For those not familiar with the GRENADE engine, see the thread in the Builds board hall of fame to get up to speed on the story from a few years back. She is a 2 bolt main cast crank and piston 150k mile worn out 357 ci small block chevy that eventually made 738 whp on 25 lbs boost and a 140 shot of nitrous and lived to tell about it. It also propelled a 3663 lb 1988 Trans Am to a best of 9.37@150mph virtually unharmed for 2 summers.

I dug out the long block after a few years of retirement and am going to document the teardown to see how close it (if at all) it was to exploding! Here are a few picsto get things started. I think im going to ring and bearing it and plop it into my 71 chevelle with a budget twin turbo setup in the near future. Note the 2 bolt block, cast pistons and NO ring seal. Ring gap was .090 top ring on the piston i pulled and bearing clearance is around .003 mains ans .0025 rods with fairly light bearing wear. Enjoy the pics!

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Alright i had to tear out the pistons before calling it quits for the night. I nearly fell over laughing when i pulled the piston out the ALWAYS oily #7 cylinder and measured the ring end gap. Would you believe the top ring has an UNBELIEVABLE .320 gap? Check out the pics if you dont believe me! Ha ha ha!

How is that possible? Never in my life have i seen such a worn out ring. And people think .030 is too big for a street motor.

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You and that engine disgust me sir! Lol

 

Ha ha, i disgust myself with the crazy stunts i pull. That motor was worn FAR more than i expected but look what it teaches a guy. Loose race motors last forever. It had custom low tension rings, loose bearing clearances and basically the high mileage replicates a race motors tolerances. The ring gap is what gets me because id think such poor ring seal would contribute to melting down that piston due to bad heat transfer thru the ring pack.

It never really smoked or did much wrong to indicate how shot it really was. It had a bad carb on it for years and was heavily ring washed judging by the wear on the sides of the rings. They are REALLY loose in the ring groove and resemble a dykes ring in a motorcycle engine.

 

A few things I am curious about:

The crank is cracked or not

A straight edge agains the rods/check for bending

Signs of bent pins.

It sounds like there was not a ton of flex to the crank and caps, well less than one would think anyways.

 

Someone had a bad day and mis measured the gap on 7?

To think i would have bought a single ring set to fix.... I guess i should save my money next time ;-).

Keep up the good work

 

Crank is going to get magnafluxed and the rods will be checked for straightness. It doesnt show any major signs of abuse and for the most part, its just like tearing down any other worn out motor. It has excessive copper showing on the TOP bearing on the #1 main like belt tension related and some of the bearings show edge wear from crank distortion.

It needed .003 on the mains to accomodate the crank flex. The main caps show minor fretting before i torqued them to 85 lbs and they never got any worse.

 

The only 2 ways I've heard of rings killing a motor is:
1. Too tight of a gap (obvoiusly)
2. According to some users on the bullet, you can rattle a motor just right, and the gaps end up lining up. Then oil gets into the combustion chamber, then it gets killed from the octane being significantly lowered. I saw a thread where a mod motor blew up from that.

 

I call B.S. on the octane issue with an oiling cylinder. Unless that engine was pumping smoke like a chimney there is no way that much oil could actually pollute the incoming charge especially on a boosted motor thats throwing pressure into the pan past the dead rings.

What im pretty sure CAN happen is on a motor thats on the ragged edge of lean, dead rings lose the ability to transfer heat out of the piston head into the cylinder wall and the piston can cook under hardcore power.

 

Largest ring gaps Ive ever seen was on a older Diesel Jetta (80's.) I shit you not, all of the rings had to be .250." Not sure how it ran, but he did use a gatorade bottle as a catch can. Whenever he would get somewhere he would just dump the oil back in the crankcase. :lol:

Anyways, Id love to see where this thread ends up going.

 

subscribing!

 

Its going to the engine shop tomorrow and ill post what he finds.

 

Sorry I misspoke, it shook the rings from a flexing cylinder.

 

Thats interesting. The rod being bent says a lot about why that engine failed. Too much advance and massive detonation will cause that to happen at a very high power level.

 

Subscribing. That engine gives me hope for my build.

 

Dropped it off today at the engine shop. I did figure out the #7 hole with the .320 ring gap was mostly because the ring had been broken on installation and had been screwed up for 1000 years. It was broke so clean it wasnt obvious. Now thats a race motor eh? Ha ha.

 

A little extra mass in the exh never hurt nothin'

 

Add that to your sig.

 

Is it wrong that the GRENADE is the favoritest motor ive ever owned?