Sprint car engine autopsy re-edit. 

this video took the mystique and rocket science out of these incredible engines that like I mentioned budding engine guys like me have often wondered what goes in such an engine to get it running again after a seizure, and it brings us right up close to things that can be repaired and run again. Great stuff mate and a very very good video,,,, and anyone who appreciates mechanics should watch this video.

Dirty on the outside but so clean on the inside! Love the diagnostics, much like a forensics process.

Found this video really interesting and enjoyable to watch, love seeing how you get your head around things and find a way to solve the issue, I much prefer to watch a 20 minute long video like this and learn a thing or two rather than one of those 4 minute or so long videos where they cut out all the drama and hassle and just make it look like a piece of piss. Really good video, love it, thanks.

Now I see why my dad used to chew my ass out every time I didn't cover every single opening on an engine with rags even if I was not working on anything major.

Glad to hear they went with an aftermarket block, factory blocks are great on the street at moderate power levels, but I would never expect one to live long in an application such as a sprint car...

If I thought I dropped anything, I would tear it back down, no question what so ever! Keep em coming!

Man the damage to the block, like you said it's amazing it held together and didn't make scrambled eggs out of everything else. Still unfortunate someone dropped a nut into that otherwise stout motor.

don't go back to 4 bolt caps unless they are splayed its why the main web breaks like that and a lot of initial timing 36deg and more

thanks heaps for the vid, very informative, love learning about what makes these things tick and how to keep them alive

ZIGgassedUP, I commend you for your patience dude. 90% of these replies all know how more about engines than a machine shop. After all, they drive the fastest Mustang and don't like anything that's not theirs. Just found the video, keep up the good work!

By the look of the pitted main cap surfaces in the block and the mating surfaces of the caps, the block had a bad align bore machining. It is called main cap walk. The main cap mating surfaces of the block must be smooth and flat, the cap mating surface machined flat and the caps need to press fit into the registers of the block. Then the crankshaft main bores must be align honed parallel and round to within .0002 of an inch. The crankshaft has to lay parallel in the main bearings or it hammers the bearing and or the cap in the block depending on how far out the tolerance is. It also appears the the piston had a ring land lift due to ring flutter from too much groove clearance, or possibly detonation occurred to cause it to lift. The chunks of metal in the combustion chamber is the busted up piston ring. I have seen insides of thousands of engine blocks, many of them racing engines, but I have never see one that had the main web completely broken out like that one.

Great video, There sure seems to be alot of experts out there......

Those springs above the lifters, I've never seen them before. I'm assuming they help relieve valvetrain stress? What are they called?

The block is singing Spandau Ballet. I'm broke, THIS MUCH IS TRUE.

My last motor was a 406, mild build 500 atfw, sounded awesome with gear drive and comp cams, 10:5.1 comp. I had std caps, they are actually a lot stronger than 350 single caps, chev made a bowtie block with splayed caps, dart makes a little M block with 4 bolt caps, but my research favored the splayed billet caps. Im no mechanic so you probably know all this. I ended up getting the 502 with blower and i pulled the 406 and sold it. Water coolin was an issue but got on top by cooling the oil with larger cooler, running front to back manifold water cross over piping, reduced my pulley sizes to spin the water pump faster which was a hv edelbrock. Result was engine ran at 190-200f, on 40deg C days it did get to 230f

I'm building a four bolt for drag car. Had it fillled up to the water pump openings to give it a bit more strength. Just can't swallow dropping a couple of grand on an aftermarket block. My machinist told me to keep the revs around 7000 and no spray or I would need an aftermarket splayed block. I would rather make what I have work. Eight years out of a roundy round motor is amazing.

Cool vid. There are all manner of 'engine talk' vids on RU-vid, but not many racing engine tech vids. Great post-mortem. Thanks from the USA.

Need to make a video on how to rebuild a sprint car engine.

I've only run into this once myself, but your diagnosis about the number one is likely correct (hydraulic-ed the cylinder), and is likely the cause of the block failure. Once it cracked that main loose, it likely let that cam bearing move, and most likely is were it lost oil pressure at. This engine was seconds from shitting it guts out the oil pan, when it stopped. The nut in the number six didn't help, but certainly wasn't the cause of this damage!

Your oil filter mount still has the bypass in it.it can bypass dirty oil ,we used to plug them off using 1/4 pipe plug.

Them are some STRONG rods no doubt!

Polished main caps, nice prep work, nice rods and crank too. Actually broke the main cap web! Holy smokes. Just a little carelessness by someone with the air clearers off cost the owner a lot of $$$$.

