Roughly how often (how many runs) should major engine components such as rods, pistons, valves, cranks, etc. be replaced?

I don't think I've ever gone long enough without either wanting to upgrade or blowing it up to even consider this!

quote:

Originally posted by David_D.:
Roughly how often (how many runs) should major engine components such as rods, pistons, valves, cranks, etc. be replaced?

That's a very general question that really requires a specific answer! So define the usage of this motor in question.

We all know more rpm, more HP means less life.

The same pistons and rods that are in a 500 horse engine won't need the replacement intervals that those in a 800 horse engine will need.

Curtis

quote:

Originally posted by TOP38: That's a very general question that really requires a specific answer! So define the usage of this motor in question.

We all know more rpm, more HP means less life.

That's an excellent point!

3335 lb 74 Nova
406 CI (654HP at the crank)
Dart Little M block
Howards sport rods - Rods and crank have 1160 runs (mostly 1/4 mile) on them. They were magged and checked with new bolts 352 runs ago.
Callie's Dragon Slayer crank
Diamond Pistons
AFR heads with original valves (newer valve springs)

Pistons, block and Valves have 627 runs on them.

Powerglide with 1.80 straight cut gears
8.5 10 bolt with 4.30 gears

Launch at 4600, shift at 6800, trap at 7200, some whomping at the top end.

Well there is more to it than that. You also have to consider the quality of the crank, rods etc. At same power level and RPM the Winberg or Callies Magnum crankshaft will last longer than say a Scat crank. The higher the horsepower the higher the quality of the rotating assembly is required to live.
In general a lower Hp motor will last much longer than the higher Hp motor will.

To answer the question of when to replace internal engine components that depends on quality of all the parts, one weak link can wipe it all out. It depends on horsepower and RPM and more.

Unfortunately, it appears 40 years is the limit for a four bolt block, steel crank, forged piston, 425 horsepower 396 being shifted at 6,300 rpm. Autopsy not yet conducted. Take care. Tom Worthington

quote:

Originally posted by Tom396:
Unfortunately, it appears 40 years is the limit for a four bolt block, steel crank, forged piston, 425 horsepower 396 being shifted at 6,300 rpm. Autopsy not yet conducted. Take care. Tom Worthington

That’s funny! You found the expiration date! Did u find parts? Went out to the building I’m storing parts in today. I have some parts.

Pistons usually get tell you when time to replace such as too loose in bore or ring lands wore out. I think 6 years is the most I got out of a set of pistons.
I got 9 years out of a set of eagle rods in 850 hp big block Chevy but the motor was never spun over 7200 and 12 years out of Callie’s Magnum crank. The crank is still standard on all journals and in my spare motor. The rods were swapped out so who knows how much longer they would of lasted.

Well not really an easy answer, as I had 700 hits on my little 414 combo I did not like the leak down on the front 2 cylinders. Heads looked great but had a few things done to freshin them. Bearings looked good all they way around but new now, block got a little clean up with new rings. I believe this is better than waiting for it to die on the track. Funny the cars ET had not slowed down I just felt like it was time. Spending a little now out weighs a new build. Get my 2 cents

quote:

Originally posted by David_D.:

Howards sport rods - Rods and crank have 1160 runs (mostly 1/4 mile) on them. They were magged and checked with new bolts 352 runs ago.
Callie's Dragon Slayer crank

Just because a crank is magged doesn’t make it good. I thought the same with a 1000 hp rated crank I had magged that had less than 500 runs previously in a 625 hp engine to have it fail 170 runs into a new build and put a hole the size of my fist in the rear of the block.

Because I cannot build or rebuild a race engine and rely on a race engine shop to do everything, my rebuild method is now this. Replacing the entire rotating assembly with new is much less expensive than reusing the old imho. Using less expensive components rated for the HP of the build and replacing can be more cost effective than reusing / rebuilding higher HP rated parts for someone like me.

quote:

Using less expensive components rated for the HP of the build and replacing can be more cost effective than reusing / rebuilding higher HP rated parts for someone like me.

that is what i have done also,cheaper part and cycle often.even the better stuff will break if another issue is present

quote:

Originally posted by markemark:
Just because a crank is magged doesn’t make it good. I thought the same with a 1000 hp rated crank I had magged that had less than 500 runs previously in a 625 hp engine to have it fail 170 runs into a new build and put a hole the size of my fist in the rear of the block.

How did you confirm it was the crank that failed first?

quote:

Originally posted by CURTIS REED:
How did you confirm it was the crank that failed first?

The crank broke at the forward cheek #4 main for the 7-8 rods. The crank now in two pieces, rotated the broken cheek over the other half of #4 main and pushed the crank out the back of the engine. The 7-8 rods remained on the journal.

Broke the convertor snout and transmission pump also.

quote:

Originally posted by markemark:

The crank broke at the forward cheek #4 main for the 7-8 rods. The crank now in two pieces, rotated the broken cheek over the other half of #4 main and pushed the crank out the back of the engine. The 7-8 rods remained on the journal.

Broke the convertor snout and transmission pump also.

]

That had to hurt.

That motor is broke

The last big block I vaporized, by price comparison, I found I could get a crate long block for about what I would spend on individual components and the labor and machine work to build one.
My current small block zz4 350 has close to 1200 runs, still has 210 lbs compression, 98% on a leakdown. Pulled a rod and main bearing out to look and they havent even wore through the coating yet. With that many runs it did make me nervous enough to roll in a set of rods and mains, new chain and gears,lifters and rockers.
Just for a little more peace of mind.

Other than a cast crank, the only one I ever saw break like that was an Eagle 5140 BB 454...

Engine was still running and flexplate was wobbling.....and had just made a run !!


Block survived.....had it line honed and reused it.....

Broke this Liberty/Scat crank at 163 runs during a 4th round win (opponent broke out). The engine was still running, started vibrating bad around half track so I shut it off. It had tossed the alternator belt and when I got out of the car I grabbed the balancer and could move it around.

Took it apart and the crank came out in 2 pieces! Hurt it on a Sunday had the engine back in the car with a new crank and running on Friday, going 7.40s on Saturday. Luckily there was no other damage.

Hard to imagine a steel crank could fail that bad and with so few runs...but it's
Made in China steel.....


When you see some of the things they actually do build on a grand scale over there you wonder how the he-l-l any of it stays up !!