[ho428]

Last race I picked up a very bad vibration, finally kicked the belts off and the engine spiked to 260+ before I shut it down.
Found out the stock dampener broke and the pilot came out of the crank, not sure which first but I ran all day with the vibration before the belts came off.

Fixed everything, new SFI dampener, changed the oil, looked ok, ran it through several heat cycles in the driveway, no problems everything seemed fine.

At the track testing Saturday was it's first time back out, very slight high speed vibration but couldn't tell where it was coming from, rpm or speed related. New rims and old tires with build up on them, thought it might be a balance issue.
Ran one session ok, about 5 laps (12 miles) but didn't push it hard.

Second session, shifting in the 6200 range, vibration seemed less, tires were getting clean, 5 laps, smelled oil. Came in and the VC gasket (neoprene) was leaking, pulled it apart and wiped it down looked ok and reinstalled.

Third session, ran 10 laps hard, light high rpm vibration. smelled oil again, blew gasket again. Damn thing was running strong though.
Pulled the VC and oil looked funky, a few very tiny specs on the rockers, saw the Alternator belt had shredded, oil catch can was full, drained it and it smelled bad, like when I had water in it a couple of years ago from a cracked now sleeved #8
Also, the catch can had been bone dry since I sleeved the block, this was the first time anything had been in it since.

Got home and cut the filter apart, oil is very dirty for a fresh 10 qt change, no big particals but swirl your finger through it and shine a light and you see very light glitter swirls.

Think the crank is walking in the mains and toasted the bearings? Can't see anything just reving it, but the vibration and kicking the belts is all new. Not sure about the water stink, haven't had a chance to pressure test it. Also leaks a little oil now at the rear main.
Staring to wonder if the dampener coming apart did some internal damage. never had one come apart before.

Took some pics of the oil but the swirls don't show in the camera, catch can drain pic after letting it sit overnight. Thought the swirls might be gas since I richened the carb up but the oil feels slightly gritty.

I have a race in 4 weeks, not a lot of time for a rebuild.
Opinions?

[mechanickeith]

Better get buisy!! Sounds like it needs to come apart. Better catch it now instead of it coming apart on the track at rpm!!

[russ467]

had a similar instance years back. This was on a street car. didnt blow head gaskets but kept kicking belts and bad vibration. it finally granaded. crank was broken and 3 main caps were cracked. Never could figure what caused what.

[ho428]

It's due for a rebuild, got over 500 miles of road racing on it. With only two races left I was hoping to milk it through the remainder of the season.

Oh well, start pulling it tonight to see what I find. A quick re-bearing would be nice, but I'd never get that lucky.

[andyleonard]

I hope it's 2 unrelated problems. And I hope you can pop the pan off.

After the compression check looking for a bad piston - causing blowby and vibration - the next place I'd look is at the end play at the thrust bearing. You can get a quick preview by levering the dampener or the flywheel back and forth - book says .006, so if you have big movement there you can see, pan comes off. Pan's coming off anyway. But assuming the new VC leak, crank seal leak, full puke tank and the stinky oil is probably caused by excessive and new crankcase pressure, why would main bearing trouble affect ring seal? Unless it's really gone wrong in there, the crank is bent or moving bigtime and you have used up your side clearances on the rods and are tilting the pistons creating high speed blowby. Don't know if your pins float or not. Or maybe hit a head with a piston due to a bad bearing and squeezed a ring. Hope that's not it. Don't like the ongoing vibration in any case. Does the clutch feel funny? I was missing the 3-4 shift with a McLeod hydraulic release bearing due to .010 too much thrust clearance. Replaced the thrust bearing and the trans was perfect.

I changed the main bearings and checked the rods on mine the other day. 2 hours from oil-out to oil-in. Take a magnetic dial indicator under there with you. Turning the crank by hand with the pan off and the plugs out will show up anything really scary.

But all the sudden leaking means you have big ring seal issues.

[Bruce Meyer]

Have your crank magged. There is a good chance its cracked. Same thing happened to me many years ago. The balancer shifted so I pulled the motor apart and found a lot of bad bearings and a cracked crank.
The machinist said crank was flexing around, after it cracked, beating the bearings and balancer to death.

[ho428]

Once I get it torn down I'll post back what I find. Bad thing is I'll be pissed if I don't find the problem.

I have another N Crank and set of new pistons, might go ahead and get the new lightweight Tomakawk rods if I have to bore and prep my spare block. Been running SD rods for awhile, they could probably stand freshening up.

Probably get Clemets to check the KRE heads for square, the temp spike and appearence of water in the oil has me worried. Another .005 off wouldn't hurt, the finish wasn't that great to begin with.

I had the only V8 at the track Saturday, lots of motorcyles and a few Porsches, only 8 cars total. Just a Test and Tune day.
Had a couple guys come by the pits, said it sounding awesome on the track and asked where I was shifting. I said around 6200-6400 most times.
Their response was in a PONTIAC?

For road racing a Pontiac I guess that does seem to be asking a lot, but it's held together fine for almost two seasons until the stock balancer let go, my bad trying to run 40 year old OEM parts at that rpm though.

[ho428]

Should have the engine out tonight, got everything unhooked last night.
Since I may not have a lot of time I'm weighing my options figuring the worst. Drained all the water and oil, both stink to high heaven.

If I have to build another shortblock here's my options.

I have another 350 block, I have another 3.75 N crank, I also have a 4.0 forged Scat crank.
I was planning on new rods, but I could get BBC 6.8's and go with Forged Probe 350 pistons instead of 6.625 rods and my Clevite slugs. Rods cost about the same, pistons add a little.
End up at 383 cu in vs 365 but an all forged bottom end now.

