1SLwLS1

iTrader: (6)

Alright, old 346 engine locked up and was tuned with 799 heads and MS4 cam with stock injectors, ya ya, I know.

So I am putting in a 408 this weekend and 42# injectors. Obviously, with the stock injectors on the new 408, it would run crazy lean and the compression was ~10.5:1 and now it will be 11.5:1, so I probably shouldn't fire it with the stock, 26 or however many # injectors stock are, right...? Should I chance just firing it with the 42# in there compensating for the new displacement or will the MAP and O2s do their job and increase output to meet the AFR?

I will be towing this 120+ miles to get tuned, so I want to make sure it will run and there are no strange noises before I go through the hassle to find out something is damaged or not installed properly.

Ideas? Advice? TIA!

C5kid

iTrader: (12)

stock are 28#

i'm not sure what to say about firing it up. it may idle and run, but the fuel trims will be all over the place. but on the other hand you may wanna fire it up to listen for and wierd noise's, leaks, etc, before you tow it 120 miles

98nxz28

where are you getting tuned? im lookin for a tuner im doing a 427 in my camaro and looking for somewhere to go.

BLK02WS6

iTrader: (2)

You don't want to fire it with the 42# injectors in it without being tuned - it will be in open loop when starting up cold and pig rich... might wash the rings. If you can't get the baseline tune in it for the new injectors, I would start it with the injectors that match the tune in your PCM currently. It will be fine for running it a bit and heat cycling everything a couple times before heading to the tuner...

What cam/heads are going on the 408?

1SLwLS1

iTrader: (6)

Yea, I didn't even think about ring wash. MS4 and 799 until I can get some more $$$. This is definitely a budget build, but I figured I would get as many cubes as I could now, and pick up the cheaper stuff as I go. Just have a solid foundation.

I am towing it down to Victoria, TX. That is where Pat G does his tuning.

BLK02WS6

iTrader: (2)

With the same heads/cam, it will run good enough on the tune you have to make sure everything is working alright... before you go for the tuning, put the new injectors in, and don't start it again.

I tuned a combination similar to that several years back - it made pretty good power and awesome torque... good for a street car.

1SLwLS1

iTrader: (6)

Yea, I have looked at some dyno and racing sections with this combo. YouTube has a few as well. I think the average was around 470 rwhp and 440 rwtq but those were all with LT's so I won't be disappointed either way. This build cost me $0 and it will fix the previous problem of having a duty cycle in triple digits.