1G High turbo back pressure and headgasket failure .

[1SIC1Gb]

I've run into consistent headgasket issues lately and I was wondering if high back pressure could cause it to blow headgaskets.

Turbo : 67mm Holset on a 12cm^2 Holset housing.
Engine - 6 bolt 10.5:1

I am now switching to a 16cm housing but I first blew a cosmetic gasket on l19s at around 30psi
Next I oringed (stainless)the block, receiver groove in the head with 1/2 l19s and head inserts, and it made it through the dyno just pushed a little coolant .

Anyone have any input on this ?

 

[donniekak]

What does your timing map look like? What fuel? Were the block and head resurfaced?

 

[1SIC1Gb]

I'm running about 19 degrees up top. E85, block and head were fresh.
The second time it was pushing with the oring setup on a copper hg

 

[donniekak]

I'm running about 19 degrees up top. E85, block and head were fresh.
The second time it was pushing with the oring setup on a copper hg

What compression ratio, and what's time my at peak torque?

I've never had any luck with copper, or known people that did. With fresh surfaces, l19's, and a cometic I have no problems running 40 psi from a smaller turbo(35r) which should be making the same, if not more back pressure than your setup.

Another difference is the auto. How are you getting on the converter? Any knock?

 

[1SIC1Gb]

If have to look at the log.

I get in the converter with a 35 shot dry.
Compression is 10.5:1
No knock to speak of.

 

[1SIC1Gb]

I don't know, this is a 12cm^2 housing which is really small for the amount of compressor I'm running. Just wondering if it's a possibility that the high back pressure is causing headgasket failire

 

[Black95TSIawd]

What do your spark plugs look like?

 

[donniekak]

I don't know, this is a 12cm^2 housing which is really small for the amount of compressor I'm running. Just wondering if it's a possibility that the high back pressure is causing headgasket failire

It is small, and exhaust gas reversion leads to knock.

What are you tuning with? It's hard to believe you are popping head gaskets with o ringed setups at only 30 psi with no detonation.

As brought up below, are your plugs showing splatter?

 

[1SIC1Gb]

The plugs look fine. It's tuned on link v3. It's down now with the engine out and I can't find a log.

It wasn't oringed when the cosmetic gasket .
It is now with the copper hg.
The gasket looks totally fine . But it was pushing a little at 40-42psi

 

[honda_burner]

cracked head?

 

[bastarddsm]

19* seems like quite a bit of timing to me. Keep in mind the peak cylinder pressure rises exponentially with those last few degrees of children.

I don't think the high pressure back pressure is causing the hg issue directly. Your peak cylinder pressure is in the 3500psi range, so ~100psi from the turbine is small potatoes.

My car is bad on back pressure. During some testing I unhooked the wg signal, boost would spike to 50psi at 5300, and fall to 40psi. back-pressure chilled right at 90psi. Even on a composite gasket and cheap ARP's I have basically no hg issues. Car makes enough jam to go 137, and its 3100-3200lbs.

I think a lot of your issue is the 10.5:1. That really adds a lot of cylinder pressure. I bet you could drop to 9:1 pistons and get a bit better head gasket reliability with only a small power gain.

 

[1SIC1Gb]

Good info, I'll get it back together and check the log.
I am somewhat limited on hg choices due to the oring setup.

 

[jakelandry]

Just cause the ethanol can take the 19* that's a lot on a 10.5:1 comp engine. How are your cams degreed?

 

[1SIC1Gb]

If you're talking about when I built the engine, no I didn't put a degree wheel on and dial them in.
The can gears haven't been changed and are set at 0 still

 

[jakelandry]

If you're talking about when I built the engine, no I didn't put a degree wheel on and dial them in.
The can gears haven't been changed and are set at 0 still

Depending on how much was removed from the block and head you would probably be surprised how far off the timing can get. I've had a total of .01 removed from the head I currently use and it threw my timing off by 3.5*. May not seem like much but on a high compression boosted motor that can completely change Engine behavior. Is that your problem? More than likely not but it could be a combination of numerous small problems like that.
I know I'm not saying anything that someone who builds their own motor doesn't know but sometimes it's easy to overlook things and small suggestions can lead to bigger ideas.

