head bolts

[shayne]

figured id ask if anyone knew if the headbolts for a dohc 24v 6g72 are the same shank length and thread pitch as the ones for a 12v sohc.
thanks.
i found an application from arp for the 24valve dohc in studs but i dont know if they will be a different length.

[Sundance 6g72]

noo clue

i know 1g dsm headbolts work (brent used them?) but he might have had to cut them down a little bit? cant remember

another thing, does the rear head fit on if the block is in the car if you use studs? something is telling me that its tricky.

anyways, id like to know this too. I could see if a sohc headbolt goes into a dohc block tomorrow when i visit the yard. there is a couple dohc blocks and plenty of 3.0s that i could steel a bolt from.

[Ondonti]

All headbolts are the same.

ARP are a downgrade compared to OEM bolts. I used 1g DSM headbolts in my mains as a project that worked out well. DSM bolts are about 3 threads longer then our OEM main bolts and are the same high quality as our head bolts. More thread engagement and a better bolt. Not necessary for anyone's project that I know if at this point. ARP base model dsm studs work in our mains, but again, they are a downgrade over oem DSM 1G bolts. 2nd gen DSM's are TTY which is why ARP is an upgrade for 2G cars.

The ARP's are "base model" and stretch easily. OEM do not stretch and are proven over 1300whp. Even custom stool steel headbolts have not shown any improvements. ARP base model bolts are only an upgrade for motors that come with TTY or a lot quality bolt.

I don't know of any high power 6g72 that is actually running that is running anything but OEM bolts. There are people who invested in those custom tool steel studs but their cars never stayed together or failed to seal the heads.

OEM Mitsu MLS is also the best gasket for huge power (I don't use it at the moment and will avoid forever if possible just to prove a point). This is because its bore is small and that keeps the sealing ring nearest to the center of the chamber where the cylinder head is stronger and less likely to flex. When people do big overbores they prefer to chamfer the pistons and keep using a small bore OEM Mitsubishi gasket. The cometic gasket is not so great because it only comes in 95mm unless you order something custom. 95mm headgasket behaves like a 95mm bore without having a 95mm bore :( At that point you need O rings or very careful safe boring tuning. Mine actually sealed but I knocked really bad and pushed. Not saying its weak but I never tried to make 800whp on it. 500hp is not remotely close the the sealing needs of the high power 6g72's out there.

[Sundance 6g72]

yeah they are the same.. i took a dohc bolt and put it into a sohc block and it seemed to work out just fine.

http://a7.sphotos.ak.fbcdn.net/hphotos-ak-snc7/374625_10150523250018899_534573898_10442952_393443 312_n.jpg

[shayne]

i must respectfully dissagree about the arp bolts being the weaker bolts, but i digress, thanks for the info. good to know that the dohc headbolts are the same size.

[Ondonti]

i must respectfully dissagree about the arp bolts being the weaker bolts, but i digress, thanks for the info. good to know that the dohc headbolts are the same size.

You are allowed to disagree with facts. ARP base model bolts are the only non custom arp that are produced for us and the material is a lower quality then OEM stock bolts.

Well proven in 8 second 4g63 and 8 second 6g72 motors. The only upgrade is Tool Steel (L19 or H11 or something like that) which ARP does sell for other platforms. It is not an upgrade for the 6g72 as the stock bolts hold 1300whp in multiple vehicles (Russian and American) and 1000whp in a few others.
Nobody runs ARP base model bolts. who is fast or makes big power, that is a fact.

[black86glhs]

YEAH!!!! He knows his shyte!!!!:D

[Ondonti]

Well, it would take a huge amount of evidence for every single 6g72 builder to rely on stock headbolts in the most expensive customer builds they do. Nobody would avoid upcharging their customers for "necessary" parts on a bulletproof build unless it was a bad idea.

6g72 ARP headstuds also neck down so the shaft is a smaller diameter then OEM bolts. OEM does not stretch, ARP does. You can bend the crankshaft and separate the mains girdle from he block before an OEM headbolt will think about budging. Push a little coolant on ARP and they are done. Once ARP stretch, they are junk because they have yielded.
The original 6g72 ARP were actually meant for Pinto motors and just happen to be similar dimensions. Only recently was there a change and I still don't think they are 6g72 specific. Just because its listed on a website does not make it true.

[RoadWarrior222]

Ya know, I'm getting the feeling that this motor was one of the last to be designed on the "well that ought to be be plenty good enough" principle, rather than the computerised FEA modelling...

[Ondonti]

Computers for the loss.

Interesting how back in the day plenty of motors were still super weak. A lot less duds these days but no real hidden gems.

Also interesting how Mitsu cheapened a motor after it was already in production (the 4g63) when it came to the 2nd generation but they actually dumped more unnecessary strength into the 6g72 (4 bolt mains and forged crank, they even seem to have lied and said it was nitrided). To be honest, the 6g72TT was strongest in 1993, and got weaker every year after in the turbo cars. The last years of turbo the rods are supposedly slightly more lightweight and the top ring is placed higher up. 1993 is the money year with best pistons and still forged crank. It is questionable if there was any actual strength lost in the rods, possibly erroneous information. The thing they didn't do is upgrade the drivetrain in the 3000gt for reliability on the racetrack. Its the center diff that is the biggest junk for racing and it took 19 years to get an LSD replacement and its 100% aftermarket. THeir own racing attempts with 3000gt's were failures in the drivetrain department. They sure kept upgrading the evo drivetrain over the last two decades.