Header/manifold dyno test

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VERY Interesting post!
I don’t do magnums just cause I’m old school and have too many motors as it was when sb magnums came out. I’m not opposed to them I just never collected any.
This dyno test intrigues me.
I thought the 340hp’s would have shown more than the 318’s even with that mild cam magnum, I’m sure they do with other builds/combos, cam etc. but that was surprising.
The 318 vs. 360 logs also interesting that they were so similar in hp. I kinda thought the 318’s were little chokers even compared to the 360 larger ex innards but still logs.
I have headers ( won’t say the brand but they are but not the good ones ) on my street Scamp and I dislike them ( hot, stinky leakin, speed bump paint removin, gasket blowin, noisy…Ok enough of that ) but the car came with 3” collectors on full exhaust so I was bein cheap.. my bad.
24 years later I am looking at the manifolds on my shelf and realizing how young and foolish I was when I built the car.
Since I'm not looking for E.T.’s I will be putting cast manifolds back on the car. Hahaha, Yes the headers are still on the car! old and foolish now.
The post shared has helped solidify my decision to go back to manifolds and once again thanks to FABO members for spreading awareness.
This machine will soon be CO free again…whew is it dizzy in here!?
E47B8CC2-529B-4C1F-B2F7-7A91370D3F40.jpeg
 
Be aware that the cam in the motor is so small that it barely has bumps on it. So the exhaust isn’t the choke point. The test is kind of pointless and shouldn’t be used to say “headers are only worth 15 hp”, or whatever the difference is.

Put a better cam in the motor and I bet the differences will be much more significant.
 
DionR said:
Be aware that the cam in the motor is so small that it barely has bumps on it. So the exhaust isn’t the choke point. The test is kind of pointless and shouldn’t be used to say “headers are only worth 15 hp”, or whatever the difference is.

Put a better cam in the motor and I bet the differences will be much more significant.
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True overlap likes long tube headers , but most wanting to run manifolds are probably not trying to push it over 350hp with fairly mild cams doubt even with something like an xe268h cam the difference between manifolds wouldn't grow much if at all, what I take away from it any 360 manifold is fine no need to spend $$$$ on 340 one's, and if you already got 318 manifolds on your not losing much, probably the same with 273 one's.
 
DionR said:
Be aware that the cam in the motor is so small that it barely has bumps on it. So the exhaust isn’t the choke point. The test is kind of pointless and shouldn’t be used to say “headers are only worth 15 hp”, or whatever the difference is.

Put a better cam in the motor and I bet the differences will be much more significant.
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I cannot disagree, but I believe they did that on purpose. They wanted to show the differences in the different styles of exhaust on a close stock style engine.
 
I put headers on an otherwise stock 73 340 back in the day and picked up seven tenths in the quarter (15.1 to 14.4).

That was with a 3.21 open rear end. Traction was no issue stock, but was a real problem with headers. A sure grip would have run a couple tenths quicker.

For whatever anyone thinks this is worth.
 
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Does anyone remember all the cam numbers on that crate engine??


I suppose I could get the book out but I don’t know if I have any from that era.

TIA
 
From the article;
“Its docile nature is the result of a mild cam, with minimal overlap and stock .385/.410-inch intake and exhaust lift”
To magnum people is this stock truck cam?
 
The 300 crate used a stock mag 360 cam. I don’t know the lsa but I’d bet it’s way up there. Like 118 or more.
 
not even 15 hp
11 lb ft
10 hp
on a 300 hp stock motor
as stated before
no less then 5 dyno test

that includes tunning the pos
 
The 318 has more lift (.432”/.432”) than the non rt 360!
.410”/.417” on the 360?
Crazy world were livin in!
 
Be careful with the published cam specs on the magnums. The info wasn’t updated very well and the 5.9 shows the old 360 valve sizes even though the heads are the same as the 5.2. Pretty sure the valve lift even used the 1.5 ratio to calculate it. So, I wouldn’t trust the cam specs.

I had a 2000 5.9 cam reground by Bullet and asked if they would run it through their cam doctor to get the OEM specs. Let me see if I can find a post with them.
 
QUINN FORBES said:
The 318 has more lift (.432”/.432”) than the non rt 360!
.410”/.417” on the 360?
Crazy world were livin in!
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Yea and it’s been published (not sure how accurate it is) that after 2000 all the 5.9s got the R/T base cam
 
Brutal, guys just tryin to build an engine with bad intel.
Good thing for this site being there for actual #s.
 
Again data that shows Vizard is not wrong but not enough data to show he is correct either! He says in a V8 tube length is a second order effect because of the way the pulses occur in a V8. What needs to be done in a test is vary the collector length. He says on a V8 that is the most important parameter. Also I can’t tell if they had an H pipe between banks. It does not look it. That is something else that is missing that would be interesting.

Nice to know my choice of no headers on my engines that are built for low end torque is not a bad choice. I always model my builds in Performance Trends and that analysis showed I was giving up little by not using headers as well.

In-line 4s or 6s on the other hand the firing order is perfect for the front bank to scavenge the rear bank and you can get a serious torque boost which I have seen in the models and real dyno data I have gathered from various sources.
 
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So with a difference of an average 15hp/tq gain for $1,000 headers compared to exhaust manifolds? I’ve seen this chart when it came
Out and realized headers were not worth my it on my resto car, even with a 400hp crate engine. Think I’ll go with shorty headers on the duster next cause I hate working on starters and power steering boxes through spaghetti metal tubes.
 
migsBIG said:
So with a difference of an average 15hp/tq gain for $1,000 headers compared to exhaust manifolds? I’ve seen this chart when it came
Out and realized headers were not worth my it on my resto car, even with a 400hp crate engine. Think I’ll go with shorty headers on the duster next cause I hate working on starters and power steering boxes through spaghetti metal tubes.
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With a stockish cam yes.
 
Jim Kueneman said:
With a stockish cam yes.
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and that's the key! anything past a stock cam the gains are much more impressive and the argument of price for hp/tq starts to swing back toward favoring headers.

jim, with your experience and analysis is there a hard break off point in lift where the for/against is a good line of demarcation as they say? in a mild street combo, that is.
 
junkyardhero said:
and that's the key! anything past a stock cam the gains are much more impressive and the argument of price for hp/tq starts to swing back toward favoring headers.

jim, with your experience and analysis is there a hard break off point in lift where the for/against is a good line of demarcation as they say? in a mild street combo, that is.
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I have not experimented like that with the V8, just the slant. If I had to guess it is like everything else it is just a progression. Part of the problem is everything is intertwined. The minute you start upping the cam you start lower cylinder pressures so you should up the compression to compensate which will give more power and a different answer. That is what was so confusing about trying to do comparison runs when I started running the models. You can't just change one factor and do a comparison because the minute you change one factor you have de-optimized something else that you should update first but then you are changing 2 or 3 things at a time and what does the result mean then? I have just designed an engine (or used someones build) then changed between stock and headers to see what it does.
 
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