Blown head gasket, likely cause????

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Valvebounce

Valvebounce

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we've got a 340/418 stroker motor. Which is still pretty fresh. but it's blown a head gasket. In spectacular fashion!
I've not seen a gesket pop this severely before. So am looking for some insight into why it did this. motor has brand new RHS heads from Brian, and the decks were machined when the motor was built. (<1000 miles ago) As well as it's never been cooked or over heated.

any suggestions on Why?
 

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Are those "pits" on the quench domes? If yes , Id go with detonation.Detonation creates huge pressure spikes in the chambers.No 5 beside it looks to be failing too. Also,if those are detonation pits, you might consider checking the rod bearings, and the other head gasket as well.And finally, do something with the timing to prevent a subsequent failure.

But if those are not detonation pits on the quench-domes,then I guess the usual reasons; inferior gasket,lack of sufficient fastener torque/or retorque,a too-smooth surface machining,or, too much cylinder pressure.
That is a "spectacular" failure. lol. Did the hard surfaces survive?
 
I cant say for sure, but I think those spots in the pic are droplets of coolant. To Be 100% honest it's actually My dads motor. And he lives 40 mins drive from me. So I asked him to email me some pics, after he rang me today.

I'm hearing what you're saying about the cylinder next to the blown cylinder. However cylinder number 2 looks worse. Although not as bad as poor old number four.
 
I vote detonation, it got me too. I put aluminum heads on and changed pistons to lower compression 3 years trouble free now. Good luck.
 
Pushing head gaskets that way in a small Mopar is classic detonation/pre-ignition. Check and verify timing--reduce total timing--make sure no vac leaks are present. What is the cam specs and vehicle weight/rear gear? Spikes in cylinder pressure are the culprit here-guaranteed. I have done this a couples of times myself. J.Rob
 
Build spec out to?
You mean the compression ratio?
I think the cam is around 284 adv.
Icon forged slugs, (The lower comp ones)
I rang the old boy this morning. I tried him last night when I last posted, but he must have gone to bed already. He's going to check the crowns for damage after his breakfast. (It's only 1050am here as I type this)
He confessed his biggest problem is that after 50+ years of engineering, he's pretty deaf. And he can't hear detonation anymore. Told me that when he started the part time job he works now they did a hearing test as part of his pre employment medical. And he said he could only make out the first two beeps.
Might be time to invest in one of those knock blocks with warning lights?
 
I think most of us are in agreement that is detonation.
Double check piston tdc to mark on crank. Did you re-curve you dist? The reason i ask is that you may have set the timing at idle, and not realized that there was to much mechanical advance in the dist causing it to be over advanced. So when your dad was having fun with the long skinny peddle, it when into detonation. :burnout::violent1:
 
All of those fire rings are OVAL.....Looks like you were on your way to popping through all of them. Detonation for sure.

I don't see how you couldn't feel it in the pedal or hear it while that was going on myself.

You will need to pull both heads and replace both head gaskets without a doubt.
 
I might add that the drivers side of the engine is referred to as the left side,as are any other direction specific parts on the car, and the pistons on that left side are numbered 1-3-5-and 7. While the cylinders on the passenger side, the right side,are numbered 2-4-6, and 8.So pic #4 is showing the left bank of cylinders; numbers 1-3-5 and 7.
If you knew all that and were simply referring to that last cylinder on the left side as the 4th from the front, and number 2 as being the 2nd from the front,well then,my apology.
Also, with that amount of detonation, if that was my engine, I would be inspecting the rod bearings too.And of course, backing down the timing and/or looking for better, more detonation-resistant fuel.
 
Actually, the drivers side of this car is the right side. As we drive on the left side of the road. I actually posted that particular post after a friends birthday party, So I was somewhat impaired. lol

Since it was built, it's been run exclusively on either 98RON, (That's how fuel is rated here) which I think has an AKI of 93. Or Leaded race gas. There's a small gas station on the outskirts of town near a speedway that sells it, so long as you're putting it into a can, or racecar/boat, they sell it to anyone.
So it see's a fair bit of lead.
Funny, because whenever I smell av-gas on the street, it's almost always an old white haired guy driving a muscle car.

