71chevy said:I have had several attempts at building a motor but just cannot seems to understand what components to match. I had a local builder put a 383 together for my 71 chevy truck in hopes that I would have better luck. It sounds really good at an idle but the street performance is not that great. I have restored everything on the truck except for the motor and interior so I am good at a lot of things mechanically but I am not getting the idea of matching stroke, compression, cam, heads, intake, carb and ignition. I just want a decent sounding lope that can smoke the tires whenever I am at city street speeds.
Here is what I have
350 block bored .30 over
400 stock crank
5.7 rods
forged flat top 4 valve relief piston
Patriot performance 190cc aluminum heads
Roller rockers 1.6
Edelbrock Air Gap RPM intake
Quick Fuel Q-750 carb
Summit HEI distributor
Elgin Hydraulic cam 1011P
350 Turbo tranny
2300 - 2500 Stall converter
3:08 gears
I had it dyno'd and it had 300hp and 302 tq at rear wheels so it isn't a huge dud but it doesn't perform well on street.
I was going to start with 3:73 gears and maybe a TCI 3000-3400 stall. If that didn't help maybe putting a carb like 670 street avenger and maybe an MSD distributor with 6al and blaster coil. If that didn't help I was going to research putting afr 190 or 195 heads on it and possibly a retro fit hydraulic roller cam.
Any suggestions of where to start would be great...hopefully its not a complete rebuild.
Thanks for your time
Mike
ok lets look at that combo and see whats not going to match well and why its not working as you expect.
Elgin, Hydraulic Flat Tappet Camshaft, Chev SB
Chev SB
Lift: .490/.490
Duration: 300/308
Duration @ .050": 232/234
Lobe Separation: 108 LC
Rough idle. Upper end power, 3500-6500.
you stated you had
2300 - 2500 Stall converter
3:08 gears,
you also say you have Patriot performance 190cc aluminum heads, when i look for 190cc Patriot performance 190cc aluminum heads
i see 185cc, and 195cc come up and 64cc and 72cc combustion chamber sizes
http://www.jegs.com/i/Patriot-Performan ... 0/10002/-1
http://www.summitracing.com/parts/PAR-2171/
ProMaxx Performance#723-2180 comes up as Patriot performance 190cc aluminum heads on jegs
190cc Aluminum Cylinder Heads
Small Block Chevy
2.02''/1.60'' Valves
190cc Intake Runner
64cc Combustion Chamber
Angle Plug
Assembled
theres nothing wrong with the cam used or heads but that cam, will not work in that application with that gearing and converter stall speed, your compression is a bit high for typical pump octane gas,especially if you have the 64cc combustion chamber heads and assuming you have a standard block that has not been deck milled and your quench is nearly correct you should have a head gasket in the .020--to-.024 thick range which puts the static compression some place in the 10.5-11:1 range
because of the compression ratio you really can,t drop back to a lower duration cam easily so going to a 3300 stall converter and 3.73;1 rear gear would help allow your engine to operate in the cams intended power band, you did not mention headers, and exhaust, youll need a low restriction exhaust and headers to get that combo to breath, Id also point out that swapping to a 200r4 over drive transmission would help a great deal once you swap to the high stall speed and 3.73:1 rear gearing so I would plan on swapping to a 200r4 rather than buying a high stall converter for the th350