Log-style headers...pros?cons?

So my project of swapping a 302 into my 1954 ford has reached the point where I need to put some exhaust on this thing. Now due to my lack of planning, I have extremely limited space to run headers. I need to fabricate them myself so I bought the kit from speedway. however, I don't think that I will be able to run individual pipes for each cylinder. So i began creating something similar to a "lakes header". Except mine is made entirely out of 1 5/8" inch tubing. I noticed that on most "lakes" style headers the big pipe that the primaries join into gets bigger as it goes back. (stick with me here I know this is probably hard to explain without pictures). Today I did more research and found something called a "log-style" header which I think would work as well.

My question is, how much performance will I lose by making the entire design out of the tubing which is the same diameter? If I build my "lakes" style design without the pipe increasing in size as it goes back, will this harm my engine/cause strange things to happen?

-Also, has anyone used a "log-style" header before? It seems like this design wouldnt have very good flow, but it would fit perfectly and be relatively easy to make. I'm pretty new to header fabrication techniques so bear with me. I'll try to post some sort of pics here to provide a visual aid. Any help is appreciated!

-I'm attaching some photos of "log-style" headers below. Would these cause backpressure issues or redce horsepower a lot?

 

Not sure the pros and cons but I like how they look. I would run some in my Victoria.

 

I agree. It seems like they would have piss-poor flow though. Which isn't too big of a deal since I'm not builing a race car but im worried that they cold restrict the exhaust to the point of causing some weird runnability isses.

 

Seems to me it would not have much of a restriction difference from a cast manifold.

 

True. Actually When I did a google image search for "log-style headers" a few manifolds popped up. It seems that the term is used to describe a lot of maifolds too

 

I think your biggest issue will be with the 1 5/8" tubing. I know a 302 is pretty small, so I think the log header would be OK. Probably as important as the header pipe, is what are you going to do with the exhaust after the header? Back in the day when the 302 was new, in a non-performance car, the entire exhaust may have exited through a single exhaust not much bigger then your 1 5/8", if your adding complete dual exhaust, you making an improvement from original. Personally, I'd step up to a pipe diameter closer to 2" for your header tube and dual exhaust.

Small diameter exhaust tubing is not usually an issue at lower rpm, its when you build rpm that it gets too restrictive. It will take someone smarter then me to determine at what rpm that restriction becomes an issue. Most guys like bigger stuff, even if it makes things worse, so you may not get a good answer. Gene

 

You run small tubes with small engines. They look fine to me for what you are doing.

 

I plan on building some sort of flange at the back of the headers where I can mate up some regular sized exhaust pipes. Probably 2" dual exhaust or something like that. The 1 5/8" tubing is just for the header itself.

 

Pros - You have to have something or burn your valves.

Cons - Everything else works better.

If you look at an FE lodged inside a T-bird you will see them, great space savers but a compromise. The hell with it, enjoy your car.

 

yeah burning the valves is my biggest fear with this idea. I think I'm going to go with something of a combination between a lakes header and a log header. A While ago I had started building some headers that had a pipe coming about 2-3 inches off of each flange, then joining into a common pipe. Basically a lakes header except the main pipe is not angled like a lakes pipe, and it doesn't increase in diameter as it goes back, it's all just 1 5/8" diameter. Maybe I'll post some photos when it's done. (unfortunately I only get to work on the car once every few months so it'll be a while)

 

I've seen alot of early 302's with exhaust ports only as big as your thumb.

 

1 5/8" is fine coming off the flage, but you need a larger pipe for the log. Go with something at least as large as your head pipe, I would suggest 2 1/2" running back to the mufflers and 2 1/4" tailpipes. This would have a balanced flow as the exhaust cools some in the mufflers and needs a smaller pipe to maintain velocity. This combo has worked for me many times and makes for a happy motor that produces good driving characteristics but still has great revability.

 

So you disprove it with an ad hominem? Where is your proof?

 

This is my home made flathead header. 1 3/4" then it steps up to 2". A 2" log manifold will work just fine on the street where you rarely go above 5 grand. You could increase it to 2 1/4" between 3 and 4 but that's as large as I'd go if you want 2 1/4" exhaust pipe. An 1 5/8 log is too small. IMHO

All the racers design their headers for WOT. The log type won't perform at WOT as well as racing headers.

Hedman made headers back in the day for engine swaps and not for the highest HP. Many were a log style. I like them because they look old to me. Looks are more important than an extra tenth in the quarter mile to me.

Stabbing the primaries directly into the side of the log at a 90* angle creates a lot of turbulence inside that restricts the flow. A "Y" connection coming in at an angle is better. Besides they look prettier.

