MAX RPM stock chevy 400

[PackardV8]

So many variables - the only sure thing is above 5,500 none of the factory 400" parts can be considered reliable. In order of likely failure:

1. Pistons
2. Rod bolts
3. Rods
4. Crank
5. Main caps
6. Block

However, all the SBC 400" parts have let go first under the wrong set of circumstances. Sometimes, the carnage was so bad, it would have taken a forensic metallurgist to determine what let go first. I remember one instance where NOS and a missed shift was involved, after driving over the rotating assembly, there was not a single usable moving part remaining. Can't blame that on the Chevy engineers.

Bottom line - with intelligent use, the 400" SBC is the best bang for the buck ever.

jack vines

[levisnteeshirt]

^^^^ so true ,, its a roll of the dice if you have a good one , some people have great luck with them ( and its luck ) , best one i've seen has 10 years use in circle tracking , left a 2 bolt main and had straps put on the caps , his philosophy was , if its limber , don't make a stress point with splayed caps , which in this case , seems to be working ,, its not a high rpm engine , they turn this one 6200

don't make a stress point with splayed caps Could please explain where the streess point is.

I think splayed caps are the way to go as they tie the pan rails in with the webbing which makes for a much stronger lower end.

I wish I could base all my info on one block that went for 10 years LOL

well , it seems to be working , only 400 block i've ever heard of being ran for 10 years or better , he will fix a 400 block with splayed caps for a higher HP type of motor thats for a stock block class , but in about 2 years its cracking in the main web , and any where else one might crack ,

there is one 400 block that runs at the track I tech , its been running above 5 years , factory 4 bolt block , 625 hp motor , I say thats luck , no cracks , it was refreshed last year , looked great inside , for how much longer ?? who knows , it was running last night , finished 3rd ,

could you please explain why you constantly try to take what somebody posts , and try yo insult them , thats what i want to know , and if you are so good , why aren't you in Charlotte working for a nascar team ?? my friends shop that i refer to , was approached by Richard Childress to come and work for him , because of everything he had heard about him , so , put that in your smartass pipe and smoke it

[CNC BLOCKS]

^^^^ so true ,, its a roll of the dice if you have a good one , some people have great luck with them ( and its luck ) , best one i've seen has 10 years use in circle tracking , left a 2 bolt main and had straps put on the caps , his philosophy was , if its limber , don't make a stress point with splayed caps , which in this case , seems to be working ,, its not a high rpm engine , they turn this one 6200

don't make a stress point with splayed caps Could please explain where the streess point is.

I think splayed caps are the way to go as they tie the pan rails in with the webbing which makes for a much stronger lower end.

I wish I could base all my info on one block that went for 10 years LOL

well , it seems to be working , only 400 block i've ever heard of being ran for 10 years or better , he will fix a 400 block with splayed caps for a higher HP type of motor thats for a stock block class , but in about 2 years its cracking in the main web , and any where else one might crack ,

there is one 400 block that runs at the track I tech , its been running above 5 years , factory 4 bolt block , 625 hp motor , I say thats luck , no cracks , it was refreshed last year , looked great inside , for how much longer ?? who knows , it was running last night , finished 3rd ,

could you please explain why you constantly try to take what somebody posts , and try yo insult them , thats what i want to know , and if you are so good , why aren't you in Charlotte working for a nascar team ?? my friends shop that i refer to , was approached by Richard Childress to come and work for him , because of everything he had heard about him , so , put that in your smartass pipe and smoke it

Where is the stress point from putting splayed caps on a 400 SBC. I need an answer as I have been puttingn splayed caps on blocks for many years, That being said GM Bowite, Dart, Ford MotorSports and World have been putting splayed caps for many years, So your saying they are causing a problem by putting them on.

[ could you please explain why you constantly try to take what somebody posts , and try yo insult them , thats what i want to know , and if you are so good , why aren't you in Charlotte working for a nascar team ?? my friends shop that i refer to , was approached by Richard Childress to come and work for him , because of everything he had heard about him , so , put that in your smartass pipe and smoke it/b]

I don't try to insult any one, You always say this guys engine did this, This guys engine guys engine did that sounds like all hear say to me.

And yes I spent some time down in Mooresville NC years ago and did look at some offers made to me to work for some cup teams, I can make more money doing what I am doing working for myself. All my shop equipment is paid for and the trucking business is all paid for.

Actually I have sent blocks to Hendricks for some of the builders that work there that build engines on the side. So far they have been happy.

[b]So wghat is your claim to fame and how many blocks do you machine and how many engines do you build in a years time??? What is your line of work??? Just trying to compare apples to apples here!

Wern't you the guy in this thread that tryed telling me how good the camel hump heads were over the Vortec heads, This guy di d that and this guy did this LOL

http://www.stevesnovasite.com/forums/sh ... p?t=194753

[blue88]

So.. from what I am hearing.... pretty much all stock 400 stuff is time bomb.. I guess I will take my chances.. since motor cost me all of 0 and what the heck else I going to do with it.. collect dust on floor? Time to throw cam and some heads on it.. and spinner til she pukes.

