Jughead

What's the difference in BB rectangular port heads and oval or round ports?? Will headers match up to each?

tworottiedogs

I think that it is the intake side that is different. The exhaust side is the same so there is no difference in the headers.

69 N.O.X. RATT

This is a heated debate amoung guys running big blocks, which is better for the street, oval or rec. port. In my opinion it depends on what you want from the car. In general rec. port heads flow more at uppper lift numbers and rpm levels. There is a lot of room for debate and opinion, but in a 454 I like good oval heads (Edelbrock, Chevy, Brodix, or Dart) up to around 575 Hp levels. The Chevys are the highest flowing out of the Ovals. If you have stock ovals they can be worked over to flow as well or better than the aftermarket heads.

If you want to run more than 600 HP and over 6500 rpms then rec port is probably the way to go.

The header ports are in the same location unless they are raised port, that is usually only in serious aftermarket race heads.

I am making around 580 HP in my 454 (+.030) and I am running Edelbrocks RPM's. If I had it al over to do agian I would have went with the Chevys or small rec ports. If you check chevyhiperformance.com they have a flow sheet of most big and small blocks heads, it is very informative when choosing the heads for your motor.

Air Flow Reasearch says if you take the flow of your heads at max cam lift and multiply it x .2571 x number of cylinders = how much HP your heads will support on a perfectly tuned normall aspirated motor.

Example: With my solid roller (.646 lift) my heads flow around 286 cfm (a little small for my motor) x .2571 = 73.5. 73.5 x 8 = 588 HP :chevy

bigvette1

69 NOX RATT gave the best explaination that I seem in a long time. Its the intake that is either oval or rect. Exhaust all the same. Here is what a local engine shop that does tons of dyno work says.

For a street car use the large ovals, (not the peanut ports) Large are 75 or earlier. The ovals will have a higher flow and velocity of air into the chamber.
For a rat running above 4500 rpms the rect. due the larger volumn of air flow.

Jughead

Thanks, it sounds like the ovals are for me. I don't plan on racing so there won't be many trips to 6000. I just don't like to get beat at lights! I'm looking for more low end!

69 N.O.X. RATT

70 Stingray: How much power and torque are looking to make, have you decided on a head yet?

Jughead

I don't want or need anything exotic, I don't need the best crank, pistons or heads. I'm looking to generate about 425+HP and 500+ torque(fly).
Here's the engine 454 HOI woulda bought if I could afford the $4,500 bill + shipping. I just couldn't swallow that large of a cash outlay. I can handle small hits, but a slash to the jugular would hurt!

I just started looking at parts and saw the Edelbrock performer heads. They look affordable. Edelbrock claims that if you use their heads, cam & intake combo you can generate 1.2 HP/CI. That'd give me 545HP.


[Modified by 1970 Stingray, 8:03 AM 3/21/2002]

MassVette

Good explanations given here......The heads on the ZZ/502-502 hp crate are aluminum oval ports with 2.25" s/s intakes, 110 cc, with a c/r of 9.6:1. The heads on the 454 HO-425 hp are iron rectanglular port, 2.19" s/s/ intake, 118 cc, with a c/r of 8.75:1. The old 427/435 hp TriPower 'vette motor was rectangular port, the 400 hp TriPower was oval port. The 396/425, 427/425, L-88, and LS-6 were ALL rectangular port motors.
Aluminum can take a higher c/r because of increased heat dissipation.
Traditionally, most all H/P BB Chevy's have run rectangular port heads. The "new" large oval big valve aluminums have come into their own recently, and perform very well, but lose some flow after 5-6000 rpms. Chevy has a 2.25 s/s intake aluminum head in rectangular port configuration,too, for the same price as the ovals.
BTW, according to my friend who works for GM Performance Parts, BOTH heads are made by Edelbrock. GM's version has larger intakes (more hp) and costs less money, though. Both heads are a real good choice. But there are MANY more intakes available for the rectangular port heads. I have the oval ports on my 502, and they work great, BTW. But if I were going to build, I'd use the rectangles because of the intake choices and upper end flow. My 2c.
:yesnod: :chevy :chevy :yesnod:

Flareside

FYI, all oval port heads are not created equal. The new Edelbrock/GM aluminum ovals (the ZZ502 head) are considerably larger than the older OEM ovals. The old heads are around 260cc's with 2.06 valves, and the Edelbrocks are around 290cc with bigger valves. Rectangular ports usually start around 305cc and go up from there. You don't need rectangular ports for your rpm and hp goals.

