Stock 400 short block rpm limits - Chevelle Tech
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post #1 of 12 (permalink) Old Aug 31st, 19, 11:47 PM Thread Starter
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Stock 400 short block rpm limits

How hard can a stock short block 400 be pushed? Cast crank, cast rods, cast pistons.

Did anyone see that episode of Engine Masters where they shot a ton of nitrous at a 305 stock short block with cast everything and it made like 350NA horse at 6000rpm?

Just wondering if my stock short block 400 would stay together if I spin it to 5000rpm on a regular basis. Right now I think it hits 4500rpm if I just let it rip in drive. It's a mild cam but I think it would be quicker if it shifted at 5000-5500rpm. Its the chevy 350 horse 327 cam.

Looking for someone that has experience with these engines and can tell me it will spin 5000 all day long or no friggin way.

I bought the complete short block for $300. It's been a fun budget build. Lots of torque. I can remember when the 350 wasn't even able to peel out from a stop and now this thing is a smoke show.
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post #2 of 12 (permalink) Old Aug 31st, 19, 11:55 PM
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Re: Stock 400 short block rpm limits

Should be just fine
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post #3 of 12 (permalink) Old Sep 1st, 19, 1:06 AM
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Re: Stock 400 short block rpm limits

i heard below 5500rpm with the stock rotators
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post #4 of 12 (permalink) Old Sep 1st, 19, 9:27 AM
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Re: Stock 400 short block rpm limits

5000 isnít an issue for a stock engine.
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post #5 of 12 (permalink) Old Sep 3rd, 19, 12:33 PM
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Re: Stock 400 short block rpm limits

Several years ago my son grabbed one of my 400 short blocks and dropped in a Blazer. I had three at the time that were stock rebuilds (cast pistons, stock rods, cast rings) for when an engine was needed (his definition of needed is a lot lower than mine)! Take a 19-year old "young adult", add 400 cubic inches that belong to someone else, bolt on a set of rebuilt heads and upgrade the cam, then see how many 4-wheel burn out you can do! Despite my cringing, it held together @ 6,000 RPM on many occasions!

My son put about 15,000 miles on that engine that way before I got it back. Still had 55psi oil pressure, did not smoke nor did it make any funny noises. I cannot say they will all hold together that well, but that one sure did!
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post #6 of 12 (permalink) Old Sep 10th, 19, 5:02 PM
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Re: Stock 400 short block rpm limits

It's been a while now but I was at Island Dragway for a test/tune day with a friend of mine and his Nova.There was a guy there with an El Camino that had a 400 SBC and I asked him about the motor.He said he shifts at around 5200 and it never exceeds 5400-5500.He said that is the way to making those 400's last. IIRC he was running 11.50's or thereabouts.
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post #7 of 12 (permalink) Old Sep 10th, 19, 5:32 PM
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Re: Stock 400 short block rpm limits

Quote:
Originally Posted by MNmalibu View Post
How hard can a stock short block 400 be pushed? Cast crank, cast rods, cast pistons.

Did anyone see that episode of Engine Masters where they shot a ton of nitrous at a 305 stock short block with cast everything and it made like 350NA horse at 6000rpm?

Just wondering if my stock short block 400 would stay together if I spin it to 5000rpm on a regular basis. Right now I think it hits 4500rpm if I just let it rip in drive. It's a mild cam but I think it would be quicker if it shifted at 5000-5500rpm. Its the chevy 350 horse 327 cam.

Looking for someone that has experience with these engines and can tell me it will spin 5000 all day long or no friggin way.

I bought the complete short block for $300. It's been a fun budget build. Lots of torque. I can remember when the 350 wasn't even able to peel out from a stop and now this thing is a smoke show.
I used to spin my 406 to 68-7200 all the time. I have another one that has forged pistons and 5.7 rods, won't hesitate to spin that one to 6200 with a hyd. cam at all. 5K, It will last forever.
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post #8 of 12 (permalink) Old Yesterday, 7:28 AM
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Re: Stock 400 short block rpm limits

Quote:
Originally Posted by MNmalibu View Post
How hard can a stock short block 400 be pushed? Cast crank, cast rods, cast pistons.

