documented cylinder wall side loading. Besides the loss in hp due to friction, if the op's standard bore cylinders are already worn (perhaps to edge of useful service) then the loads imparted by the short rods might wear it out that much faster.
5.7 rods / 3.75 stroke = 1.52
5.56 rods / 3.48 stroke = 1.6
and for the record..
6.0 rods/ 3.48 stroke = 1.72
Using the dimensions supplied, it looks as though the short rodded, short stroke combo will achieve the arguably more desirable ratio.

 

Rod to stroke ratio is quite simply the ratio of rod length to engine stroke. In other words, stroke/rod length. ei: 3.00" stroke/ 6.00" rod = 2:1 rod to stroke ratio. Rod to stroke ratio is important in different ways for different applications. A lower rod to stroke ratio will create more low end torque by increasing piston velocity in the upper half of the stroke. Higher rod to stroke ratio will increase stability by reducing rod angle and side loading, thus desirable in a high revving motor. Higher rod to stroke ratio can also reduce an engine's tendancy for detonation by reducing piston velocity in the upper half of the stroke.

 

Thats what I was getting at, it would have a BETTER ratio than A 3.75'' stroke 383ci with 5.7 rods, and thats one combo that I have never heard of a side loading issue or busted rod as a result of side load, I personaly myself cant even remember hearing of it when they where useing the 400 5.56''rod on the 3.75'' stroke crankshaft to make the 383

 

block life span was one of my concerns, with the old style alluminum forged piston requiring more room than these new forged or cast and there is ony .135'' differance in length about 1/8th shorter so don't belive it will take over 200rpm away my engine and side load increase is minimal to say the least and short rods making more torque I think for 50.00 the pistons was a great deal, I have a gentlemen that is going to trade me even my 5.7 GM X-rods for a set of reman 400sbc rods, now I need to decide on rod bolts and the rings, chrome moly? or cast? or plasma moly, what is the best ring these days, I have always heard that chrome rings wear the block faster and are harder to seat than cast, and the plasma babies where not around in my drag racing days of yesteryear, I was wanting to hold the cost for rings down to 100 bucks and order from amazon if I can, did GM put 906 vortecs on the 305?

 

No point using anything more elaborate than chrome-moly for 400 HP.

 

Get a 307 crank and build a 327. Just my vote.

 

Better to use a 327 crank for that then.

Any benefit from a "better" rod/stroke ratio a 327 might have over a 350 would be would be obliterated by the loss of displacement

 

I aint buying another crank when I have this standard size forged steel GM crank, I am doing the very best that I can with what I have to work with, why dont peole read the original post, money is why I'm using the forged 327 pistons that I got for 50 bucks,not because the stroke ratio is better because it's not better but I can live with it, I was concerned about the ratio but have laid that to rest in my twisted mind, because the 1/8th'' shorter rod with forged pistons has to be stronger than cast pistons and 5.7 rods, this is not some fantasy engine build where we delete the crank and drop and drag a new one, it took me a long time to find a stock gm steel crank for 200 bucks, not fantasy engine build where we race them on desk top dyno, this is a poor boy building back as good as he can, not as good as they come,

 

So we gonna balance this rotating assembly? Find a set of stock 400 rods and have them resized with new bolts?

 

2:1 rod to stroke ratio is ideal for a race motor(6K+ redline). While this is hard to do in a small block chevy, we try to get as close as possible when building a high rev motor. Ive seen alot of 383s do okay on the street. Seen a few of them fly apart on the oval. They do suffer side loading issues and more importantly, the long stroke short rod creates way too much harmonic loading on the crank to handle high revs. However, they do make great torque and for the street, they do fine. When built with lightweight rods and pistons and a chrome moly crank, they even do okay at the strip.

I share my experience with you only to educate. The final choice is always yours. I agree that for a street application, 400hp or less, your combination should be fine. Ofcourse, be careful of final deck height as youre going into unfamiliar territory in your crank, rod, piston combo. You may end up getting those pistons machined to provide ample clearance.

