Torched head gasket & deck, burning ground straps

Hi guys, I am having a little issue here

First time out and down the track with a new combo, twin turbo BAE hemi efi. Ran the car about 500 and pushed head gasket burned the head and deck out number 8 . In taking it apart I noticed 6 was showing some weird markings in the chamber next to the o ring as if it was getting ready to go also. Number 8 rod bearing fell out of the rod and was really smashed, number 6 bearing was similar but not as bad. 8 and 6 both have ground straps melted, not melted off but all smoothed out and melted looking. All wrist pins except one had to be beat of the piston as they all tweaked some.

My consensuse tells me that the timing was too advanced due to the ground strap on the plug being melted among the rod bearings and wrist pins.

I intially thought i had 2 injectors go bad as 8 and 6 egts started to get hot but apon seeing other cylinders wrist pins and having a AFR of 3.2 3.3 and egts in the 900-1000 range i assume its not a fueling issue.

I did have excessive timing out of it down low to get it through the shake zone and about 21 deg from about 2.4 until 3.5 when it let go. Some have said if you get too much timing out down low the exhaust vavles get so hot the engine will pre ignite and do what it did. I think the timing was maybe not what we thought or what ecu said at 21 and maybe we had a good bit more causing the issue.

Any info or advice would be appreciated.

Thanks,
Billy

 

We had some issues with detonation once. EGT went down during detonation on our combo and it didn't respond to fuelling untill we put a lot more fuel in. Cylinder temperatures were high though. We burnt a hole in a piston and the ground strap was missing as well.
An other familiar issue is well done pistons deformed up to the point that you can't get the pin out and the piston rings will be jammed in the ring glands. This happened on a new setup which was also solved by adding fuel.

HTH,
Marcel

 

very similar combo to yours NRE /BAE hemi twin 91s and bs3 what sort of timing are you using down track ?? i pull a lot more timing than you early in the down to 15 degrees and run with no issues how fast you running with this combo ?
we run speeds getting near 245 so far with zero damage and iv run this for 2 years without taking the block out of the car and im no where near as lean as you afrs above 4.1and higher
your egts are very low for a turbo car i usualy see 1200/1400 degrees with zero damage looks like fueling to me

 

Don't know anything about turbos, but sounds like severe detonation. The marks you talk about on the heads by the O-ring is the head slamming up and down on the block. Make sure your ignition is correct, should be in the low 20's if you have lots of boost. Again, I don't know anything about turbo combinations, but if it were a blower, definitely not over 11 to 1 compression.

 

good point Ken
compression ratio what you running?? if this a pro mod motor with turbos bolted straight on you will have trouble

 

Guys the combo went 3.92 @ 197 on this pass and was do e at 3.40 into the run.

How can you think its fuel when your egts are hotter and afr is leaner. 3.2 3.3. Is richer than 4.1.

Its leads me to think its timing. Seems we maybe had more advance than we think. Also 6 didnt burn anyrhing other than ground strap and only melted it a little bit.

Comp ratio is 13:1

 

sorry my mistake talking out my ass with the afr we are using i was reading the wrong file, we are a bit richer than you but we also have a fair bit less compression and inconell
exhaust valves we have been struggling with a clutch for two years and just moved to a rossler deal,

what do you run for timing down track ?
you said its your first hit on that combo...thats impressive numbers
iv never seen egts as low as yours in a turbo car, especially with the comp your running so i was thinking maybe its not burning properly...ie you cant have a fire without fuel but with that et and speed i doubt that, do you run closed loop? what was your previous combo?

 

What are you running for ignition hardware, ECU control, and crank trigger setup?

 

Prior combo was very similer to this one with slighty less compression.

Car went .989 2.62 3.93 @ 197 cylinder 8 egt went through the roof at 3.38 seconds and 6 was starting to go up with it.

526 BAE HEMI, BS3 ECU PTE 550 INJ w/ 225s, MSD GRID, MSD PRO MAG 44, Leahy crank trigger with RCD 4 magnet wheel.

Base timing with mag plugged into itself is 25deg. We leave the starting line with about 5 deg on timing until 2.5 seconds then ramp it back to 21deg never been higher than 21 deg for total timing.

