[JLBIII]

Thinking about replacing the stock '68 #16 heads on my 461 stroker with a pair of KRE D heads this winter. Engine has a 230/236 cam and .572/.578 lift with 1.52 rockers, 800 Qjet, stock intake, long branch exhaust manifolds going into 2 1/2" exhaust pipes and 3.36 gears. Car is a '68 Firebird street/strip setup.
Was wondering if I should keep the KRE heads as-cast or opt for the 290 port job. Will probably keep the stock intake or go with a Performer RPM to shed some weight. Also thinking about switching to 1.65 rockers. Thanks

[b-man]

As cast.

With exhaust manifolds I don’t see the point of porting to 290 cfm.

[leeklm]

In a previous motor similar to yours I had a set of iron heads and RA manifolds flowing around 230cfm IIRC, bolted on set of KRE 290 heads and was VERY happy with results. In addition, my back was saying thank you when working with the aluminum heads! Pretty sure you will not regret the move ported or unported!

I tried several intakes on that motor including stock, rpm, and Holley SD. All worked well, in the end I stuck with OEM. The Holley felt faster as it came on strong in the mid range, but oem seemed smoother throughout the rpm band. Again, my back preferred aluminum, especially if installing while in the car!

Sent from my SM-G965U using Tapatalk

[i82much]

what is this exhaust manifold nonsense? I'm sorry sir, but the point of having an old hot rod is to join the ranks of us wretched souls out there constantly chasing down header leaks, straining our shoulders contorting ourselves to replace oil filters around the dang header pipes, burning ourselves every time we try to do a little work in a hot engine bay ... seems to me you are taking the easy way out!!!!

Kidding of course. Smart move. Better to have a car you can enjoy than a car you have to constantly mess with!!

[72projectbird]

Always port, gasket match, blend everything real nicely. If you have it all apart, there's really no reason not to.

Ditch the manifolds.

[steve25]

Rule one.
stop listening to people who have a grinding burr, chucked up in a grinder, but no easy access to a bench and a velocity probe who tell you that in regards to a aluminum head just have at it and happily gasket match away, especially on the exh side!

It’s your money, but I would not go into my wallet to pay for 290 cfm heads that will then be forced to pump out thru exh manifolds, it’s a lot like trying to stuff 12 golf clubs in a bag made for 8!

You might also want to think twice about adding 1.65 rockers to a duel pattern cam that’s working the valves in a higher exh number flowing aftermarket head.
With the 4.210” stroke of a 455 you will find the power it produces will drop over 1.5 rockers due to over scavenging the cylinder.

[grivera]

I went through this with my bird which has a the same cam specs, LB manifolds and an RPM intake - I bought from Butler and had them ported so there is room for growth later. Also, this ensured the went over the heads rather than selling as cast and them not being looked at. I don’t regret the decision one bit.

[JLMounce]

I have as cast KRE D-ports on my 455 with a slightly larger cam (232/238/112). I am more than happy with the performance of these heads out of the box, direct from KRE.

I don't think you'll be disappointed in not doing the 290 port.

That said, I'd like a little more out of this engine and spending the couple hundred extra at the time of purchase to do the 290 port would have saved me money in the long run, as I plan to have port work done on these heads. So my advise would depend on if you're wanting to grow further than what the as cast head can do for you, knowing that manifolds need replaced with quality headers to see the benefit of that extra porting. If this is a one time deal that you don't ever intend on opening back up, and don't intend on going to headers, there's no point in doing the porting IMHO.

[chiphead]

Are the KRE D port heads in stock? How does their performance compare to a set of edelbrock D ports?

[JLMounce]

They are probably within spitting distance of each other. The KRE heads made for the larger inch engines has an ever so slightly smaller combustion chamber. 85cc vs 87cc for the Edelbrock offering.

A standard .030 over 455 with a basic SpeedPro piston that sits a bit in the hole will put you between 10:1 to 10.25:1 or so. Running somewhat mild cams in the low 230ish duration space, I don't honestly think one head would be better than the other. If you're pushing the envelope, you might start to see some separation. I know some people, including KRE is claiming to be able to achieve around 340 cfm out of the KRE head, albeit in a quite inefficient manner. My talks with Jeff Kauffman on my heads, he likes his Dport at 290 cfm for best street power without sacrificing too much port efficiency.

