Hero to zero in 2 runs. LOL Pictures inside

Safe tune up for 15 runs. 13:1 motor.. No problems. Wanted to turn it up a but so 08 winter,we took 1.5 point of compression out by milling tops of domes off of pistons and opening chambers up. Measured thickness of pistons, and still tons of material left on piston. Heres the step by step on raceday 2009.


1. Safe looking plugs, car repeated performance from 08 even with less compression and same GPM
2. Found one cold cylinder, ( cylinder 6 ) and took 2 sizes out of that hole
3. Spun blower from 25over to 30over, added .30 of a gallon to tune up
4. Two runs with 30 over, and this was the result to cylinder number 6

















That was on a BBF on cylinder number 6, second from front. Cylinder number 2 also has piston damage not as bad but again second from the front. This is on a BBF 548 ci wedge K11 rotor 1471 Littlefield not a front discharge. How did two of the coldest looking plugs burn up? Oh and this was with 30 degrees of timing no egts.


I’ll try to take some pictures of the plugs, although I cant seem to take good ones.



Thoughts or let me know if you need more data.

 

Maybe some trash in the nozzle, did you check it? Odd that the one you changed only two sizes burned up.. Maybe it was marked wrong.

 

I did check the nozzel, didnt see anything blocking it by eye.


Good idea, I should check the nozzel to see if it was marked wrong.. Wouldnt that be a bitch

 

Mike

I have been basing all my tune up off of plug reading. With that and your advice with the spark plug reading 101.. that and some guidance from the guys who flowed my system.

Number 6 plug had less cad burn on the spark plug basering, it was just starting to burn like 1/10TH the way around, where the others were close to 3/4 burned.

Ya, Ive been tosing the idea around that the increase from 25 to 30 over was more then was expected, and it simply got lean or too much timing for the boost. I honestly thought it was plenty safe, and this surprised the hell out of me.. Like my post title says, Hero to zero in 7 seconds. Im humbled.

 

ohh.. MSD 10+

 

Is that a cometic gasket? In the first photo it looks like the gasket is distorted around the upper right bolt hole. Was it sealed up still?

 

I dont see how your tunning the way you did caused that.

First you shrunk the nozzle which up'd the system psi, then you fattened the main up and turned the blower up. The increase in blower should have yeilded more fuel as well since your catching rpm quicker with more boost. I think something else came into the equation. Maybe some oil was present in that cylinder??? Sure looks like some oil accross the dome on that piston.

 

am I all wet or is that a strange place to burn a piston? I'm wondering if 30 deg timing plus extra boost didn't create a detonation problem.

 

Whats the head look like?

I had a piston look like that last year. I had a port line go bad. The plug showed too much cad burnt off but the ground strap was not melted. The head started to burn/erode where the chamber meets the flat quench. Mine was to sharp at that point and caused a local hot spot.

 

What if that hole was so lean it was not making heat on the plug and not hurting parts.Could the extra boost have put it over the top ? Or the extra fuel made it lean enough to hurt it

 

Yes Cometic.

To my knowledge, it was still sealed up.. but I did have blowby in the cooling system when I did a leakdown, so its possible that the gasket in that hole did give up the ghost.

 

What ground strap, it was almost completely burned off on that run.

 

When you upped the OD, you should have added a solid .8-1.0/gallon to the motor. It seems to me that it was obviously (by the photos) lean the way it was run.

How was the tune up before you changed the OD? Was it close? Or was it pretty safe?

 

Had a real weird one happen to a friend before. Motor had a cold hole but couldn't figure out why and car ran good. Seems under load it had a small gasket leak and got enough water in cylinder to keep it cool. Leaned hole and after a couple passes water level went down enough and it got hot, ended up looking sort of like yours.

 

It was safe, but getting close to close Honestly. 3/4 cad burned on basering on most.


So your suggesting, one gallon extra for 5 percent more overdrive? If thats the case, I am way out to lunch. Does anyone else here agree with JRB?


Ive heard a few suggestions, one being.. if the tune is the safe and your turning up the wick... take the overdrive change in this case 5% and times that by .6 for how much fuel to add.

In this example... 5 x .6= 3% more fuel. 9.1gpm x 3% more fuel = .27gpm

So I added .3 of a gallon to the 9.1gpm tune up.

I was racing at 4500da, approximately 30psi of boost (only reading gauge )


Ive also read Mike Canter say that one pd of boost increase requires .3 more fuel as well.. But a person doesnt know how much boost hes going to make, tell he makes it.. so that method seemed flawed at the time, lol


Have any of you guys done a cylinder pressure test on your engines by doing a cranking compression test? If so.. what was it ? I just wonder if my camshaft profile is creating to much cylinder pressure. I will look up my cam timing, and post it here for you guys to give opinions.

Thanks for all your time, its appreciated

 

Just to be clear here Mike,

The safe run at 25% didnt show heat on the plug, but the run that melted , burnt the strap right off the plug.

 

Thanks James, but I didnt run water that weekend.

 

I just reread your post............



When we tore down, I did notice small bubbles at the quench sharp edge on the head, only a few, nothing major.. We rolled the edge over, and thought because of how thin that sharp edge was it wouldnt take much to get hot and didnt think much about it. Dropped the compression down and you know the rest.

If we did in fact create a hot spot there, what happens? The piston did infact burn on the quench area.

Are you on to something here Sodak