I was a dork for not having this tested on the dyno, I am sure the guy had 1 3/4 BBC headers sitting around the shop somewhere.
That being said, as a possibility I am tossing out the idea of switching from my 2" primary coated hooker super comps (I would probably not dread the term "change all the spark plugs" either) to a set of 1 3/4" coated whatevers.
I guess my questions are are most headers made to the same length or will I need to get my x-pipe collector things re-fabbed if I change headers?
And will I pick up low end torque and not kill high rpm hp with a set of these things?
Mind you that the guy who installed my cam and dyno'd it said there is no need to really ever go above 6200rpm, but he said the motor will rev straight to 7500 without thinking about it and not break, but there is no need or reason to do it. So say that the engine for all practical matters never sees the high side of 6500, although I have a 6800 chip inside the MSD box (that I have hit a few times).
I have to admit the big tube headers just have this menacing look that I might miss, but maybe I am missing out on a little free power because of these things. I am not quite sure what substances the first guy who built up the motor was taking, but right before he ran it on the dyno he called on the phone and was like, "I am about to dyno the motor, expecting about 650hp, do you want to drive down and see it?" I didn't, but it made 550hp not 650. This is where alot of my bigger-is better equipment came from, the heads, the headers, so on and so forth..
I am not sure that it could be partially my fault that when I dropped the block and old pistons/rods off (he never gave my rods back, which I didn't notice until like a year later) and gave him a deposit that the original intention was to build a blow through carb procharger'd engine, but I called him up 2 weeks later and said to nix the blower. He did take like 6-7 months to build the thing, so I wonder if that made a difference, and it probably also explains why he decked the numbers right off the block pad after I explicitly explained for him not to do so..

sorry for the story here..

Matt

Matt,I would assume the header length might change..you either need to loosen all the hangers,and hopefully move the exhaust a little within reason forward/backward,or add a bit of pipe,or lose a bit.I don't think it would be drastic.You might need new reducers though,if you have 3.5" collectors on your current headers and are going to 3" collectors with the smaller tubes.
I would get these:http://store.summitracing.com/partdetail.asp?part=WLK%2D86110

Matt before you run out and buy new headers ( comparing on dyno is the way to go ) you may want to consider just changing your collector diameter or style ...even 1/4" makes a difference .......I am in the process of having a custom set of equal length headers built .... a rule of thumb the builder uses is true horse power and the chart I saw is between 560-580 2" with 3 1/4" collectors ......at 550hp the guideline was 1 7/8 with either 3" or 3 1/4" collectors and he always suggest going smaller if not sure ....all this info is based on open header performance

BTW for those that use the Flowmaster merge collectors for 2" primary tubes the collectors are 3 1/4" FWIW

Originally posted by CDN SS:
BTW for those that use the Flowmaster merge collectors for 2" primary tubes the collectors are 3 1/4" FWIW The ones I'm running on my car have 2" primaries and 3.5" collectors. I welded the flange on them myself as they don't come with any.

http://www.flowmastermufflers.com/cgi-bin/flowmaster/C200250350.html

The 2" set I have are 3 1/4"od never used them, but when Stahl reccommended 3 1/4 collectors on my custom set he's building I was curious and measured the flowmasters and that is what they are ?? Actually for primarily street use he really suggested 1 7/8 with 3" collectors .he and Headers by Ed are real big on equal length tubes and sizing the collectors ......

Well, I'm certainly no header expert, but I can tell you that my FlowMaster Scavenger collecters have a 2" primary and a 3.5" collector. As I said I welded them up myself. The narrow in the middle creating a cone which is supposed to create a vacuum effect. Based upon my experience I would say it works. My carb was lean after welding in the merge collectors with no other changes. Would they work better with a smaller collector? Would my engine have more torque with smaller primaries/collectors? Maybe. I'm pretty happy with the way it runs smile.gif

Well I have had this idea in the back of my mind for a little while. When I had the 12" stock converter in my tranny just to get the car home I did a chassis dyno with it. I was a little suprised to see the torque numbers to be 426rwtq. The engine dyno was done with my headers, my x pipe, and my mufflers and my tailpipes on it, along with my alternator and water pump. Those numbers were 565hp, 550ft-lbs. The did this last cam swap says he doesn't understand why I'm not running a faster MPH than I am right now, as he called me when he dyno'd my old cam on his stand (540hp) and said he didn't understand why I had said I was only running 113 in the 1/4.
It is possible he wasn't taking into account how "portly" my car is (4000-4100lbs depending on gas and whether you weigh me in the winter or summer heh).
So back to the chassis dyno with the stock converter. It chugged out 461hp for a 18.4% loss and 426ft-lbs for a 22.5% loss. I was kinda surprised to see a bigger torque loss than hp loss.
I tried to do a chassis dyno run with my current converter in, and when I nailed the gas at like 2500rpm, it just jumped to 5200 then "grabbed" and did a 3 second run to 6800, producing 425hp (I think) and 392tq, but the company that built the converter insists that chassis dyno numbers are essentially meaningless with a performance converter if you can't lock it.
I had always thought I was suffering with a little low end torque loss because of the headers, but I always had small, torquey cams, and now I have a larger, less torque-producing cam (from off idle to 2800, from 2800 on the power is there, and new cam beats the old one for torque from about 2800 on, but below that its like one or two cylinders are shut off). So I was thinking this could perhaps be a way to help compensate for this effect. Maybe I should look into those, what are they called, 4-2-1 header collectors? that I think it was Ed? who said they are good for 10hp or so?

Right now I am just in the market for new wheels and tires for racing.
I am suspect of my torque converter and there is the slight possibility that there are a few hp tied up in the headers/collectors, but those would be "add on" hp because the engine was dyno'd with the exhaust. Right now I think there is something in my driveline eating a few more hp than it should.

Ed doesnt care about HP, he said they were good for X amount of ET. ET is what matters, and that is how he measures changes.

Starting with a car that he can dial within .02 right off the trailer with no timeshot, and .01 or closer accuracy after the typical 2 timeshots.

Well someone equated Ed's gain to a hp # along the way I suspect, and I suppose thats how it got in my head.
Last time I read he was running 1 3/4 headers with the those weld on flowmaster collectors.

I'll try not to use his name in my posts, seems to get people uppity..

Yes, he uses 1-3/4" Primary tube Dynomax headers with the flowmaster collectors welded on.

Matt,

If you are looking to boost low end TQ then 1-3/4" primaries should help. At your current power level/ET/MPH they probably won't cost you much higher RPM power either.

That being said, I would recommend that you get the car dialed in and get it to dead hook before changing anything else. Otherwise, any TQ increase you may see will likely show up in tire smoke instead of ET reduction. You will also not be able to truely tell what the changes were worth in the ET/MPH department.

Brian,

How's your car coming? The last I saw it was looking pretty good.

How much ET/MPH were the 1-3/4" headers worth compared to 2" headers? What were the results of the A-B-A testing with a control car, on the same track, with like DA?

Jason,
the car is almost done, i'm waiting for UPS to drop off the parts they're holding hostage.

He did the testing with the Scavenger collectors, not the primary tube size. however he may have results from a similar comparison with another car. Next time i get ahold of him i will ask.