4mul8r

I can get my hands on a 406 engine. Here are the specs:

Short block:
Block was milled (.010 I think), and quinched.
Cylinders were bore matched to the pistons.
Pistons are KB Hypereutectic 9.6:1
Crank, and Rods are balanced (supposedly the pistons were too, but I cant see anything taken out of them...so I am not sure).

New everything else (timing set, bearings, rings, gaskets, etc)

When I emailed the seller about the rods he replied:

"It has the stock 400 rods (balanced), so I *believe* they are 5.566" long. In any case they are just a bit shorter than the 350 5.7" rods."


My car would be driven (fairly hard) daily and taken to the strip and road couse fairly often. I was planning for my setup to make peak power right at around 5,500rpm, shifting at around 5,700. The rev limiter would be set at 6k.

I was told by one of my friends that these rods would suck after 4k rpm. Is this true?

RB83L69

Sounds to me like some stock 400 parts.

They will last to 5000 RPM occasionally at least a few times, if you put good quality bolts in the rods and then get them resized since they'll need it, and if the crank hasn't been abused in its past. Otherwise, expect short life out of it. It won't go to 6k very many times at all before something gives up. With stock rod bolts, I doubt it would make it past 6k one time without something coming out the side of the oil pan.

4mul8r

So would I want to get the 350 rods and pistons if I went with this block then?

RB83L69

No; 350 rods & pistons won't fit a 400. That's why there's 350 rods & pistons, and 400 rods & pistons.

If you plan on making live for any length of time in the duty that you describe, you need better parts than stock. You can use that stock stuff if you want, but I can pretty much guarantee, it will cost you more in the long run to upgrade it after it blows up, than if you upgrade it before it blows up. And in this case, the "long run" is actually not very long at all.

377Z

iTrader: (1)

Crap! I have stock 400 rods (with ARP bolts) for my 383; I thought they'd be good to 6000 RPM. The motors apart and if I understand correctly and they shouldn't go beyond 5000, now would be the time for me to upgrade them.

The thing is, I have good L2256F's I'd like to use, but I've only ever seen one aftermarker company that makes a 5.565" rod--Eagle--there 4340 and cost ~$550. Ouch. Are there any other options in terms of 5.565" rods?

377Z

iTrader: (1)

Forgot to mention, crank is cast too; don't know the limits of this piece either.

I'm not trying to make a racecar out of stock parts, I just want to know what the limits of what I have are so I can choose cam and intake to work in this range.

I thought I had finally decided on a converted LT1 intake for induction, but if I shouldn't spin this thing over 5000 RPM ever, there's no sense in it, I'll either upgrade or stick with LTR.

If I need to upgrade, what does it need to be to see 6000 on a 'regular' (i.e. weekend driven for fun, occasional stip time but all accumulated miles won't be 1/4 at a time) basis?

RB83L69

The stock rods aren't so bad, if they've had a relatively easy life; but they REALLY need better bolts.

THe next weak link is the cast crank. They're bad about breaking from high RPMs.

Problem is, if this is a built-up short block you're looking at, you can't put new rod bolts in it without tearing it down and sending the rods to the machine shop. If you can get the parts before assembly, it might do OK, if you're careful.

4mul8r

Everything is disassembled...so if I needed something better it would be perfect...However, he's wanting $1,300 for this setup...

Is that a good price? It doesn't seem too bad...unless I have to go replacing the rods, pistons, and crank,....if that's the case, then what did all my 1300 go towards?

My setup will be seeing rpm's in the mid 5k very frequently (I also love to drive around at 3-4k holding it in 1st and 2nd gear). I don't want to have to tear this thing down to rebuild it every month. So what crank, rods, and pistons should I get that would support those rpms? Or am I better off going with a 383?

SSC

I'd listen to RB.
I dont know how many 400's Ive seen with factory rods sticking out the the pan, most were bolt failure some the freaking rods snapped in half. Sucks finding a stash of 400's to find all of them destroyed beyond a reasonable builder.

Advice, if you build anything with stock SBC 400 rods have them checked, ballanced and can you say ARP?

RB83L69

Those pistons are OK. The stock rods are OK, within reason. But they need new bolts. I'd look for a better crank.

I don't see $1300 in the list you gave. I wouldn't pay that for that collection of parts. Looks to me like a $300 core, a set of pistons, rings, & bearings, some small parts, and some machine work... but not $600 worth of it. I'd have a real hard time paying very much more than $1000 for that group of stuff, knowing what it is and how much it costs to duplicate it.

