Did I chose the wrong heads?

[ChevelleNut]

I'm building (very slowly) a 489 BBC for my 1/8 mile bracket car. I thought I had it all figured out on what I was going to do, but now, since I've got all the parts, I'm second guessing myself. Here's the specs on my engine....

489 BBC
12.5:1
Mechanical flat tappet
262/265 @ .050
.620/.629 lift
Brodix RR BB2 Plus 312cc rectangle port
Weiands Team G p/n 7522 4500 intake (built in 1" spacer w/ long runner dividers extending into plenum)
1050 Dominator

The car...

68 Chevelle
Unknown weight (fiberglass front end, gutted interior)
Th400
12 bolt w/ 4.11's
28-10.5x15's


I'm guessing to be shifting at 6700. With the 270 Oval RR heads flowing the same numbers (a little better) up to .650, did I mess up by going with the 312 rectangle ports? I may be over thinking it. I tend to do that. Lol

[PRH]

Would it make more power with some CNC ported AFR 315’s??

Probably.

[ChevelleNut]

Would it make more power with some CNC ported AFR 315’s??

Probably.

I'd just be in the game for Brodix. I'm a little over an hour from them and I've got to support the home town boys.

I'm just curious if the 270 oval port Race Rite's would be a better choice on a 489 turning 6500 - 6700 rpms than the 315 rectangles would be with my cam. The 315's don't flow any better than the 270's from .650 and below.

[Walter R. Malik]

I'm building (very slowly) a 489 BBC for my 1/8 mile bracket car. I thought I had it all figured out on what I was going to do, but now, since I've got all the parts, I'm second guessing myself. Here's the specs on my engine....

489 BBC
12.5:1
Mechanical flat tappet
262/265 @ .050
.620/.629 lift
Brodix RR BB2 Plus 312cc rectangle port
Weiands Team G p/n 7522 4500 intake (built in 1" spacer w/ long runner dividers extending into plenum)
1050 Dominator

The car...

68 Chevelle
Unknown weight (fiberglass front end, gutted interior)
Th400
12 bolt w/ 4.11's
28-10.5x15'

Some people may disagree however I have witnessed;
In a cylinder head ... mean port velocity, volume, discharge coefficient at all valve lifts and combustion chamber flame front, have just as much, (if not more), effect upon power production than actual mass cfm of airflow, as long as it is not terrible.

[ChevelleNut]

I'm building (very slowly) a 489 BBC for my 1/8 mile bracket car. I thought I had it all figured out on what I was going to do, but now, since I've got all the parts, I'm second guessing myself. Here's the specs on my engine....

489 BBC
12.5:1
Mechanical flat tappet
262/265 @ .050
.620/.629 lift
Brodix RR BB2 Plus 312cc rectangle port
Weiands Team G p/n 7522 4500 intake (built in 1" spacer w/ long runner dividers extending into plenum)
1050 Dominator

The car...

68 Chevelle
Unknown weight (fiberglass front end, gutted interior)
Th400
12 bolt w/ 4.11's
28-10.5x15'

Some people may disagree however I have witnessed;
In a cylinder head ... mean port velocity, volume, discharge coefficient at all valve lifts and combustion chamber flame front, have just as much, (if not more), effect upon power production than actual mass cfm of airflow, as long as it is not terrible.

I'm not the smartest person there is and I'm not runner up either, but I was thinking if the 270cc oval port will flow as good as a 312cc rectangle port, the velocity would be better on the 270, therefore being the better choice? Especially since I'm not going over the lift numbers where the rectangle port only does slightly better. I may be wrong though. Wouldn't be the first time.

