Originally Posted by Mr. M
First off let me say hi - new to the forum.
I have a question or more like seeking opinions on my build. Bear in mind that this truck is almost a daily driver and occasionally tows a bass boat. Doing this on a semi budget, currently the heads and carb I am flexible on as I will buy a set - and maybe a new carb.
Let me list as much of the details as possible - Curious as to what kind of horse power I can expect and if you all think it's a decent package.
Vehicle: 1971 Chevy Cheyenne C10, 1/2 ton 2 wheel drive
Transmission: TH350 with 2000-2200 stall.
motor: 71 350 4 bolt main - .20 bore
Crank/Rods - stock .10 over
Cam - Comp Hi Energy 268/268 454/454 - 110 deg lobe separation
Pistons: Flat Top, 4 valve relief, Hypereutectic Aluminum, 5cc
Intake: Edelbrock Perform
Carb: 650 Holley
Exhaust: Headers, duals, 40 series flow masters.
Heads: 72cc Chamber heads, cast iron, 165cc intake runner volume, 2.02 intake, 1.60 exhaust. (Summit)
Ok, that should cover it.. Do you think these heads will be decent for what I have bearing in mind - daily driver. Is there anything that doesn’t go well here? Intake? Carb? Etc…
Thank you in advance.
This is the type of build that many young fellows might undertake on a budget, so let's examine it.....
First the heads.....
The Summit tech guy only has flow at 0.500" valve lift, 210 intake/138 exhaust. That's about the same flow as production 434 or 462 Chevy heads and should work fine for your application.
I think in this case, I would opt for a stock cast iron intake manifold and mount a rebuilt Quadrajet on it. The stock manifold will max out the low end torque that you will need for towing and the tiny little primaries of the Q-jet will maximize your fuel mileage. Plus, when you get down on the loud pedal, the huge secondaries (BUHWAAAAAAAA
) will be music to your ears.
Here's how I see the head flow....
0.100" 57 54
0.200" 123 97
0.300" 171 123
0.400" 203 133
0.500" 210 138
0.600" 217 140
These numbers were arrived at by playing with the numbers posted on the Stan Weiss site for production 434 and 462 heads and are the best SWAG I can come up with.
If you have a virgin cylinder block and don't do any decking to it, the block deck height will be 9.025". (If the stamped suffix numbers are still legible on the passenger side of the block deck at the front of the block, it's probably virgin). If you choose pistons with a compression height of 1.560" (choosing a piston with a compression height of less than 1.560" will be a mistake), the stack of parts you will be using will be 9.000". Deduct the stack from the block deck height and find a piston deck height of 0.025". If you use a shim steel head gasket (0.015" thickness), that will put the squish at 0.040" and will make the motor nearly detonation-proof on pump gas with a reasonable static compression ratio and cam to match. Here's the gasket.....
Wipe down the block and heads with a good solvent to make sure they are clean of any oil or other material and install the heads dry.
With a cylinder volume of 724.63cc's, heads with 72cc chambers, pistons with ~5cc eyebrows, piston deck height volume of 5.2cc's and gasket volume of 3.25cc's, I calculate the static compression ratio at 9.48:1. Absolutely perfect for a pump gas motor with iron heads.
Here's the cam you have chosen....
12-210-2 - HIGH Energy
Install it 2 degrees retarded on these 0.050" tappet lift numbers for a Dynamic Compression Ratio of 8.26:1.......an excellent pump gas number for use with iron heads.
IO (1) BTDC
IC (37) ABDC
EO (41) BBDC
EC (-3) ATDC
Here's a DynoSim of this very affordable and common sense build.....Look at that torque curve....flat as a pool table.
Max volumetric efficiency 83.5% @4000 rpm's
Max BMEP 169.9 lbs @4000 rpm's
The slightly looser torque converter should put you right on the numbers from the git-go. Well done.