Head Gasket,Cracked head or hole in piston

-
A

A360

Benton
Joined
May 31, 2006
Messages
199
Reaction score
9
Location
Perth, Western Australia
G/Day fellas from Oz

As my shop where I have my engine work is closed for two weeks for the holidays
I have a question which some on may be able to help with.

I was racing the other night when lifting off just after the line I lost all power and had to get towed back to the pits (embarssing)

I had spark and fuel but the engine would not fire (la 360) two hours later
got it fired up and drove home ,approx 40mins with a slight miss getting worse as I got close to home.Car still starts and runs fine albeit on 6/7 cylinders ,now for the question.

I have compression in all pots
It is pushing out excessive mix of smoke and fumes from the head area through the rocker vents actually like a kettle.
rocker covers are off and all rocker gear is ok ie valvestems,rockers,springs etc.
There is not a smoke issue through the exhaust pipes.

My theory is one of the following which may or may not add up to the compression test results.

Head Gasket,Cracked head or hole in piston?

thoughts?

Cheers

Benton
 
My money is on the head gasket, I hope that's all it is. Did that to my chevy(along time go) the same way.
 
I had this same happen with a crate chevy motor. It ended up being a burnt valve.
 
If you have any poping through the carb,you bent a valve or hurt a cam lobe.The other is you broke some rings and have now excessive blow by causing the excess air pressure in the valve covers.mrmopartech
 
I haven't seen a compression test or the results so this is where I would go first, post it then we can help you better.
 
BJR is absolutly right without the comp test everthing is a guess.
was it a fresh motor?
with what very basic details you have provided i would guess
broken rings, maybe piston or ring lands. ( best guess )
hope i'm wrong, good luck
 
First pull all the spark plugs, you should be able to see which cylinder or cylinders it is. The pull that head off, if its the head gasket going you should be able to see the damage. If the gasket looks good, then get the head check out, if its fine, then you need to pull the pistons out because the rings must be damage.

Thats how I would go about it, you have a problem that needs to be repaired, why waste time running a compression test ?
 
Thanks for the responses, will post compresson numbers

some more info
mid 12 sec 360 combo
10.5 - 1

there is no popping etc through carb
excessive fumes/smoke is not coloured ie not black ,white , blue
Pushrods spin nicely in my fingers

No contamination of either oil or water and is not over heating

Pretty soon I reckon I will be whipping the head off after double checking
all before

Thanks again

Benton
 
After pondering the compression numbers and 1 + 1 = 3 I decided to run a compression test again.

The results
Looking in from the front
Right Bank
1/ 150
2/ 160
3/ 150
4/ 150

Left Bank
1/ 165
2/ 160
3/ 145
4/ 50 (Damn)

So for a number to be this low (50psi) the thoughts would a hole in the piston or rings what ever though, a tear down will be required:pale:

Not a good Christmas pressie

Benton
 
Ouch, Tuff break :( sounds like a teardown is the way to go to find out for sure. Let us know what you find.
 
found broke piston in front left 1 and front left 4

Detonation?

Photo0089.jpg


Photo0091.jpg
 
Thats some hard luck, Brenton,
Wierd how both pistons broke at the same place like that, what type
of piston are they? [ what brand, cast or forged ]
Do the other pistons have damage like pitting, scarring?
What type of ignition system do you run, type of wires, are the wires
run in a loom with seperators?
What type of fuel, fuel system and induction?
Do you use any power adders.
 
''Thats some hard luck, Brenton,
Wierd how both pistons broke at the same place like that, what type
of piston are they? [ what brand, cast or forged ] KB Hyper
Do the other pistons have damage like pitting, scarring? No all other 6 are 100%.All bores including the ones with pistons are 100% although will have an honeWhat type of ignition system do you run, type of wires, are the wires run in a loom with seperators?Mopar Elect 9mm eagle leads yes seperators
What type of fuel, fuel system and induction? 98 octane,elct fuel pump and 750 DPDo you use any power adders.No''
 
any telltale marks on the head gasket like it might have blown out and sucked cold air when you lifted and caused the pistons to crack. did you ever miss a gear that night and maybe over rev and cause piston to valve contact
 
Head gasket was fine
Auto so no over reving I shift at 5500.

Had issues with severe ping last season but problem went away this season(coil)
Thinking that may have been the stress cause that resulted in this problem
 
Hi Benton,
After looking at the pictures, I'm not totally convinced preignition
was the total cause of the piston failure.
The edges of the breakage is too sharp, preignition usually pits and
melts things a bit before failure like in the the 2nd picture.
I'm wondering if maybe ring end gap and a lean condition then detonation may have
combined to cause the problem at high rpm.
At what rpm did you notice the rattle or ping during last years racing?
 
Hi Benton, bummer by the way, if you're planning to go over the remaining pistons with a magnifying glass you really ought to look for minute cracks from the piston top edge down to the first and second ring land. I've seen catostrophic failures like that on new pistons from severe detonation or you may have got a couple bad pistons, but not likely. Can you get a close up shot of just the pistons, top and side view. Also can you take a closeup picture of the actual break of the piece that broke out, you'll need a good digital with macro setting for this.

Terry
 
At the moment thinking detonation was the starting point ie making a weak spot, but not the trigger to cause the failure.

4000rpm + 2nd and 3rd gear was the beginning of the pinging

Once the pistons are out I take some photo's for you.

Going to forged pistons now
 
Hi Benton,
I hope you don't mind, I spoke to Bob Borowick from K-B Silvolite.
He was eager to help.
He said he would like for you to look at this address and see if it
helps in determining your failure.

http://www.kb-silvolite.com

Click Tech Info

Bob also gave me his personal e-mail address and phone number
which I will PM you.
He tried to access this website while I spoke with him but was have
trouble getting into the site.
Hope the info helps and you come back stronger and faster!
Good luck
Carl

bantamhemi.jpg
 
You must log in or register to reply here.
-

Back
Top