big block hellp

i am looking at getting a holley big block intake but was wondering if it matters a bout oval or rect. i think my truck has peanut port heads i want to get better heads. just wondering if the one i can get a deal on will work. thx


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yes it matters. get the oval for your truck which will fit most heads offered.

look for 049 or 781 heads.

While you "can" put rectangular port intakes on oval port heads, the performance will lack drastically. If you have oval port heads, make sure you put an oval port intake on it.

cuz its a grate deal i think $150 i just dont want to buy it and it to be no good to me. sorry about my spelling its not so good the only way to tell it to pull the intake rite

Pull a rocker cover and look for the casting number it'll be a series of 6 or 7 or 8 numbers in a row.

Then go here and look them up, it'll tell you which ports your heads have:

http://www.mortec.com/bbc.htm

Of course for a hundred fifty bucks you could just start a manifold collection, most every rodder has one.

Bogie

that link is in my favorites on my computer lol . when i bought the big block i ran the number on the block mortec clames its a 2 bolt block and it is. it also clames it has oval port heads thats if Thar stock of course

I think you can trust the claim of the C/N being an oval port. Unless some mad head porter got in there and carved them square. Mortec's information while not totally complete against all the factory's production, is reliable.

The situation you want to avoid is having manifold ports that are larger than those of the head. The blunt edge the mixture runs into is very disruptive of flow. Going the other way (head ports bigger than the intake), while not ideal, is a lot less messy on the air flow. When ever flow encounters a disruption such as that, an event known as "vena-contracta" occurs which is the name given to the flow actually reducing into a space significantly less than the physically available area. This happens in both directions but is really a massive disruption/reduction of flow area when met blunt on. Chamfering the edges does help quite a bit if you can't otherwise avoid big changes in cross section with blunt edges.

Bogie

well gust in case i will pull the valve cover off and see. what side is the code on hay and thx for your help .

Is 490-781 The Code On The Head. If So Whats So Good A Bout Those Heads?

Those are 781 heads which should be oval port, open chamber heads. They are great for low end torque. Rectangular heads are the more serious racer, hi performance head which is really not much good unless you are turning over 6000 rpm because that's when they are just starting to get with the program.

u guys really seam to know your stuff . never did know much about performance but the help from u guys is grate. where is the number on the head left or right in the rockers?

336781.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports they good or suld i look for some thing better or are they good heads to work with

The 781 heads are good heads. They are probably the best ones you will find without going aftermarket. The 049 and 781 both have large combustion chambers which create a rather low static compression ratio with flat top pistons, somewhere around 8:1 usually. I would look for a dual plane intake with decent length runners. This should help you in the torque department. A single plane manifold works better at higher rpms.

this it the one that i am thinking about buying rpm range 4500 to 8500 dose that sound right

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Awfully high RPM range for a big block. Looks like a single plane intake too. I wouldnt buy it myself.