I've seen that happen with a harmonic balancer was vibrating and it took the main webs out of the block . Those stock blocks are good up to 600 hp . Maybe in a drag engine . They were built for station wagons running about 4500 rpm .i think the main started walking after the crack developed .

All I can hear is money, money and more money! Expensive lesson to learn. This is why I use stripping trays with dedicated places for every little bit and a set of specially made bungs to protect every orifice when working on an engine.

cool vid. good music. Damit Jim! now we know why the block broke. if that rod is straight I will be shocked. it all HAS to be related. would you really trust any part of the bottom end again? that crank is trash......it moved enough to break the block. how many revs you want to turn? how much hp?

As Spandau Ballet plays in the background. One chill shop.

That sucks! That nut sure got pissed off for being dropped in there. Hope you get it back together soon.

Thanks ZIG, good information for every wrencher and there is a Lot of good info in the comments this generated, you just have to filter them carefully.....

Just a crazy thought but could the broken main journal be machined square and a steel insert be machined up and fitted? Got to be worth trying to save what is a pretty good engine? Four bolt mains,steel caps etc too good to scrap. If it was down to me I think I would have a go. What you got to loose? Got a big chunk of 4140 left over from another job and milling machine quiet at moment...

Sprint car engines are beat on really really hard I am still amazed some of the stock blocks last as long as they do not splayed.

Autopsy is right, that motor was really killed!

Ouch! Beautiful engine expensive hobby. Sorry for your loss.

Thats a real shame mate, the wife wants a 383 for her 67 impala because its so big. Cant believe the amount of damage to the block just because of a bolt . The owner must be in tears ,was a very tough engine.

would you consider smaller diamater bolt on the outside of the 4 bolt mains so that you drill out less material on the block and keep some strength in the mains webbing ???

Wow that sucks and it didnt destroy all the parts in the engine you are right that is amazing later

I can't believe it didn't puke all over inside. Crazy stuff for sure. I got eagle in mine also. Maybe we'll get to see the new one all snazzy.

Never saw damage exactly like that before. It was so close to scraping the whole engine. To bad that 1 nut caused all those problems.

There is not much cross sectional area of casting to support the main cap after it was removed? Big bore motors do weaken the block a lot. This is where tie bolting the block with extra long high tensile studs comes into its own. Cast steel block anybody?

Wow that little nut tried to push that crank rite out the bottom. Thats what happens when you use them strong rod's they dont bend instead they are stronger than the block casting. That nut didnt look like it stayed in there to long ive seen them beat the hell out of a piston in 30 sec that one looked like it did its damage and got out along with its buddy the peace of piston. Owe the carnage. Look how that block broke at all the thin spots of the cast it fallowed the weakest spot all the way around that main cap.

Hey man what a mess looks like you got a great boat anchor. FINS UP 👍 👍

what a mess... very interesting to see. Thanks for the video!

Wonderful video ! many thanks for this moment....have a nice day

that piston with the broken land showing the top ring was damaged by detonation and the same for the broken bulkhead.. i must be missing something here .. is there a rules reqiurement to use oem blocks?.. sprint car engines here use dart iron eagle blocks and dry sump oiling

so let me get this straight.. you knew something could have been dropped into the intake, and yet ran it anyhow without at least trying to put a scope down inside of the spark plug holes or something?

Chevy 400 4 bolts are much weaker than 400 2 bolts. Also, the "010 020" blocks are the strongest of all production small blocks casting, from 283-400. The ideal setup would be to find as many 400 2 bolts with "010-020" numbers, and have splayed caps machined to fit. 800+ hp would live without worry to bottom end.

It sure did eat that block ! What a shame ..

The 350 based crand will work on a 400 with bearing spacers.

Should have line bored the main bearings to keep the bottom end working great..maybe have the new block line bored as well. Looks like your ring gap was too close on assembly..that's exactly what happens when the ring gap closes up on a piston. A dart SHP block would be your best bet for a block..the 400 requires a 400 crankshaft because of the main bearing size. If your gunna put the work unto making the other block a 4 bolt I would also recommend making it a splayed 4bolt

Zig whats he doing with the block? I have been looking for a stuffed one to make a table from. Paul

...I haven't been inside that many automotive engines, but that block/web sure looks pretty thin in this cross-section...?

I had an engine builder that did the cam bearings in my 400 sbc street motor tell me to look for the "mexico" sbc blocks because they had higher nickel content and were more durable.

the main webs cracked, maybe from to much lead from the magneto, or bad fuel, with open headers its hard to hear dentonation, but a bolt went down, one of the injector tubes, I can never understand why any body would run with out air filters, why no gear drive for the cam?

