327 Street Build - Impala Tech
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post #1 of 6 (permalink) Old 12-16-2015, 11:12 PM Thread Starter
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327 Street Build

Alright so I am in PA and winter means time to order car parts and start building my 327. My goal is 350-400hp. I was thinking of running an msd hei dist. W/msd wires and platinum plugs, 600cfm edelbrock Carb and performer intake and a set of headers. As to what heads/cam setup etc. Not sure what to go with. Any input appreciated
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post #2 of 6 (permalink) Old 12-17-2015, 09:30 AM
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Heads is what makes an engines power. The 426 Hemi used to be a 426 wedge engine. Famous for being the first production big block engine to hit one horse per cube! What you never heard of it? Probably because it used the same heads as used on the 383 or 440 and only the Hemi got the hemi head (that will also bolt on a 440 or a 383 as they use the same cylinder centers and bolt circle) Perhaps the hemi is famous for the hemi's ability to breath and as such make horsepower.

Ignore the old standards like the Camel Hump aka Fuelie heads. They where designed in 1956 by engineers using a slide rule and appeared on the 283 horsepower 283 fuel injected Corvette motor. Modern heads are designed on super computers using fluid dynamics and as such will out flow anything offered by Chevrolet (though Chevy spent millions redesigning the SBC head in the nineties to offer the Vortec head in 1996. This head will keep up with aftermarket heads up to it's upper valve lift limit of 0.440". Aftermarket heads support valve lift of 0.680" before coil bind or interference with the keeper and the valve guide.

You want the smallest intake port volume that flows the most (you basically double the flow rate to determine the horsepower potential of an engine). This is why head manufactures push their flow rates even though no one raves a flow bench. (and why you have to be critical of how those numbers where obtained as many used a 4.125 inch bore to measure the flow when you can not obtain that bore size on anything but a 400 cube small block). The larger the fixture size the more air flow the flow bench will produce at any given valve lift. Similarly larger valve sizes result in greater flow numbers so a head advertised with a given flow rate when tested with 2.08" intake valves that is sold with 1.94" inch valve size for less money will have a lower flow number.

AFR is famous for offering the highest flow rate for any given size port as cast (they discourage head porting as it hurts their computer designed flow rate). Most companies like Brodix or Dart offer you a thickness chart telling you how much material can be safely removed from their head's ports and combustion chamber as they expect you to pay twice the cost of the head's purchase over again to get them professionally ported.

In heads bigger ports yield higher flow rates; but bigger isn't necessarily better. For this reason I discourage people from bolting on high performance rectangular port heads on a 396 or a 427 as you need a 500 cube or larger motor to take advantage of those larger ports. A smaller oval port head on a 396 or 427 will make more useable power and behave better on the street than the big rectangular ports will.

Find a budget and we can advise from personal experience a good head choice.

Big Dave
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post #3 of 6 (permalink) Old 12-17-2015, 05:42 PM Thread Starter
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Great info! Makes sense. I like it. Being that I have a lot of work ahead of me aside from just the motor and also this being a street car not a drag car I don't want to dump a massive amount of money just into the motor (at least not yet). So I guess I'm shooting for middle of the road? Reliable, not overly expensive and good power output.

I'd like to piece it together just because for me it's a little easier. So my next question would be what parts do I need to compile for a full on head build? And also what brands are recommended?

I know for sure I'll be needing a roller cam and lifters, the heads themselves, rocker arms, springs, studs. Sorry if I'm asking a lot of questions but to reiterate from other posts I'm a newbie with these old school motors.
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post #4 of 6 (permalink) Old 12-18-2015, 02:04 AM
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Any motor made needs a roller cam because only roller cams can survive for long with today's motor oil. Support for flat cams disappeared Dec 20, 1999 when the last drop of motor oil was made with the full compliment of ZDDP chemical additive in the oil that a flat tappet requires. Current ZDDP levels with a high mile greatest level of sacrificial metal is only 40% of what was in SAE 30 motor oil graded as SE/CD back in 1968.

Edelbrock makes the castings that GM Performance Parts sells in their catalog and puts upon their crate engines. They differ from a standard Edelbrock head and why they don't say Edelbrock on the end instead being marked as GMPP Signature Series heads because they use larger diameter valves and are partially CNC gasket matched and pocket ported. Crane Cams makes al of the roller rockers for GMPP and the valve springs and keepers as well as the being the source for the roller lifters used in the engines though Crane actually buys their roller lifters from Morrel. I mention GMPP because Chevrolet engineers specified these parts as being reliable enough to offer them with a full GM one year warranty as if it were installed in a new car (when these parts are bolted on a new GMPP crate engine.

