Ok my friend tore down his Dart 350 racing engine today after it broke idleing in his yard. Below are the pictures of part of the #4 piston that we found when we pulled the heads. There is a hole in the cylender wall about the size of your palm. The exhaust pushrod is bent but there isnt a scratch on the head or on either of the valves. The rest of the piston is under the baffels in the oil pan. The wrist pin is still in the rod but the rod isnt broke or bent and the clips must be in the oil pan too. Here is the build specs on the engine. car was running on race gas. Any ideas about how this happened at Idle. Idle was set at 800 rpm and was just warming up. The sparkplug was destroyed and i think that thats what the piston hit.

the engine made 430 hp at 5800 rpm and 425 ftlbs tq at 5200

4 bolt mail chevy 350 block new not used
Sealed power hyperutectic pistons 9.8:1
Race preped eagle steel crank
Childs and Albert ZZ Gapdura file fit rings
Durabond cam bearings
Gm Pink forged steel rods
Arp wavelock rod bolts
Clevite 77 tri metal main and rod berrings
Comp cams custom high output lifters
Cloytes true roller timing set
Comp cams valve locks
Comp cams XE chrom molly hardened push rods
Dyna gear race oil pump
Dyna gear pickup
Arp steel oil pump drive
After market oil pan baffeld 5 qt
Aftermarket timing cover
Arp head bolts

heads
Dart heads 200cc Trick 49cc Chambers with power making features. Bowls blended
Features: Severe duty 2.02/1.60 valves. Comp cams 1.25 springs 7 degree super
locks. 3/8" studs, guide plates, p.c. seals , chrome molly retainers. Heads are
gasket port matched. 1.6:1 proform roller rockers.
Comp cams Custom series muscle car cam.
Features: 110 centerline 488-488 lift corrected 1.6:1 ratio = 530/530 lift.
228/228 duration @050. 100% streetable and will run vacume access.

Edelbrock performer rpm intake manifold.



machine work

Select Hi Tin block 4 bolt main
Align bore and checked for run out. Full race clearancing
Mag Check -pressure check
Hot tank - jet wash
Bore Torque Plate honed to give a true finish.
Shotpeen rods
Dynamic balanced assembly
File fit rings - blue print clearance
press- pistons to rods
install cam berings and freeze plugs
port blue print cylender heads

Pictures are below.


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A pic down the bore at the rod and pin would help...
Why cast pistons?.....What kind of clips? Professional Install?
What was the timing at? Was it tuned for AFR and timing?
How much time on the motor? Doesn't look like much...

Clip came out...pin scraping up and down bore until it created a seize point for it, then carnage?

Kinda need to see the whole picture if you know what I mean, we are getting only 25% of the equation...

 

the engine was built by a repuitable builder and the timing was set at 0 and and the carb was tuned to a slight rich mixture and the motor had a little over 6 hours on it. wasnt even broke in yet. no hispeed passes or anything. the engine was brand new

 

Not much to go on, someone might have dropped a nut or screw down the intake. If the exhaust push rod was bent the valve was definately hit by something. If there wasn't a mark on the valve it was probably soft piston pieces. So which came first the hole in the cylinder or the broken piston??

 

You had 49cc chambers and still only had 9.8:1 compression?

 

How fast did it stop running?

Also, what kind of condition is the timing set in? (Chain & Gears)

 

Well,using hyper-u-crap-tic happened.
Ya might have damaged it while tuning or on the dyno or it may have been defective or a valve hit it.
It was damaged prior to "idling in the yard".
Man using those pistons with that caliber of block and that HP level is unheard of-- almost.
I used a set at customer insistence in a 356 Ford with 11-1 and blow a hole in one with the timing on 110 fuel and it wasn't to high(35 total at 3500)
I wouldn't put hyper piston's in my lawn mower.

 

Guess I was just lucky with mine that held up over 1800 passes and 5-6K street miles then? end of stock cast crank snapped off and caused alot of valvetrain damage but block, rods, crank, rod/main bearings, and PISTONS all looked brand new yet!!

For no more power than the motor made I seriously doubt that had anything to do with it, probably just a fluke deal with an imperfection somewhere.

 

Yep ya were lucky.

Fluke deal???????
Imperfection somewhere???????

Ya THINK???????

Still wouldn't put them in my lawn mower.

 

Honestly it lasted longer than I ever anticipated, was expecting less than a full season at the pwr level these ALL STOCK parts made, but I think it boils down to having a builder that knows wtf he's doing to begin with. No different than anything else IMO, you can take the best products in the world then let a hack or wanna be put it together and it wont last. But take an expert and give him shiit, he'll make it work alot better than the hack with the best parts.

Not implying anything to anybody, but I've seen too many guys that think they know what they're doing, but in reality have no idea. Same goes with guys in my construction trade too.

 

A builder can't add strength.
From what I see in the photos it yanked the top off of the piston.
This is caused by long stroke,short rod,&RPM's.
A good forged piston would not have done that.

 

ya want a guy that thought he knew what he was doing? guy made a custom alternator bracket out of angle iron and set the alternator such that it required him to relocate his overflow catch bin for his alternator, once he found a belt for it, it didnt line up, and he burnt her up of course. he also had an unshrouded mechanical fan that was bent and walking his water pump pulley all over the place.

but i think it's natural for guys to think they know what they're doing, then screw up and be humbled by it, and realize there's something to learn yet, i mean how lost do you have to get before you ask diections? lol

NOW THAT PISTON, if you have all the pieces and can assemble them in the shape of the piston I might be able to draw up some sheer and bending moment diagrams (force distributions) and try and figure out where it cracked first and use that to figure out exactly what hit what and seized where, long shot, but it might give an idea

 

Your probably right, but I can also promise if that had been a forged piston he would've lost alot more that he has since forged components like to explode and cause as much collateral damage as possible instead of just breaking that component.

But I totally understand where your coming from and we all know what works for one guy causes nothing but problems for another...especially when it comes to all things mechanical.

 

If forged don't break there IS no collateral damage.


I will say again a forged piston would not have done that.
Forged pistons are not known to ****** the head off of them.
Whenever ya break a piston there is always damage to the cyl and head.

 

Pictures of the cylinder head would be useful. If the pushrod is bent then suspect a seized or galled exhaust valve/guide. Pistons break like that from mechanical interference. You'll probably find a good piece of the deck of the piston that will show valve contact. That's where my money would be.