I always used 2 bolt main Chevy 400 blocks because outer bolts on 4 bolt main weak the main web of block. Reason being the thin block web left after the outside bolt holes leave thin material. Always used 2 bolt and never had that problem in customer Engines. Only factory Chevy 400 sbc engines do this.

Shit. Got damned lucky if you ask me. A lot of usable parts. Lucky it didn't grenade!

Tripods are great. Love the engine opening though

Probably some water or oil in the threaded hole before installing the stud and hydraulic cracked on torque down.

broken piston, broken block------yeah those rods and crank are still good!

Great vid mate. How did it not fly apart!

Wow - that sucks, new boat anchor.

I have seen that on stock engines cracks on 4 bolt blocks

So.. The guy who "thought" he dropped something in it. "I thought I did, but I guess not. I won't bother trying to find out for sure."

What casting numbers were on that block?

Looking for the rebuild video. Wheres he at with the motor now?

Awesome ! I have a lot of Australian car friends...........

So much for that nice set of angled plug heads. they are shot.

1 nut...15 cents, damage to motor...$$$$$$

That's why you NEVER use a stock configured 4 bolt main block form Chevy. That is there weakness. Use a 2 bolt block with splayed main caps and you won't have this problem. You are taking about using a 400 CID block, 4 bolt main, you are going to have the same problem again.

ouch. can't put a band-aid on that one

Whoa!! Can't believe how little metal holds onto that crankshaft when ya turned the broken piece over. Not a very good design. Makes sense to screen each of the intakes to prevent the nut job that fell in.

Why would use a stock GM 010 block in a sprint car?

Where did you get the intake and injector pump

Where do you guys race at ?

Are those sb2 head's ?

Oi. That looks expensive. Bearings should have been changed out long ago looks like.

When I worked on race cars it was outlaw street class running a 406ci chevy we had a 406ci that we decided to make into a 410ci it was awsome had massive power and torque he would just walk away from the pack well one day it shit the bed and when we tore the engine down the piston had left a nice big hole on the inside I have never seen this before and have never seen it since I am 100% positive the piston going to the inside was due to head bolts stretching and leaking coolant into the cylinder and then hydro locking pushing the piston through the inside wall.

Personally I dont think the factory blocks are good for more than about 600HP and 8000 rpm. I have seen that happen before and detonation or hydraulicing will [as you said] bust them,, Though really any block. Dropping a nut down the induction too will do it! Poor old motor it seems was abused something chronic. To quote Smokey Yunick,, timing chains are an instrument of the devil! Though gears too have inherent problems such as transmitting valve train harmonics into the cam and breaking them. Plus on a sprint all the power drives from either end of the cam

What kind of motor is that?

what heads are those ?

So where did the nut come from?

that's a four bolt for yeah. why I run a two bolts with a stock Chev block

I always preferred chains over drive gears. with a major engine blow up :- chains= you could always salvage most parts and do a rebuilt Drive gears= engine total detonation nothing salvageable complete throw awayLucky he was running a chain

I once lost a @#%%!~ Torqux head in a motor. Pulled out of the socket and flew away. Had rags covering everything. But once you have lost something is deeply disturbing. Never did find it and I think it just vanished down on the ground somewhere as it never turned up in the sump either. Anyway the very first thing I after losing it was to get a bendy magnet tool and put it down through each plug hole in to each cylinder because the one time you don't double check something is the one time you are going to turn something that is decent and working properly in to junk :/

The exhaust bolt pattern threw me off

That is a shame =why is your HP so low for a 410?

No one noticed one hole was down???? The end would still have come, but.

Thanks Zig!

Both late 70's thin wall casting, not worth building for race duty.

Them brits they call a light a torch and an engine a motor. Must be using fluoridated water in their tea.

So you obviously had the main cap nuts off prior to the video. Why would you screw them back on, only to screw them off in the video? Why not just leave them off so all you had to do was lift the caps instead of waste all that time standing there, spinning nuts with your fingers?

ever cryo a block ?

Yer lucky the thing didn't grenade all over the place.....holy cow!

most interesting imca modifieds run 2 bolt 400 s dont they

Yep rooted.

That cylinder head is fixable. fixed worse blown up heads than that

Yeeeeeeeaup! Yeeeeeeaaup! there's the problem. I laughed well for that remark

Doesn't take much to destroy a perfectly good engine.......I have been there and done that though on a Mazda rotary engine.....not a pretty sight.

you should make a coffee table o the old block

Check the oil filter for possible collapse. Someone did that on purpose.

PEOPLE sure we're giving u shit weren't they, I mean from engine building to camera operation...lol dam. The way I see it is if no-one had ever dropped a foreign object in engine,it probably would have been a different outcome.

So, we're you sabatoged or not mate?