How much rpm and hp can a 400 small block handle?

[Scott Liggett]

Re: How much rpm and hp can a 400 small block handle?

I think the block will handle the 500 hp goal. Like others said, get ARP rod and main bolts or studs. You could spend $1500 on those 882's and they still won't flow like those AFR's. I believe if you want 500 hp without nitrous, go with the AFR's.

I have a HV Melling pump in my stock pan. It hasn't sucked it dry yet. If you're worried, over fill it by 1/2 a quart for racing. I did that a lot when going on long road trips when I cruised at 3500 rpm.

[SuperBuickGuy]

Re: How much rpm and hp can a 400 small block handle?

my experience - the 406 I just blew up was where I found the limit - and what surprised me is where that weakness is... not the rods, crank, or even pistons... but the siamese bore got too hot and it blew a hole through them at the head gasket..... the hp was 700 with the B&M blower on it... although, even hurt it was 400 hp and 500 lbs torque (6 cylinders working).
Too cold, you'll split the water jacket (did that too), too hot or hotspots (882 heads) and it'll bore a hole between the cylinders.

[SpiderGearsMan]

Re: How much rpm and hp can a 400 small block handle?

BLOWERS SHOULD RUN O RINGED CYL HEADS AND COPPER GASKETS
and a bow tie block or equivilent

[JeffMcKC]

Re: How much rpm and hp can a 400 small block handle?

I have 400 I just cant kill it, was a 2 bolt to start its been over 750 and 8.30s before as a single four motor "ALL MOTOR" set up, its been a Dirt Mod motor twice, it was a 393 I think, then a 625 HP Drag Week N/A Motor. and a Pump Gas Drags Motor twice. I am Gutting it and using the Rototating assembly out of it for this years Drag Week.

It will go back in the corner till its needed again, its not failed me yet over 9000 RPM before "by mistake" unloaded 8500 in the lights.

Done right they will live,,,, till they dont, I just hate not using it best block I have ever had but 8 lives are gone I know

[SuperBuickGuy]

Re: How much rpm and hp can a 400 small block handle?

BLOWERS SHOULD RUN O RINGED CYL HEADS AND COPPER GASKETS
and a bow tie block or equivilent

the max the little blower could make was 9 lbs of boost so I figured it didn't matter : oh well, a $400 bottom end - no real loss ;D

it's also one of those factors in my thoughts of LS power

[yellomalibu]

Re: How much rpm and hp can a 400 small block handle?

Here is another question i have ran into from reading forums is not to use a high volume oil pump with a stock pan or it will suck the pan dry and cause damage. Any one have thoughts on that should i just get a good stock melling pump?

If the bearing clearances are correct, a stock replacement pump really should be sufficient.

I, for no good reason really, always put the high volume oil pumps in motors. Never sucked the oil pan dry... but then again, I don't do land speed racing or similar driving. If you intend on traveling at high speeds/ rpms for extended periods of time, I'd stick with the standard oil pump... because I know someone who did, indeed, kill a motor by sucking the stock oil pan dry.

...and another vote for the AFR's . My 406 with AFR 195's has been 11.teens in the quarter mile in the Chevelle, probably close to 500 hp. ... and the new AFR's are better than the older models I have.
*edit* ...with a stock crank, two bolt mains with stock main bolts; though I did use Eagle 5.7 rods with their ARP bolts. When I freshened it, there were signs of cap walk.

[Eric68]

Re: How much rpm and hp can a 400 small block handle?

The problem is cracking with the block in the deck at the steam holes and the main webbing near the outer bolt holes. The other issue is the thin cylinder walls and problems with ring seal due to distortion from the head bolts.

Stock rods even with good bolts should not see more than about 6000 RPM, there are tons of inexpensive aftermarket 5.7" rods out there that are vastly superior than the OEM 5.565" rods for about the same cost as reconditioning 30 year old iron.

The other problem with factory 400 blocks is that they have core shift and one block may live at 8,000 RPM and 700 HP for years where another will fail in a 400 HP application. Before you pay for any machine work I would highly recommend having the block checked for cracks and the cylinder walls sonic tested for proper thickness (thin spots are bad, especially on the thrust side)

With that being said, your motor is together and is fine now, just run it. Chances are good that it will survive at 400-500 HP for a long time. Just be aware that there is a chance it will be one of those with a defect or thin spot and will go kaboom.

[min301]

Re: How much rpm and hp can a 400 small block handle?

The problem is cracking with the block in the deck at the steam holes and the main webbing near the outer bolt holes. The other issue is the thin cylinder walls and problems with ring seal due to distortion from the head bolts.

Stock rods even with good bolts should not see more than about 6000 RPM, there are tons of inexpensive aftermarket 5.7" rods out there that are vastly superior than the OEM 5.565" rods for about the same cost as reconditioning 30 year old iron.

The other problem with factory 400 blocks is that they have core shift and one block may live at 8,000 RPM and 700 HP for years where another will fail in a 400 HP application. Before you pay for any machine work I would highly recommend having the block checked for cracks and the cylinder walls sonic tested for proper thickness (thin spots are bad, especially on the thrust side)

With that being said, your motor is together and is fine now, just run it. Chances are good that it will survive at 400-500 HP for a long time. Just be aware that there is a chance it will be one of those with a defect or thin spot and will go kaboom.

Very good info, before sinking money into it, have it checked
for cracks, core shift, and sonic check it.

[SpiderGearsMan]

Re: How much rpm and hp can a 400 small block handle?

what is dart's new 400 going for ? 1500 ?

[CooL-NeWeLL]

Re: How much rpm and hp can a 400 small block handle?

Yea the SHP is round $1500 i think the next engine for the chevelle will start with one of those and all forged internals so i can make some real power.

[oldsman71]

Re: How much rpm and hp can a 400 small block handle?

Ill take the MIN advice and just polish the stock ones save myself some $. Im only looking at maybe 550hp at most, but i do have a nitrous kit but i dont think the stock 30 over pistons will handle that. Here is another question i have ran into from reading forums is not to use a high volume oil pump with a stock pan or it will suck the pan dry and cause damage. Any one have thoughts on that should i just get a good stock melling pump?

Stock Melling, with a good pickup(retained), good oil pan and/or a windage tray should be all you need.

it doesnt hurt to use the heavier presser relief spring if you turn it over 5800