377Z

iTrader: (1)

In my case the shortblock is at the machine shop, and the rods have been set up with ARP bolts in them--unfortunately I already spend the money on this (I did not know better). Had I not done this already I would have no problem buying better stuff to begin with; I just don’t want this stuff to go to waste thus I’d like to:

1) get an idea of the acceptable RPM limit for properly prepped stock 400 rods
2) know what is involved in properly prepping the rods and verify the shop did this
3) get an idea of the acceptable RPM limit for a cast crank

With this info I can decide whether or not I can live with the compromise of a motor that will live in this RPM range. Are there any processes that can be performed on the stock rods to push their tolerance of RPM up a bit (that don’t cost more than better rods)? Based on other combos observed here, the engine will likely never produce over 350 HP at the flywheel using this rotating assembly due to whatever cam/intake/exhaust I’ll choose & the heads I have.

RB, with reworked stock rods w/ARP, cast crank, and the L2256F’s, what is the maximum RPM you would recommend?

I’ll tell you, there’s not enough time in the day. I’d love to have the time to work in a machine shop part time to gain some actual experience with this stuff.

RB83L69

With stock rods, putting the better bolts in is a huge improvement. Other things you can do to them to help keep them from breaking, include shot-peening them to relieve the internal stresses that are frozen into the forging, and grinding any and all irregularities off of them, so that the flexing stresses that occur to them and maximize on the surface, don't have "stress risers" to operate on and selectively break. Given that, you can run them at 6k with reasonable safety. But you'll probably find that by the time you do all that, you'll have as much money as you would in better rods; except that you'll still have a bunch of stock rods instead of better ones.

The stock crank.... no way. If you do that to it, it WILL break. Probably at the front of the #1 rod journal, where the front end of the journal meets the throw. That's the highest torsional stress point in one of those cranks, because of the lightening they do (drilling through the throw). Check Lunati & Eagle, both of them make forged cranks for around $300 that are adequate for 6k blasts.

I would not recommend taking a stock crank past 5500 more than a few times, or past 5000 frequently. It will live a very short life if it hits 6000 with any regularity.

What heads do you have? It may turn out to be pure wishful thinking that the motor will produce meaningful power at that kind of high RPM anyway. If the heads won't flow it, then there's no point in twisting the motor up that far; in fact the car may go faster if the motor sees less RPMs, i.e. within its flow limits.

377Z

iTrader: (1)

Exactly what I'd like to avoid; putting a dress on a pig.

I'm glad I found this out the easy way; I'd rather buy a crank now as opposed to a whole engine later.

Doh, I figured 6000 was reasonable; obviously this may not be so and I realized I have no basis to assume so (go easy on me please, I do remember what they say about people that assume ). If this is a sick crack pipe dream, let me know:

The heads are the World Products stock replacements--1.94/1.50 valves, advertised with 170cc intake runners & 67cc chambers, iron. Plans are to smooth casting irregularities, smooth the slight ridge in the bowl, and slim the valve guides, and unshroud the valves. Probably will keep the stock size valves unless large gains are to be seen from going to 2.02/1.60's if the bowl is blended. Incidentally, I plan to start another thread on this once I can borrow a digital camera (hopefully tonight) as the casting looks better than I expected & there doesn't appear to be much that can be done outside of recontouring things (which is waaay beyond any knowledge I posess, so thats a DIY disaster I'll just avoid). At what RPM will a 383 max out these heads?

Thats what I'm after, achieving maximum power in the range my parts limit me in.

4mul8r

My heads are very nice AFR 190's with port work by total engine airflow. They flow 276.6/227.0 @ .5000

I have a complete ported superram intake setup from top to bottom. lpe 219 cam and 1.6 roller rockers.

I was assuming that peak power would be around 5500. I would set the rev limiter at 6k because I would definately not want to rev higher than that, yet it does need to handle up to 6k.

My blown 350 in my car currently was usually shifted while racing or driving hard at 5200. I did occassional and accidentaly peg out my tach a few times....probably causing some drivetrain damage.

377Z

iTrader: (1)

Waaay out of my league! I pray to get maybe ~230ish/170ish at 0.500 with hopefully corresponding decent low/mid lift #'s. From what I've seen it can be done, just hope I can do it.

