74 K5 Header Questions?

[FM Keller]

After researching forums I keep reading about clearance issues (Spark Plugs, Starter, A/C bracket) I was wondering what MFG and model are you guys running and is there any issues?, I guess the standard size most are running is 1-5/8" but what type? short, long Tri-Y , and what size collector? 2.500" or 3.000" ?
No issues with smog, thats why I went 74.

 

[mechted]

Do a search for Hedman Elite 69830. Someone did an extensive write up, and it has since morphed into a discussion of all the different header options and problems thread. Worth reading. (Assuming you are still a small block and want long tube headers)

I did first fire of my motor on Summit brand cheap steel headers, and burned 3 spark plug wires/boots in 1 hour of engine operation. Since then I changed out the headers for 69830s but haven't refired yet. (other issues)

 

[FM Keller]

Im going to try Doug Thorley Tri Y long tube Headers

 

[my kids took the truck]

I have a set of those. Back in '94 I bought them. They have the nickle coating. After 20 years, 40,000 miles and lots of mud, they are still good.

The coating has turned to rust around the hot spots. Thorley said the coating is not warrantied but if I take them off and send them in, for a few hundred bucks they will make them like new with a ceramic coating.

I have the same exhaust gaskets, never a leak, same for the collectors. There is one sparkplug that depending on my mood can be difficult to get. Sometimes I use a wrench on a socket to get it, other times it comes right out. Without the fender wells it is easier.

I've never burned a sparkplug wire on them.

The starter used to get hot enough it would not turn over on a hot day after driving, just, click... click... click. I'd have to hit it with a wrench before it would go. A sheetmetal heat shield fixed it. Recently I added some heat shields for the fuel line. I measured my fuel line near the headers and is was 120 deg F on a cold night.

The transition from the collector to exhaust pipe is a bit close to the transfer case cradle. It is tight and leaves a sharp up-bend in the exhaust pipe before running along the t-case. If the headers were 3 inches shorter it would line right up.

Also, there is no room for a cross-over.

I've never used any other headers or ram horns, so I have no comparison. I hear that ram horns are just as good as the headers. The ramhorns would have some benefits over the headers. The ramhorns line up the exhaust with the transfer case. They don't wrap around the starter. The fuel lines probably don't get as hot. There would at least be a chance to tuck a crossover somewhere before the transfer case. There are no problems with sparkplug access.

 

[FM Keller]

Never knew about Ram Horns, not allot of info on them for the chevy 350, seems every time I talk about getting headers my truck friends say get ready for exhaust leaks, thought with a 3/8 manifold plate warping would be non existent?

 

[my kids took the truck]

That big flange on the Thorleys does the job. At the junkyard I have seen the cheap headers with thin flanges. Look in my last picture, you can see that flange.

You will not have gasket problems or exhaust leaks.

 

[Georgia_BigBox4X4]

Ram Horn Exhaust Manifolds

http://www.castheads.com/manifolds-carb/exhaust-manifolds/corvette-exhaust-manifolds/

 

[my kids took the truck]

I found this thread over at chevytalk with an actual dyno comparison of ram-horns versus some large looking headers. The difference between the two is not much. I'd hope the tri-y header would have pulled more low end than the full length headers did.
http://www.chevytalk.org/fusionbb/showtopic.php?tid/256915/

Over at corvetteforum I found this discussion about real world experience with both headers and ram horns. The consensus seems to be that the difference is minimal. Again, the comparison is with full length headers, so I'd hope the tri-y headers would provide more low-end.
http://www.corvetteforum.com/forums/c3-tech-performance/809890-rams-horn-manifolds-vs-headers.html

Speedtalk talks about all these numbers and the tests they have done, but nobody posts any actual data - take this one for what it is, they claim ram horns are not bad anyways.
http://speedtalk.com/forum/viewtopic.php?f=1&t=20464

Hotrod has the closest discussion for comparison of sbc cast-iron to full tube headers to tri-y.
http://www.hotrod.com/how-to/engine/116-0312-exhaust-pipes-test/

My conclusion. Using the chevy talk data comparing the ram horns to the full tube headers, I can see the headers are worth 10% across the board. When I add in the Hotrod test comparing full length to tri-y, I see that the tri-y losses on the bottom and top end, with gains in the mid. If the tri-y compares equally to ram horns, then I'd expect the ram horns and tri-y to have exactly the same performance in low and high range. The tri-y most likely edges out the ram horns in the 4,000 rpm to 5,000 rpm range with 40 ft-lb of torque and 60 hp, more or less 20%.

Personally, I don't ever get past maybe 3,800rpm, only when I want to get on the freeway and see how the tune is, and about then my kids throw their arms in the air and scream that we are going 'fast.'

Years ago, when I would go to 6,000 rpm, I remember there is a strong pull from 4,500 to 5,500 and by 6,000 it flattened out. I have stock small port heads and a dual plane low rise intake - the goal of the build was torque. To that goal, the tri-y do not help low end. As hard as it is to admit, according to the data, I should have used full length headers for improved low end performance and in reality some ram horns would have been the best bang for the buck. Without a direct comparison between typical sbc truck torque motor with ram horn, tri-y, and full length, this is the best I can infer from what we have.

I have to admit, the tri-y look nice. And I have no problems with exhaust leaks.