Header diameter and step vs non step

What header pipe diameters are you running on 512-533 cubic inch combinations? Also, has anyone done back to back comparisons of step vs non step headers? We are building a new set of headers and I have enough 2 1/8" U bends to build the whole set. Wondering if it is worth it to buy some more 2 1/4 bends to make step headers. I'm planning to run 4" collectors.

i'd do the step.

How much RPM are you turning, and what length primaries are you building?

IMO the physical ability of the exhaust port to flow,,,,,enters into this mix also. I don't think your P-51 heads have been ported and flowed have they? I believe straight 2.125" header primarys will be fine. To me it's more important to get the primary length around 30" to 31", and have as few of bends as possible.

Hope this helps,

Charlie

Charlie no my ports are still as shipped from Kaase. We are eliminating the upper a-arms on the car so we should be able to come out of the port much straighter with this set. They still won't be as good as a chassis car but I think not making an immediate right turn will help.

Curt wrote:How much RPM are you turning, and what length primaries are you building?

Shifting at 6600 RPM. Primary length still not determined for sure.

Another thing I'd like to consider is room for expansion. I plan to get these headers coated so they should last for a while. I really don't want to build another set any time soon. Future plans include a 4.3" stroke. Charlie if my heads were ported would you change your opinion on the 2 1/8"? With my chassis set up there will always be quite a few bends in the tubes unfortunately.

for the step size .. is it a stick or auto trans?

Well, if you are planning for expansion, you're going to coat them etc., getting rid of the upper A-arms and coming straight out,,,I'll throw you another curve. What about going ahead and putting the Chevy header flange on them, and building 2.125" stepped to 2.250"? You ask why?

Because with my BBF to BBC header adapters, you can build Chevy flange headers for your present P-51 heads, and then later if you switch to TFS A-460 heads,,,your headers will bolt right up, without an adapter. Food for thought?

The Fab Shop headers that were on Krisse's dragster the year she won the Ford Bash were 2.125" stepped to 2.250". That was in 2009 and the engine was a 572 CID TFS A-460 headed unit. The exhausts flowed 325 cfm barefoot without a test pipe.

Charlie

c.evans wrote:Well, if you are planning for expansion, you're going to coat them etc., getting rid of the upper A-arms and coming straight out,,,I'll throw you another curve. What about going ahead and putting the Chevy header flange on them, and building 2.125" stepped to 2.250"? You ask why?

Because with my BBF to BBC header adapters, you can build Chevy flange headers for your present P-51 heads, and then later if you switch to TFS A-460 heads,,,your headers will bolt right up, without an adapter. Food for thought?

The Fab Shop headers that were on Krisse's dragster the year she won the Ford Bash were 2.125" stepped to 2.250". That was in 2009 and the engine was a 572 CID TFS A-460 headed unit. The exhausts flowed 325 cfm barefoot without a test pipe.

Charlie

Like Charlie sez...PLUS... you will not have that aggravating bolt jammed up against the side of the tube, like when you have a big tube with BBF flanges. I really like that feature of the "non-Ford racing header flange" design that he mentions. At least worth considering...
Keith

BOSS 429 wrote:for the step size .. is it a stick or auto trans?

C-6 auto.

c.evans wrote:Well, if you are planning for expansion, you're going to coat them etc., getting rid of the upper A-arms and coming straight out,,,I'll throw you another curve. What about going ahead and putting the Chevy header flange on them, and building 2.125" stepped to 2.250"? You ask why?

Because with my BBF to BBC header adapters, you can build Chevy flange headers for your present P-51 heads, and then later if you switch to TFS A-460 heads,,,your headers will bolt right up, without an adapter. Food for thought?

The Fab Shop headers that were on Krisse's dragster the year she won the Ford Bash were 2.125" stepped to 2.250". That was in 2009 and the engine was a 572 CID TFS A-460 headed unit. The exhausts flowed 325 cfm barefoot without a test pipe.

Charlie

How thick are your adapters Charlie? Even though we are making more space it will still be a little tight. I'm not sure they would fit. Food for thought though. I'm not sure if I'll ever go the A460 route although I should probably never say never Thanks for the input.

My Ford flanges work great, no hackin the adapters up to make um fit good............... Besides I'm not sure with his tight chassis the A heads would work..........they may be in the same spot but it seems they are higher up.

Like what Jon said, the A-460 exhaust port is higher up, or raised relative to the P-51 port. I forgot about that issue, so maybe it's not a good idea.

As for the thickness of the adapters, they are about 3/4" and the bottom and narrow to about 1/2" at the top. In other words they are wedge shaped to accomadate the outside angle change between a Ford head verses a Chevy head.

Hope this helps,

Charlie

I was wondering about that. I thought the A-460's were taller. I realistically don't see myself switching to A-460's. As fast as you guys are going with P-51's now I don't think I'll need to switch (at least not in this car). I already have a set of Jon Thee flanges too so I'll probably just go that route. I'm leaning toward ordering some more U-bends and making the step headers. That way even if I upgrade to a 533 or 557 I'll have enough header. Thanks.

512Fairlane wrote:

Curt wrote:How much RPM are you turning, and what length primaries are you building?

Shifting at 6600 RPM. Primary length still not determined for sure.

I think you have your sights set on to large of a header; 2 1/8" to 2 1/4" with a 4" collector about 16 inches long, (or longer), would be more in the ballpark.for a light stick shift race car with a 533 inch engine.

With an automatic and well over 3.000 pounds ... 2" to 2 1/8" with a 4" collector at least 24 inches long would be more in your ballpark. You may get away with a 2nd step of 2 1/4" IF the step is large and the first step is 2", otherwise the entire header would probably be better at 2 1/8" tubing with a 3 1/2" collector. The lengths will usually just rock the curve one way or the other to favor power above the horsepower peak or power below the torque peak.

Dang it Randy just when I think I make a decision you have to get me thinking some more. Since my last set was 2 1/8" to 2 1/4" I guess I could stay with 2 1/8" just to see if it makes a difference. I have a feeling just improving the port exit area will make the most difference. Since I have enough 2 1/8" material I may just stay with those. When we switched from 2" to the step headers on my 466 it seemed to kill some bottom end but didn't really affect overall ET. I ran some 3 1/2" reducers off of the 4" collector to get some of the bottom end back. The 512 seemed to like the 4" collectors without the reducers. Hmmm. I'm not even going to ask for opinions on merge collectors .

You better listen to Randy, he's giving you some pretty good advice.

Charlie

c.evans wrote:You better listen to Randy, he's giving you some pretty good advice.

Charlie

I know he always does. I believe 2 1/8" was your first answer as well. 2 1/8" it is! Now I'm going to bed.