Well, pipemax gave me dimensions, with input of 6200 stall , Max hp 7400 shift 7500. 550 cubic inch, 1,000 to 1,025 hp, 2900 lb car and driver.
2.08 1st step, 2.18 second step. 14 inch each, from the valve head. I am considering merge collectors.
Would like input on merge collectors and a good source for everything. It has Been a while since I have built a set. The 2 1/8 set I built in 1997, but they are showing their age. I am hoping there is power to be had in 2 step plus merge collecters, which I don, t have now.

Are those PipeMax diameters the tube inside or outside?
I was guessing 2-1/4 tubes, which is OD, so assuming 18g (0.049 wall) that is 2.152 nominal ID.
I believe in the step header design, just a little bit more work and typically material waste.

Fill out the form on the Burns Stainless page and they'll tell you what you need. They typically recommend a merge collector with a megaphone and reverse cone for a high horsepower drag car. Just depends if you can fit all that under the car or not.

I just finished a stainless set for a combo similar to yours. LIghter car, little milder engine. Same CID and RPM.

We used 16 ga. 2 1/8" primaries 30" long, with a 3 1/2 to 4" merge collector. Looking to help out a flat torque curve on a .90 car that goes in high gear on the stop.

Talk to Rich at Cone Engineering. Parts to build any configuration collector you want. Perfect, fabricated parts. No stamped out stuff. He can offer advice. Merge collectors very close to performance of a 100% fabricated part at a fraction of the price. Tell him I sent you.

Burns is top shelf stuff if you want to go there and have the budget. Would never recommend against them.

IMO talk to the guys at SPD. They are the best out there and know their stuff. I can tell you what I have done over the years on my stuff and my experiences, but all I will say is MOST Mopar guys have stuff thats WAY to big on their combos.

I would agree with that. Calvin Elston has written a bunch on that topic. He recommends matching the tube to the exhaust port unless you have a really good reason to do otherwise. In the Mopar world it can be hard to do since the ports are usually rectangular rather than a circle.

My best pull was with the shops dyno headers, 2 1/4 primarys and if i recall a bit long. My 2 1/8 x 30 were down about 7 hp up top rpm. If I do ever get a set of 572/13 heads, my goal will be 1,000 to 1,025 hp. So I hope 2 1/8 to 2 1/4 step headers will be best, and what ever collecter is going to pull best in the mid range or overall. I am running a Torqueflite 2.45 low 1.45 second gears, 4.56 rear with 33 inch tall slicks. mph should be about 158, at 2900 lbs.Thanks for the input . A few calls are in order, along with taking stock of any more comments.

I thought about 2" on the ones we just did for this 555. Opted for 2.125. Never even considered 2.250.

Headers are such a black art. I'm not sure anyone truly completely understands what is going on inside of them when the engine is running. If the engine operated at the same RPM, under the same conditions, all the time, it would be easier. But it really is a compromise. Change one thing in the combo, and it all goes out the window.

No substitute for years of experience, trial and error, and data - especially if you're after that last couple of horsepower. I never try to second guess guys who have it.

I built my own and used cone engineering for my parts, they have info on how to size and tune a merge collector. When I ran my headers, the results were "interesting".

https://www.coneeng.com/how_to_place_order.html


Joe

I like the way you are thinking. Even if the stepped headers ended up down 5 hp at peak, if they gain enough at the converter speed (shift recovery) they may ET better.

I agree. Five hp at the start of each gear is probably worth ten up top.

Get the one where they all merge in the turbo.

On my 484 hemi with f2 procharger we dynoed it with hooker 2.125 inch and then with tti 2.250 and it was down 50 hp at 6000 rpm with tti ,also lost 60 fpt at same. boost was same on both

I saw the same results on the first motor I dyno tested, it was a pump gas M.W. motor with the stock X ram and small 1962 and 1963 Carbs.
We started off the testing using a set of the old Hooker BB A body 1 7/8 inch primary pipes with 3.5 inch collectors, we did jetting, ignition timing and valve lash testing and peak RPM testing for both torque and HP.
This motor was the first BB Mopar that shop (Pettis Performance) had tested with their then new DTS engine dyno. The owner made up a set of Dyno headers that had 2 1/4 primary (O.D.) I think with 25 inch long pipes and a 4.0 inch collectors and we swapped them onto that motor with no other changes and it made more HP and Torque all the way from 2500 RPM to 6500 RPM
That shocked all of us, we all thought it would hurt the bottom end and help the top end, WRONG
All the BB Mopars I've tested and raced liked bigger exhaust , just like adding more air into the motors with more fuel
Test, test and test some more to go faster and quicker

As I recall, those Hooker A-body headers were so freakin long they never made good peak HP numbers. They were designed for a small 383 CID to help the torque moving a less than light A-body of that time.

Just got off the phone with Cone eng, parts on the way. Also Jericho GTX has a set of individual cylinder flanges with stubs, which I have my name on. The fact that I can build the headers and leave two or three tubes bolted up while I work ought to help welding time a bunch.
R
The plan is ;. 10 inch 1st step of 2 1/8 16 Ga, 14 inch 2 1/4 for second step, over all 10 inch of collector with a 3 1/2 inch merge, to 3 to 4 inch cone.
Joe, what was "interesting" about the results?

First price of the puzzle showed up today😁thanks Jeff!! 440Jim, all demensions of tube are exterior.

I switch from a regular 2.25 26in header to a 12in 1st step 2.125 and a 2nd 12 inch 2.25 with a 3 1/2 inch merge, to 3 to 4 inch cone. When I put the merge headers on an B1 MFI 512, the engine went dead lean. The fuel pressure was the same, the engine was just moving a lot more air or pulling the initial fuel through the cylinder. I ended up putting more fuel in it to get back the HP. Went from a .920 BSFC to 1.105 BSFC to make the same power. The cam was a 282 292 with a 112 LSA. So I ordered a new cam 282 284 112 LSA. The new came didn't make any more HP, but it did make about 20ft more torque, up to peak TQ. Has a super flat curve. LOL I wasn't expecting results like that considering how small the exhaust valve is on a b1 head.

One more thing, SPD (I think) recommends that the header tubes be arranged so the firing order goes in a circle when entering the collector.



Joe

PS those flanges are NICE, does Jeff make them?

Jeff doesn't make them. Not sure who does.
Your results were interesting all right. They back up what Rick at Come talked about. Extra torque where it does the most good . Also i Iike what happened with your cam needs. 572/13 heads have a huge exhaust valve at 1.88. my current cam is 284/296/113 and . 878 int lift.,. 796 ex lift. Less than Indy's 285/305/112(?) Recommendation.