yay I broke my cherry.


This is obviously too lean but the hole is right in the center. This is a wiseco piston, are they known for that? I would have expected the hole to be near the exhaust port.

Well that sux!

Looks like deto to me http://pilotodyssey.com/Fuel-Squish-Detonation.htm

thx hoser, I'll check those out. A few more things that make me lean towards it being lean,


1. cooler temps
2. higher elevation
3. I went from a 9 to 8 plug the week before
4. I have been in this motor (( Internal Combustion Engine ? )) many times and it always had a nice almost rich carbon cake on the piston, it seems to be gone now.

motor (( Internal Combustion Engine ? )) had 175 psi the week before, running fresh 93 octane. is that too much compression for 93 octane? its about the best gas I can get easily here.

Hey Sun,also look at your head studs Mate,they look stretched to me-overtorqued over time.
I would replace them,cheap insurance...Baz

Sorry to hear, but sooner or later it bites everyone. 175lbs is well above stock, what did you do to get that? I can't remember what you have done to your 350.

Cooler temps will give a slightly leaner condition, but higher elevations would actually richen the mix. You would have to have a fairly significant elevation change to make much of a difference.

I have run 9,8,and 7s in my 350s. I normally can't tell much difference according to my EGT, just less build-up on the piston dome and exhaust areas as they get hotter, but I run my machines well into the rich side of things(dark chocolate plug chops).

I have never holed the center of a piston. I have shattered them, scuffed them and siezed them many times in my early days learning jetting and before I started doing leakdown testing. Do you have any pics of your last check, I like to see the "wash" on a piston dome. That is another great way to check burn/jetting conditions other than plug chops.

Gary

MUD and Sand will pull more out of an Engine!!! ALWAYS bump up a jet size when in either!!!

I have a hillside honda head on that one, it upped the compression a bit. Its also why the studs are so long. Last I checked the piston it looked great. Nice thin carbon layer, and you could see the flow marks, perfectly symmetrical. May have a pic somewhere. Before this race the motor (( Internal Combustion Engine ? )) was running rich. It would foul plugs pretty quickly. every 90 min of run time or so. I never leak down tested this motor (( Internal Combustion Engine ? )), I bought it from a mechanic would had just rebuilt the entire thing. I pulled the head and the piston was new so I never went farther than that. I guess I really need an EGT.

fouling plugs when/where??? at WOT (Wide Open Throttle), mid throttle or idle???

all the time, not sure where exactly the most. I would just have trouble cranking it and notice the plug was fouled.

175 psi is to high of compression for 91 octane. Make sure the squishband is correct for that bore. I would do a 50/50 mix of 110 or 112 leaded fuel, run an egt to help get you a safe tune and do a leak down test, just to be sure there are no gremlins hiding. And fatten it up 2 jet sizes.

Dooooop! I,ve seen a few of them before. Does make you feel kinda bad. Can you give us a pic of the head. I burned up five on an odysse before I got a handle on it back in the day. It happens. I bet it ran like a bad out of heck before it let go. Time for new parts.

make sure all circuits are jetted right, then When you get into a muddy area go up a jet size...

What head gasket you running?

stock gasket but just one of the thin layers from it.

Run the whole gasket when you assemble.

Did you ever check the squish? You know how to do the solder trick? This info is from memory but should be close I think....all three gaskets are around .028 and the 2 thin ones are around .007-.008. Race squish(.025-.035) race gas req'd and head dome shape very important. Hi-proformance squish(.035-.055) hi octane pump gas works best, dome shape somewhat important. Better than stock squish(.055-.085) burns any pump gas, dome shape does't matter much. Stock squish (.085-.100) runs but can be much better. My humble opinions. There are some great articles on squish around if you really want to understand whats going on. Adnoh is very good in this kinda stuff, maybe he will spill some knowledge on us! Hope this helps some.

Gary

I never checked the squish ..... I guess its more important than I realized. I read a few of the articles hoser pasted for me, and I'll try the solder trick when I get it put back together.

Here are pics of the dome and my plug, certainly looks overheated. Gonna order a new piston and check the squish. I can see debris down the exhaust port, hopefully when I get the jug off nothing major will have made it down into the bottom end.

Oh ya, that was very lean. I am sure temps past 1350 easy according to the plug.

Here is a pic of my 420/350 melt down a couple of years back. I not sure if anything was in the bottom end, felt fine turning by hand. I could split the bottom end and clean each bearing by hand or try to flush it. I decided to pour some straight gas in the bottom end, spin the crap out of the crank, shake it around some, then poured it out onto an old towel with a couple of white paper towels on top to see if I could find any stuff in there. Tons of crap came out! It took several flushings to get it clean. After it was cleaned, I added a 50/50 oil/gas mix to relube the bearings.

Just something to consider. The metal particles are aluminium and should be a lot easier on the bearings than a bearing failure(steel particles), but I don't like the idea of any particles in there. It can't be good on the cyinder/piston walls.

Gary

Would do me a big favor. Take that plug and cut the threads off and measure the smoke ring or lack of. This may conferm a thought. I take it the plug is the 8 was it used or new ?