I think I would opt for the head that is available at the time. That's possibly the Edelbrock head currently.

[Donovan]

Get the ported versions up front and use your current manifolds, intake and exhaust. Later when you get the itch again to claim more HP you just need to bolt on headers and an RPM intake. The additional airflow will be fine sitting there dormant until uncorked. The bolt on parts or simple to swap versus wishing you had that pro porting.

[steve25]

Here’s some very important details to keep in the forefront of your thought process when it comes to bolting on heads and intake system parts that may have either too much port area and or levels of intake flow that you can’t take full advantage of with the way the motor is built, or within the intended power range of the motor.

Nominal gas speeds ( average ) in the 350 to 400 ft per sec area make the best use of kinetic energy to pack the cylinder up to above 100% just before the intake valve closes.

This velocity to pressure increase ( Ram effect )
takes place as the square of the air’s velocity, so it’s no small thing to over look or not take maximum advantage of.

When strictly racing motors are involved the maximum port air speed should be between 300 and 350 fps, and you had better have everything about the car and the motor set up to then run in a narrow 2000 rpm wide power band so that port air speeds do not go below that 300 number, or above that 350 number!

Also a big detail to keep in mind is that with a high performance cam, the intake stroke last for no more then 180 degrees of crank rotation.
If you want to then look at a given motor up at 5000 rpm the air mass that the motor is running on has only six thousands of a second to go from the inlet of the carb on into the cylinders.

Looks like average port velocity is darn important to average power production to me, how about you?

[PAUL K]

Without over complicating things. I don't think the OP needs ported heads. Usually the as cast heads are a bit rough. If the OP has the ability and desire, the "as cast" heads will pick up nicely with a basic clean up. If one stays conservative and uses common sense you will be rewarded with a nicer pair if heads and a great feeling of accomplishment.... JMHO

[PunchT37]

Get the 290 job. Pontiac ports are already small for our cubes. Wonder why folks like the LS so much?

[steve25]

And what’s the minimum port area in the average aftermarket Pontiac head that can flow …290 cfm and the stock Chevy LS ?

[PunchT37]

I have no idea. But, I stand by my recommendation. He`s spending money anyway, and he`s got 461 cubes. I got 330`s on mine with 2.20 valves and it runs great.

[b-man]

If he upgrades in the future then by that time the heads will likely need freshening and can be ported along with a matching intake at that time.

Right now he has a good chunk of change invested in his exhaust manifolds and associated items to make those work. Those of you saying to put on some headers are missing the point of his post. He’s running long branch manifolds and is asking if porting would be useful and depending on your opinion it’s either yes or no, he’s not adding headers or a 3” exhaust.

I would save my money and run them without porting keeping the 1.5 rockers if it were my car, it will be a nicely matched combo with the stock intake and exhaust manifolds.

[OCMDGTO]

Port them and you'll have room for growth. I'd keep the 1.52 rockers and try the RPM or T2 which should take 100lbs off your nose. 3" headpipes before the mufflers should give you a couple tenths if you plan to go to the track. Ported KREs are 8ish weeks out, currently.

[JLBIII]

Thanks for the replies. I've decided to use the KISS principle and go with the as cast heads using my current rockers and manifolds for now. I think the 290 ported heads might be a little bit of overkill with the current engine specs. Also if I decide to go for more performance at a later date I'd probably want more than 290cfm heads. Currently my best time is 12.68 @ 107.98 and I still have fun cruising the hiways at speed.
FWIW I still have the original numbers matching 400HO engine and TH400 trans that I pulled out for the "new" engine build. The current engine is a '73 400 block with period and date correct heads and manifold that I can use on the original engine if ever needed.

[JLBIII]

Update: I ordered the KRE heads almost 3 weeks ago after talking to Jeff Kauffman. They were delivered to my house yesterday. Going to be a busy winter here.