At this point, if the crank I have can only safely be taken to 5000 RPM I'll just go ahead and put it together with cam & intake suited to idle-5000 RPM operation--I figure I'll get this thing assembled and running super-mild for now & save for the more hi-po stuff for the next go-round. The 700R4 in the car right now shifts at about 5000, so I shouldn't need to mess with it.

RB, I'd like to use a rev limiter to have an extra element of safety with this motor. Is it as simple as setting it 100-150 RPM over the shift point?

By the way, sorry if I jacked your thread 4mul8r; just didn't want to start another one that had basically the same inital questions.

Lonestar

[QUOTE]Originally posted by RB83L69
[B]No; 350 rods & pistons won't fit a 400. That's why there's 350 rods & pistons, and 400 rods & pistons.


350 rods will fit a 400, but you have to machine some clearances for the rotating assembly to clear. We do this to our 400's all the time.

RB83L69

Yes I know that. I also know that what he actually asked, which is whether 350 rods & pistons will work in his 400, won't happen. Keep in mind, this whole discussion is about a bunch of stock or stock replacement parts.

350 pistons are of course a different bore size than 400 ones. And if you use the 350 rods, you have to use something other than stock 400 pistons. You can buy lots of different pistons for that combo (3.75" stroke & 5.7" rod), but not stock ones, and not near as cheap as stock ones.

On the other hand, if I was going to all the trouble of putting 5.7" rods in a 400, I'd probably get better ones than stock anyway. Unless I was rules-limited or they were the PM ones or something. Alot of the better rods have more clearance to the block to begin with than stock 5.7" ones do.

377: Yes, you can help insure the motor's survival with a rev limiter. I think you'll find that with heads that flow 230 CFM on the intake, you'll run out of flow somewhere between 5000 and 5500 RPM anyway; so picking a cam that provides peak HP (shift point) at 5000 or 5200 ought to work out pretty well. I'd guess that about 225-230 degrees intake duration will put it about where it wants to be. And that's a rather mild cam. I had a XE274 (230 @ .050") in my 400 for a while, it ran real good.

377Z

iTrader: (1)

RB83L69: Thank you for all of your help & your patience, I'm sure you get sick of the wierd stuff some of us with little experience come up with.

I'll be sure to get the heads flowed before I pick the cam to verify expectations.

BadSS

I put over 40,000 miles on a 408 with stock crank (indexed and held down with ARP studs) and 5.565 rods (shot peened w/ARP bolts) running the heavy TRW pistons before I sold it. The engine started out around 480 horses with an additional 175 shot (6,000 rpm shifts) and ended up (after about 4 years) around 550 horses with a double stacked 175 / 300 shot (6,400 engine / 6,000 button). I drove it daily and ran it hard,,,, constant tuning and running it at the track almost every weekend. I also averaged around 15 lbs of nitrous a week through it.

I've built at least 8 similar combination (stock crank and rods- arp bolts) that shifted between 5200 - 5800 rpm and these guys were running them almost as hard as me without any problems. The key to it holding together and lasting is good machine work and making sure it's put together right.

The 5.565 rod builds were years ago though. I use aftermarket cranks and rods on most of the builds I do now, because as others have said,,, with pricing today the "upgrade" is cheap insurance. However, for something running under 6 grand,,, I wouldn't worry about it,,, especially if you already have everything like 377Z. Just make sure the build is good. Also, RB is right on the money on the camshaft. I've build a few 406's with heads flowing between 230 - 235 cfm with both 218/ 228 - 110 and 225/225 - 108 cams and they shift out between 5300 - 5500 rpm (depending on the intake, headers, and exhuast system) and are a BLAST to drive.

As far as the parts list for $1300, I wouldn't pay that myself, but if you don't want to run down the parts and have the machine work done for yourself,,,, then it might not be that bad of a deal. ONLY if you know and trust the guy that did the work (or you can check it yourself - or pay someone to check it for you),,,, there was next to no core shift on the block,,,, and the rods have ARP bolts. I would not run stock 5.565 rods with stock rod bolts in a performance application.

4mul8r

Sorry, I've been gone awhile..I wasn't getting my email notifications of replies to this topic.

Ya, I have no clue why he is asking that much. He started out asking $2,300..... He says he has over 1k in machine work and receipts for it.


So you think if I got ARP bolts that I'd be able to use all that stock stuff with no problem?