Cool shootout; 472 HEMI Stroker - Headers VS Manifolds

https://www.youtube.com/watch?v=nBed8HkXlow

Every swap from manifolds to headers has been more power for me too.

The last pump gas 472 C.I. hemi motor I dyno tested in SO CA on a DTS engine dyno at Vrbancic Bros. in Ontario, CA did a little bit better, 625 HP @ 6200 RPM) than theirs did

I've never run manifolds on my car.

yeah numbers seem a little disappointing .

Tex

The dyno testing I did when I was developing my fast motors does not agree with there's whatsoever. 612 versus 588 horse, and 795 vs 762 horsepower. Nicks Hemi seemed to stumbled at the top end of the pull with the manifolds. I wonder if something was going away, or if the jetting was off?

Nice numbers for a semi mild small block stroker, but a 472 hemi?

Watch this vid and to me it tells so so much.

https://www.youtube.com/watch?v=2SbInV5RVM8

He said they had problems with that engine that cut down the power. 80 lbs of spring pressure on the seat.

How? Cam selection? Better suited to the manifolds?

What does it tell you? J.Rob

I watched one of his vids with a G2 that had a misfire and rough idle for a few seconds after a pull. They could find nothing wrong and deduced it was a pushrod problem?

I called him the next day and told him if he looked at his VE% numbers it would read abnormally high like in the +hundreds of percents maybe 700-800%.

I pretty much guarantee he had an exhaust valve seizing open. He didn't believe me I don't think. Swore the pushrods fixed it. J.Rob

I spoke with that guy once. There was this "You haven't heard of me? But I'm famous!" attitude that totally put me off.

Take the same motor, test it with two different cams, and try the headers and manifolds with both cams.
One cam, manifold friendly, one cam more of a typical mid-level bracket race cam that needs headers........ and you’re going to see a big difference in the spread in power output between the manifolds vs headers with the two different cams.

Trying to come up with a blanket figure to say headers are worth “xx” power over manifolds is kinda pointless.
It’s absolutely one of those “it depends” things.

Someone here recently tested a 505 with TF240 heads and observed a 90hp difference.

A headers vs. manifolds dyno test on a performance engine is a waste of time. The engine is either tuned for headers or it is tuned for manifolds and just changing the exhaust without changing the tune gives you bogus numbers.

Headers vs. manifolds is one of the "forks in the road" that you take early in the engine build process.

You guys are dead on, as usual. In my F.A.S.T. builds it was known that the class rules required factory intake and exhaust manifolds, and a 2.5" exhaust system to the rear bumper. Cam profiles were selected accordingly. The same motor with a radically different cam would have different results in a manifold vs header comparison.

Bringing this back from the dead.

The 612 vs 588 horsepower, was that on as-cast or ported manifolds? Trying to decide between headers and porting my manifolds.

Thanks!

When I was deciding on the final pieces for my 540 Hemi, I spoke to Indy about the exhaust. I was considering the 2 1/8 rather than the 2 1/4 TTIs. But they told me that the Hemis did not like any exhaust restrictions. So I have the 2 1/4 tubes and 3" straight thru exhaust with electric cut-outs. I have not experimented with the exhaust to know what works or what doesn't. Just passing along some advice I got from someone that probably knows what they are talking about.

Coming up next,,,will a rochester 1 barrel out perform a pair of dominators..Tune in next week to see if 78 series polyglass will out 60 hooiser 34.5 17 16

With out a doubt it’s not everyone’s cup of tea. But to some, me included, like a stock looking muscle car that performs better than expected. There were a couple of thing here that made this an awful comparison. One there was no tuning done after the switch to manifolds. The jetting will not be the same for both. The other thing is look at the exhaust on both set up. It’s clear that it was pretty much open headers on the Hemi but was run through 2.5 inch exhaust pipes on the manifolds. I’m not saying the manifolds will perform with the headers but the playing field was definitely tilted in this comparison.

^ Yes, obviously the headers will outperform the manifolds, that in itself is not the question but to what degree is.

Right now I have manifolds that fit perfectly and bolt up to my exhaust with no rattles/leaks/problems so for those reasons it's tempting to re-use them with some port work.

Nothing crazy, all iron 426.

Would I leave 50hp on the table? No, but if the 24hp example above was with untouched manifolds and that differential could be brought closer to 20 with port work or even welding I would certainly consider that option.

