My 454 Rebuild

[Supercharged111]

Don't be afraid to lay into it either. The LT1 in my Camaro refused to seat the rings on the Dyno, I must have made 20-30 pulls and walked with 248whp. About 5 minutes on the track though and it was a completely different animal. I just drove it like I did any other time, WFO accelerating and heel toe downshifting in the brake zones. This applied pressure both ways. I went right back to the Dyno after that event and laid down 275whp (then choked it down to 260).

 

[L31MaxExpress]

Don't be afraid to lay into it either. The LT1 in my Camaro refused to seat the rings on the Dyno, I must have made 20-30 pulls and walked with 248whp. About 5 minutes on the track though and it was a completely different animal. I just drove it like I did any other time, WFO accelerating and heel toe downshifting in the brake zones. This applied pressure both ways. I went right back to the Dyno after that event and laid down 275whp (then choked it down to 260).

My 383 refused to seat the rings around town or on the dyno too, I guess it was just not long enough durations of WOT to do the job.. Drove a 2 hour trip with some long grades at 70-90 mph and suddently it too was a different engine. Rings really seated, started making more power, the whole rotating assembly turns more easily. The rings in mine were very tight to start with. Once it broke in I had to reduce the opening on the air rate screw on the throttle body. Went from 20 IAC counts at hot idle to none.

 

[Spareparts]

Drove 60 miles with wot on some decent length hills. She appears to be using some oil still, not much though. I would imagine when the rings get seated in that will stop or it better!
Still idling a little rough but either Black Bear will need to re tune it or ill need to switch back to the old black box ecu to cure that.

 

[Spareparts]

Update time.
It is still idling a little rough and into part throttle whereas the old engine idled smooth as glass and im convinced it's the tune in the 0411 that is the problem but here is my plan.
I'm going to check compression this weekend and i expect it to be good on all cylinders. If it checks good then I'll change a few sensors.
I'm sure both front O2 sensors are original and changing them is probably a good idea anyway so will do that.
CMP is set at ± 0.2 ish.
It seems impossible to get a friday afternoon appointment with Black Bear and that is the only time i have free for weeks to come so if nothing cures it i will need to change back to the old black box ecu.
I think everything mechanically is good so pretty much only leaves the tune. Mileage is up and power is way up!

 

[BeXtreme]

Update time.
It is still idling a little rough and into part throttle whereas the old engine idled smooth as glass and im convinced it's the tune in the 0411 that is the problem but here is my plan.
I'm going to check compression this weekend and i expect it to be good on all cylinders. If it checks good then I'll change a few sensors.
I'm sure both front O2 sensors are original and changing them is probably a good idea anyway so will do that.
CMP is set at ± 0.2 ish.
It seems impossible to get a friday afternoon appointment with Black Bear and that is the only time i have free for weeks to come so if nothing cures it i will need to change back to the old black box ecu.
I think everything mechanically is good so pretty much only leaves the tune. Mileage is up and power is way up!

what kind of mileage are you seeing? I'm not too concerned with mileage on my swap, but I'm expecting it to be far better than the 8-10 I'm currently getting in my truck with the carbureted 350/TH400/NP205

 

[Spareparts]

Just anecdotal evidence so far.
I usually use just over a 1/4 tank of gas driving back and forth to work 4 days a week. This week doing the exact same thing was just under a 1/4 tank.
Maybe tomorrow i can get a exact reading if i drive any distance.

 

[Spareparts]

So here we go. Spent the morning messing with things.
I did not change the O2 sensors according to Torque and Dash Command they are working. Properly i don't know but they are reading.
Can not find any vacuum leaks spraying everything with carb cleaner.
There are no misfire counts. Reads 0 so maybe it can't read that? Spark plugs are all firing.
Did a compression check and to my surprise all cylinders are dead on with only 120psi. Had a friend stop by for a few minutes and his gauge read the same.
Changed out the 0411 and put the black box back in and it made a noticeable difference for the good but it still feels a little off.
Now im thinking i have a weak injector but no clue what one it could be but the old engine did idle smooth so maybe not.

The compression though really has me wondering. I expected more.
The block and heads were surfaced 0.005 each and a chevy performance head gasket when compressed is 0.022 thick and bored 0.030 over.
Nowhere i can find has what a decent cranking compression test should be. Maybe 120psi is great?
Possibly the machine shop installed a improperly ground cam? This one
Other than the slightly rough idle/part throttle it seems to run and sound great.
Any thoughts you want to offer?

 

[Piratehunter]

to me it sounds like a slight vacuum leak somewhere or injector not fully seated. I noticed an injector raise up when setting the rest of them and tightening the rail. A carefully placed slotted screwdriver and an open hand tap seated it.

 

[Spareparts]

Found the compression spec and a new or properly rebuilt 7.4 should have about 180 psi compression.
So been thinking about this and believe either the machine shop installed the wrong pistons or cam, Either it was wrong grind or not ground properly? To much overlap?
I do remember thinking the cam lobs look kinda small but at the time i did not have another cam to compare it to when i pulled it out to check the PN.
Now how to proceed?
The pistons i can not do a thing about or really check. The PN is listed as the proper piston for my engine.
I have a good stock original GM cam shaft i could swap in but man that's a lot of work if that is not the problem.
Don't know what way to go

 

[Supercharged111]

Is this thing even broken in yet?