Vbb199
B-rate Hillbilly Customs
- Joined
- Jan 12, 2018
- Posts
- 8,937
- Reaction score
- 15,050
- Location
- Salisbury NC
- First Name
- Vince
- Truck Year
- 89, 79
- Truck Model
- 89 Suburban R1500, 79 C10
- Engine Size
- 350, 502
Nothing super duper exciting to tell, ive been doing transmission tuning as well as fuel/spark tuning, optimizing the truck.
These atlass 4200s were quite ahead of their time for GM. They utilized VVT, known as variable valve timing... which is controlled hydraulically. If youve ever rode in or drove a honda with VTEC, its very similar. The VVT essentially manipulates cam overlap.
Its only on the exhaust cam, but it really allows the truck to FLY at the higher rpms, as the base VVT angle is set at 12° in the 4500-6500 rpm range. That stock setting alone feels like a mini turbo kicking in. I played with it a bit today and got it ramping in 17-22° along that rpm range and man does that truck rip.
My wideband o2 sensor for whatever reason is buggy, so i may just buy a new one from AEM. Its the old turbo lumina sensor/gauge, so i havent fiddled TOO much with higher rpm fueling and spark, as i have no way to see where i am in relationship to the commanded fueling... so i'l order one soon.
Im quickly running out of overhead on those stock injectors, theyre 26 lb/hr injectors and im presently at 90% duty cycle around 6k rpm.
Ive sent it on to 6500 and the thing STILL seems to be pulling. Perhaps i'll get brave soon and send it to 7,000... im just afraid of beating up my transmissiom too much... we'll see.
Im dying to swap cams in this thing or play with E85 gas, with the 10.2:1 c/r, ya gotta keep timing low at peak Tq, for fear of spark knock, where as some E85 would really liven it up... but my injectors would max out.
Perhaps i'll look into throwing a set of 60 pounders in ive got laying around.
These atlass 4200s were quite ahead of their time for GM. They utilized VVT, known as variable valve timing... which is controlled hydraulically. If youve ever rode in or drove a honda with VTEC, its very similar. The VVT essentially manipulates cam overlap.
Its only on the exhaust cam, but it really allows the truck to FLY at the higher rpms, as the base VVT angle is set at 12° in the 4500-6500 rpm range. That stock setting alone feels like a mini turbo kicking in. I played with it a bit today and got it ramping in 17-22° along that rpm range and man does that truck rip.
My wideband o2 sensor for whatever reason is buggy, so i may just buy a new one from AEM. Its the old turbo lumina sensor/gauge, so i havent fiddled TOO much with higher rpm fueling and spark, as i have no way to see where i am in relationship to the commanded fueling... so i'l order one soon.
Im quickly running out of overhead on those stock injectors, theyre 26 lb/hr injectors and im presently at 90% duty cycle around 6k rpm.
Ive sent it on to 6500 and the thing STILL seems to be pulling. Perhaps i'll get brave soon and send it to 7,000... im just afraid of beating up my transmissiom too much... we'll see.
Im dying to swap cams in this thing or play with E85 gas, with the 10.2:1 c/r, ya gotta keep timing low at peak Tq, for fear of spark knock, where as some E85 would really liven it up... but my injectors would max out.
Perhaps i'll look into throwing a set of 60 pounders in ive got laying around.