3.3 AFR is quite rich plugs plugs dont show much

I assume most think 13:1 is a bunch of timing but the car hasnt had more than 38 - 39lbs of boost yet. The legal roots guys ran 13:1 with a good bit more boost and timing that is why i believe my timing may not have actually been 21.

What I am trying to establish is the fact that timing burns the ground strap, correct? if thats the case I have to assume that was my issue being the egts are cold, o2 is reading rich and we melted the strap and torched the head.

 

i guess theres many ways to skin a cat
we have lower comp up to 52 lbs of boost and 25 degrees downtrack

I think if your just at 21 and its burning up something went wrong with the timing I just use a bs3 with the launch retard upgrade with an msd mag pick up and 44 mag
earth straps burn off with detonation iv had it on a n20 car when its gone lean so id guess its not confined to ignition timing problems only
I ran a legal roots deal with 42 lbs on 13 to 1 but the charge temp in a turbo car is way higher than it was with the roots look at what the tafc guys do with their comp ratios with their 50+ psi screw cars and the screw charge temps are pretty cool as theres not the internal friction of a roots
hope you get it sorted out sounds like a real fast car when its sorted

 

If you have decent boost and lots of compression, I think you will still detonate hard. If you can't take compression out, drop the timing to 15 like someone suggested earlier. Detonation till take out the plug straps, knock out the bearings, and pound the heads up and down. With all of this happening, its luck the rods didn't come out.

 

When you say "prior combo", do you mean that you have run this exact set of ignition hardware and ECU hardware prior, and all worked fine, or is this new hardware to you in your new combo?

What I'm getting at is has this set of hardware worked okay in the past, and what if anything might now be different?

Have you verified that you are getting the timing that you expect and have you scoped either your trigger signal or your actual timing? To me it sounds like you are not getting the spark advance that you think, or you are getting it at completely the wrong time in some cases. Electrical interference? Poor crank trigger signal? Got the cap/rotor phasing in a reasonable window?

 

Yes other combo had the same parts. Yes I set timing to 25 with mag plugged into itself verify with timing light, then plug the BS3 trigger wire into the mag and set test timing to 35 and sure enough it is 35 then try setting it to 25 and sure enough its 25.

I am really dumb founded as I have friends that of run same comp ratio same basic camshaft same fuel system, boost, timing etc and havent had issues. I am not sure what went wrong where I just know I never want to have this issue again.

I am taking some comp ratio out of it now and going to check all wiring etc.

Thanks,
Billy

 

In ND awhile back there was a device being marketed which would allow a person to datalog their actual live timing at the plug, net of all variables. I don't know if it is still around or not? Might be a good diagnostic tool.

 

I would get the injectors tested or check wiring on those 2 cyl the only time i have had egt spikes like you had is when a injector stock closed it burnt piston plug and smashed rod bearing

 

Good point. Also, check that your duty cycle is not overly high and that your fuel pressure differential is not too large. Mike can give you the appropriate #'s for his 550's. I don't know who's 225's you have but you might want to check with that source too. You running one driver per injector or two injectors ganged to one driver?

 

I originally thought it was a bad injector. I have sent all inj backs to the supplier and all checked out ok, they say.

The thing that had me second guessing was the the ground strap being the only thing that started to melt. Bearings smashed, pins bent no melting on pistons, chamber etc.

Billy

 

I have a fair bit of experience using BS3 on big power blown and turbocharged vehicles. Most issues generally stem from not following the correct configuration and setup of the system. If you have some data, I wouldn't mind taking a look and seeing how your tuneup(lb/hr) and spark advance correlate to see if it's way out in left field. Sometimes on the turbo stuff you will hurt it during the spooling procedure and then it will actually go catastrophic during the pass. There are a mulittude of different things that could be causing your issue, we just have to narrow them down a bit.

I will send you a PM with my email information.