Edelbrock is in the middle of the road in terms of a performance brand, but is best known for delivering the best bang for the buck (not the most horsepower available, but the most horsepower per dollar). They have a very nice system of top end kits that are listed by the amount of horsepower you want to make per cube of engine size for a SBC which is the industry standard for gauging horsepower per dollar.

A SBC makes an economical (that is a relative term not absolute) one and a half horsepower per cube. Put the same level of effort (parts and pieces) into a big block and you are lucky to see one horse per cube. this difference is a function of the difference in the design of the two engines. You can easily obtain two and a half horsepower per cube with a SBC just that you are going to pay through the nose for it and the engine will be an all out race engine unsuitable for street driving. You can easily exceed any amount of power that a SBC can make with a big block by simply building a larger displacement big block (they can be made as large as 907 cubic inches today just not economically).

This all assumes normally aspirated, as adding a power adder such as NOS or a blower just ups the amount of power that any engine can make equally across the board so there is no advantage given one engine over another. In terms of competition with a door slammer the state of the art is a Pro Stock car that makes roughly 2,400 horsepower limited to a maximum of five hundred cubic inches. The current winningist car is a big block Chevy (actually one through seven of the top ten are BBC with the others being Hemi powered). These are exotic and expensive and illustrate that unlimited horsepower isn't enough as the winner is determined by who gets their horsepower to the ground the best with limited traction (chassis and clutch tune) not the most power on a dyno.

Here on this page of Edelbrock's web site you can pick (butget) just how fast you want to go. It lists the horsepower range per cubic inch of displacement for the five levels of Edelbrock power. The base is a totally stock head and intake that replaces a stock cast iron one. it offers no performance gain over stock other than being lighter than the cast iron parts it replaces. The top is Edelbrocks idea of flat out competition which as I pointed out isn't going to win you many races as there are products available that will make more power, you just will pay a lot more for it.

http://www.edelbrock.com/automotive/...ion.shtml#pppl

Big Dave
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post #5 of 6 (permalink) Old 12-18-2015, 04:49 PM
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hey Walt, welcome to the site in case I missed it.

you know you can potentially get a variety of 'options' here, but like Dave said, knowing budget will help.
Are you doing the rebuild yourself? Rings and bearings too?

Getting HEI and accompanying 1-wire alternator is something you just gotta do - it doesn't have to be MSD parts if you are on a budget. Shop around.

I don't know about the Performer intake, it's not a lot better than stock like say the Performer RPM.
You'll be fine with a basic 1 5/8" primary tube header. Search on here for Dadstoy recommendation for a brand that I can't remember.

Cam size should match the heads you'll have. Depending upon finances, for iron heads you could go with Dart versions. Basically, something between 170cc and 190cc intake ports should do really well.
If you are keeping your stock pistons, that plays into the head combustion chamber size and cam selection due to the end-result for static and dynamic compression ratio. Not trying to bore you, just saying these parts are a system and need to all align with your driving goal. You'll get to 350-400hp easily and be very streetable, everday.

BTW - have you considered a replacement torque converter to get the car off the line quicker? That couple hundred bucks goes a LONG way to seat of the pants feeling.
Or perhaps a 4-speed automatic? (are you currently a Powerglide 2 speed or the TH350 3speed auto?)

HOW A NOVICE REBUILDS A 66 IMPALA CONVERTIBLE:
http://www.impalas.net/forums/blog.php?u=1432
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post #6 of 6 (permalink) Old 12-22-2015, 02:54 PM
 
 
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My experience has been that the short 3.25" crank of the 327 makes it a poor choice for a street engine. I have owned several over the years, and compared to the larger stroke engines, the 327 is usually a dissappointment.

A 350 has the same 4" bore, but utilizes a 3.5" crank, and therefore produces more low-end torque, and more overall power all the accross the rpm range.

You are not going to get 350-400 hp out of a 327 without running high compression, a big cam, and having to rev it up into the higher RPM's to get power out of it. None of those things make sense for a street car.

I would suggest building at least a 350, if not a 400 small block, instead.

It costs the same to build these engines, so why not start with something with more displacement?

Last edited by kookykrispy; 12-22-2015 at 04:39 PM.
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