What happened here

[moparzrule]

Quote:

Originally Posted by R/Tony Yep I saw that... and maybe you're right, I have changed the headgasket this time ... Ok, so I will do the 4th piston mod (gary's mod) and check the timing issue, Also I am planning to add a new set of injectors (1000cc) any store suggestions ?... Now how can I tell If I need to change the block ?.... those JE pistons were in std size, and I have just bought a new set of venolias in .020, so I can cut this block and make a good rebuild... but I dont know if this block is still good for big HP's. Thanks.

You re-used the headgasket last time? Mopar gaskets are once and done gaskets, not meant to be re-used.

Holy crap 1000 CC's!!! No real need for injectors that big on any 8V. +40's which are like 550 cc's can handle over 400 WHP. After that people usually upgrade to the 72PPH injectors which are like 800cc's, and no one has topped them out on an 8V.
Scroll down to the Siemens (Deka) injectors-
racetronix - index

It's a common block right? I did not see any major scoring in the cylinders that .020'' wouldn't clean up no problem.
Perhaps a suggestion for you while you have it at the machine shop. Get some main studs and have the shop align hone the caps. A lot better strength for the bottom end.

[R/Tony]

Quote:

Originally Posted by moparzrule You re-used the headgasket last time? Mopar gaskets are once and done gaskets, not meant to be re-used. Holy crap 1000 CC's!!! No real need for injectors that big on any 8V. +40's which are like 550 cc's can handle over 400 WHP. After that people usually upgrade to the 72PPH injectors which are like 800cc's, and no one has topped them out on an 8V. Scroll down to the Siemens (Deka) injectors- racetronix - index It's a common block right? I did not see any major scoring in the cylinders that .020'' wouldn't clean up no problem. Perhaps a suggestion for you while you have it at the machine shop. Get some main studs and have the shop align hone the caps. A lot better strength for the bottom end.

Yea I re-used the headgasket, since I suspected that something was wrong and I would be changing the gasket anyway.

Maybe the 1000cc injectors are too big, but all the big ones are in the same price, 755cc, 800cc and 1000cc are 355dls, so If I can choose anyone I will go bigger

Yeah its common block thanks for your suggestions !

Quote:

Originally Posted by phantomrt Cool... now I see that some very extensive work was done to this thing. Has anyone tried a reverse flow cooling system? It would require an electric universal water pump, somekind of custom water box to install where the original water pump belongs, and the thermostat to be mounted where the lower radiator hose attaches to the engine--in that "water box." somehow. There's a lot of 10:1 compression engines nowdays that run perfectly fine on 87 octane gas. Their combustion chambers are better designed to prevent detonation, but the reverse flow system keeps the heads much cooler, thus greatly reducing detonation.

Do you have more info ?

I wish to prevent heat and detonation no matter what !

[Gutfeeling]

For some reason I think you just didn't have enough octane. You can inject as much fuel as you'd like, but with improper octane it'll detonate! For you next runs, try just using some 104 unleaded sunoco or even 110 race gas (probably will kill your o2 sensor depending the amount of lead it has) and if you want to cool it more, install an alky/meth kit.

[moparzrule]

The type of damage to the piston shows a lean condition.

[turbo_daytona91]

either the cylinder walls were honed wrong or the block is warped

[moparzrule]

Quote:

Originally Posted by turbo_daytona91 either the cylinder walls were honed wrong or the block is warped

If that were true there would be deep gouges in the bore.

[moparzrule]

Not really strange that the number 4 did it, cuz he's making a lot of power with no number 4 cooling mod so that cylinder will run the hottest.

[t3rse]

Looks like straight detonation to me.

[R/Tony]

Quote:

Originally Posted by t3rse Looks like straight detonation to me.

Quote:

Originally Posted by moparzrule The type of damage to the piston shows a lean condition.

Well Im most on detonation side... the AFR was 10:1 on a LC1 and all the pistons looks pretty similar.

Quote:

Originally Posted by Gutfeeling For some reason I think you just didn't have enough octane. You can inject as much fuel as you'd like, but with improper octane it'll detonate! For you next runs, try just using some 104 unleaded sunoco or even 110 race gas (probably will kill your o2 sensor depending the amount of lead it has) and if you want to cool it more, install an alky/meth kit.

I was running toluene and xylene, and according to my notes I had 100octane... but I guess I will need truly race gas.

[shadetreeshop]

I noticed a nice spike in your MS datalog , are you using the stock style Peak & hold Injectors ?

you may want to look into Knocksense for the MS

[R/Tony]

Quote:

Originally Posted by shadetreeshop I noticed a nice spike in your MS datalog , are you using the stock style Peak & hold Injectors ? you may want to look into Knocksense for the MS

Yeah that spike killed my piston for sure !! eventhough I was having litle detonations... Actually I have to activate the knocksensor in the MS, bacause its disabled and I dont know how to connect it.

[shadetreeshop]

I'm using a GM ESC Module and gm Knock sensor from a Early gm Feedback CCC Carb motor , your spike is probably attributed to the low impedence Injectors causing a ripple in the B+ Plane inside the MS . Remember it only has 1 12vB+ input into the box , you may have to add another one to keep that spike from messing with the logic level B+

It has to do with the way the injector drivers limit current to keep the Injs open and the colapsing field inside the inj backfeeding thru the 12v+ plane. either move to High Impedence Injs to get rid of the spike or do a search on MSEFI on Map spikes.

You'll notice that the spike happens in your timing/map/Pw and maybe a few other places, you MS may also be sensitive to accel enrichment, My problem was every time it spiked it would dump more fuel , and if I made the lag filters larger it wouldn't sense Throttle input very well.

My .02 cents.

BTW I've built 3 of these things.

[phantomrt]

Question about the spark angle...

It undoubtedly spiked big time, but that seems to be at closed throttle--possibly during a shift so that should be okay? However, I see the max. value as being 57 (degrees?) and a minimum of 21. Does the base ignition timing of 12 degrees have to be added on top of those figures? That would be a minimum of 33 degrees of advance. Even 21 degrees seems a bit much to me for 20 PSI of boost or am I incorrect?

Maybe I'm not looking at the log correctly...?

[phantomrt]

Oh, and I do not know much more about reverse flow cooling systems. For all I know the casting has to be different to prevent air pockets or something.

In regards to the voltage spikes caused by the injectors, that can also be remedied by putting diodes in parallel with the injectors, right? When the field collapses, the resulting reverse voltage spike should get shorted out by the diode.??

[R/Tony]

Quote:

Originally Posted by shadetreeshop I'm using a GM ESC Module and gm Knock sensor from a Early gm Feedback CCC Carb motor , your spike is probably attributed to the low impedence Injectors causing a ripple in the B+ Plane inside the MS . Remember it only has 1 12vB+ input into the box , you may have to add another one to keep that spike from messing with the logic level B+ It has to do with the way the injector drivers limit current to keep the Injs open and the colapsing field inside the inj backfeeding thru the 12v+ plane. either move to High Impedence Injs to get rid of the spike or do a search on MSEFI on Map spikes. You'll notice that the spike happens in your timing/map/Pw and maybe a few other places, you MS may also be sensitive to accel enrichment, My problem was every time it spiked it would dump more fuel , and if I made the lag filters larger it wouldn't sense Throttle input very well. My .02 cents. BTW I've built 3 of these things.

Whoaa !! ... thanks man, I knew it, something its wrong but I wasnt sure what was the problem or what caused that spike, actually Im about to buy a set of stage 2 injectors, they are high impedance arent they ?