This question has been asked a hundred times, which is better and how much do you give up if anything.

Well here you go;

350 Olds
7a heads, 2.00/1.62 valves
Mahle 4.100 10cc piston (You know the one Dale says he doesn't like cuz the valve pockets are too deep)
Molnar rods
Custom Hyd roller, Solid roller lifters, 1.6 ratio rockers
Stock pan, hv pump
RPM Intake
Quick Fuel HR 780VS
Long tubes are my dyno headers, 1 3/4, 3" collectors, 2.5 pipes and mufflers
Shorties are Thorntons w 2.25" pipes and mufflers

A couple of things to make note of, the long tubes made more power and tq EVERYWHERE, not just at peak. And I didn't have to rejet. In other words it made LESS power with the same jetting.
And the owner mentioned that he heard "a little back pressure is good for low end". It clearly isn't, bigger pipes, more power everywhere.
Note, it was a really nice day when I ran it with the dyno headers. In fact so nice that I had a correction factor of 99. Meaning you have to add about 4 (1%) to both columns. So, it really made 426 that day, not 422. Same with the tq, add 4 across the board.

Let the arguing begin!

 

Curious to see sometime what shorties vs stock manifolds would be.

 

The Shorties ARE better. But they ain't cheap. And I think they might make more difference on the small blocks cuz the stock small block manifolds are even worse than the W Z's.
HOWEVER, the more mods/cubic inches you have in your build, the bigger the difference will be between long tubes and shorties.

 

That's great data. Thanks for doing the comparison, and thanks for posting the results.

 

These are the 2.5" outlet shorties? No prebent true 2.5" down pipes for manifolds or these Thornton shorties. So 25ish HP and 15 ft-lbs? I think the Sanderson and Hedman would fall between the two, since both have 3" collectors. Of course Sanderson's welds are hit and miss. I think the gap would close with 2.5" dual exhaust. I had that behind my Sanderson headers.

 

You’re very welcome.

 

Excellent post

 

Thank you Mark. Pretty much what you have always said.

 

That’s a big difference.
Excellent data.

 

Good post.
It's always fun to see back to back data.

 

Thanks for posting the data.

 

How about the next test, std electronic dist, vs the same with an ign box, vs an aftermarket HEI?
I’ll bet I dispel another myth.

 

The ignition tests would be interesting. I would also like to see the current setup versus Sniper 2 with Hyperspark Ignition Control.

 

Can’t, apples and oranges. You can do so much more with ECU controlled timing vs a std dist.

 

Fair enough. You could leave out the Hyperspark part.

 

I’ve already done a half dozen carb vs TBI stuff. TBI’s NEVER make the same power as a comparably sized, well tuned carb, NEVER. Always a couple of percent less.

 

You could always do a test like Motortrend did and "clearance" a set of headers with a BFH and compare it to an unmolested set. Truthfully, I think the Motortrend test was inaccurate. They never installed a full exhaust on the engine they tested. They just had it sitting on an engine stand attached to a dyno and compared bashed vs. fresh headers. Damaged headers could result in turbulent exhaust flow if attached to pipes, mufflers, etc.

 

If you have an extra set of headers I can bash up, send them to me. In fact you can even send them already smashed to your liking. I’ll do the test.

 

The numbers tell the story . You don't have to rely on he said she said bullshit .Always look forward to these tests, thank you

 

I wanted Mark to test my Sanderson shorties. They never got done due to the custom down pipes needed. Even equal sized exhaust, still probably 20 HP and 10+ ft-lbs for shorties vs long tubes. But the shorties still produce 15 HP and TQ over even Thornton SB manifolds.

 

Your shorty headers would probably be even worse than these because of the entry way at the flange. It was horrible.
And I’m not sure I’d put a number to the difference between shorties and manifolds. A lot of it depends on the cam and overall combination etc.

 

Did you forget the pics of the Sanderson's was posted on here ? They were absolute crap !!!!! I wouldn't have wasted a set of gaskets on them, let alone buying them. Believe what Cutlassefi has just posted.

 

True, that was the worst set I got from them. I went full length Chinese stainless for that reason. Helps they cost 1/2 as much and looked way better. If I find 4wd truck, they may get called into duty. There was another test put up on this site a while back. I believe it was in the neighborhood I put up for HP and TQ.

 

You mean these? They don't use gaskets, only collector gaskets. Just high temp RTV at the head. This is my 4th set, it will be my last.


Only one of the tubes is restricted by their shitty weld job, the rest just look like ****. Don't deal with Century Performance. Their stance was an uncoated header is unfinished. You are supposed to fix Sanderson's sloppy work. I will fix it before installation. I asked Mark to clean up the worst spot before getting them coated. The test is apples to oranges due to the discontinuation of the 2.5" Ram Air Restorations mandrel bent true 2.5" down pipes. Of course the full length wins, just not 100% apples to apples. Through 2 1/4" exhaust on the full length, then it is a fair test. The shorties are already at a disadvantage, is my point. I like Mark, have dealt with him many times and will continue to.

 

I guess I should explain a bit more.
i did the 2.25 pipes with the shorties because that’s what my customer has in the car.
However this morning he informed he may go to 2.500” pipes. But I’ll bet it won’t make that much of a difference.
And unfortunately I didn’t have my fuel flow meter working. THAT would tell the real story. Even though the shorties made almost 30 hp less, I didn’t have to rejet vs the long tubes. Kinda tells you about the efficiency of both doesn’t it.

 

That makes sense, what he is actually running. I did run 2.25" duals with better Sanderson shorties in the 5A 307 headed 204/214:cam Olds 350 powered Z71. I had Flowtech 1 5/8" long tube with 2.25" duals on the same motor. But TBI vs Qjet and more importantly a 3.06 first gear vs 2.52 first gear and 3.73 vs 2.78 gears. And the 265/75R16 was only 1.5" taller than the 235/75R15. The Z71 definitely pulled harder for the reasons mentioned but doesn't mean the shorties were better. It also out performed stock 5.3L LS trucks idle to 4500 rpm, that is apples to apples​​​​​​. The 1 5/8" vs 1 3/4" is another advantage, so hard to get a completely apples to apples test. Didn’t mean to act like Dale here, sorry if it came off that way.

 

do you wake up in the middle of the night sometimes screaming my name?