I have KRE 290 heads, 2.07-1.66, flow 270 at .550, 62 cc chambers but might need a cut, may end up at 60 cc.
Might also switch from the T-2 to Tomahawk intake regardless of which shortblock since I have a new PRO built 800 cfm carb that came in today.
MSD ignition.

Camshaft choice would be the kicker, Been running a Solid tappet or go solid roller this time around?
What RPM range would this new 383 run best? Around 6500-6800?
But, problem... What kind of real HP numbers are we talking about? Too much and I get bumped up a class.
I have about 10.6:1 compression now, 383 would end around 11.5:1 even at .010 in the hole.

At 3250 lbs race weight I can't have more than 380 hp at the rear wheels, which equals around 450 or so at the crank.

Pretty sure I can hit close to that with the 365 this time around. I was at 332 at the rear wheels with carb problems.

[ho428]

Pulled the heads, rods and mains, a few shiny spots and scratches but no worn or spun bearings and the cylinder walls all look ok. Cam has some wear but no wiped out lobes.

Still finding fine sand like grit in the bottom end though, not a lot but enough to worry about.

I’m beginning to wonder if it’s casting slag that broke off and got ground up, I deburred the block but lots of hidden areas that are tough to see and reach.

[fsted]

Broken rings look like that. Have you checked them yet?h

[andyleonard]

Did you do a compression check before tearing down? Have you put a dial indicator on the crank yet? Were the head gaskets leaking?

[ho428]

Haven't check all the ring packs yet but no cylinder scoring, no compression check before tear down, suprisingly the head gasket seal was good. I thought for sure I'd see something there.Some of the bearings have some minor scratches in them, as expected.
I'll finally have time this weekend to check each part very close.

Checked endplay on the crank, nothing excessive, didn't have my gauges but barely moved. Thrust bearing has even wear on the faces, not burnished.
Crank is going to the shop Monday to have it checked.

I'll pull the plate off the oil pump and check the gears as well. Got a new pump coming.
Seeing as I can't find anything major I'll just clean it up and re-assemble. Baffling to say the least.

I even asked my wife to look at it before teardown, asked her if she saw anything odd, as little as she knows about engines she asked what all the little specs were.
When I drained the engine I left the oil in a pan overnight, dragged my finger across the bottom the next day, felt like an even coat of sand settled to the bottom. So I'm not imagining it, just can't find the culprit. Weird.

[TIN TIGR]

glass beads?..if ya clean your block or heads it gets caught everywhere..sneaks out after assembly , like gremlins..

[andyleonard]

Any chance something went through the engine at the track? Is your carb open when you're working on the car? Any big spins through the sand? What was the vibration and the smelly coolant?

[ho428]

Took everything apart, finally found several valve seals worn on the outside, not sure that accounts for all the grit though, but since it's non magnetic it could be.
Main bearings look fair, rods look pretty good, could probably polish them out, not sure it's worth it though.
The crank shows signs of the vibration from when the balancer went out at the last race, hard pounding wear on one side of the journals only, all journals.
Pics didn't come out very good though.

Crank goes to the shop today, not sure what to do about the valve seals, KRE built Heads, I'll have to call Jeff and see what he says.

[70 lucerne lemans]

looks like your springs were dancing around pretty good,maybe some retainer to spring contact as well.Are you running spring cups?They will help locate the inner spring.

[BruceWilkie]

Originally Posted by 70 lucerne lemans

looks like your springs were dancing around pretty good,maybe some retainer to spring contact as well.Are you running spring cups?They will help locate the inner spring.

Not only do spring cups cut down on spring dance they cut down wear on the spring seat itself. IMO mandatory for aluminum heads. (actually most any non stock application a good idea). Might be your "grit" in your pan.

If cups are present do they fit snug?

[ho428]

They have a spring cup, looks like the cup is the same size or slighty smaller than the seals though. So yeah, the springs could be dancing around. Definitely some spring to seal contact.
Same seals turned 180, lots of them have wear on one side, others it's 360 degree wear.

I shift in the 6200-6400 range, solid flat tappet, 1.65 rockers, lift= .561 intake-.584 exh, run it in 40 minute races, so it gets quite a workout.

[andyleonard]

You tore down to find the vibration and the blowby that filled the oil puketank and stunk up the oil. Also the water...but the headgasket was good.

You have found the vibration...probably a slightly bent crank from the dampener event...and you may have identified the suddenly appearing grit in the oil as alloy from dancing springs...but how did the oil get into the puketank, out of the rear main and out the VC gasket without massive ring blowby? Something has happened relatively recently to pressurize the sump. If it wasn't a broken piston land (too bad about no compression check) then what was it? Don't want a block fault here.

Can you pull the pistons and see what's broken?

[ho428]

All pistons are out, all rings are good, no cylinder scoring.
I have no idea what would cause the puke tank to get filled and oil stink.
Could possibly be a couple of the seals have worn through? I've haven't check them that close yet. Lot's of carbon on a couple of pistons. Others have just a little build up.

I have had issues at that track before with oil loading up in the VC's, have to run 1/2-1 qt over to keep the sump covered. Long sweeping RH turns there with sustained RPMs. Left VC is the one that kept blowing out over #7.
I talked with KRE awhile back about the oil returns being to small, ended up with restrictive push rods to keep more oil in the bottom. Still plenty up top, nothing looks dry.
Since the heads are off and apart I worked over the oil returns to enlarge the opening and smoothed out and radius on the oil return holes. Running an external return line is not something I want to tackle right now.

But internally I can find nothing broke, head gasket seals looked real good. Ran this engine for almost two years.
I will get the head face milled, never was crazy about the finish on them.

Not sure how I go about finding smaller diameter seals, seems about my only option right now.