why do i keep blowing headgaskets??!

[dmjensen]

yeah i ordered arps from IE.
but they haven't shown up yet so now i get to wait.

[The Humjet]

Yeah i ordered them last night. Ie sugests 60ftlbs, should i go more or will that be good?

Are you talking about the arps studs or MB bolts?
ARP will supply torque specs paper in the box. My guess it would say to torque to 70ft-lbs with arp moly. They usually specify to torque it down 10ft-lbs more than standard.

[Hey_You]

Another way to clean out your bolt holes is to fill them up with brake clean, let them sit for awhile (hour or 2), and take a q-tip to them. Then follow up with a bunch more brake clean and compressed air or q-tips if they are really dirty. Failure to do so could result in a cracked block around the holes.

[dmjensen]

Also i forgot to mention but we have no way of getting 93octane in dubuque so the highest we have is 92 WITH ethonal. Otherwise i think we have 91 without ethonal.

So i know i was probally way off on afr now since i was running lower octane gas with ethonal. Should i try to fatten it up to mid 11s on 91w/o ethn or will 92 w/ ethn be okay?

[dmjensen]

Yeah i ordered them last night. Ie sugests 60ftlbs, should i go more or will that be good?

[The Humjet]

I can't rate arp head studs anymore highly. We use them heaps with the engines we build and they're certainly a stout bit of kit. You also torque the arp studs more than you would with standard bolts.
An Ls1 motor for example is notorious for stripping threads out when tensioning up heads with standard bolts, due it having a weaker aluminum block. With the arp studs or bolts you rarely face that issue of stripping threads.

[dmjensen]

yup, i did reuse the washers before.

i think im just going to have to fork out the cash for arp studs. I just want to do it right and do it once and be done haha

[The Humjet]

I would set the final torque at 70ft-lbs. If your threads can handle it.
Your head has been on and off the block a few times now so that's one of my concerns.
Try and do as much prep as possible to get the bolt holes clean. I usually run a tap down the threads and clean it with brake clean and an air gun. And then I just lubricate the bolts with a bit oil. Were you running washers last time you bolted up the MB bolts?
Looks like your getting back on track now. Let's hope that the freshly resurfaced head can solve your problem.

[dmjensen]

alright i just got my head back yesterday (looks awesome :up:) but now me and my dad are having a dispute over whether or not we're torquing down the bolts right.

we used the 30ftlb wait 5 min, 40ftlb wait five, up to 60ftlb

but other places say 22ftlbs then 90 degrees and then another 90 degrees or something like that.

what is the right way to torque metric blue Allen bolts?

[dmjensen]

the head is warped over the last cylinder where it keeps pushing the gasket.
i could fit a .006" feeler gauge under it and a .007 would fit in one spot...

so im going to get it resurfaced and pressure tested this week

[The Humjet]

Not a ruler, a machinist's straight edge. It's a tool used with feeler guages to check if surfaces are in fact, straight.

Straight edge from summit racing

I didn't say there was anything wrong with your method. I've never used that method before. Why would I when I can check it on the mill with a dial indactor customers always get their heads machined regardless. It was the OP that said he didn't check with feeler gauges just a straight edge.

Anyway OP like I said before get the head pressure tested and resurfaced while its at the machine shop. And get working on your tuning. 13afr is on the lean side you'll wanna be around the 12s. And get some det cans, on high performance car you shouldn't be hearing it by ear. If your hearing it while your driving then that certainly explains your original question.
Also start working on the timing maps. And post it on here or even e30tech so the more experienced members such as nando can review it for you and explain where you went right and wrong. This all part of the fun of turboing your m20. Learning and gaining experience for future projects.

[dothadance]

lol, the title on the front page only says "why do i keep blowing..."

[Jaxx_]

the first time it blew it took a coolant hose off with, Tuesday night i just had a nice cloud of smoke behind me more than just steam... also it could be just noisy m20 I'm hearing, but the car is gutted so i can hear almost everything

...i dont even...

[dmjensen]

You are most likely to blow a HG on a boosted car by detonating and lifting the head, which will almost always pressurize the cooling system because the pressure is much higher in the combustion chamber.

Also, you won't just "hear" detonation. You need a knock sensor, or det cans as suggested previously. If it's loud enough to hear inside the car, you've got far bigger problems.

I'd back off the timing and fatten it up. I wouldn't want to be leaner than 12:1 at WOT in a turbo street car. Timing is far more important, though. Your gasket is probably already done if you're getting steam out the tailpipe.

the first time it blew it took a coolant hose off with, Tuesday night i just had a nice cloud of smoke behind me more than just steam... also it could be just noisy m20 I'm hearing, but the car is gutted so i can hear almost everything

[lcoleman]

Coolant looks and smells fine, its leaking directly into the cylinder. I think i could hear detonation last time i drove it with my hotter plugs and i put in the colder ones so it sounded lile it had gone away but its hard to tell with an open wg dump and loud exhaust and everything else

You are most likely to blow a HG on a boosted car by detonating and lifting the head, which will almost always pressurize the cooling system because the pressure is much higher in the combustion chamber.

Also, you won't just "hear" detonation. You need a knock sensor, or det cans as suggested previously. If it's loud enough to hear inside the car, you've got far bigger problems.

I'd back off the timing and fatten it up. I wouldn't want to be leaner than 12:1 at WOT in a turbo street car. Timing is far more important, though. Your gasket is probably already done if you're getting steam out the tailpipe.