Low compression, high flow, no power need advice.
05-17-2016, 03:54 PM
#1
Teching In
Thread Starter
Low compression, high flow, no power need advice. Ok, so I used to have this SBC build:
383ci, 64cc/200cc aluminum heads, -4cc FT pistons, (~10.7CR?)
Lunati Voodoo Solid .520/.540 241/249@.050 110 LSA cam
Mighty Demon 750 carb, Team G Single plane/mid rise intake
3000 stall, th350, 3.70 gear, 28" tire
this combo dynoed at 416hp to the wheels in my old (3600 lb?) camaro, ran 12.3s on foot brake, radial tire, pump gas at the track.
Since then, my powertrain was put into my (2840 lb) Mazda REPU pickup. THEN....i blew up the bottom end. I found a donor 350 short block with a lot of miles on it, and strapped my whole top end back onto it as a quick fix to keep the truck running. If I had to the guess, the pistons in the donor look like the old 8.2-8.5 dish pistons, which by my best calculations i can figure would put my compression ratio right around 9.2-9.5 with the 64cc heads, factory deck height, etc.
Ran the truck at the track a couple weeks ago, didn't get much of a launch out of it because it just lit my street tires up. Netted a **** 2.178 60', as was expected. But the best E/T i could break all night was 13.72 @ 101.8mph (VERY consistently though). Played with jetting and timing and still kept hitting the same time. I know i should expect a drop, but that much? My calculator would estimate my wheel-hp at around 250.
So i think back to the things that I KNOW are wrong with the build, like the fact that I have only up to 9.5:1 static compression with 200cc heads and a cam that asks for 11:1, the truck definitely feels somewhat slower, but it still feels quick besides being a bit lazy down low, though that might be a sign of the weight. I can understand the motor getting lazy down low, but is it feasible to have that much of a drop in power from losing 30 cubes, and 2:1 compression, with all else remaining the same?
That said, I have another Solid Voodoo cam, which happens to be a step down: .505/.520 233/241@.050 110LSA which asks for 10:1 CR
Would it be a good idea to try swapping the cam out for this one? Or would i be in the same boat and wasting time? Should I just go buy a cheap 70's melling RV-style cam? Or would I still be flowing too hard with the heads for that even to be effective?
The goal is to build another 10.5 short block in the future, but im trying to figure out something to keep me happy in the meantime. Looking for some advice from the pros out there.
383ci, 64cc/200cc aluminum heads, -4cc FT pistons, (~10.7CR?)
Lunati Voodoo Solid .520/.540 241/249@.050 110 LSA cam
Mighty Demon 750 carb, Team G Single plane/mid rise intake
3000 stall, th350, 3.70 gear, 28" tire
this combo dynoed at 416hp to the wheels in my old (3600 lb?) camaro, ran 12.3s on foot brake, radial tire, pump gas at the track.
Since then, my powertrain was put into my (2840 lb) Mazda REPU pickup. THEN....i blew up the bottom end. I found a donor 350 short block with a lot of miles on it, and strapped my whole top end back onto it as a quick fix to keep the truck running. If I had to the guess, the pistons in the donor look like the old 8.2-8.5 dish pistons, which by my best calculations i can figure would put my compression ratio right around 9.2-9.5 with the 64cc heads, factory deck height, etc.
Ran the truck at the track a couple weeks ago, didn't get much of a launch out of it because it just lit my street tires up. Netted a **** 2.178 60', as was expected. But the best E/T i could break all night was 13.72 @ 101.8mph (VERY consistently though). Played with jetting and timing and still kept hitting the same time. I know i should expect a drop, but that much? My calculator would estimate my wheel-hp at around 250.
So i think back to the things that I KNOW are wrong with the build, like the fact that I have only up to 9.5:1 static compression with 200cc heads and a cam that asks for 11:1, the truck definitely feels somewhat slower, but it still feels quick besides being a bit lazy down low, though that might be a sign of the weight. I can understand the motor getting lazy down low, but is it feasible to have that much of a drop in power from losing 30 cubes, and 2:1 compression, with all else remaining the same?
That said, I have another Solid Voodoo cam, which happens to be a step down: .505/.520 233/241@.050 110LSA which asks for 10:1 CR
Would it be a good idea to try swapping the cam out for this one? Or would i be in the same boat and wasting time? Should I just go buy a cheap 70's melling RV-style cam? Or would I still be flowing too hard with the heads for that even to be effective?
The goal is to build another 10.5 short block in the future, but im trying to figure out something to keep me happy in the meantime. Looking for some advice from the pros out there.
06-12-2016, 01:42 PM
#2
TECH Apprentice
The smaller cubes with lower compression and same induction package is begging for less duration on tighter lobe centers. Something in the area of 230 at .050 on intake and exhaust on a 106 lobe spread pulled down to 102 would make it accelerate much better. You would likely have to contact someone about a custom ground cam to fine tune the specs to where they need to be.