I had the LT1 engine replaced in my '94 Z28, got it back 3/18/11. It runs fantastic! My question is about how long until it's good and broke in? Also, I am not getting the best gas mileage, will it possibly improve as it's driven and broken in more? Any advice for me regarding this new engine??

Thanks!

 

i was easy on mine till the first oil change or about 1k. didnt push it to the max (6k) till about 3k miles. i still take it easy till its up to operating temp. thats more important than anything. have you by any chance changed the 02 sensors yet? did you have the injectors cleaned and flow tested? check fuel pressure too.

 

I will ditto craby. Take it easy for about 1000 miles. No WOT until 1500. Regular (not synthetic) oil for 1000. The gas mileage should improve.

 

I have about 2000 miles on it so far, changed the oil at 500 miles. I generally take it easy on this car except I let it loose on the freeway when there are no cops around. Also, I live in Northwest Arkansas, it gets warm and muggy in the summer and freezing cold in the winter. Which oil weight would you all suggest? They put 10W30 in it at the oil change place.

 

Craby,
I haven't changed the O2 sensors yet, probably a good idea. Good suggestions on the injectors too, I will get on that. Thanks for the info, that's what I needed to know!

 

Probably the most important thing in a new engine is to get the rings seated and mated to the cylinder bore before the hone marks are smoothed out. The sooner this is done the better it will be. One of the best methods is to "whip" the engine. That means driving at different speeds, using short full throttle bursts without over revving and allowing the car to coast back down. When the engine is at WOT, cylinder pressure forces the rings hard against the cylinder wall making the rings break in faster . When coasting down, engine vacuum increases allowing some extra oil to be drawn into the cylinder which provides additional lubrication for the rings.
IMO 10W30 is a good all around weight, but if the winters are really cold you may try switching to 5W30, and during the heat of summer 10W40 is a good choice. A lot also depends how the engine was built. If it was built with racing clearances heavier oil will be needed, so keep an eye on the pressure gage.

 

gm calls for 5w30, thats what im using. 10w30 will work fine. whats your oil pressure?
maybe for piece of mind test the evap system and make sure the fpr is ok.

 

Oil pressure looks fine, but I will keep an eye on it. Thanks for all the info! This car is running great and I want to do everything I can to keep it that way.