Whats the most miles youve ever gotten out of a chevy 400 before a rebuild?

[DustyNova]

Just curious ive heard stories of 350s going to 300k so i was wondering if a 400 could do the same

[4x4toy]

The th400 in my 85 C20 has 340k miles on it. It was never serviced until 315k miles. Still shifts great, leaks from everywhere though.

[greg64]

Dusty, you're talking 400 small block aren't you? Not transmission.

I think engine life comes down to how frequently the oil is changed, and how many short trips (cold engine starts) the engine has to endure. And of course, abusing the engine or overheating it won't help either.

After that, I think the 400 is at a disadvantage compared to a 350. Shorter rods put more piston thrust on the cylinder wall (faster wear). The piston has to travel further for a single stroke (more wear), the piston speed is higher. The cooling isn't as good (siamesed cylinder walls). On the plus side, the main bearing journals are larger in diameter.

But in the end, i suspect how the engine is cared for might count for more than the above design factors.

[school boy]

Greg pretty much nails it.
Personally, I have seen a 350 go 30,000 miles before it needed replacement; boy never changed his oil. Then again, I know of one that is still going with 350,000 mile but the owner cares for the truck greatly.
A 400 on the other hand, the only first hand experience I have had was the one I bought out of the original 70's big body car and I believe it had around 120,000 miles. Up on tear down, everything was great, was a running engine before pull, except the outer cylinder walls had excessive wear. The kicker is im not sure how the engine was cared for.

[Chevy_mud_truck]

The one I just rebuilt for my 78 had about 270k to 280k and every thing still look good inside

[Chevy_mud_truck]

And from the before pic it wasn't taken care of and a after pic all cleaned up and rebuilt

[KQQL IT]

Depends on abuse. I've killed the case on one, the current one has been 8 years and a hundred plus passes at the drag strip.

[Tom]

The OP can't mean transmission or else he would have asked about TH350 and Th400's. He asked about 350's and 400's, that means engines.

[Chevy_mud_truck]

Well I feel silly for not reading the first post close I see every one post and fell right in with useless info then

[93M6Formula]

A motor (if that's what OP is talking about) is only as good as the person who takes care of it. If you neglect it and don't do ruitine maintenance, expect problems.

[86c20]

its all in care yes but it is in the way its made too. we all no that some years they changed things to save money and thats when heads crack or the rods go or what ever.

no with that said i have seen some of the mexican gm crates that are said to be junk (most are i have 4) go over 250k all the way to 375 but it was low hp the guy took grat care and used it light plus all highway driving a 70. it all plays in.

i think that a real number for miles on a avage motor would be around the 150-200 make before it really should be looked at hard for a driver. if you are plaining hard work or high hp rebuild it anyway.

[DBLSPRT68]

My Father purchased a 1974 Impala 400 brand new. He took very good care of the car, and it lasted 350,000 miles +. Had it rebuilt, and drove it another 100,000 before selling the car. I would have loved to have it, but sold it in the car......