I have a 406. Recently I noticed that I am smoking on full throttle and a when I let off. The heads I have now are world S/R's.
Car performs good but I have smoke on full acceleration and when I let off and after a high RPM cruise. I found a leak path between one head and the intake. When the heads were ported the tool slipped to the intake face. I found that when I shaved the heads it opened up a leak path.

The iron heads work good on this combo (12.99 1/4 @ 110) I am going to get another set of heads and was thinking about the Dart Platinum iron heads.

Question is what to get as they have 180 and up runner lengths. What dictates runner length requirements?

Engine is a 9.5:1 406 comp XE274H cam, automatic trans, 3:73 rear.

I'd get 200cc heads. The 180's might be a tad small for your combo.

You might also look into Pro Topline (now owned by Comp and called RHS)

110mph is a 12.0 run (with everything perfect) at sea level so you're making the HP.

I'm running the 200cc Iron Lightnings from Protopline and I will say they work great.
If your heads aren't salvagable then these might be just what you're looking for.

I got mine here--> http://www.tristatecylinderhead.com/catalog/ great deal too.

I'd get a set of aluminum heads with 210cc runners and 2.05 intake valves,
also bump the comp up a full point, (bowl work would help), all these things
will get you more power across the rpm band. More cam would make a big diff too.

Step up to some performance heads.
Canfield part #23-500-65 are excellent
Jegs also has them as their house brand.
available in straight or an=gle plug and 65 or 72 cc chambers.

I'm running 215 cc heads on my SBC 406. In an attempt to remove some confusion; the cc's mentioned are not the length in centimeters of the ports indicating a longer port, but the volume of the ports in cubic centimeters (bigger area in the runner).

A larger volume provides more higher RPM performance at the expense of lower RPM throttle response due to lost air velocity. Just think of a river flowing slowly were it is wide and deep and then speeding up as the channel narrows near rapids.

By the way I would run a compression leak down test. Your symptoms to me indicate weak oil control rings.


Larger Dave

As LD has mentioned the cc is not the length it is the volume of the runner. I am not trying to confuse you but keep in mind that differernt heads with equal runner sizes are not created equal. As with his example with the river. A narrow tall runner at say 200cc volume has different characteristics than the same 200cc volume runner that is wider. The narrower port generally means the velocity the air travels will be faster again generally producing crisper throttle response and a more torque oriented engine. More of your newer designed heads will have a taller narrower port. This is done so that you get the velocity that makes a motor happy at lower rpms and still move enough volume to make good hp. It use to be that a 180cc runner was a healty street size runner but it is more and more common to see a 190 to 215cc runner on a solid street/strip performance engine in the 383 to 400+ ci range.
[What dictates runner length requirements?
If you mean runner design, many things:
What do you want from this combo? Max ET at the track at all costs or some good driving manners? Fuel milage? Are you intending to stay with the 406 combo for a while or are you thinking of a stroker or destroked build in the near future? What combustion chamber size do you need to get the compression where you want it? What cam will you be running the same one or possibly a change?

These are just a few ways to determine what you need to be considering.
Also you can look at several of the large names like Brodix (http://www.brodix.com/Head%20index1.html#Anchor-Small-47857), Dart (http://www.dartheads.com/chevysh.aspx), or AFRs (http://www.airflowresearch.com/)website and they somewhat explain what each head is designed for.

I have a 406. Recently I noticed that I am smoking on full throttle and a when I let off. LD as usual is most likely correct. ;) But it could possibly be unburned fuel. What carb are you running? Did it just start this or have you made some changes recently?

Steve

Ditto on the canfields. You won't find a better flowing head for cams with around 0.500" lift for the same money. Plus, their customer service is incredible and they build heads based on your cam, not prefab like most. I have them in my new 406 with a luanti cam (238@50, 0.48" lift).
Steve is right on with the runner analysis. Bottom line is you want smallest runner that gives you the necessary flow for your application. This keeps torque up and provides maximum hp over desired rpm range.
If you call Canfield, you get to talk to owner. Just tell him your build and he'll recommend onr of his 3 available sbc heads.

Thanks all. I did do a leak down test. No problems on the lower end. Great responses to my question on the runner sizes. I am going to keep the 406 as is for now. It is a fairly new build. As for what do I want, I am happy with the performance of the current combo, it is very driveable and fun.
A smaller combustion chamber (64cc) will bump my CR a bit as my current heads are about 70CC now. I probably can get into the lower 12's if only I could stop spinning the BFG drag radials. Maybe a set of Mickey Thompsons when the heat goes away (Phoenix Az. summer now)

Just remember thats a small bigblock in a matter of speaking tq sould not be a issue. It needs to be able to get air in and out. I would say a 2.055 or 2.08 intake with a 1.6 exhaust go with the small combustion chamber and if your worried about the compression getting to high get Aluminum heads. Definitely a little bigger cam would be a bonus. The bigger cam can help in several ways. One it can kill a little tq which in your case will actually make you a little quicker if your blowing the tires off also it will make up for it on the top end with more hp. In some cases you can go a little over kill on tq to where it hurts like when trying to get a radial to stick. I'm not saying radials wont run fast I'm just saying if you don't have the suspension to really make it work take a little power off the bottom end and move it up into hp. Smoking the tires has a cool factor but kicking out some consistent ETs and winning races IMO gains respect. :thumbsup:

Steve