Don't get tempted by the bigger is better mantra but there is a good street compromise. You don't need huge pipes for a street 302. IMHO

 

That restricted area also keeps the temperature up in addition to having turbulence. Over time, the metal in the exhaust valve has been through so many heating and cooling cycles that they can distort and you actually lose compression, or worse, a chunk comes off and does horrible things to the cylinder and/or wall.

You have to be careful who you say that to because there are those that equate thermodynamics to believing in the tooth fairy.

 

Hmmm. I guess I need to find a way to make the primaries come in at more of an angle or create some sort of y-design. I'm not trying to make maximum horsepower but I don't want to hurt a valve or create any runnability issues by running the primaries into the other pipe at 90 degrees. Hopefully my fabrication skills are good enough!

 

There are literally hundreds of thousands of Harley engines running short, open pipes in all kinds of weather. There isn't a problem with valves warping or burning.
I wouldn't worry about that problem, you should be fine if you step up the diameter after the flange.

 

Exhaust manifolds do 2 things, relieve pressure and channel heat from the engine. The example you show would do poorly at each. The exhaust pulses would try to re-enter other cylinders (when they are at low exhaust valve lift) and it would trap heat and that'll drive you nuts trying to keep the engine cool.
Somewhere around you is a professional fabrication shop that can make a set of headers for it, time to lets a pro earn his keep. I've built many sets of headers and that isn't a job that you want to blindly get into.

 

All you have to do is look at 352-390 stock FE exhaust manifolds to see that it won't hurt the valves or the engine. I like to call them bricks. The exhaust will find it's way out. The idea is if you are going to make some, make them as graceful as you can. Nobody was born a fabricator. You have to start somewhere. Use U-bends for the primaries instead of straight pipe. Tin snips can be used to work up to a good fit. The more you try the better you will get. You might end up with some scrap pieces but that's OK too. The experts never show them.

These sure are not the prettiest headers but I did want the home made look and they HAVE to be better than the stock 352 bricks. They look pretty descent after blasting and painting. I wanted them to look like they were made in 1964 and not 2004.

 

The Lincoln Mk VIII had a 4.6L DOHC V-8. One one side the engine had a decent looking header type manifold. On the other side it had a log manifold with short runners that entered at 90 degrees. To help the transition between the runner and log, the log part of the manifold was "ovaled". Having the log manifold on one side cost nearly 20 HP on the stock engine!

Bottom line, a true log manifold(intake or exhaust) can be a convenient way of connecting things together. But, it's an improvement only when the parts replaced were absolutely terrible.

 

Burned valves? Explain Pls.

 

If you motor is not a hight HP motor and you are not racing....................these would be fine...................don't worry about them.

The guiding principal behind designing headers is called "Scavenging", and this gets into VE and reducing pumping losses in the exhaust side of the motor (remember the V8 we know and love is only a basic "Air Pump"............in with the good and out with the bad), then there are step headers or super-heated solid pulse model some engine design software models use..................and of course my all time favorite famed pioneer person, Smokey Yunick, said to add HP "Look for a low-pressure area in which to dump the exhaust"............and it did work.

So again, unless you are building a race motor don't worry about it, just use them.

IMHO

 

THis is well said. I agree with this.

 

Tommy knows whats he's talking about. It's all about airflow. You don't want any turbulence in your pipes. Any restriction or anything causing a low airflow will have negative results.

 

I wasn't talking about the outside. Whether you like it or not, the exhaust valve is indeed exposed to more heat than the intake valve. The exhaust valve has its stem exposed to the heat. We will have to agree to disagree.

 

Tommy, those look like what I'm contemplating. Glad to see the pic, thanks.

 

You cannot prove a negative. He does not require proof, you do.

There is NO BODY OF EVIDENCE that this hypothesis is real. The plural of anecdote is not data.

Bonus points if anybody can tell me how an Aluminum alloy piston would survive in an environment that would burn a steel or stainless steel valve.

What CLAYMORE says about the temperature differential is correct, and we can even take it to the extreme. How about a P51 Mustang, cruising along at 39,000 feet, where it is -40ºF, blowing exhaust out of a 9-3/4" tube, and nothing else? We're not all speaking German now, are we?

 

plenty of differing opinions on this subject!

mine?

run whatcha got in the pics--you may hurt performance, but you're not going to hurt your engine.

 

Look at any F1 engine, Air craft engine,top fuel engine,in fact any hard working internal combustion engine where the exhaust is pumped straight out . if the engine is running so lean it burns valves ,thats a fuel supply issue not an exhaust problem ,even cooling problems in older designs burn valves but have nothing what so ever to do with exhaust design .
Some folks subscribe to the potato in the exhaust pipe method . Their thinking is that an engine must have back pressure to work efficiently so if a spud is jammed up the exhaust the amount of power developed must be amazing.
Engine Guru David Vizard has proven time and again the less pressure in a pipe means more flow so the bigger the pipe the better the flow resulting in more power .