If it is quarter mile performance there is more to going fast than headers or manifolds. As for Exhaust Manifolds and they are a nice factory piece I would leave them alone and find ones that are already altered or buy a set of repros and port them with no hear riser. At one time in I isle at Carlisle Mario sold Auminum Hemi exhaust manfolds. You save a lot of weight running those and I believe a few FAST hemi cars have them on. Every area of the motor can be altered for more HP like the stock intake manifold with a Vanke Mod,, changing rocker ratios. Leaving a little on the table is not a bad thing.

It's not an original hemi car, I believe the manifolds I have are reproductions.

Didn't know they made aluminum ones, very interesting.

I'll provide some at the track results from two of my cars, both wedge powered, not hemiroid powered, with the muffs and pipes on versus no muffs and pipes removed.
Example #1 was my 1969 Dart GTS 440 powered street and strip bracket car at LACR 1/4 mile back in the late 1990s or maybe early 2000, the car ran 12.29 ET at 109.4 MPH with a new set of M/T 105x28.5x15 with 11.0 lbs. in them on the first run at around 6:000 PM on a Friday night T&T with the 2.5 inch exhaust system that consisted of a set of Hooker 1 7/8 A body fenderwell headers hooked up with about 16.0 inches of 2.5 head pipes to a set of Thrust 2 1/2 inch in and out Corvair Turbo muffs with a set of 2.5 inch side pipes going over to the rocker panel directly in front of the rear tires. 2nd run was with 10.5 Lbs. in the slicks 45 minutes later with no other changes, the car ran 12.27 at 109.5 MPH, the last run that night was around 9:00 PM with 10.0 Lbs. in the slicks which resulted in a run of 12.23 at 109.7 MPH.
This was a 3 day event with T&T on Friday night with the gates opening at 4:30 PM , first TT at 6.:00 PM stopping at 10::00 PM. Saturday the gates opened at 8:00 A.M with the first TT at around 9:00 :AM, closing at 10:PM Sunday had the same schedule with closing at the end of racing.
I got to the track around 9:00 AM and removed the exhaust system from the headers back and let the tires down to 9.5 Lbs. with no other changes and made the first TT run around 10:30 AM, it ran 11.39 at 117.6 MPH I didn't believe it so I made another run at around 11:10 AM on the other side (L/S) of the track, which with that car was normally around .02 to .03 ET slower. It ran 11.42 at 117.7 MPH
I did some similar testing with my last street and strip car at Madras, OR a 1/8 mile track it had a pump gas 512 C.I. low deck stroker motor with a six pack and a complete 3.0 exhaust system with the same Hooker headers off of the old Dart fed into 3.0 inch pipes ran to the rear of the car with a set of Magna Flow muffs that where 3.0 inch side inlet by 7.0 inch thick by 14.0 oval with a 3.0 inch center outlet with a piece of perforated straight through pipe in it, the muffs where mounted at the rear bumper with 45 degree turn downs straight out of them. That car ran a best of 7.01 ET at 95.3 MPH with the system on and it picked up to 6.98 ET at 95.5 MPH with the complete system removed I'm thinking the weight was where the small perforamnce gains where made, not the exhaust system restrictions
Happy Thanksgiving to all

Some of the ‘62 “ Swiss cheese” catalinas had aluminum exhaust manifold, but they found that they would actually start to melt.

On the 588 horse motor, the exhaust manifolds were bone stock. On the 762 horse, they were extrude honed and ported.

Something that’s important to keep in mind here is........ depending on how the cam is configured...... the difference between the headers and manifolds could vary greatly.

A cam designed to minimize the losses when used with manifolds isn’t going to gain as much by going to headers as the cam that essentially requires headers is going to lose by running it with ex manifolds.
One might show a 20-30 difference....... the other could be close to 100hp.

The takeaway is....... there is no standard answer as to how much headers are worth.

As with just about everything relating to making more power...... “it depends”.

Thrush turbo mufflers really kill power if you're making some. I had a set on my Plymouth, and I spent 3 summers chasing various issues that made the car just feel like it was 100 HP down from where it should have been. Finally one of the last changes was mufflers (changed to Ultra Flos) and the car felt night and day different.

There was actually an episode of Motor Trend's engine masters some time later and they found that the Thrush mufflers were the worst of all the Turbo mufflers tested. Mine sure did sound good though. They were the Thrush Hush, which is different than the California Turbo model.