In my final post to this thread Ill share this bit of wisdom. You can do with it what you will. I have built many motors. All of them were budget motors to some degree. Few people have unlimited resources to build whatever they dream of. Of the motors that I built from kits or parts combos without machining, some ended tragically somewhere during the season, others did okay. Without balancing and verifying tolerances, its just a toss of the dice. All of the motors that I have had balanced and clearanced have finished the season flawlessly. Many, after a quick teardown to look for any issues went right back in and ran a second season before being rebuilt. Thats the value of good machine work.

 

Couple of thoughts.

1. Many an engine builder will say to put in the longest rod you can.
2. The longer the rod the lighter the rotating assembly.

 

Thanks alot everyone! please yes dirt man I have a shop to balane to assembly for 150.00 once I tell him the bob weight, but I have another problem, i;m sure its the reason that you dont read of this combonation at all, and I do have the 4oo rods located and an even trade for 5.7 rods I have, but UPS delivered the 327 pistons and somthing that I had'not figured out is this, the piston is hitting the counter weights about 1/8th before BDC so it's machine the bottom of the pistons on the flat area below the wrist pins, which I'm not sure how this will weaken the piston, or to take a 1/4 all the way around on the counter weights of the crank, I was planning on taking it to have it balanced as soon as I get the rods & rings weighed, now another bump in the road, any idea what it would cost for either remedy? I just might be able to grind the botton flat area just under the wrist pin myself on a bench grinder just as long as I keep a close eye on the weight and remove the same amount each time, I really do thank everone that has tried to help, Can I down load pics to this thread?? if so I can send a pic of the area that I need to grind and compare to so stok pistons so everyong could guess on the strength issue,

 

Yes, you can attach pictures. If you take material off the counterweights, you'll probably have to add the weight back somewhere, and that's going to mean expensive slugs. It'll be cheaper to mill the pistons, if you can.

 

I just dont feel that there would be enough meat left holding the underside of wrist pin where it's hitting, if it where just the skirt I would not sweat it at all, And I also was wandering about tha same exact thing on decreaseing counter weight diamiture then having to add weight back, how common is it to decrease the counter weights rotation diamiture??? I was looking at some light weight steel cranks in an old catolog and they where 47 pounds, I was gonna weigh mine tomorrow, I thought I weighed it because it felt heavier than the cast iron crank that I pulled out, I thought the steel crank was 53 pounds but cant remember for sure, but I am sure it weighed more than the cast one, what is the normal weight of 2 peice rear main seal, 350 steel crank?? seems like there would be stock weights on the complete rotating assembly, that way if stock parts are used there would be no need for re-balancing it but I have not found it yet, the rods are gonna be an even trade and the forged piston where on 50 bucks, so I could spend a little and still be money ahead, or just buy elcheapO cast flattops W/ cast rings, but I really wanted soooo bad to build a little tuffer bottom end, man I'm down in the freakin dumps over this,

 

Why do you need a tough bottom end? You're only shooting for 400 HP.

 

Guessing he edited his original post to 500hp/ 68k? With vortecs I'm guessing some kind of power adder?

 

because I went ahead and ground the guide bosses down in the vortecs to accecpt a 600 lift cam and I can always change heads and cams down the road, I decided to forget gas millage and go with a stall converter, I have 4 sons with the oldest driving in 6 months so I will probly move this engine over to A 74 vette and give it to him to drive, and for some reason after I get to rolling along 15-20 MPH I cant help but mash the gas pedel to the floor every single time I take off, and right now it's no horse power but cant a fella dream big

 

Not a lot of point to a Vortec with .600 lift.

 

regaurdless now it back to the pistons and rods, I guess I can get new 6'' rods and pistons for about the same cost as 5.7 so thats the road I'll go unless I find another great deal along the way,

 

So what you you working with at this point?
Crank.
Rods.
Pistons.
Heads.

