6 Bolt vs. 7 Bolt. Which is better for what?

[fmars62]

Idk if there is a thread similar to this so sorry if there is i searched and havent found anything.

But anyway, i remember I read somewhere that a 6 bolt is better for this... and a 7 bolt is better for this... but i dont remember what it said. Can you guys help me out? I know a 6 bolt is stronger but what would a 7 bolt be better for and what would a 6 bolt be better for? And just ignore the crankwalk topic please.

 

[ed1380]

6 bolt head has larger ports which means better top end with some sacrifice in power down low

 

[jimbob_843]

6 bolt has the highest stock bottom end record. Also it has bigger stronger rods and head has bigger ports. 7 bolts have held their ground but too many have you know what to give it a good rep.

 

[kenuwine4g63]

Umm..The 6-bolt is a pretty good engine. The rods are strong and like said the head has way bigger ports. The 7-bolt is also a good engine. And with the CW issue i really believe that it depends on how you manage the engine with maintnence. I've had 5 DSMs all were 7-bolts even the one i have now except one. And ummm no CW here. But If your goin stock bottom and maybe a few head performance parts like just cams and want to run a pretty nice size turbo i say go 6-bolt. It can handle the extra stress thrown at it

 

[little-razcal]

This is only my opinion
The 7 bolt head is very different than the 6 bolt head in the actual design and performance. The 6 bolt head, like stated, has very large ports which can flow a great deal of air. The 7 bolt (95'+) head, has smaller intake ports creating higher velocity. There are multiple other changes in the bowl and guide area's as well. This higher velocity helps in making more power down low through the mid-range. IMO the best combo for a engine under 700-800awhp would be a 6bolt bottom end with a 2G head. You will greatly improve your drivability on the bigger turbo's with the 2G head. Anything over 700-800awhp, you would want the 1G design to maximize airflow and not have any restriction. This of course is my opinion, but there is a reason why Mitsubishi changed head design midway through production. With that said, I have a 1G head, so I am not biased. Bigger is not always better in certain situations. You will get a thousand opinions on this, but just know that both heads will make power, only the 2G will shift the powerband a bit. Good luck.

 

[AwD4g63TsI]

The different head comparison has been noted. 2g head for better low down response, 1g head if you want max flow. As for the block though-the only comparisons I can see are these. 6 bolt=bigger rods and no known issues. 7 bolt=smaller(weaker) rods and a possibility of CW. I know plenty of people with no CW issues on their 7 bolts, but the fact remains that it may happen to your build. If you are starting from scratch and have the option of a 6 or 7 bolt block, I don't see why anyone would choose a 7 bolt.

 

[ed1380]

Also a thing about the 7 bolts. The 98 and 99 blocks were slightly revised and less prone to cw

 

[turboglenn]

i thought it was 97-99 that were revised? IDK though, i got rid of mine fairly early on after popping it at the drag strip due to faulty wideband tuning.

The 7 bolt blocks do make better boat anchors, the 6 bolts make better engines

 

[ed1380]

Nope. Just the 98 and 99

 

[fmars62]

wait what was revised in 98/99?

 

[gofer]

Idk if there is a thread similar to this so sorry if there is i searched and havent found anything.

Strange. You should have looked through our sites FAQ's, seeing how this is one question we see A LOT.

DSM FAQ's

---> Is a 6-bolt motor better than a 7-bolt?​

---> 6 bolt vs. 7 bolt [merged] 6bolt 7bolt 6-bolt 7-bolt six bolt seven bolt
​

wait what was revised in 98/99?

The thrust bearing, its split so CW cases never existed (to my knowledge) on the '98-'99 7-bolt.