October 17, 200421 yr it just occured to me where a source of detonation might be on ea82t's just a wild theory.. well since almost all ea82t or well any ea82 usually get that crack betweent he valve seats that crack then could become and area where the metal gets a bit hotter on the edges of the crack and poof preignition.. i know sharp edges in the combustion chamber are bad.. and i happened to be randomly thinking about detonationa nd then thought of the subaru between the seats crack thing.. soo.. anyone think i am just insane. on this theory or could it be valid?
October 18, 200421 yr Sure enough.. I'll bet they are a detonation source. Someone suggested smacking the area lightly with a punch to kind of do away with the sharp edges... for just that reason.
October 18, 200421 yr Both of you are crazy. I think that is a good idea....i would like to experiment with no cracked one...but I dont ahve any. lol all of mine have those cracks. That and i dont get Det anymore for some reason....
October 18, 200421 yr ha i have a brand new set still in the boxes LOL NNNNNNNNNNOOOOOOOOOOOOOOoooooooooooooooo!!!!!!
October 18, 200421 yr you'd really be pissed if i told you what i paid<G> Nothing I bet. No, wait, someone PAID YOU to take them? Edit: we shoudl get back on topic soon. lol
October 18, 200421 yr no i wish they were thrown in to the deal when i bought my three door sedan i also got a rear lsd, rear disk brakes, spider intake, a complete turbo moter, and 6 good turbo units.and lots of other parts for 450
October 18, 200421 yr Author ok that settles it.. you offcially suck now.... but other wise good snag dammm
October 18, 200421 yr Author i had a bit better idea maybe than a punch beating have it tig'd over with extra material added to boot go at it with a sanding rool on a die grinder and make a nice smooth small hump there makes it stronger gets rid of the crack and bring your cr up a itty bitty tiny bit badside is it would also add maybe a tiny bit of restriction to the valve breathing .. maybe depends on how much it was built up
October 18, 200421 yr i think its a very good place. i got the punch idea from an old harley mechanic. those heads cracked alot =].
October 18, 200421 yr Author hmm so.. if harley and suby crck heads alot... does that make us all a bunch of crack heads? hmm the mind wanders/wonders./
October 18, 200421 yr if you weld em they will most likely recrack. I have used the punch method with sucess. it just brings the gap back together. but then again I never had much problem with pinging. probably because my car has been intercooled since I first built it.
October 18, 200421 yr if you tig weld on heads, the valve seats will pop out at your face like hot flying saucers of death! take my word for it =]
October 18, 200421 yr I think SOP for cracks between valves (at least in other Al heads) is drill-and-fill, aka plugging. IMHO, I don't think the crack would have much effect one way or the other over detonation. Sharp edges are usually an ignition point (as in preignition) and not something that would cause the endgas to overheat. Plus it is located pretty close to the primary ignition point (spark plug). Speaking of minds wandering... what would be neat to prevent detonation is a second ignition point. Can't really put a second spark plug on our heads , but what if we could put a deliberate blemish on the endgas end of the combustion chamber that could "preignite" the endgas before it reached detonation conditions? Something running hot normally but able to get hotter as flame front approached? Maybe coated in a catalyst that lowers ignition temperature??? (Now, where's my Lithium... :crazy laughter: )
October 18, 200421 yr if you tig weld on heads, the valve seats will pop out at your face like hot flying saucers of death! take my word for it =] as for intentionally ading a sharp edge for preignition? thats just crazy talk. the problem is not where the preignition happens so much as when. if you light off the mixture while the piston is still compressing on the up stroke you are creating tremendous amouts of pressure in the wrong direction. hence holes in pistons and launched Rods. I have a dead VW 1.8t here that died due to preingintion caused by running under boost lean. a verry expensive mistake.
October 18, 200421 yr as for intentionally ading a sharp edge for preignition? thats just crazy talk. the problem is not where the preignition happens so much as when. if you light off the mixture while the piston is still compressing on the up stroke you are creating tremendous amouts of pressure in the wrong direction. hence holes in pistons and launched Rods. I have a dead VW 1.8t here that died due to preingintion caused by running under boost lean. a verry expensive mistake. Wasn't talking about preignition per se, but more like pre-detonation. I know that preignition can be worse than detonation, since it stresses things moving upwards AND can heat things enough for detonation on later cycles. I was thinking of something to cause semi-controlled ignition of the endgas. Now, I don't think that there is any practical way of doing this... might work on a steady-speed industrial engine, but then you wouldn't be flirting with detonation in that application, would you? and i told you that I was searhing for my Lithium!!! LOL Now where is it... Oh, and my wife's Mitsubisihi ran 100k after getting its head crack TIG'd... don't know how long it lasted with new owner. Sometimes miracles happen.
October 18, 200421 yr Guys, Your approaches may be too complicated. We all know the cylinder temps are too high because the combustion chambers get 'too' hot. Simply doing things like a lower thermostat, oil cooler and intercooler should be enough to thwart detonation. At the least, a good intercooler should be enough. Riding around with post 200F intake temperatures seem ridiculous to me, I don't care how low your compression ratio is. And some of us are riding with low (or lower) octane gas. Just remember Subaru's slogan from back in the day, "Inexpensive and built to stay that way". That's just a cool way of saying something was built cheaply. Again, keep boost in check by not running your turbo out of its efficiency range. Reduce coolant temps by getting a slightly cooler thermostat. Install an oil cooler. Install an intercooler. If auto, heck install a tranny cooler. Even that may help reduce engine bay temps. Cool!
October 18, 200421 yr Guys, Your approaches may be too complicated. ... Way too serious! I think we all know about temp issues (I personally disagree with running a much-lower t-stat for general use as some would have me, but at least you didn't say 160F). Definitely charge temperature reduction. Definitely reduce thermal stress on engine/tranny with proper coolers. I think that Oddcomp is just vamping here, trying to get people thinking. Like I was when talking about second ignition source. If we stuck with traditional "that's the way it works and always should", then we might be driving flat-heads with hot-tube ignition. Oh, and rear-wheel drive by chain. I think that you are right, but odd was sort of blue-skying. Fun to do once in a while.
October 19, 200421 yr Author ok lets see... a: i hit 220 f deg at max boost 10psi.. b: i run the gas i can afford.. cheap... c: even when i had a disty i never had much if any detonation problems now that my motor gets enough fuel with the ms box i do not see or hear any detonation and can run a better timing degree off and on boost i do have a intercooler but its not installed wish i could find my datalogs i did of the stock suby ecu managment of fuel versus what the ms does. anyways it was just a random thing that i thought of what with cracked metal is usually sharp metal and sharpmetal in a cylinder heats up faster ect ect or so according to all my books i have ... good sized stack... about 3-4 feet high i think i have no idea if i have cracked heads .. bet i do when i do eventuall rebuild it i want to solve or correct that problem so i was looking for other theorys on my theory
October 19, 200421 yr ...i have no idea if i have cracked heads .. bet i do when i do eventuall rebuild it i want to solve or correct that problem so i was looking for other theorys on my theory Hey, I have some cracked heads if you want to throw them on for comparison!
October 19, 200421 yr Author wow really?!?!?! thanks cool yay and stuff no sadly i thinnk i will passs for now hell wagon is still in driveway untouched since you dragged it home for me been sick plus other stuff
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