Did anyone see that episode of Engine Masters where they shot a ton of nitrous at a 305 stock short block with cast everything and it made like 350NA horse at 6000rpm?

Just wondering if my stock short block 400 would stay together if I spin it to 5000rpm on a regular basis. Right now I think it hits 4500rpm if I just let it rip in drive. It's a mild cam but I think it would be quicker if it shifted at 5000-5500rpm. Its the chevy 350 horse 327 cam.

Looking for someone that has experience with these engines and can tell me it will spin 5000 all day long or no friggin way.

I bought the complete short block for $300. It's been a fun budget build. Lots of torque. I can remember when the 350 wasn't even able to peel out from a stop and now this thing is a smoke show.

Add -186 double humps and you built the engine in my first '65 Elky. I abused that thing and it never missed a beat. 6K rpm was usually a daily thing. The low end on that combo builds is pretty high.
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post #9 of 12 (permalink) Old Today, 1:28 PM
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Re: Stock 400 short block rpm limits

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Originally Posted by 71350SS View Post
It's been a while now but I was at Island Dragway for a test/tune day with a friend of mine and his Nova.There was a guy there with an El Camino that had a 400 SBC and I asked him about the motor.He said he shifts at around 5200 and it never exceeds 5400-5500.He said that is the way to making those 400's last. IIRC he was running 11.50's or thereabouts .
*EDIT* I don't know what I was thinking when I wrote that yesterday but with the 30 minute edit time I couldn't change it when I first realized my mistake.What I should've wrote was that he was running around 12.50's or thereabouts.
Also to get back to original question, the stock 400 rotating assembly with those shorter connecting rods and heavy crankshaft.Is that a stumbling block to running higher RPM's ? No stock 400 came from the factory with a forged crank so you don't have that to lean on either.Yes I know you don't need a forged crank to turn some R's but it doesn't hurt either.
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post #10 of 12 (permalink) Old Today, 2:39 PM
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Re: Stock 400 short block rpm limits

A very good friend of mine used to turn these at 72-7600 three nights a week during the summer in his IMCA stock car. What he found, he could get 15 nights out of a set of cast pistons. If he went over that count it was a timebomb, as a pin would pull out of the bottom the pistons around that time. What he did, was to replace just the pistons, no rings or bearings, never balanced at 13 nights of racing. Mind you back then these were claimer motors that could be claimed after any race for $300. After he started replacing pistons at 13 nights he never had another windowed block. This was back when a set of forged pistons were more than his stock car cost and most guys were still scrapping together junkyard engines to run, "when racing was fun" as he says.

BTW tracks where he knew he would get claimed at he would put a "high" night engine in for the new owners benefit.
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post #11 of 12 (permalink) Old Today, 2:44 PM
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Re: Stock 400 short block rpm limits

I drag raced mine to 7000 rpm for years without any problems. 2 bolt, stock cast crank, stock rods, forged +.030 pistons, all balanced.
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post #12 of 12 (permalink) Old Today, 6:07 PM
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Re: Stock 400 short block rpm limits

Quote:
Originally Posted by BB68 View Post
A very good friend of mine used to turn these at 72-7600 three nights a week during the summer in his IMCA stock car. What he found, he could get 15 nights out of a set of cast pistons. If he went over that count it was a timebomb, as a pin would pull out of the bottom the pistons around that time. What he did, was to replace just the pistons, no rings or bearings, never balanced at 13 nights of racing. Mind you back then these were claimer motors that could be claimed after any race for $300. After he started replacing pistons at 13 nights he never had another windowed block. This was back when a set of forged pistons were more than his stock car cost and most guys were still scrapping together junkyard engines to run, "when racing was fun" as he says.

BTW tracks where he knew he would get claimed at he would put a "high" night engine in for the new owners benefit.

We did the exact same thing in the late 90's. 400 SBC with a cast bottom end in an IMCA modified. We usually spun it to 6800 RPM. Here in Canada it was a $500 engine claim rule. That 400 was a great engine. It would come apart for freshening every 10-12 races or so. After that I got into sprint cars and engines got much more expensive.

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