Burned Piston?

[Moose]

I got water in my oil and suspected a bad head gasket, but when I pulled the heads off this is what I found. I'm guessing the motor strarted running lean at top end?. What has me puzzled is I checked all the sparkplugs after each run and they all were black as in rich after each shut down. Any ideas?.
The first pick is of the gasket on the odd # side of the motor(pistons 1 thru 7).
The 2nd pic is a closeup, look at the small openings of the water holes (rust around it) shouldn't they be bigger, could this have created a hot spot at the cylinder?.
3rd pic is of #1 piston.
4th pic is of #8 piston, the gasket on this side of the motor was still o.k.
http://www.hotboatpics.com/pics/data/500/1088R0010088.JPG http://www.hotboatpics.com/pics/data/500/1088R0010087.JPG http://www.hotboatpics.com/pics/data/500/1088R0010080.JPG http://www.hotboatpics.com/pics/data/500/1088R0010083.JPG
Moose

[Fiat48]

She was plenty hungry. Possibly running out of fuel. I believe I am seeing the top ring on #8 piston. Check all the ring lands on all pistons when apart. Head gaskets appear to be burned instead of pushed.
I'd say fuel pressure/supply and or jetting. Clean the black off the plugs with some carb spray and get a good look at em. Picture them if you can.
List carbs, jetting, how much blower, timing, etc.

[Heatseeker]

Moose, that sucks dude!
At least you didn't burn it down like I did to my first blown motor. Alot of water gets in the oil when a cylinder gets two chunks taken out of it.

[Moose]

2 Holley HP 830's (78's) (88's), BDS 8-71 7lbs boost, Aeromotive Boost Referenced Bypass Regulator 9psi, MSD locked out at 32deg total, Autolite 23's spark plugs still black after Chemtool (no pic camera won't zoom in that close), Clay Smith (mech) pump 140gph 14-16 psi.
Moose

[Rexone]

What kind of fuel you runnin Moose? Could be a little lean or just inadequate octane for the effective compression produced by 7 lb boost. Also, any intercooler? That can be a big factor too. My guess is no since you didn't mention it.

[Fiat48]

Originally posted by Moose
2 Holley HP 830's (78's) (88's), BDS 8-71 7lbs boost, Aeromotive Boost Referenced Bypass Regulator 9psi, MSD locked out at 32deg total, Autolite 23's spark plugs still black after Chemtool (no pic camera won't zoom in that close), Clay Smith (mech) pump 140gph 14-16 psi.
Moose
830 Carbs: Looking at the jet chart at Mortec most 830
s have a 78 jet or larger in the primary. I'd think you would need a bigger jet using a blower. Carb guys will have to speak up on that one. Carbs are not my cup of tea. If any power valves were removed and blocked, then jetting should have been increased 7 numbers to replace that power circuit.
Autolyte 23 is a hot plug...equivalent to a 5 heat range in NGK. So, I would think there would be plug damage. Maybe the sooty plugs are idle mixture or large secondary jetting. Maybe you hurt it while on just the primary side which was jetted too small.
Check the rod bearings and see if any have spread by miking the width of the bearing. If it has been hammering, usually you'll find the bearing is wider in the middle (top rod bearing).
Melting that piston where you did is common if the motor was lean. It goes for that edge on the intake pocket. Cutting torch.

[Rexone]

Originally posted by Fiat48
Maybe you hurt it while on just the primary side which was jetted too small.
Melting that piston where you did is common if the motor was lean. It goes for that edge on the intake pocket. Cutting torch.
Good point. We used to see this alot in ski race turbo engines that were lean on the primary side because in lots of races they ran right at the transition point for long distances. Too lean = adios pistions, especially with marginal fuel quality (as in not enough octane rating for the blower or turbo)

[superdave013]

when you got the pistons did you massage that area at all? You have to take off the sharp edges there and blend it in. If not you will burn them in that spot every time.

[HP350SC]

You need to run a better head gasket too, those look like the stock gaskets merc uses. and they will not last under boost. At least go to a fel-pro.

[Petrofied]

How much overdrive on the blower, I see 871's with as little as 5% over pull the float bowls down on the hit of the throttle. How large are the needle and seats. I run .150 alky needle and seats in all my carb aps. Just because you have good supply dosn't mean it can get in the carb-bowl. Thats why we have injection, with injection it's hard to run outta fuel supply. My $.02
MR.P.
P.S. Have your heads maged, I find when they but the rings or torch a piston the heads crack between the valves. Good Luck! :)

[Fiat48]

Good point on the needles and seats. It's a restriction area for sure.

[HP350SC]

Going back and looking at my pictures when I replaced head gaskets is making me nervous. Motor has 75 hrs. total, 5 hrs.with 7 lbs. boost intercooled Whipple. Stock cam and heads. 30 deg. total timing. Single 1090 Demon. Plenty of fuel delivery to carb. Can't remember jets offhand, I wanna say 84's and 94's.
#3 looks worst, although piston tops look like it's running richer than the above motor. Moose, did you clean tops of pistons before pic?
Anybody think I'm on borrowed time?

[HP350SC]

ooops forgot pic..

[Moose]

Ok, I found the problem, my harmonic balancer spun just enough to throw off the timing mark and I put to much advance in it. That will learn me for not buying a better balancer when I put the blower on it. New pistons and and a lighter wallet coming up!.
Thanks for all the help guys!.
Moose