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I know headers are best but the stock big block manifolds look pretty efficient by design, the point of my post is to gain more knowledge from others of whom know more about these things.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
A simlar test showed 14 hp and 11 foot lbs....so i would go +_ 5hp around that depending on exhaust on a stockish build....maybe on a higher hp build it would be more of a cork so up to 50hp if its a 500hp build
The only thing efficient about that manifold was the cost per unit during production.
Looking at how the #1 cylinder basically takes a 90° turn into the #3 cylinder, with #5 essentially dropping straight down and #7 jetting forward and down, all to meet up at a collector opening that's quite small. From an efficiency standpoint, it's not cutting it.
It it better than a typical log style manifold? Yes, but can it come close to touching the performance of a header? No, no sir.
It's been way too long and I don't have the numbers any more, but I remember on the dyno I made more torque with the cast iron manifolds. HP was down though.
The only thing efficient about that manifold was the cost per unit during production.
Looking at how the #1 cylinder basically takes a 90° turn into the #3 cylinder, with #5 essentially dropping straight down and #7 jetting forward and down, all to meet up at a collector opening that's quite small. From an efficiency standpoint, it's not cutting it.
It it better than a typical log style manifold? Yes, but can it come close to touching the performance of a header? No, no sir.
They are not as bad as you make them out to be.
Depends on what headers you are comparing them to. The only worthwhile headers are equal length long tube headers. Their is no gain with the shorty headers over the factory exhaust manifolds for these factory BB ones or factory Hemi exhaust manifolds.
They are not as bad as you make them out to be.
Depends on what headers you are comparing them to. The only worthwhile headers are equal length long tube headers. Their is no gain with the shorty headers over the factory exhaust manifolds for these factory BB ones or factory Hemi exhaust manifolds.
They're certainly not good. I'd argue a well designed shorty with at least a 2.5" collector would out perform that manifold, and certainly a long tube with a 3" collector would pimp slap it. Especially if we're talking long tubes with collector extensions.
They're certainly not good. I'd argue a well designed shorty with at least a 2.5" collector would out perform that manifold, and certainly a long tube with a 3" collector would pimp slap it. Especially if we're talking long tubes with collector extensions.
Then you would be wrong about the shorty headers. There was a recent thread about this that if you search for it you will find some results.
Then you would be wrong about the shorty headers. There was a recent thread about this that if you search for it you will find some results.
I searched, I found, I read! Thank you. I built the motor myself and it dyno'd at 630 with those exhaust manifolds... just wanted to roughly know how much I might be giving up, ya know. I think I'll keep em' for the time being...if I do headers I'll most likely go the side pipe route.
I think the only time you would see a gain with properly designed headers is at WOT or near redline
the stock BB manifolds are very well designed and durable and work great for a street car, for some reason
people like to criticize them for the purpose they were made to do, there better than any other stock BB manifold at that time
Then you would be wrong about the shorty headers. There was a recent thread about this that if you search for it you will find some results.
A shorty with equal length tubes, 2.5"/3" collector with a spike will outperform a stock Big Block manifold, flat out. I've personally seen it, watched it on dynos, and have seen physical numbers on time slips at the track showing improvement with similar air temps and DA. But yeah, I'm wrong.
It is what it is. If people wanna run stock manifolds, more power to them. Leaving power on the table isn't something I'm cool with, so I jump right past the shorty headers and use good long tubes with calculated extensions.
I guess it comes down to what kinda build you're after. If stock appearance is what you're after, stick with then manifolds.
A shorty with equal length tubes, 2.5"/3" collector with a spike will outperform a stock Big Block manifold, flat out. I've personally seen it, watched it on dynos, and have seen physical numbers on time slips at the track showing improvement with similar air temps and DA. But yeah, I'm wrong.
It is what it is. If people wanna run stock manifolds, more power to them. Leaving power on the table isn't something I'm cool with, so I jump right past the shorty headers and use good long tubes with calculated extensions.
I guess it comes down to what kinda build you're after. If stock appearance is what you're after, stick with then manifolds.
Myself and others obviously disagree with you. Most that want shorty heads want them to mate up to factory side exhaust and they are worth nothing for a power gain over the factory exhaust manifolds.
No reason to talk about long tube headers as I agreed with you in my first post in this discussion.
if you have proof of dyno results that show any significant power gain with shorty headers over the factory Corvette exhaust manifolds on the same engine then post them.
@Tranz Zam what kind of shorty headers are you talking about? It sounds like you have experience with capri length long tube headers, while everyone else is picturing shorty headers like the 81 C3 SBC, or McJacks.
Look up Sanderson Headers in Torrance CA.
Here is the dyno run sheet performed by Chevy Action Magazine where they compared their short tube headers to long tube headers on the same 433 cu in big block engine.
You would be surprised at the results from 3000 to around 5000 rpm.
To read more look at there Header Tech section of their web site.
Sanderson’s have been one of the best quality headers on the market for the past 50 years.
I would run them on your big block over the stock manifolds in a nano second.
They will perform better, sound better, look 100% better and save a ton of weight, being that they only weigh 16 lbs.
There will always be some people who disagree, but are they providing dyno sheets as proof or just talking trash.
The Sanderson Short Tube headers I purchased for my 496.
Last edited by OldCarBum; Mar 7, 2023 at 07:53 PM.
Not looking for comparisons of long tube headers verse shorties but rather short tube verses factory exhaust manifolds.
The OP asked a question about stock manifolds and everyone knows long tube headers perform better than stock manifolds.
The information I posted was for the OP to compare.
It is “HIS” thread!
Myself and others obviously disagree with you. Most that want shorty heads want them to mate up to factory side exhaust and they are worth nothing for a power gain over the factory exhaust manifolds.
No reason to talk about long tube headers as I agreed with you in my first post in this discussion.
if you have proof of dyno results that show any significant power gain with shorty headers over the factory Corvette exhaust manifolds on the same engine then post them.
Listen man, you obviously have some sort of issue with me. Why? Who knows?
There's plenty of shorty headers that'll put the hurt on stock manifolds. If you want to move the goal posts and say the shorty headers must mount up to the stock exhaust without modifications, obviously squeezing more power of of the header becomes tougher, but not impossible.
I mentioned long tubes because we're talking about efficiency. I was using them as a benchmark for maximum efficiency, in which I cam compare the gains from a well made shorty to.
I dont really understand the hostility towards me? Can more power be made with a well designed shorty? Yes, even if one must stick to stock exit location and collector size. The scavenging effect of a well made shorty alone blows away a stock manifold dumping exhaust pulses wherever they want to go.
I'm fine with you disagreeing with me. That's totally cool, but damn it seems I touched a nerve by simply saying I have seen and documented improvements over a stock setup.
Manifold efficiency
