BLNLS1/RX7

iTrader: (2)

If I had to guess on what you have posted I would detonation was the cause.

ChevyChad

iTrader: (50)

No pushrods were bent at all..

I just don't understand why the crack would form in that location if detonation caused it. I mean, detonation occurs in the cylinder and combustion chamber right? So if it was detonation, wouldnt the crack have originated from the cylinder itself, and not from the water jacket area? Thats whats got me baffled.

Yea, there was more dark areas than that. I was just starting to clean the surface of the block to prep for the new gaskets with a scotchbrite pad when I uncovered that crack. Here is a pic of what the deck looked like immediately after I removed the head:

http://i24.photobucket.com/albums/c1...Picture014.jpg

Maybe this pic will help? It does look like for certain it was lifting near the #6 cylinder.

Here is a pic of the head gasket I took off. Maybe it will help with the analysis too..

qqwqeqwrqwqtq

I have seen other aluminum blocks cracked in the same manner on multiple cylinders due to detonation (cause was bad fuel).

ChevyChad

iTrader: (50)

I see.. I am running 91 octane (highest we can get at the pumps around here) and 100% methanol with my alkycontrol kit. Maybe I need to crank up the dial on the meth more...

qqwqeqwrqwqtq

That would also be assuming you have perfect distribution of the meth.

Are you running a speed density tune? If not, you should be with 16psi.

Tiago

iTrader: (27)

Chad, how much timing on the tune? got a scan from some pulls you can post?

ChevyChad

iTrader: (50)

the current timing is set at 17°. I don't have any data logs for the current setup unfortunately

I really want to do an SD tune, but I don't know of any tuners around here that can do it. I am running a MAF tune right now.

Tiago

iTrader: (27)

hmm 17deg doesn't sound bad, but maybe you got some bad gas or lost fuel pressure, never know.

if you don't log your car regularly you wont know if it was knocking or not :p

ChevyChad

iTrader: (50)

I look at KR always on my interceptor. I have it set to KR all the time. I have never seen it at even 1°. I don't log it with a computer, its just what I see on the gauge, and also, if I have a passenger, I usually have them watch it when I am getting on it. Thats not to say I've never got any at all, but I check it a lot. I should probably look for some sort of logging software tho at least to verify everything...

El_Diablo

iTrader: (9)

Hey Chad, Brett at XP does SD tuning in Oklahoma City.

Slowhawk

iTrader: (12)

Solid motor mounts?

A KR gauge is almost useless on a car like yours.If you see kr it's ussually too late.

BlackScreaminMachine

iTrader: (17)

Meth = Poorman's race gas. Like said too in this set up under load, any detonation can lead to a "too late" situation.

Good gas, conservative tune should have saved it. I think it sucks that it happend. Looking at the cyl head, that dark spot on the 3rd one over, Me thinks that is where it lifted too.

ChevyChad

iTrader: (50)

Thanks for the tip. I didnt know that. You know how much he charges by chance?

No solids here.. They are stock motor mounts..

Meth = better than pump gas alone in my book..

How does a good tune stop the heads from lifting? Seems that its a certain power level combined with insufficient head gaskets that is likely to lift the heads from all the stuff I've read around here. Not tryin to be a smartass here, just wondering about your statement assuming the tune and gas was the culprit. I know it was running a little rich, I can verify that with the autometer wideband I am running. Rich wouldnt cause detonation tho would it? I thought that was due to lean conditions.

slow67

iTrader: (2)

In these situations, detonation is usually caused by too much timing, not enough octane, or a combination of.

BlkHwk

iTrader: (8)

Even if you get a tune you need to get some logging software. So after a run you can go back and see whats happening on a graph. I trusted a tuner once and that's what took out my original motor. I'm not saying to not have someone tune your car but you should be able to log data like afr, timing, boost,kr,iat's etc. I have gauges in my car to watch stuff but when you can go from 60 to 130 in a matter of seconds it's pretty difficult to drive, shift, watch the tach, afr, boost fp and that dog gettin ready to cross the road. LOL
Runnin a little on the rich side can help resist detonation some by reducing combustion temps a bit.

Definately go SD. What heads are you runnin?

ChevyChad

iTrader: (50)

I'm using AFR 225 heads.

For those of you who are saying detonation, would you think that detonation blew up my intake manifold as well? I'm still baffled by that incident too. I find it kind of hard to believe that the intake blew up, and I found this crack right afterwords as coincidence. I'm almost willing to bet that whatever happened may have caused both... Or one led to the other, etc..

BlackScreaminMachine

iTrader: (17)

If the set up requires good gas and not that Weasel ****, then you buy race gas.

Here is the limitation on a STOCK style PCM, you cannot adjust the tune per cyl like with a BS3 set up. Timing and fuel requirements can be made more heavy for the back cyl. Or with the stock PCM tune for the weak cyl and let the front half run rich, there are distribution issues with stock style intakes.

When it comes to fuel, you can either drown the cyl with fuel or get a better quality that burns at a slower rate and your not making it overly rich. At some point that cyl got HOT. It was pushing through that gasket and the rapid heating and cooling as well as pressure cracked that block.

The tune is to control the combustion, at some point it went beyond the limits of that cyl.

When you build another motor, def SD tune it with a quality place, and make sure its safe.

Tiago

iTrader: (27)

Not if you tuned for it and loose it at a later time... then you're screwed. It can help if you tuned without it and than added it for safety. I just don't trust it period, don't want complications

its not just power that lifts heads, you dont' make 1/2 enough power to have that problem its detonation/tune, or poor installation in most cases.
What AFR were you running?

ChevyChad

iTrader: (50)

Why do you say the stock manifold has distribution issues? That myth was busted by a shop on this board that put a stock style intake on backwards, and it was still the rear cylinders that got hotter, so whatever the issue is with the back cylinders getting hot, it is not the intake manifold.

And I know there are a lot of people around here running pump gas + meth on setups that make more power than mine makes. This is a street car, not a track or race car. I'm not gonna make a special trip for race gas every time i need to refill on fuel...

ChevyChad

iTrader: (50)

Last good tune i had was without meth. But that was also on my old setup with the stock heads. I have since added meth in as extra when I installed the AFR heads. AFR was around high 10.8~11.2ish with the meth like it was running when it blew up the manifold.