Take a look at the Merlin iron ovals from World Products. You can get them for around $1200 per set brand new, and they include the bigger valves. Depending on your budget, they may be the best bang for the buck. (If money isn't tight, Dart also makes a killer oval port aluminum head).

You should pick a cylinder head, then get the pistons that give you the compression you're looking for.

Start saving your pennies :D I've already got the major components for my engine, but the smaller parts are nickel and diming me to death! I've got a list $2000 long.... :lol: Now I understand why a high end crate is $10k!


[Modified by Flareside, 8:33 AM 3/21/2002]

69 N.O.X. RATT

70 Stingray: If you don't think you will be bitten by the horsepower bug later, and depending on your budget for the heads you would do fine with the stock large ovals. 425 HP and 500 lbs of tourque out of a 454 is very easy to achieve. Remeber the L-36 (low HP 427) was rated at 390 HP and 460 lbs tourque, with the large ovals, very small cam, stock exhaust, and a Q:U

If you want to run aluminum heads because they are cool, then I would lean towards the Darts, Brodix OEFI -1 or the Chevy ovals. I have, but am not a big fan of the Edelbrock Performer RPM's. Their low lift flow numbers are not that good ( where your cam will be for 425 HP ) compared to the three I mentioned. I am running a soild roler so I make up for a lot of it at the top end flow numbrs. For a 425 Hp engine the darts are probably the best, out of the aftermarket aluminum because they have a 269 cc intake port. They flow as well as the other heads but because of the smaller intake ports they produce more velocity.

Intake port volume is not the only indicater of eventual flow, it is usually, but not always. It is not uncommon for one head to have a smaller intake port, yet out flow, or flow as well, as one with a bigger intake port (the Darts are an example). If you find this situation then go with the smaller intake port. Because of the increased velocity it will produce more torque, and power thoughout the rpm range, especially the lower rpm levels.

Massvette: I beleive that the vast majority of the aftermarket intakes are availible in either oval or rec. from the Performers to the Victor jr's to tunnle rams :chevy

Flareside

69, here's some more info to really confuse you. ;) All of the engine builders I've spoken to about my 540 said *not* to go only by flow numbers. There are heads out there that flow great on a bench (which pushes a steady stream of air), but do not perform as well when trying to fill a cylinder through an opening and closing valve attached to an exhaust system. Port volume has to match up with your displacement and rpm. I have seen flow sheets that show that the Canfield 310s flow considerably more than the Merlin 345s, but I also have dyno sheets that prove the Merlins will make more torque across the board on the same 540 engine. The volume of the port makes a difference.

-Joe

69 N.O.X. RATT

Flairside: I agree with your above statements, and on your 540 it really makes a difference. 70 Stingray is only trying to make 425 HP out of a 454. His combination is a lot more "generic" than you 540. I was not trying to say that port volume does not make a difference, its just some think that is the only way to measure flow. Bigger port does not always mean bigger flow.

What kind of power are you looking to make with the 540, what cam are you going with.

While we are at it what rear end gears are you going to run, and what is you first gear ratio with the Richmond. I have the ROD in mine with a 2.77 first and 3.70 in the rear. Pulls like heck 1st through 5th and 2300 rpms at 80 mph in 6th.

Jughead

Wow! This is great. This is the info I need. Thanks.

But let me clarify that I certainly don’t want to target 425HP, I’ll certainly accept more HP & torque as long as it doesn’t require anything exotic. I am on a budget(sort-of) and really can’t afford a $900 crank—but that’s the topic for another post.

True, I’d like to get the best bang for my $ but am considering aluminum heads to save some weight. The Merlins are tempting though($1300). I’d save about $750 by using them over the GM aluminum. Is the lighter aluminum worth it?

You guys are on a roll here, what kind of pistons and cam should I use to get a streetable 454. What kind of HP would I be looking at? Keeping in mind the best bang for a buck philosophy.

Thanks
Len

Flareside

As much as possible! :lol: In reality, it will probably wind up around 625-650. I spend most of my time cruising around at low rpm in the mountains, so I don't want a real lopey cam. Something in the 246* at .050 range with around .620 lift on a 112 or 114 lsa. I want killer low end. Solid roller. I'm still debating the new AFR 325cc heads (If they can ever actually deliver :mad).My Richmond has a 3.04 first gear (road race model). The car is currently sporting a 3.55 rear, and I also have a complete 3.08 to rebuild and install. After reading about your rear problems, I may just send it to Tom's for the works ($$$!!). I probably run the 540 with the 3.55 and see how I like it before I rebuild the 3.08. Which do you think will work better?