[rebelrouser]

You said you will be bracket racing. Your engine combo looks like a lot of the builds I have done over the years. give or take a few parts. If you are bracket racing, why worry if you are losing or gaining 20HP ? Be more worried about how long it will stay together, and how the weather will affect how it runs, and how good will it hook. Not sure if you are box or no box racing, but that combo should go low 10's easy, that is fast enough , at least for me, to be fun. I race NSS which is index racing, with no electronics, and my car ran 9.70's in the heat this year, I can tell you that back when my car ran 10.50's, I won a lot more races. NSS is limited to a 10.5 tire, and while 90.70's and wheel stands are cool, the 10.50 combination would hook and go at any track any weather. Of course the driver is getting older too, so race while you can, and just have some fun.

[ChevelleNut]

You said you will be bracket racing. Your engine combo looks like a lot of the builds I have done over the years. give or take a few parts. If you are bracket racing, why worry if you are losing or gaining 20HP ? Be more worried about how long it will stay together, and how the weather will affect how it runs, and how good will it hook. Not sure if you are box or no box racing, but that combo should go low 10's easy, that is fast enough , at least for me, to be fun. I race NSS which is index racing, with no electronics, and my car ran 9.70's in the heat this year, I can tell you that back when my car ran 10.50's, I won a lot more races. NSS is limited to a 10.5 tire, and while 90.70's and wheel stands are cool, the 10.50 combination would hook and go at any track any weather. Of course the driver is getting older too, so race while you can, and just have some fun.

I understand what you're saying and I've thought that a lot. Longevity is definitely high on the list. I guess I was wondering if the 270's would be more efficient since they flow the same at the lift numbers I'm going to be using. If it's more efficient with the oval port heads, I figure it'll be easier to tune and less finicky if its running the right head.

Low 10's will be faster than anything I've had before, so it should be fun for a while. I'll be running No electronics.

[rustbucket79]

Have you considered going right to the source for information? Since you’re their customer either way, I’m certain they would want you matched up with their best option, and have real world results.

[ChevelleNut]

Have you considered going right to the source for information? Since you’re their customer either way, I’m certain they would want you matched up with their best option, and have real world results.

I want to do a little bench racing.

[MT Jeff]

Does the car have a cage in it? Once you go 9.99 things change. Keep that in mind.

[ChevelleNut]

Does the car have a cage in it? Once you go 9.99 things change. Keep that in mind.

6 pt roll bar

[ClassicComp]

Should run 6.20’s or better in the 1/8 mile.
Probably weighs close to 3300/3400#.

[cpmotors]

Personally, you are putting too much stock into just flow numbers.
IMO, the 270 isn't enough head for your plans.
Experience wise and in my dyno testing, I would have used the RR294 in your application with some port work.

[mt-engines]

BB3 O would be my first pick. The BB2 would be my second choice. The 312s are better choice if you plan to keep going faster vs 270's. You can port them down the road if you decide to go larger in cubes, the 270 Ovals are too small for any kind of upgrading in my opinion. Some bowl work picks the 312s up.

Upgrading to a .780" lift solid roller with 268@.050 will wake it up immensely.

If this were my build I'd start with the BB3 298cc heads. But nothing wrong with what you chose, those heads down the road can make some serious power when properly prepped.

[1980RS]

I'm building (very slowly) a 489 BBC for my 1/8 mile bracket car. I thought I had it all figured out on what I was going to do, but now, since I've got all the parts, I'm second guessing myself. Here's the specs on my engine....

489 BBC
12.5:1
Mechanical flat tappet
262/265 @ .050
.620/.629 lift
Brodix RR BB2 Plus 312cc rectangle port
Weiands Team G p/n 7522 4500 intake (built in 1" spacer w/ long runner dividers extending into plenum)
1050 Dominator

The car...

68 Chevelle
Unknown weight (fiberglass front end, gutted interior)
Th400
12 bolt w/ 4.11's
28-10.5x15's


I'm guessing to be shifting at 6700. With the 270 Oval RR heads flowing the same numbers (a little better) up to .650, did I mess up by going with the 312 rectangle ports? I may be over thinking it. I tend to do that. Lol

You need some more cam with those new heads. You may need like others have said over .700 lift. PM me I have a really nice low use Lunati I am not using and need a smaller one for another project, make you a swap.