BUILD THREAD 86 GP 2+2~Blown 6.0

[81cutlass]

Finished the wiring oops repair and took it to the coin op wash to remove the 16 months of mouse blood and urine.

Also took it for a short drive and seems good! Its a bit rich at idle but not bad, quick hpt update and should be good.

Besides the cam having a bit more chop everything seems about where it was when it blew up.

Gotta wait for a good rain storm to wash the roads off before I take any real drives and find an open track for a test day but otherwise feeling ok where it's at.

 

[81cutlass]

Diddly squat update #4251.56

Put the shop back together

Dug out one of the spare parts I had. I had traded a pair of decent grey belt retractors a few years ago with the goal of replacing the passenger side on the cutlass because a mouse chewed a hole through the belt. I had the drivers side still sitting around and the buckle was missing the trim and the belt was fraying on the 2+2 so I swapped the belt. Old, left, better, right.

And tuning. When this thing hits 88mph (you know the line lol)

I had the 80lb injectors cleaned and flowed when i went through the engine. Now that I have it running the tune has been off in odd, all over the place locations. The injectors did open up 3-5% when they cleaned.

It was consistently 10-15% rich at idle and 10ish% lean up top. I also lost about 1.5psi with the same pulley vs the old setup. So stuff changed. New cam, different compression, yada yada.... There are some reasons why it makes sense and some reasons why it doesn't. Anyways new build so I am over analyzing. I am also referencing a wideband sensor that is near 9 years old with 20k miles so who knows haha.

Nothing is telling of a problem in commanded idle trims, commanded vs observed RPM, and no obvious misfires. This new cam seems to 'lump' harder at idle and I have been chasing a 'ghost' misfire assuming thats why it's rich, but all the header primaries are warm. 10% rich switching to under 3% error at 1500rpm and then 10% lean under boost just seems odd, it seems like the whole fuel map 'tipped' with 1500-2000rpm being the fulcrum. I can't find a misfire so I'm chalking it up to its just a new cam and cleaned injectors so stuff changed and it needs a retune.

I think the rich at idle is due to injectors being cleaned and lean at boost is a better cam. The current cam is a direct replacement from BTR of the one I had (Stg 2 Blower) but the new one is the 'torque' series and better in some way I am unsure about. The new cam must flow better under boost and it's lost some PSI so its just flowing the same CFM at less boost so its more efficient which is good. Spent a couple drives tuning it and its within a few % of commanded now so it's fine. I also switched the blower pulley from the 2.55" to 2.75" to pull some more power out. I can only run 11.50 at sick summer and the car has run 11.10 at 127mph so its going to bust out of my allowed tech speed, especially if its using more fuel at less boost with more compression. It was making 11.5psi on a 2.55" pulley but now its 10psi. I am hoping the 2.75 pulls another 1.5psi out and I can make 8.5psi and some timing out to trap in the 122's and maybe yank some timing out.

So more fuel under less boost with more compression is good for my goal of 10's, but not good to turn in a pass every day on sick summer, so time to slow it down haha.

Hopefully the weather holds out and I can get some test passes at my 'home' track which is reopening this year under new management in 2 wks. It's been closed since 2021 so it will feel good to go back home and get some test passes on the new setup.

 

[64nailhead]

Take the smaller pulley with you - trust me.

Your description of the fueling makes sense for a larger cam. Just keep it above 1900-2000 when cruising (unless you’re picking up grandma from church to head to the grocery store)

 

[81cutlass]

Took the car to Rock Falls yesterday for a test session. Trailered it as I now have access to a decent trailer and pickup and didn't want to mess with breaking at the track first time out on a new setup with a toddler at home.

Since I don't have a roll bar I'm limited to 11.50 for sick summer so I had to figure out how to slow it down and be a bit more consistent.

Put the lower boost pulley on and replaced the 4yr old Hoosier DR with some MT street R's

Pass 1: 3400rpm on the 2 step, 21 psi tires, tried to give it ~50% throttle and then go WOT when the clutch grabbed. Bogged off the line but 1.87 60ft, 11.68 at 124mph

Pass 2: 3400 on the 2 step again, 21psi in the tires, gave it 100% throttle at the line and spun and had to pedal. 11.66 at 124

Pass 3: 3400 again 20.4psi, tried to see if I could pedal it back to 50% throttle but it wasn't repeatable and it was like 30% and bogged hard, 2.16 60 ft and a 12 sec pass

Pass 4: my brain isn't capable of consistently getting the throttle open to the same % ever tone so I pulled the 2 step down to 2600 and went 100% on the throttle. It bogged but it felt smoother and consistent, 1.83 60 and an 11.70

Pass 5, put 3100 2 step and it 1.78 60 and an 11.54. it still bogs a bit, around 2600 rpm after the clutch grabs but it's enough to not totally kill the momentum so that's where I'll leave it for now.

So next month if I'm slow I can put a few 100 extra rpm in at the launch and if it's fast I'll take some out. It has 1.55 60ft with 4400 on the launch rpm so I've got a lot of variability to play with.

It trapped consistently and shifted good, fuel looked good and went down the track consistently.

Made 8-9 psi up top. Basically the only easy variable I have is launch rpm plus its kinder to the drive line and it's not going to have any issue hooking at the line at only 3000 rpm on the line so probably the best 'safe' option for 5 different tracks.





Cooper and his dad who now own the wagon were there, Cooper is 14 now so he was getting his Jr Street license.

Car is 3855 without me.

So with me in the car is 4040lb, with the trap speed it's probably 620 crank HP.

So my to do list for the next month
1. Fluid change
2. Install cupholders
3. Get some better method to adjust my front shocks
4. Get AC working
5. Get trailer wiring and a hitch figured out

Should be enough to keep me busy

 

[pagrunt]

Took the car to Rock Falls yesterday for a test session. Trailered it as I now have access to a decent trailer and pickup and didn't want to mess with breaking at the track first time out on a new setup with a toddler the pitcrew trainee at home.

Fixed that for you.

 

[Supercharged111]

Trailering is the only way to go. Walking sucks.