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Ive also noticed head lift issues on the 4g63's due to overly advanced ignition timing at higher rpms with ethanol fuels. I have personally had head lift isssues 3 times with my own Evo 8. the car was always between 40-50 psi of boost. .40 over bore (86mm) and with a JE proseal MLS gasket fitted. first time lifting the head the car had 20* by redline, this combined with 11:1 CP pistons, and Ignite racing 114 Octane Red (not knock limited at all) lifted my head on the dyno, literally melting the alu head and blowing the gasket to pieces.
the second time around, i replaced the head with another evo 8 head that had much of its deck material machined and was passed the machining marks. As most of you already know, this is a big no-no and should not be used, specially in an application that is going to see large boost and cylinder pressures as mine was. I decided to try my luck anyway. This time around, used a Cosworth head gasket, with a folded stopper which acts as a "wanna-be" o-ring. This time at around the same ignition timing the head started to flex and push coolant at about 45psi. Would fill up the reservoir everytime I would get into boost.
Now up until that point, I was doing all of the mechanical work on the vehicle, including the engine assembly (as that is what I do for a living) but did not have anything to do with the tuning as the owner of the previous shop i used to work for was a tuner and he opted to help out with my build by tuning the car for me.
some time passed by and I opened my own shop (Specializing in 4G63/4B11/VR38's) around the same time I also installed a Link g4+ ecu on the vehicle, along with a custom composite head gasket, with H11 tool steel o-rings that would go around the cylinders. The turbo was also swapped out from the standard mounted 6466 PTE, to a Forward facing FP super 99 which has a 72mm compressor inducer. Now I am not a professional tuner, hence why I am on here, learning from masters like Andre himself, but because it was my own vehicle and money, and I already had a pretty good understanding of all the basic tuning aspects, I tuned the car on E90 (Same ignite 114 octane fuel mentioned before). at about 50 psi, I had about 8.5/9* of timing by redline. Everything was great and the car pulled like a freight train. However one day, when I was being greedy and cocky, I ran into some boost spike issues from my mistake, where I had the MAP limit technically disabled, and was tuning in open loop BC. Spiked to 67 psi and lifted my head again, punched out all freeze plugs, cracked my block and bent a rod. (bearings still looked brand new during disassembly lol)
Since the link had to extrapolate in the regions past 50 psi in the ignition tables (which I did NOT have zones for) it also ridiculously retarded the ignition to bout 7degrees ATDC when the boost spiked. contributing to my issue further. But hey, we all learn one way or another! I have learned more than I ever would have by running into these issues.
Moral of the story, make sure the tune is spot on, dont run too aggressive of ignition timing up top specially with higher compression pistons. Try-Oringing the cylinder head (stainless steel) and receiver groove the block to allow the HG to crush around the CC and seal it up. Custom gaskets with sealing rings also work great like Andre noted. Usually MLS gaskets with the folded stopper design like the Coswoth, HKS, and some other brands work good, OEM works great with an O-ring'd head and receiver grooved block.
The 4g63's are much less likely to run into head gasket failure issues if the bore size is kept below 86mm, as the point between the cylinders get thin, and o-ringing becomes almost mandatory for big boost. There are also other options such as using 12mm head studs.
Hope you can take some stuff away from my experiences with my 4g63 head lift issues!
Might be a silly question, but did you guys resurface the block?
Did you check the quench (head surface to piston deck clearance)? that can be a problem with some engines with it promoting detonation. IIRC, the danger zone being 30-60 thou' - but that may depend on engine and whether I recall it correctly.
I would definitely follow that up with others familiar with those specific engines.
Hey Roni, thanks for sharing your experiences. I've replaced more head gaskets than I care to remember on our drag engines and I've tried just about everything to seal these engines. the solution we ran in our own drag car was an HKS stopper type MLS gasket that was 1.2 mm thick coupled with a stainless o-ring in the block with a protrusion of 0.005-0.006" and a set of 12 mm L 19 studs. This was a solid solution that worked well until we got into the mid 50 psi vicinity. We tried a copper gasket with o-ring and a receiver groove and couldn't hold 40 psi :(
Retarding the timing or running ultra conservative timing is a potential option but in my opinion is a bandaid for a gasket solution that isn't up to task. Basically you're purposely detuning the engine to keep the gasket intact. One way I have used that technique though is to retard the timing and reduce boost around the area we see peak torque. Peak torque is where the cylinder pressure is highest and hence where we are most likely to lift the head. Once you're past peak torque you can feed the boost and timing back in. For some comparative numbers on our drag engine we were 11.0:1 on methanol and with 54 psi boost we were still seeing 18-20 degrees ignition advance by 10,500 rpm.