 

[familyMAN]

Why not back off the timing 3-5*? 19 seems aggressive since you are blowing HG and still throwing boost at it. Start lower on timing, add boost, then add some timing back if you can.

Also, peak tq timing is very important on the auto because you may end up right where the converter starts to couple and you end up hanging out right near peak tq for awhile.

On my car if I shift at 8kish in 2nd, I drop to 6k in 3rd and just hang there for a little as vehicle speed continues to rise. Same if I do a 3rd gear pull...Boost builds and gets quickly to 5-6k and then hangs there. If you are past MBT with e85 at that rpm range, you are just adding unnecessary cylinder pressure for an extended period of time.

 

[biglady112]

It is the copper head gasket. Hands down. They are garbage. Put a stock head gasket on it and enjoy.

 

[donniekak]

It is the copper head gasket. Hands down. They are garbage. Put a stock head gasket on it and enjoy.

While I agree the copper gaskets are junk, he also blew a cometic.

 

[1SIC1Gb]

I am running an oring block with a receiver grove in the head. I can't just run any gasket. I debated trying a composite but I don't thing the fire ring will conform like the copper did to the oring .

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[Kapok6]

I like composites.

 

[Diamond Star Werks]

19* degrees timing is a lot of timing for your high compression. Like bastard said pressure from the turbo is cake compared to the internal cylinder pressure. My suggestion would be to back of to at least 15* timing maybe 14* and increase you turbo pressure to make the power. You have plenty of room to increase pressure if your only running 30psi. IDK your exact turbo but this compressor map is for a which is for a pro hx52 billet 67mm. You'll see with your 67mm you have plenty of room for more boost. On a 10.5 engine there isn't any room for more timing really. Your going to keep pushing coolant till you back your timing off IMO.

 

[1SIC1Gb]

Good info guys, I'll get it back together. It blew the cometic setup at 30psi. But the oring setup did make 42psi but it was pushing coolant .

I'll give that a shot when I get it back. Don't know if yall have seen my build thread but it's been a mess with machine shop issues .

 

[bastarddsm]

Yeah dude I feel bad for ya on all that, but then when it works it will be all better

 

[wishihadatalon]

I think you have got the point from the previous posters, but I agree with the timing being too high. If you are trusting your factory knock sensor, I highly recommend resorting to reading plugs. When I see posts on here about head gasket problems, I immediately assume the poster is running too much timing. It seems the DSM formula for power is switch to Holset turbo, run e85, turn boost up past 30psi, and set timing at 18+ degrees. I've never seen this formula work long term for people.

FWIW, on my car, I have been running 30psi on a 60mm hx40 with a .70 BEP t3 housing on the stock bottom end. Looking at the plugs, I don't feel comfortable running any more than 15 degrees of timing. I use standard arp studs and a permatorque gasket and have never had an issue with the HG. The car at 3300lbs has run a best of 100mph in the 1/8th with a slipping clutch and usually picks up between 28-31mph on the big end of the track. I've never had an issue with head gasket failures.

 

[donniekak]

I think you have got the point from the previous posters, but I agree with the timing being too high. If you are trusting your factory knock sensor, I highly recommend resorting to reading plugs. When I see posts on here about head gasket problems, I immediately assume the poster is running too much timing. It seems the DSM formula for power is switch to Holset turbo, run e85, turn boost up past 30psi, and set timing at 18+ degrees. I've never seen this formula work long term for people.

FWIW, on my car, I have been running 30psi on a 60mm hx40 with a .70 BEP t3 housing on the stock bottom end. Looking at the plugs, I don't feel comfortable running any more than 15 degrees of timing. I use standard arp studs and a permatorque gasket and have never had an issue with the HG. The car at 3300lbs has run a best of 100mph in the 1/8th with a slipping clutch and usually picks up between 28-31mph on the big end of the track. I've never had an issue with head gasket failures.

I agree on the timing. I run a fp bolt on 35r setup, and at 40 psi I'm running 14* at 8500 rpms. That's after working up from 12*.