Dirteater19

Hey guys,

Should be an easy question but I can't find an answer on the internet. Basically, I wanna take my C6's 10.9 to 1 CR down to 9.5-10 CR and want to know if I'll need to re-tune immediately.

Now before anyone loses there mind and say I need a tune for any change, I do plan on tuning eventually, but I'd like to break in the new pistons and motor with about a 1000 easy miles before going WOT on the dyno.

Its got an A&A vortec V3Si on it now with a 3.8 pully and stock diameter balancer. I'll probably go with a 3.6 or 3.4 pully during the tuning to regain lost hp and hopefully get on the boost lower in the rpm.

Thanks for the help.

Unreal

Not a good idea to break in a motor on a bad/poor tune. The extra fuel and lack of timing could cause ring seal issues. Can you do it? Probably. Is it a good idea, not really. Throw it on the dyno and break it in properly with some nice WOT pulls.

Dirteater19

Thanks Unreal. I value your input since you have a lot of real world high hp and modded experience. I'll talk to the tuner and see what we can do after the rebuild.

xBoostx

Engine will likely be running reach if you didn't have a supercharger is different but with it and bad tune bad idea paying a little for a tune adjustment is a deal compared to possible consequences IMO.

By the way when I finish my engines I do drive ability calibration and then head for Mexico for some wot adjustment then change oil and head for the dyno.

Dirteater19

Thanks Boostx, I won't worry so much about the engine not being broken in.

Unreal

My break in on my motor was, warm up, check for leaks, etc.
Around the block a few times, drain oil, replace. 8 mile drive to dyno. Strap down with 11 miles on motor, make WOT pulls tuning. At 11 miles made 920rwhp, at 12 miles made 1018. The rings set nicely.

xBoostx

Nice that's how is done

Dirteater19

Haha, thanks guys, appreciate the feedback. One last question, should I shoot for 9.5/1 or closer to 10/1 CR. Again, this is only on a V3Si on 3.8 inch pully currently, possibly pully down in the future to spin it at it's max but not over spin. No plans to go bigger. No E85, no meth, just 93 octane. Want to keep it as steetable at possible and not lose any more off boost torque and throttle response than I have to while still keeping it dead reliable. Just gets me how it does fine with the stock 10.9/1 CR when I only had 91 octane available but everything I read said this was no bueno.

TurboLX

Yes, the lower CR will require different ignition timing across the board at the bare minimum, and most likely will affect VE too.

If your tuner does his job right (part throttle mapping of VE and MAF curve before WOT), your rings will be seated and the engine will be just fine before any WOT work is done.

Tech

Yeah.. from everything I've read.. a couple of heat cycles, change oil, retorque head bolts/studs, check everything over and let 'er eat. For me.. I have a new clutch so I'm going to put some street miles on it before WOT dyno tuning..