The dizzy is one of those horrible chinese ones with the magnum style lead ends on the cap. Which I have on his case about for ages. (why the hell do you have a $150 dizzy on a $7K plus engine etc) He's off to Hawaii later this week, so I think he's getting a new dizzy sent to his friend there. (Postage down here can be quite expensive sometimes)

An old car he used to Daily drive, (non mopar POS) would rattle it's nuts off too. I said to him a few times, holy hell, how much advance are you running? It's pinking it's nuts off. He just couldn't hear it.
 
It will be interesting to see the other bank. If you only have one cyl that is detonating, you could have a air fuel ratio problem in that bank, port, manifold. or a dist that is out of faze on one cyl.
 
So he's been looking for a cost effective ignition upgrade.
This one looked to him to be good bang for buck. Being semi retired, a $700+ billet distributor isn't really an option. The car is a primarily a street/occasional tow car. Although he might let me run it down the strip for him a couple of times a year. (If we ever get past these teething problems!)

He likes the look of these http://shop.whiteperformance.com/DO...-COIL-DISTRIBUTOR-BOX-WIRES-PB-13-MSD-STR.htm
Which are most likely available from speed shops here too.
Any feed back good or bad about these? The bloke over the road from me fitted one to his 350 after it died and refused to start in my driveway one afternoon. By Chance my dad was at my house that day, and he took great delight in Razzing him about how his inferior Chev wouldn't start. (I got the mopar bug from years of brainwashing from Dad lol)

any and all feedback is greatly appreciated.

It's pretty obvious that I'm going to have to lend an ear to the further tuning of this motor, to prevent further gasket failures.
 
I see no need to spend on an ignition upgrade, dial in what u have. use a timing light, check timing slot on damper to tdc. do a cranking comp. test and retorque heads etc.
 
That distributor doesn't say MSD on the wire cover and have a plug like all MSD distributors do so I'd bet dollars to donuts it's a Chinese dist. very similar to what your dad has now
 
If she was detonating that bad, the rod bearings might be hammered too. Food for thought.
 
skrews said:
If she was detonating that bad, the rod bearings might be hammered too. Food for thought.
Click to expand...

x2. And for 1000 miles that seems like a lot of oil build up on the pistons. I think you have more problems here than blown gaskets. The gaskets are only one symptom of it, and probably one of several.
 
I view head gaskets on a SBM as fuses. The rod bearings are more than likely OK but you may want to inspect them. As has been said--This gasket failure may have been a blessing in disguise. J.Rob
 
There are no marks on any of the pistons to suggest it might have more serious damage.
He's bought one of those MSD all in one dizzys for it. (The one in the above link was a POS too.) The dizzy he's bought has the scope to limit timing etc. So, much tuning is going to be needed. It's not unreasonable to assume that, given the state of that fire ring, that oil could have been drawn in to the cylinder from the valley. He did have a grizzle that he thought there was more blowby than it should have had. But I'd say it was probably leaking out that gasket.
 
I disagree 100% on the oil contamination - in my experience it is unreasonable to assume that. If you don't see oil in the intake ports, then get a close up of the cylinder walls and post it. My money's on the wrong wall finish for the rings used and the result is rings that have not seated, and potentially never would. You may not see damage on the pistons from detonation, especailly on a decent forged material. You will more than likely see it on the rod bearings (the backsides) & the main cap mating surfaces. This thing really should come out and be closely inspected.
 
You know your shizz Moper. I've been ghosting here long enough to know that.
This engine is running some fangled rings. I think they're total seal, with some powder on the bores. tungsten something or other, or some such.
it wasn't seen to be smokey when last run. If it uses oil, or blows by after the heads go back on it will have to come out again.
 
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