327 Engine - Impala Tech
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post #1 of 5 (permalink) Old 07-23-2015, 11:50 PM Thread Starter
Join Date: Jun 2015
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327 Engine

Hi, I have a 67 Impala SS with a 4 barrel carburetor. All stock. I read these engines produce 275 horsepower. I want to upgrade the horsepower. How much more horsepower can I get from this 327 engine. What upgrades should I do to get more horses?

Thanks, AJ
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post #2 of 5 (permalink) Old 07-24-2015, 09:11 AM
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With any engine regardless of make the power is in the heads. With the stock "Power Pack" heads you can make maybe 350 horsepower with some porting following the instructions in David Vizard's fabulous book "How to Port Cylinder Heads".

http://www.walmart.com/ip/15760642?wmlspartner=wlpa&adid=2222222222701038906 6&wl0=&wl1=g&wl2=c&wl3=52993324848&wl4=&wl5=pla&wl 6=75139935408&veh=sem

and a head porting kit from Standard Abrasive's head porting kit


combined with a set of six inch reach carbide burs

http://www.eastwood.com/carbide-bead-burr-6-inches-long-set-of-4.html?fee=7&fep=474&SRCCODE=GA220010&adpos=1o1&cr eative=61491489420&device=c&matchtype=&network=g&g clid=CKiS75vn88YCFdIXHwodIKgPHw

Of course you will need a die grinder to power the head porting tools. I recommend an air grinder as it runs cooler and you have better control as the torque is limited by air pressure (an electric DC motor which most all use increases the torque output as it loads down).

Here is an electric one I have used and it lasts about a year in heavy use:

http://www.toolup.com/makita-GD0601-1-4-Die-Grinder-with-Side-Switch?CAWELAID=120204890000022907&CAGPSPN=pla&cat argetid=120204890000211521&cadevice=c&gclid=CJCEr9 fn88YCFUGRHwodSqMMKg

but I have four different air powered grinders that have different lengths and the chuck either coaxial or at ninety degrees to get into the ports.

You will also find a head holder handy though I personally bolt the head to an engine stand since I only use modern aftermarket aluminum heads that have accessory bolt holes on he end of the heads (with the exception being my Big Duke heads which I paid to have professionally ported by Larry Meaux back when I was still class racing):


That all said if you want more power (doubling your power out put) you are going to need to buy a new aftermarket aluminum head with a fast burn heart shaped combustion chamber, with raised Vortec style intake ports. All of the 500 plus SBC motors that you read about on line are capped with aftermarket heads and are controlled with a hydraulic roller cam.

Big Dave

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post #3 of 5 (permalink) Old 07-24-2015, 09:21 AM
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If you have money to burn, you could bore and stroke your 327 to a 383. That is what I did because stock appearance was very important to me, but I also wanted "more power" With stock heads, exhaust and intake, it makes 370 hp 420 torque.

Another thought to consider, a 700r4 or 200r4 transmission. The lower first gear gets things moving and the overdrive makes for more livable RPMs on the freeway.

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post #4 of 5 (permalink) Old 07-24-2015, 11:01 AM
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Depends upon your budget AJ.

You can port heads/intake for next to nothing like Dave mentioned, or go all-out and get 500hp. Totally do-able.
I also have to state, you may have the "double-hump" heads instead of the "power-pak" style of heads. The DH is more desireable but they are so old that the machining costs of rebuilding them is frequently on-par with buying better aftermarket heads. (cast-iron or aluminum)

There is a general order of progression depending upon funds and time:
*Headers and full dual-exhaust pipes
*replacement intake manifold.
*tuned carb/timing
*possible replacement carburetor
*different heads
*Bore/stroke as David mentioned.

*crate motor ? frequently cheaper or on-par with a local rebuild.

personally, with the unknowns of finding a reputable rebuilder, I went with a Blueprint brand crate motor 383. (327 or 350 block, 400cid crank).
They are sold via Jegs, Summit Racing, Scoggins-Dickey and Pace so they are reputable and I am very happy with the engine.

I concur with Dave on the transmission idea also, if you are running a power-glide 2-speed transmission, it will be like a Ball and Chain to building up the motor.

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post #5 of 5 (permalink) Old 07-24-2015, 02:31 PM
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In my opinion, keep the original 327 original. If you want more HP, buy a Crate Engine already re-worked and modify it more if you choose to. Keep the 327 in storage as someday you might just be glad you did. If you end up never using it, you will then have something pretty valuable to sell. But that particular engine will only be original to your particular car once.


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