I have my mind set up on my top end since I already have the heads although I wish I had gotten a set of AFRs. I will be running Trick Flow Super 23 195cc aluminum heads and a 242/248 (294/300) duration .540"/.562" lift 110 LSA roller cam.
Motor should shift around 6,500-6,600 RPM and be set up for a 100 shot of nitrous. Car will see less than 1,000 miles a year, weighs about 3,200lbs with me in it, 4.10s, trans braked th400 and will maybe see 10-20lbs of nitrous a year max. I'm hoping for about 400whp in the car without the nitrous.

I currently have $1,600 set aside for a bottom end; or at least a good chunk the bottom end. I have a 750cfm holley 4 barrel, the heads, the intake manifold, the long tubes, the distributor and other small parts.


I am looking into a Summit pre-machined 355/383 block for the ease of things although I don't mind having to do the final cut on the bores.
http://www.summitracing.com/parts/sum-150100

I'm a little up in the air about running a cast crank although I don't think I'd have any issues. One question, how can a crank be good for a 5.7" rod or 6" rod like this one is claiming?
http://www.summitracing.com/parts/sca-935050l

Being 62cc heads and me wanting to keep my compression as close to detonating on 93 octane as possible without milling brand new heads I chose forged Wiseco 13cc dished pistons with 1/16 plasma moly rings.
http://www.summitracing.com/parts/wi...make/chevrolet


I have concerns about h-beams clearing, yet these aren't weight matched and I don't know if I am over thinking things or not. Not weight matched or balanced but they are supposively clearanced.
http://www.summitracing.com/parts/cpi-a6000ds2a2ah

These are i-beams, rated for 550+ HP, lighter weight, weight matched (not balanced) but do not have any stroker clearancing.
http://www.summitracing.com/parts/man-14103-8

I've never been a fan of SCAT rods because of the bolt design and it being a pain to take back apart once it's on the crank but these seem too good to be true. Clearanced, matched and balanced.
http://www.summitracing.com/parts/sc...1qls/overview/



PLEASE HELP lol. I feel like I am seriously over thinking things and it's driving me insane.

 

By using ONLY the longer rods, it no longer requires the counterweights to be "flat cut" to clear the bottom of the pistons at BDC.

All of the H-beam vs I-beam stuff re. clearance is misguided. Either beam shape can be made equally compatible (or not) with stroking. Here's a pic of some H-beams, compared to stock.



Not hard to see how much extra clearance these give in the critical spot.

I think it would be sheer masochism and self-flagellation to build a 400 HP 383 with a cast crank and expect to add nitrous to that. That's a pretty good way to guarantee that you'll have to buy 2 cranks AT LEAST, and maybe a whole lot more other stuff twice too.

 

Diamond piston just came out with this tech tip related to piston's edge and top ring location with power adders.

http://www.enginebuildermag.com/Arti..._a_piston.aspx

 

I agree not to go with a cast crank.Don't fall for cast forged cranks.Nitrous is hard on the bottom end.Given the limited street use,I think a good 6" rod should be in play.

You want a internal balance crank.

 

Breaking research is that you want the top ring land lowered for nitrous? Are they going to say a thicker piston crown is better next month lol?

Thanks for the tips. I don't think I'll be spraying a big enough shot of nitrous to worry about ring land height.

 

looks like your building a stout motor.

just wanted to say, on a budget, you can build a short rod stroker pretty cheap. theres no need to clearance the block, but good to check, just in case. no special rods or small base circle cam. i just use 5.56/400 rods hung with standard 350 pistons. of course youll need a crank, etc., for the build. maybe kind of an old school build, but cheaper if on a budget.

 

If Diamond is changing a production height,which is expensive to do,they must be seeing a history of issues to warrant that change.They are a forerunner like Wisco in the business.Call Wisco and ask them what is this all about??.

And of course you KNOW about gaping the rings for nitrous.Right??.

The thing is not doing the right thing the consequences are all yours.

To use a shortly 400 rod is just plain asking for trouble.All you have to ask yourself is WHY all the newer designs are using a long rod??.Humm,must be something to that huh.

 

o.k.,...why is a 400 rod so bad?
there is no real big H.P. advantage to a longer rod.

 

It's so short that the pin height is low on the piston, increasing psiton side loading and slap. m

 

Theres not any real evidence that a long rod gives any kind of performance gain, but the short rods are terrible. The difference between a 5.7 and a 6.0 rod arent as extreme, IMO, as the difference between a 5.565 rod and a 5.7.

The main source that I trust on that is Reher-Morrison, they even have an article on their site about how pointless it is to worry about stuffing longer and longer rods in.

The thing about shorter rods is they put more side loads into the cylinder walls, and probably wear out the bores sooner.

Darin Morgan of Reher-Morrison (If I remember right, he designed the new Pro-filer heads too)

http://www.rehermorrison.com/blog/?p=89

And then you can read through this to get a more technical ideal world numbers comparison:

http://www.rustpuppy.org/rodstudy.htm



So if you go to a longer rod, do it just to increase long term reliability, not for horsepower. But make the rod too long and it gets all up into your compression rings in the piston, and that's not good for long term use either. So keep it reasonable.

