Motown 427 Short Block Build
I was hoping someone could point me in the right direction to finish out a Motown 427 short block (low comp., -20cc Rev Dome pistons). Itís going in a 69 Camaro vert. Iíve got a Currie 9Ē with 3.70 gears and a TKO-600 w/ the .64 OD.
The complete crate engine from World has 520 hp and 495 ft. lbs. Iíd like to build my engine with at least 500 hp and about the same on the torque. One trick is I need to keep this thing under the stock hood and itís not a cowl. That probably means a dual plane manifold and if possible Iíd like to put dual quads on it (just cause I think theyíre cool). I also need to be able to run the AC, pwr steering and breaks.
Iím confident I can put the engine together I just donít know what heads, cam etc.. to use. I do know Iíd like to stay hydraulic on the lifters to stay away from the maintenance of adjusting the solids. Any help would be great.
Usually, you would want to run a fairly good sized head and cam to enable this motor to breathe. In your case, if you are limited to a dual plane intake, you might as well match all the other parts up to that intake and buy a smaller head that still flows well. That will make for a very responsive very torquy motor. It will probably stop making power at a relatively low RPM, but it will make alot of power up to there. Below is what I would recommend and an article with a similar setup.
AFR 195cc (street or comp ported depending on how much you want to spend)
Performer RPM air gap intake
XR294HR cam (242 248 @.050 duration .540 .562 lift +1.6 rockers = .570 ..592 lift)
With the size of the motor, I think you should be able to get away with running power brakes, but I would call comp and see what they say. I recommend going bigger on the cam than in the article because I think it matches the motor better.
Here is a similar motor and what it did
AFR 195cc heads
236 244 @.050 .550 .550 lift solid roller cam
single plane with fuel injection
Made 560 hp @ 6200 RPM 547 ft lbs at 4700 RPM
In the article, they used a single plane and fuel injection, but I think your motor should still be around 530 hp at a lesser RPM pretty easily and more torque down low. I think it will fit under your hood. I had a 1972 ventura (same as a nova) with a small block with the performer RPM that fit, but barely. (I had a 3" or 4", not sure which one, air filter with a drop base) I dont know if your block is stock deck height, or if the Perfomer RPM air gap is taller than the Performer RPM. You can see the motor in my photo album
If you wanted to go with a dual quad setup that might fit under the hood, the one below might work, it is not cheap though.
Also, AFR's new heads have 65cc combustion chambers. With those heads and your pistons with a .045 piston to head clearance, you would be right at 10.2:1 which would be about perfect.
What carb do you think I should run?
I really like the dual quad set up.
There is an equation that you can use to estimate what size of carb to use based on max RPM and engine size. It is RPM*(Cubic Inches)/3456. If you assumed a max RPM of 6000 RPM for your setup, 6000*427/3456=741cc. This assumes 100% volumetric efficiency, which most street motors do not achieve, so in that case it is a little bit of an over estimate. According to that equation, I think a 750 would work well. If you wanted it to breathe a little more on the top end, you could go with a 800 or something like that.
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