brentlysubaru Posted March 27, 2016 Share Posted March 27, 2016 I have a 97 impreza with a 2.2 bought it about two months ago. Has an exhaust leak since I bought it, I went to fix it today I thought it was a blown out gasket on the manifold. Well come to find out I was partially correct. I could tell the previous owner messed up the bolts holding the exhaust onto the head. Two where somewhat stripped out. I got it somewhat fixed by double gasketing them should hold for a little while till I'm able to fix it better. My question is I got a set of heads off a 98 2.5 dohc and intake. They came off a running engine just had a rod knock. They have around 1000 miles on them since they where check out and then the engine got the knock. Being as Im going to have to change the heads on the 2.2 in the impreza. The bolt holes are really bad I was really surpized that I got a bolt to halfway thread in. Can I put the 2.5 heads on the 2.2? I can't seem to find any info on it. If so what head gaskets will I have to use? Thanks for any info. Quote Link to comment Share on other sites More sharing options...
matt167 Posted March 27, 2016 Share Posted March 27, 2016 You can. It will end up low compression but will run... It sounds more like your fix is in the form of a new tap and set of exhaust studs Quote Link to comment Share on other sites More sharing options...
Stevo F Posted March 27, 2016 Share Posted March 27, 2016 I remember reading about a guy who did this on the 2nd generation Legacy forum a while back. I recall he said it performed well until something else failed on the engine. http://legacygt.com/forums/forumdisplay.php/second-generation-legacy-1994-1998-95.html?s=342d2aef37be4c004ef3e837beba015a& Quote Link to comment Share on other sites More sharing options...
987687 Posted March 27, 2016 Share Posted March 27, 2016 Just fix the problem, no reason to change the heads. If the holes haven't been drilled out before, get a heli-coil repair kit and just do all 4 studs. It's really not that hard of a job. If the bolt holes have been drilled out past the diameter of the helicoil, you can use timeserts because they're often thicker than a helicoil. Either way, jumping to the conclusion you have to replace the head because the bolt holes are a bit messed up is ridiculous. Quote Link to comment Share on other sites More sharing options...
wtdash Posted March 27, 2016 Share Posted March 27, 2016 (edited) "Just fix the problem" +100 The 2.5 heads will LOwer your compression ratio, which will mean less power, esp. off idle......Although the DOHC heads do flow better up top. Some do this combo if they have 'aspirations' to add a turbo. Usual recommendation is to use a headgasket that matches the block as the cylinder bore needs to match. But as the 2.5 heads may have different ports for the oil/coolant flow, you may need a custom Cometic ($100 + ). And there is a fair bit of info out there about this combo as it's been used as a replacement in the early Legacy turbo (SS and TW) - see http://bbs.legacycentral.org/index.php, and in the Impreza - see RS25.com. There's also the DOHC Tbelt to deal with, you'll need a DUAL-port exhaust manifold/header, the valves are a shim-over-bucket which are a PITA to adjust, and the spark plugs are hard to reach....so yeah, find the best solution from the previous posted options and git 'er done. GL, TD Edited March 27, 2016 by wtdash Quote Link to comment Share on other sites More sharing options...
brentlysubaru Posted March 27, 2016 Author Share Posted March 27, 2016 I finally did get the manifold to seal. Im not sure what the previous owner did to it. They made the holes bigger on the ypipe and must have done it with it on the car because the threaded hole on the head is half gone leaving only a few threads on two of them to thread the studs into. Its not leaking right now. I was thinking of using a helicoil on them but I think the holes are too screwed up. I figured if I couldn't get it sealed up id have to change the heads and I had the 2.5 heads and intake already. That's one route that I can go. Also just found out my buddy has a set of 2.2 heads off a 95. I think I might use them instead it might be a lot simpler and easier. Quote Link to comment Share on other sites More sharing options...
987687 Posted March 28, 2016 Share Posted March 28, 2016 I'll repeat again... Fix the problem.... Do not change the head because of messed up bolt holes, that's completely ridiculous. Just use big fat timeserts so you have some meat to drill into and thread in the timesert. Even use two timeserts in eachother, almost any bolt hole repair solution is going to be cheaper and certainly way easier than taking the engine apart. There are products on the market for just this very issue, utilize them. I'd rather buy $30 worth of drill bits and whatnot to fix the problem than new heads, machine shop surfacing the heads, intake manifold gaskets, new oil and coolant, and spend my entire afternoon bent over the engine bay. But if you want the exercise of screwing around with subaru engines... I guess go ahead. Quote Link to comment Share on other sites More sharing options...
brentlysubaru Posted March 28, 2016 Author Share Posted March 28, 2016 I just googled timesert,never heard of them before. Looks like that might just work to fix it. When I go to put the new exhaust on in a about a month or so I'll try to repair that at the same time. Thanks for the info. Quote Link to comment Share on other sites More sharing options...
ccrinc Posted March 28, 2016 Share Posted March 28, 2016 Timesert products are great. We use them all the time: NEVER helicoil. Emily Quote Link to comment Share on other sites More sharing options...
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