 

i only brought this up as a budget build.
most 383 builds dont need 5.7 or 6 inch rods. its just a way for companys to sell THEYRE kit.

 

I don't like ring spacers for long mileage use,but when he said 1,000 miles or less,that would work.

The long rod debate has two sides of the story.............LPE has over the yrs gone longer and longer in rods.OEM engines has as well.

 

Just because theres not a significant power advantage doesnt mean there isn't an advantage. I would imagine the decreased piston acceleration around TDC in combination with less side loading would be a little better for long term ring seal.

 

Howards stop building a 5.7 rod stroker because they tired of complaints about side load issues.
The piston dwell with a longer rod does produce.I think is mostly torque in the mid rpm range.Cam timing is important to capitalize on that as well.
We all know there isn't normally one stand alone part that makes a difference,but building a number of changes one to com-lament the other to a sum total.

Does a 100 shot need a ring land change??. Well probably not.It is concept worth looking at to transfer heat better to the cylinder walls. I do know getting hooked on the bottle usually ends up for the user wanting more over time. Given that fact is why the tip is posted.

 

I appreciate the tip, I've built a nitrous motor in the past with two 150 shot stages. My top ring land was indeed lowered to .240" and the deck was .240" thick.
However, on a motor that will only be seeing a 100 shot of nitrous in small bursts and spending most of it's time without nitrous, I can't justify it.

The lowered ring land is really meant for larger amounts of nitrous on a more frequent occurrence.


At the time that was one of the lower options for the ring land. Glad to see more companies are making the switch.

 

And once again I do appreciate the tip. The way the car is geared with the selected trans and tire size, a 100 shot should send the car through the traps screaming. Anything more would have it bouncing off the rev limiter in the last 100 feet.

Plus I am gapping them for a 100 shot. No bigger and I will not be pulling it back apart to re-gap them lol.

 

I'm on the side of the long rod advantages being over-hyped... with one exception, and that one, being balancing.

The reason the 400 was externally balanced in the first place, was the short rods. The counterweights have to be "compromised" to fit underneath the pistons.

IMO the power, reliability, and all those other things, are there; just, really marginal. There's about a million other little details you can overlook while building a motor that will EACH have a bigger effect than that. Sure, if you're one of THOSE people that get EVERYTHING right EVERY time, and don't miss a SINGLE detail EVER (Chad, Paul, Alan, .... you know who you are) then there's a payof; for most of the people on a forum like this though, I'd bet money you could hand 50 of em an unassembled motor prepped for short rods and another 50 an otherwise identical motor except prepped for long rods, and you wouldn't be able to measure a statistical difference out of the random noise. Not in power, not in longevity, not in ANYTHING. All the "other" stuff would overwhelm its effect.

 

In regards to your rod choice I'm running a 6" Scat forged rod right now, I believe it's their pro-stock line. It was a nice piece and I'm glad I went with it. A friend of mine is running a 6.1" Scat in his LSx stroker and it's put up to a huge amount of nitrous abuse. Scat will definitely get my business in the future, FWIW

The math shows that there's less stress with the longer rods, and if you gotta buy them anyway and it's the same price, why not? Not anything to get excited over but it's just a thought. You'd be fine either way.

 

Thanks for the tip. I've ran SCAT rods in the past without any issue but I can't really stand the through rod bolts. I always have a horrible time trying to separate the rod caps when I double check oil tolerances with a plastigage.

Anyway, anybody ever try the scat ultra-q lite stroker rods? It seems to be a newer design of Scat's and all the reviews claim they can withstand 800+ hp easily.
http://www.summitracing.com/parts/sc...1qls/overview/


As far as the 5.7" vs 6" rod I am sticking with 6" because if their is a difference the 6" would be better either way. I read somewhere when Formula 1 experimented with using longer rods on a stroker motor they made an insignificant power gain but it was less stressful on the rods and kept some factory rod to stroke ratio the same. The article went on to relate it to stroked 350s and how the 6" rod was a better choice. True or not it doesn't really matter. I never see anybody saying the 5.7" is better but a bunch say the 6" is better. For the same price, why even argue it. Plenty of guys run both lengths and neither have issues worth noting.

 

Because often they're not the same price. If they're the same price it makes the decision a lot easier, though.

 

On this 383 build we used a 5.7 ARP stroker clearance press fit pin Scat rod.




Two reasons behind this decision. I don't like ring spacers for long mileage street engines that 6" rods require and unless your swapping pistons alot like in a race engine, there isn't anything to be gained by full float pins and with full floating pins more parts to go wrong with pin bushings that do wear out.

 

One of my buddies had a 350 he built come apart at the wrist pin and destroy the cylinder. Its why I went with press fit pistons on my build. A little annoying, but at least I dont have to fret about THAT happening.