 

Are the 327 pistons flat tops? I know this is off the wall, but I know people that have done this sort of thing on other combos with decent success, so here goes-

Have you checked to see how far up the pistons run in the bore with 5.7" rods attached? You might be able to make it work, with CAREFUL checking. Probably too much compression anyway with 64cc Vortecs, but maybe worth a look see? (ducking flaming arrows now!)

Personally I would not run 5.65" 400 rods no matter what. Years ago I was told by my machinist that the 400 rods were weaker at the bottom of the beam-to-journal junction.
And, every 400 core I ever tore down had more cylinder wall wear than any comparable 350 core I ever saw. Just my opinion, worth what you paid for it.

 

Well skiiny, at this pount I'm stuck in the mud, I weighed the GM forged steel crank and it's 55 pounds, maybe enough to have the counter weights ground 1/4'' but that would run 250.00 and balancing on top of that, I am looking to sell ot trade the old sealed power FT 327 slugs and get my hands on some 2256 flats top, I have a set of balanced and polished 5.7 X rods that I can rebolt and get by I guess, this crank came out of a 2ton truck year unknown, 2 peice area though, I wish I knew the target bob weight of a stock 350, I tore this thing down expecting to do just rings and bearings with a 200 dollar budget, that was months ago, I moved to the vortecs so now I need another intake, and anything else that comes up, I know the x rods arnet the best, but would think they would be equal to a $150 set of after market rods, I know that part of what I hear about stock rods has to come from advertising of the aftermarket rod manufactures, I saw and old homemade 302 with 12/1 trw's and X rods turn 10K just reving it up at the starting line, so if I cant aford a 300.00 set of rods I may just use the X rods, I run a cabinet shop and there is nothing been hit harder by the recession and housing slump than a cabinet shop, so when I land a good sized set of cabinets I will skim some of the top of the deposit and buy some parts.

 

From what my machine shop tells me ( and others here have agreed), in my application, which is engine speed below 6500 rpm, a set of stock rods with ARP bolts are all I needed. After 60 000 miles (hard miles), I've experienced zero trouble. In fact, the engine had been apart twice. Once for balancing and the other because a flat tappet cam went away. Reused the same bolts and nuts. I would think that resized stock rods with good hardware would do the trick.
It's funny because I was very much in the same situation you're in now. After the engine started to get a little noisey (remember 60k of beating it up), I found a rod bearing was starting to go (nothing to do with the rods or hardware, just a lot of heat for a long time). I had hoped for a re-ring and re-bearing with no machine work so as to keep the project on a budget of sorts. Long story short, I ultimately went for a 20 thou overbore and some Mahle coated hypereutectic pistons. Had the crank ground 10 under on rods and mains too. $1600 later I have a new (more or less) short block.
If you give yourself the time, the parts may come to you at reasonable prices. With the economy the way it is , (as you're well aware) folks are selling off their goodies to pay the bills. No telling what you might come across.

 

I got to thinking last night about my post #28. I was just thinking about the relatively small difference in rod lengths between the 327/350 rods and piston wrist pin locations compared to 400 rods, and not about the nearly 1/4" difference in the stroke between the 327 and 350 cranks.

Therefore, the 327 pistons would probably be much farther off with a 350 crank than with just the rod length/wrist pin location differences that I was thinking about.

Still, just for giggles, I'd try it on one piston/rod combo just to see how wrong it would be.

 

Here a few piston compression heights I've found:

327/ 3.25 stroke/ 5.7 rod/ 1.675"
350/ 3.48 stroke/ 5.7 rod/ 1.560"
350/ 3.48 stroke/ 6.0 rod/ 1.260"
350/ 3.75 stroke/ 5.7 rod/ 1.425"
350/ 3.75 stroke/ 6.0 rod/ 1.130"
400/ 3.75 stroke/ 5.565 rod/ 1.560"
400/ 3.75 stroke/ 5.7 rod/ 1.425"
400/ 3.75 stroke/ 6.0 rod/ 1.130"

You can calculate any number of possible stack ups. Also consider decking the block to bring a certain compression height in line with a suitable deck height.