[CNC BLOCKS]

So.. from what I am hearing.... pretty much all stock 400 stuff is time bomb.. I guess I will take my chances.. since motor cost me all of 0 and what the heck else I going to do with it.. collect dust on floor? Time to throw cam and some heads on it.. and spinner til she pukes.

ROLL THE DICE LOL

[rfoll]

RPM is the killer for any stock rotator. Keep it under 6000, and it should hold up well. One of my 400 combos ran 11.50s at 115 MPH shifting at 5500 RPM. I didn't see mention of heads, but if it has the stock heads, a swap to 64 cc heads will take you from 8:1 to 9:1, allowing you to make better use of the bigger cam.

[adams]

I have a 4 bolt 400 block that is allowing me to turn a whopping 7500 rpms in most peoples opinions that build engines on a daily basis including the man that put mine together said "why in the hell did you get a 4 bolt 400 small block" well because i thought 4 bolts was better than 2. weather i am right or wrong doesn't matter, the difference in my engine and your stock one is a 4340 3.500 scat rotating assembly 11:1 mahle pistons and some big ported 235cc pro a heads giving me a 377 based 379.6 c.i. actual, motor as someone else had mentioned earlier. i have spun this engine up to 8700 rpms on several occasions, never on purpose since my cam stops producing any significant power after 7500, but because tire spin in mud is well unpredictable. now, its lasted a year so far and no sign of letting up any time soon but everything is completely balanced which makes a world of difference.... according to a lot of engine builders... i really have no clue i just drive the truck and know what i have in it im in the boat with every one else roll the dice and spin er up a few times, chances are if it starts vibrating and making strange sounds its probably not going to like high rpms, and just go from there what the worst that can happen after a few trials? blow up a free engine?

[blue88]

I had no intentions of building a full out race motor with this combo. I don't have the money or time. I understand I cannot zing this thing above 6000 on a regular basis.. or I will have a mess and a boat anchor. My original question was.. how much would you turn it.. rpm.. with good rod bolts and basically stock components. My thoughts were... I would I be safe with 5500. I guess time will tell.. since it is going run or blown up this summer. Thanks again.

[CNC BLOCKS]

I had no intentions of building a full out race motor with this combo. I don't have the money or time. I understand I cannot zing this thing above 6000 on a regular basis.. or I will have a mess and a boat anchor. My original question was.. how much would you turn it.. rpm.. with good rod bolts and basically stock components. My thoughts were... I would I be safe with 5500. I guess time will tell.. since it is going run or blown up this summer. Thanks again.

At 550 hosre rod bolts don't do thing to make the rod stronger its still the same forged rod, I would go to better rods at least.

[Wolfplace]

I had no intentions of building a full out race motor with this combo. I don't have the money or time. I understand I cannot zing this thing above 6000 on a regular basis.. or I will have a mess and a boat anchor. My original question was.. how much would you turn it.. rpm.. with good rod bolts and basically stock components. My thoughts were... I would I be safe with 5500. I guess time will tell.. since it is going run or blown up this summer. Thanks again.

There is nothing wrong with the stock rod in that application, the bolt either when it was new
The problem with the bolt is you have no idea of it's previous life,, was it assembled with a breaker bar or a torque wrench,,,
So if you are going to take it apart I would at the least put bolts in & have the rods resized

Thing is at that point you can buy brand new Scat bushed & floated rods for not much more so why not go to a 5.7 or 6" one which gets some weight out of the piston?
That & any decent forged piston & a good balance job,, you should have a pretty fair piece without killing your bank account

[af2]

Thing is at that point you can buy brand new Scat bushed & floated rods for not much more so why not go to a 5.7 or 6" one which gets some weight out of the piston?

Yep! The piston weight is substantial going up in rpm. Like the weight of a sledge hammer with a 2 oz head vs a 2 lb head.

[BrazilianZ28Camaro]

Thing is at that point you can buy brand new Scat bushed & floated rods for not much more so why not go to a 5.7 or 6" one which gets some weight out of the piston?
That & any decent forged piston & a good balance job,, you should have a pretty fair piece without killing your bank account

X10.

Low price for piece of mind.

As a bonus, if someday a ricer pump the gas at your side on the stoplight, you always can shut it down with out any concern.

[TMSJoe]

The key here is the stock piston and short rod . The 400 was known for breaking the piston skirts when reved up. GM didn't build it for that. How high? Beats me. I would keep it 5000 or less. Or build it up with parts for the job.

[blue88]

Ok... so what is it going to cost for the aftermarket assembly that has been suggested???? Who sells the rotating assembly? Scummit? Jags? Competition products?

[cpmotors]

Ok... so what is it going to cost for the aftermarket assembly that has been suggested???? Who sells the rotating assembly? Scummit? Jags? Competition products?

Scat Rods $325
Mahle Piston Pack- $650

Have the stock crank ground at your local quality machine shop and have them balance the assembly. Buy the parts thru them and I bet they would appreciate it.
I'd spin that 6500+ no problem and have built several that have.