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Old 07-22-2004, 08:04 PM
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oval or rectangle port heads for blown 496

i'm building a blown 496 or 502 depending on rods i get for 454 block, i have some oval port heads and i'm just wondering if i should machine these or use that money towards some rectangle port heads. the main difference i've heard/know about oval vs rect. is the velocity at low end...its an 8-71 blower so it's gunna be pushin sum air...which would u guys reccommend thanks

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Old 07-22-2004, 08:33 PM
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heads

What will the end use of this motor be,,

Drag only??

Show?? street???

Keith
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Old 07-22-2004, 08:35 PM
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i'm gunna pretty much daily drive it, if not a weekend toy (depending on the gas price flux) and show definitly
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Old 07-22-2004, 08:38 PM
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heads

If they are a 049 or 781 oval i would put 2.19 intake and 1.88 exhaust valves in them and run-um..

Something to think about is if your heads need alot of machine work, you may want to price a set of merlins.......

Keith
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Old 07-22-2004, 08:41 PM
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not to cut alot of corners, would the ones i have now work with some machine work, or would it be worth the lets say "little" more to buy some merlin heads?
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Old 07-22-2004, 08:48 PM
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For a street motor you could make decent power with just about any head.Depending on how you build the engine,it can still go either way.A rectangular port setup would be best for an undersized blower being worked extra hard such as with an overdrive ratio since the small/overdriven blower will move more air at a lower rpm level and cover up the effects that the big heads will have on low end torque production,and the bigger heads will allow more airflow which will allow you to extend the rpm range of the engine further then if you were trying to use more restictive heads.Bigger ports will also make more power with less boost as long as the engine is built to utilize the setup,and the reduction in restriction in the intake tract will help keep the air from getting too hot as it is being pumped.The long and the short of it is that a big port motor makes more power but can be lazy at low rpms.If you can use the blower that works well at low engine sppeds you can cover up the lack of low rpm performance completly.
A big blower with a slower drive will run better with small ports since all blowers tend to be lazy when they arent being spun fast,and even though a big blower will move a lot of air at it's peak speeds,it wont move a lot of air at low speds and with big port heads a street engine can be a bit of a dud.
A real hot combo for a super earth moving 496 that will run on pump gas would be to build it with 7.5:1 compression and open chamber rectangular port heads,the bigger the better.Run an 8-71 with 15% overdrive and run a cam with about 260 intake and 275 exhaust at .050 and a 114 speraration angle.Top it off with a pair of hp950 mechanical carbs with the proper power valve referencing,and run a set of 2 1/8" headers.You can make an easy 900hp on pump gas at 630- rpm or so,and this combo will work great with a 2500 to 3000 stall convertor in a 3500# car.This is a seriously fast combo that wont be some prostret poser.It will run a little hot so be prepared to build a top level cooling system.Other then that,build the car to withstand the abuse and hang on.Good luck.
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Old 07-22-2004, 08:48 PM
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budget

Not sure how much $$$ you have to throw at this deal but i would assume if your going with a 8-71 you don't mind spending some...... I would go with the merlins..IMO

You will have a new set of heads not some 30 year old things that you don't know where they have been L.O.L.

There will probably be all kinds of post about what to do but in the end it's your decission... If your heads are in real good shape and don't need guides and they are not cracked that might help sway what you do i guess.... One thing i know is i have never been disappointed going with the better deal, but that just me...

Keith
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Old 07-22-2004, 08:53 PM
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i have the 8-71 bds blower and their injection system they offer now....not to vier off the original question...but is that much bore and stroke( a 496 or 502) pushing it? always thought no replacement for displacement

edit: forgot to add i want this real streetable(ha just tell everyone the shiny thing otuta the hood is a a/c compressor)
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Old 07-22-2004, 09:06 PM
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bds

If you have the bds deal i would call them and ask for there recomendation on the set-up for your intended usage.. They have more blower time then the guy that invented them...L.O.L.

I would like to here what they have to say about your set-up. I herd they are very nice to work with.... If you do call let us know what they say,

Not sure what you mean by pushing it??? Like super streeter stated you better have a mac daddy cooling system.....

Keith
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Old 07-22-2004, 09:14 PM
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oh bds people i think could put the thing together over the phone, they are helpful and i'll contact them and get back to u, just for ****s and giggles...he said 900hp....i think i'm safe to assume (*** u and me) i will/can make that much power(if i dont half *** it)...what kind of times am i looking at in a 68 chevelle...15" slick for traction...
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