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apexrig1 10-04-2012 07:06 PM

Want more power out of 427
Hey everybody I have a few questions in hoping you can help me with. A friend of mine currently has 427 bbc that ran 520hp on the dyno. Now after a few years he wants more power closer to 650hp. No nitrous. He is on a very strict budget. Now the motor has forged crank and forged domed pistons. Now I thought in my mind he could disassemble the motor have the pistons milled down to be flat tops giving it around 8.5:1. Put a weiand 177 blower ontop. Possible upgrade to a hydraulic roller.

Would this work? If not could I get input on what you guys would recommend? This is strictly a street motor in a 71 gmc half ton.

Thanks a bunch

vinniekq2 10-04-2012 10:11 PM

Depends on what is already in the engine. What heads are on the engine at this time? 650 HP is easy with a blower/turbo and 575 is very street able in normally aspirated.

SSedan64 10-04-2012 11:35 PM

If the Domes are solid they can probably be milled down enough. If they're hollow Domes no go. 10-05-2012 05:11 AM

Most 427 BBC high compression pistons can't be cut to flat top safely.

AutoGear 10-05-2012 08:12 AM

When you say strict budget, what do you mean? To me, "blower" and "strict budget" don't go together

apexrig1 10-06-2012 12:22 PM

He has the 781 oval port heads. They have been ported with 2.19/1.88 valves.

I can't see it being very expensive to do that's all. Because all he needs is to lower the compression change cam and stick the little weaind 177 on there? Or am I missing something?

Is there a way to tell if the done is hollow or not??

vinniekq2 10-06-2012 12:26 PM

who wants the blower,you or the owner? a better set of heads will add 60 plus hp

apexrig1 10-06-2012 12:34 PM

He is just looking for a way to get around 650hp or so and we figured this would work fairly good.

Can a person get that high with just changing to better heads and upgrading to a hydraulic roller? It's currently a solid flat tappet
right now.

my87Z 10-06-2012 01:07 PM


the reason most people are saying that going the blower route will be expensive is for 1 the blower is going to cost 2500+ to get it delivered. Then I would say that it would be a little dumb to run a blower on facotry heads (just my opinion) and I'm not sure those heads in the shape they are in can even support 650hp. So there is a set of aftermarket heads, 1800-2500. To do this he is looking at 5,000 easy, and that doesn't include the machine work to the pistons (i'd just buy new pistons).

Since this is a 427 BBC which is basically the same block as the 454 BBC just with a 396 crank, I would say go after building a 496, he'll have about 2500 into the rotating assy and the machine work. Then go after the aftermarket heads, and probably another cam. It isn't too hard to make 600-650hp out of a 496 (with the tq to match). Then later on if he decides he wants even more then he could toss a blower on it and be in the 750hp range (suposing the block and other parts hold up).

vinniekq2 10-06-2012 01:26 PM

my87z is correct
what I said,heads = 60 plus hp.50 cubes will add 60 plus hp,torque would go up.

or like I said 60hp for better heads and maybe 20 more with a roller cam,thats 600,,,
blower or 496 will both need new pistons.
do the math on the cost of parts and see what works best for the situation? a 496 can use bigger heads than a 427 so more power potential there

68NovaSS 10-06-2012 01:35 PM

Doesn't seem reasonable to expect 650 out of a little 177 and 427 c.i., that's JMO>...

techinspector1 10-06-2012 01:55 PM


Originally Posted by (Post 1596272)
Most 427 BBC high compression pistons can't be cut to flat top safely.

I agree. I'm no engineer, but from what I've been able to put together over the years, good engineering practice dictates that the crown thickness will equal about 7% of the diameter for a naturally-aspirated piston. The crowns on dedicated blower pistons will be thicker than those on naturally-aspirated pistons, so you would want to be adding material, not cutting material away. I don't know what the percentage of crown thickness to diameter would be with a dedicated blower piston, but common sense tells me 8% to 9%.

67-4-fun 10-06-2012 05:38 PM

I would swap out the camshaft for something like this one from Lunati Street Strip Hyd Cam - Chevrolet Big Block 285/295 - Lunati Power then buy you a 100-150 shot cheater nitrous system, good street motor then nos if you go to the strip.. 100-150 is pretty mild shot for bbc.. this setup may cost you less than $500-$600 you get the power you want and have fun for lot less than a 2 grand blower adder not blower wouldnt be cool, but i think you dont have the right SCR or the right setup for it, NOS just bolt on and go once you learn a few detail before you run it, not hard, just common sense

68NovaSS 10-06-2012 09:00 PM


Originally Posted by F-BIRD'88 (Post 1596627)
....but I would get a Weiand 8-71 and two 750 edelbrocks for it on this motor. (+ the solid or solid roller blower cam)

That would be my choice, my 383 is an 8-71 motor, two Demon 750BC's, solid roller and very streetable.

kwillymac 10-07-2012 06:15 PM

You could make that kind of power with a 427 and a 177 weiand supercharger. The pistons are a problem. I have a 454 with a 174 B&m Blower that made 670 hp and 646 ftlbs torque. Solid cam, rectangular port heads cast iron, 8.25:1 compression.

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