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Old 09-25-2009, 02:28 PM   #1
vetteztr
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427 Heads

There are several companies marketing 320cc Aluminum Big Block heads. Would these be too large for a street 427? Any experience with the "budget" versions from Patriot? Thanks!
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Old 09-25-2009, 03:05 PM   #2
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It depends on what you consider too big. They are no bigger than some of the rectangle port heads that were used by Chevy, and will work fine. A smaller port however would be a better choice for your application.
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Old 09-25-2009, 03:18 PM   #3
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Do you have closed chamber or open chamber heads now? There aren't a lot of choices if you want to keep your compression ratio up if you have closed chamber heads (and pistons). Hope you have open chamber.
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Old 09-25-2009, 03:38 PM   #4
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WHEN your talking about a car that's expected to be street driven, and geared and cammed to drive on the street, with pump gas,the larger OVAL port heads will generally produce better hp/tq than a 320cc rectangular port head on a 427 BBC, provided the compression ratio and cam and intake are carefully matched

even the stock oval ports CAN in some cases work well

http://maliburacing.com/patrick_budd_article.htm

http://www.brodix.com/heads/raceritebb.html

http://www.summitracing.com/parts/TFS-41310001/
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Old 10-01-2009, 08:49 PM   #5
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Yes way too big. I had a set of AFR 305 heads on my 468, made 708 HP and 622 tq motor only. They were rec ports, and i wish i would of went with an oval port. I spoke to Brodix and Dart, and didnt listen to them, they both told me they had a set of killer oval ports that would of been better for my combo.

My other 427 i built, i had 11.25-1 compression, Edelbrock RPM performer oval heads and a hyd roller cam. Made 550 HP and 513 tq.
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Old 10-02-2009, 06:27 AM   #6
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It should be obvious that comparing edelbrock oval ports, or mildly reworked stock heads to AFR 305-357cc heads, and an engine with a hydraulic roller cam, is hardly a valid comparison, to an engine with a solid roller , or flat tappet cam, using higher compression and the better rectangular port heads, thats designed to run a couple of thousand rpm higher on average.
as Im sure you are aware
now I have built a bunch of big blocks and its not just the heads selected that matters, and you generally try to match the port cross sectional area to the intended displacement and cam timing, but, you can compensate for some minor mis-matches in port size thru the wise selection of other components, but almost all rectangle port heads are designed for the upper rpm band and solid lifter cams that allow them to breath, most but not all oval ports are designed for mid rpm range torque combos
the 290cc and larger oval ports are generally designed to breath far better than the stock 253cc heads most guys think of when they think oval port heads
now IM sure not going to tell you that a properly built big block with oval port heads will destroy a properly built big block with rectangle port heads , but if you start limiting the rpm potential with hydraulic cams, want to drive the car in traffic and expect to drive the combo on the street on trips they can provide a very valid option

bbc oval ports making 697hp
http://www.popularhotrodding.com/tec...lock/dyno.html

http://www.profilerperformance.com/bbc-heads-174.html

http://www.brodix.com/heads/jjbb.html

http://www.trickflow.com/partdetail....1&autoview=sku

http://static.trickflow.com/global/i...reet%20bbc.pdf

http://forum.grumpysperformance.com/...6&p=1165#p1165
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Old 10-02-2009, 08:43 AM   #7
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You put a set of 320's on a 427 you better hope this motor operates from 5500-8000 and nothing below in a 2500 lb car or the thing is going to be a dead horse. My comparisons were to show that a smaller velocity runner is what was needed in my opinion on a smaller cube motor.

Just my opinion. Mind you everybody on the internet has one.
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Old 10-02-2009, 01:36 PM   #8
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The (stock??) engine is blowing smoke anyway, so I will wait on the heads until I can put a stroker in it, then go with a package heads/cam I can be sure will work well on the street. Too many projects at once! Thanks for the input!
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Old 10-03-2009, 04:51 PM   #9
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LOL!! Oval port heads produce more power than rectangular port heads??? On what, an 8.5:1 smog 454? Surely a hot 11:1 - 12.5:1 big block puts out more HP with rectangular port heads. Next somebody is going to say that a 2 barrel carb is the hot ticket.
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Old 10-03-2009, 05:05 PM   #10
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Quote:
Originally Posted by Rhino68 View Post
LOL!! Oval port heads produce more power than rectangular port heads??? On what, an 8.5:1 smog 454? Surely a hot 11:1 - 12.5:1 big block puts out more HP with rectangular port heads. Next somebody is going to say that a 2 barrel carb is the hot ticket.

Where in the RPM range are you looking? My 468 had a set of 305 rec ports, and the motor started to make power at 4500. I ended up with a 5200 stall converter, the motor was useless below 4500. The would not 60 foot worth a shit. a set of reworked oval port heads would of picked up the bottom end and still let me buzz it to 7200.

My 468 made 708 hp and 622 tq and was done by 7000. Its all in the total combo. too big of runner will not make any useable power down low, and is for an all out drag race car only think about what your doing with the car and get the correct cylinder head.

Do yourself a favor and speak to an engine designer/ builder who has a good idea of what you want.
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Old 10-04-2009, 12:16 AM   #11
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Quote:
Originally Posted by vetteztr View Post
There are several companies marketing 320cc Aluminum Big Block heads. Would these be too large for a street 427? Any experience with the "budget" versions from Patriot? Thanks!
There are some really nice charts here to help guide you in the right direction.
Also Trick Flow Specialties buyers_guide_2009
These might be of some assistance but all in all it all depends on you and what you want and what your willing to sacrifice in drivability to have the larger HP/TQ numbers. Your best bet is to call the mfg and ask a lot of questions. Personally Somewhere in the 290cc to 300cc range is a better of both worlds option. But depending on head design these could vary some. As for Patriot heads I haven't ever ran any of them myself so I have a goose egg on experience there.
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Old 10-04-2009, 07:25 PM   #12
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Grumpy, your input was very good. My 454 has a solid roller cam and related lifters and roller rockers(.646 lift, 246 duration @ .050) and Pro Topline Thunder aluminum 320 heads. I also have a very free flowing exhaust (Stahl sidepipe headers with STS baffles), Mighty Demon 850 annular carb, Weiand Team G intake, stud girdles, etc. Compression ratio is about 11:1. It pulls VERY strong right from idle and howls in the midrange and top end. Care to take a guess on the HP?
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