Jesse

iTrader: (4)

****'s getting real here, and I'm wondering about milling my head for an increase in compression instead of having some one-off pistons made. This is a common option for SBC builds. I'm doing this very thing on my 307X build for my Nova. Is this a viable option for this car? Why or why not? Is clearance going to become an issue? Looking for serious answers here, so Sl0wbaltSS GTFO.

Slowbalt2000

iTrader: (1)

Measure the ptv clearance first, determine how much you can take off, then do it.

ECaulk

iTrader: (6)

Pretty sure you can get away with some. The guy on the top of this whp list for NA 2.2 power shaved his head irrc, I just can't recall his user name

Jesse

iTrader: (4)

But... but... I'm lazy! I really need to get a second car. This one can't be down more than a day.

I'm glad you said that. I looked at his old FCOTM and it was shaved .020" with the stage 2 comp cams(whatever those are) so I'd probably assume a stock set of cams would be fine. Shaving .020" would reduce combustion chamber size by a theoretical ~1.7cc. Good enough for me. I also have the liberty of owning HP Tuners and being able to make changes. Previous guy had an 06 with trifecta(barf).

I'd reeeeeeeeally like to take that top spot on the dyno list.

ECaulk

iTrader: (6)

He also lived near Vince back when Vince was actually responsive and involved with the cobalt community

Omiotek

iTrader: (2)

You will need to compensate with a thicker head gasket. The tolerences are very minimal

Jesse

iTrader: (4)

That would kinda defeat the purpose of milling it. I wish I could just drop a few hundred bucks on a spare engine to build but 07-08 are just impossible to find, and when you do they are crazy overpriced

07blackg5

iTrader: (8)

i got my complete block and head for 400 bucks

1800 miles on it haha

Jesse

iTrader: (4)

There was one here with 236k miles for $850. I can't drop that much into a **** engine

Dipped_Cobalt

that's what I was gonna say, why mill the head then compensate with a gasket?

07blackg5

iTrader: (8)

oh wow. that's terrible

Slowbalt2000

iTrader: (1)

dude look on car-part.com

i got a 42k mile le5 from a junkyard for less than $500 picked up

Slowbalt2000

iTrader: (1)

swap to a manual that may give you a few hp hahaha

07blackg5

iTrader: (8)

Transmission delete. Weight reduction AND less drivetrain loss

Slowbalt2000

iTrader: (1)

right lol

Jesse

iTrader: (4)

Nah I like my auto. Hoping some rpf1's and light tires will free up a few HP.

Lol maybe you can convince Cobe or sl0wbaltSS of that.

07blackg5

iTrader: (8)

Will 14s clear our front brakes? The 14x7 Rpf1 are like 8.6lbs or something

Jesse

iTrader: (4)

Idk. Was looking at the 15s. 9.9lbs and some 17lbs tires. My brake rotors are 10.8" I think? I'm sure 14s would clear I just don't want them.

Omiotek

iTrader: (2)

the point is you cannot deck the head a lot without compensating because the tolerences are already close. GM even specifies this. The heads are so cheap they are pretty much throw aways. You will run into issues with the timing chain and clearances else ware.

so you wont be decking it enough to gain any compression.

Slowbalt2000

iTrader: (1)

Like i said, measure it and do what you can. The tensioner should be able to compensate for .020 of difference...

I say at least measure it out and try it. I could maybe put a test motor together to see what stock ptv clearance is.

Jesse

iTrader: (4)

I'd feel bad for asking you to go through the trouble. My main concern is that I haven't done a cam change in this car before. SBC you can check PTV clearance easily by holding the piston TDC and rotating the cam. This engine is interference-style though and I can't do that.

Honestly though, I think I'm overthinking this. If you can buy cams that offer .05" more lift than stock then a stock cam should be just fine with a .02" shave. Plus it's been done before, with a larger than stock(comp stage 2 whatever the eff that is) cam. Sure, the 07+ cam is different but there's no way it's bigger than the 06-prior aftermarket cams.

Slowbalt2000

iTrader: (1)

The 07 cams are actually the worst of all ecotec cams but thinking that just because aftermarket cams have higher lift doesnt mean they dont have a different ramp rate or duration. Still a good idea to measure it. But youll probably be fine.


My "test" motor is blown up in my garage so it wouldnt be super hard to do i just have to put it together.

Jesse

iTrader: (4)

I emailed NWAE_Cobalt so we'll see what happens. Also made a mistake by forgetting the diameter of the combustion chambers. A .020" shave would reduce combustion chambers by 3cc, not 1.6cc which would put me close to 10.45:1. Maybe even tempted to go .030" which would get me to 10.7:1

Slowbalt2000

iTrader: (1)

I guess we'll see

Jesse

iTrader: (4)

Well 07blackG5 just has to go and give me a great ******* offer on a set of stage 2 LSJ cams modded for the 07-08 L61... Maybe a spare bottom end is the way to go after all.