I decided to give this stock bottom end a run for its money. I hope to have my additional mods ready by January sometime. The reason I wanted to build the bottom end is because I will have the motor out for a head port and a lighter flywheel, but I am getting pretty handy with this stuff so I guess its not a big deal if I have to pull the motor again.

Yeah I have seen articles like the one you read, but ZZP stated in an email to me that the 2.4l did not have forged rods. I gathered that the early production 2.4l had forged rods and soon after GM stopped using them. I am going to research it a little more.

 

This is the article, fwiw..

https://www.chevyhhr.net/forums/2-4l-performance-tech-14/2-4-tech-write-up-22490/

 

And idle videos? I want to see what the idle sounds like.

 

Unless I am just used to the idle sound, it sounds like stock. I tried to make a vid in my driveway, but I live right off a busy street so its loud from traffic. I will try to get an idle with a few revs in the morning or somewhere quite.

 

I am currently doing a similar set-up working on saving my money and getting parts, who did your ECM tuning? Trying to figure out which way to go.

 

very impressive. only thing i suggest against is the lighter flywheel.

 

I have been using hp tuners since I started this project. The install and mechanical stuff is easy. Its making all work perfectly that is tough. Look into Trifecta if you want a professional to tune it, or look into a local shop with experience on this platform.

If you are good with computers then give tuning a try for yourself. It has been very rewarding in my opinion. The software runs about $650.

 

I am considering a nice clutch kit from ZZP, but it comes standard with the Fidanza aluminum flywheel. If I don't go that route I am considering the Exedy steel flywheel. The Fidanza is 8.5 the Exedy is 10.5lbs. I think the stock is 19lbs. I understand the pros and cons, but the performance side of me is craving it. I would love to bust the tires loose in 3rd.

 

I ordered a 2.5" stainless exhaust from ZZP for the Cobalt and all the mounting points are in the stock location except for the outer most muffler hanger. The inner hanger is correct on the muffler. The single hanger holds the muffler up np. I am waiting for a shorter tip though as the Cobalt uses a much longer tip. I ordered this cat back because I could not find a 2.5" for the HHR. Everything looks to be 2.25". The price is also right. $450 through ZZP. It is pretty loud with a header and catless dp, but this flows like a beast. Butt dyno approved. I think this was a major issue with my hp falling off on the dyno. I measured places on the stock tubing with a caliper and some points were hardly over 2" OD.

I will hit the dyno again with the 2.5" exhaust, 3.1" pulley and e85. I was planning on running the 2.9 pulley, but it looks like that will require 80lb injectors. I should have enough room to run e85 with the 3.1 though. I think the exhaust and e85 might just get me past the 300whp mark. Hopefully in the next two weeks.

I also decided that I will be going through with forged rods and pistons. I will be ordering them soon. I should be over 325whp and possibly approach 350 with the pulley drop and head port. At those levels I think failure is imminent. People are doing it on the stock bottom end, but I don't want to be uploading pictures of my block with holes blown through it like some of the guys on CSS.

 

Got most of my e85 tune done. Just need to make a few tweaks and it'll be set. It pulls much harder, but I don't think its 300whp. I am scheduling one more dyno for next week some time. I am hoping to hit 280whp. Also maxed out the 60s with the corn so I will have to get 80s to pulley down, but I will wait until I am built.