[Modified by Flareside, 5:56 PM 3/21/2002]

Flareside

Len, you're about to learn that you can build 525 hp for the same price as 425 :)

$900 crank :D You can build a 496 with a forged steel 4.25" stroke Scat crank for $599!

You can get the Edelbrock aluminum ovals for around $1660 per pair. Check out http://www.flatlanderracing.com for good prices. I bought most of my engine parts from them. I personally don't think that aluminum heads are worth it for the weight savings, but I do love the look! (and the fact that you can bump up compression with them)

Most bang for the buck? Probably a solid flat tappet cam and TRW or similar forged pistons. I wouldn't build a performance engine with cast pistons, but some people do. You can get TRW or SRP/JE forged pistons for around $500 including rings and pins. I'll let the other guys that are actually running 454s advise you on the cam specs.

69 N.O.X. RATT

70 Stingray: I knew the horsepower bug would bite. What you consider streetable and what I consider streetable could be two different things. You really need to decide what kind of power (at what rpm range) you want the motor to put out. If you want to deal with messing with the valves (solid cams) and of course your budget. You can make 500 turn key drive everyday HP out of a 454 very easily. As for a cam and pistons I like the Kieth Black hypertunictec (spelling) pistons alot. The JE sportsmans are very good also, as are the trw's.

You need to decide on what heads you are going to use before you should pick your cam. Due to the fact that one point of compression is only worth about four percent in power I would shoot for a compression ratio that is crap gas friendly 9 to 1 with iron head and 10 to 1 with aluminum. There are guys that run higher, but I think with your power goals there is no reason to push it at all.

Flairside: You are going to make a gob of tourque with that cam. In my humble opinion that is a pretty small cam for a 540. My 454 is 242 and 246 and .646 and .653 on a 110 It idles at 900 to 1000 and makes good power from just over idle to 6500. Hot Rod 427 is running a very stout 540 in his 67 maybe he will chime in.

As for your tranny I think the 3.55 rear with your 3.04 first gear is to deep. That equals a 10.7 drive ratio, with the power your 540 will make (not to mention the rpm limitations) it will make your first gear nearly worhtless. With my 580 HP 454 my 10.2 (3.70 x 2.77) is on the ragged edge, any deeper would be too much. I do not think I will every be able to use the NOS in first or probably second for that matter (once the motor is flogged in I will find out). If you go with a 3.08 rear I know you will be happier on the freeway or speeds over 60 MPH. That will give you a 9.3 first gear ratio, much more 540 friendly.

As for your rear end I know a lot of guys that have had no problems, and guys (like me) that have broke a few things. To be honest If you dont drag race the car and keep street tires on it I don't think you will have any problems. 427 Hot Rod used to run 11.20's on a stock rear behind a nash 5 speed and a stout 427, on slicks :chevy

69 N.O.X. RATT

70 Stingray: Check the C-3 for sale section, Dart aluminum ovals up for auction. :chevy

Jughead

I guess I share Flareside's view. I like the power at the low end and I don't mind a lopey cam. I drive my Vette in good weather usually on the weekends from March thru December. It's more of a cruiser but I still want the power.

I think I'll pass on any more used parts---my spouse is still giving me grief about buying a "used" engine. "How do you know it'll work?"

Flareside

Yep, it's a bit small on purpose. I want the tire burning low end response. I've talked to Jim (427Hotrod) many times about it, and he's been a BIG help. I remember him saying one time that his 540 pulled all the way to 7400 on the chassis dyno before he figured out that his tach is messed up! That cam may be a bit much for me ;) I may go into the low 250's in duration, haven't really decided yet.

Yep, that's why I picked up the 3.08. I was suprised to read that you're happy with the 3.70s before I realized that you have a 2.77 first gear. That must really help. I'd love a Richy 6-speed, but I just couldn't justify the cost compared to the price I paid for the 5-speed. Frankly, the 540 should make such broad torque that 4 gears would probably be enough :eek:

69 N.O.X. RATT

Flatreside: Well your going to have tire scalding low end regardless, the smaller cam will be more friendly. I agree the 5 speed is more than enough for that car. I do a lot of highway driving so after a lot of thought (1,000.00 for an extra gear:eek: ) I finally broke down and did it. I orded the five speed and then went back and got the 6.