Matt81

My 78 came with a set of new-in-box Hedman Headers, PN 68308. The prior owner purchased because there is a small exhaust leak at the passenger exhaust manifold, and thinking that as long as he was pulling the manifold, why not bolt on the headers. He never got around to it, so I'm wondering the same thing.

Header info below. They are 1 5/8" headers with 3" collector and ceramic-metallic coated. http://www.hedman.com/images/ePIM/original/68308.pdf

Car has a Goodwrench 350 that runs good and I'm giving it a full tuneup. The engine is in its stock configuration, with the original L82 intake and carb. Manual 4spd and running true duals - no crossovers.

This is my third Corvette but would be my first car with headers. I've read a lot of pros and cons on this site and others, but the info revolves primarily around long vs short tube headers. I'm curious as to the difference between the stock manifolds and the LT headers.

Sounds like there would be a noticeable difference in low-end torque, which I'd like. This is just a cruiser, no track time, autocross etc.

Are there any negatives? I'm wondering about excess heat in the engine compartment or cabin, noise levels, etc. Some posts show clearance as being an issue, but I believe what I've read on these particular headers is that shouldn't be a big deal.

I'll grab a pic when the sun is up to post, but the upturn bend from my exhaust pipe to manifold appear to have a fairly good restriction from the bending process. Clearly not mandrel-bent tube.

Thanks for any advice!

bruiser

I have recently put on headman headers. They are a pain in the a$$ to put
on, I had to dent one of the tubes to clear the idler arm.
Had to remove the starter and inspection cover to get them on.
Couldn't get the inspection cover back on.
Had to cut the transmission lines because they were touching the headers.
They hang too low so they bottom out when you hit a bump.
The engine compartment heat is lowered a little .
That is my experience.

jb78L-82

I have these long tube headers:

http://www.xs-power.com/chevrolet-headers-4.htm

The real collector size is 3inches internally and the primaries internally are 1 3/4inches, NOT what the website says-BTW

Giant PIA to test fit before having ceramic coated.....

I don't like LTH's for the reasons mentioned above BUT with my just rebuilt 355 L-82, roller cammed, AFR heads, and 10.2:1 compression, I was leaving much HP on the table with shorty headers with a 2inch collector hooking up to the duals with a 2 inch head pipe on my 78 C3. I have spend hours test fitting both sides before I send them out for ceramic coating this weekend.

Drivers Side:

fit perfectly BUT had to remove clutch Z bar to get them in from underneath the car. I rerouted all the plug wires through the factory OEM wire shields against the block which I purposely reinstalled during the rebuild-good move. Spark plugs, plug boots, and header bolts all fit fine. 1 QT truck oil filter fits fine with these headers

Passenger side:

Another story! These headers are built rugged with 1 3/4 inch primaries. Like above, spark plugs, plug boots,and header bolts fit fine. I did have to loosen the starter bolts to get some play in the starter to get the header tubes past the starter from underneath. Like above the idler arm interfered with one primary and required multiple removal and reinstall with dimpling of the tube to fit-not a lot of dimpling about1/2 -3/4 of an inch-just spoke live to XS power and they want to see a picture of the primary with the dimple near the idler arm to see if they have to modify that primary for future builds to clear the idler arm). OEM factory plug wire shields are a god sent for the wires.

As for road clearance, the 2.5 duals sat 4.5 inch from the road at the head pipe. The LTH's sit 4 inches from the road, losing 0.5 inchs which seems reasonable....

Stay tuned...couple more weeks before final install but in really good shape now after they return from ceramic coating since I did a ton of work up front....

Matt81

Thanks Guys! Glad to hear your thought JB78L as I've read several of your posts as an opponent to LTH. I won't be doing an install until the car is down for winter, so will keep an eye out for your writeup.

I recall reading potential clearance issues with the idler arm and the z-bar removal.

I'm probably not leaving all that much power on the table with the stock Goodwrench, and wouldn't have considered buying the headers separately, but since they came with the car, thought I'd check it out.

Here is a pic of my downturn pipe. Could they be causing any restriction with the pinched bend?

Matt81

jb78L-82

Good to hold my feet to the fire..keeps me honest

Still not a hugh fan of LTH's for a stock type engine since I think shorty's/block huggers will get the same result but on my 355 L-82 I am gambling that the effort with LTH's is worth the result...we will see. I am going from 1 5/8 inch shorty's with a 2 inch collector to 1 3/4 inch LT primaries to a 3 inch collector so these babies will allow MUCH more flow especially with the AFR heads. My 2.5 inch duals have the stock 2 inch reduction head pipe near the exhaust manifold which is really bad for flow. Any tube reduction will hurt flow but depends on the engine and how much the restriction actually reduces exhaust flow. Should be interesting....

Metalhead140

The Hedmans I had hung low, and sat below the starter and oil filter, meaning I couldn't run the long truck style oil filter (which I normally run for the larger filter area). They hung much lower than the sump, and I touched down the flange on the collectors a number of times. I now have a set of the Summit headers, and they sit higher and wider, much better for ground clearance. I had to bump the Hedmans for clearance to the idler arm, and the summit headers for clearance to the z bar. Whatever headers you run, make sure you test fit them and check clearances everywhere. The flange on the Summit header collectors is very slightly below the bottom of the sump, but I've also fitted a deeper sump so it's not a direct comparison. Definitely not as low though.

cagotzmann

So what are you doing to measure befor and after results

Do you have any 1/4 miles times.

I am always looking for real world results

Hopefully you will have something for us.

jb78L-82

Unfortunately I will not be able to do back to back comparisons. My 78 with 67,000 miles on the car has been going through its 30 years transformation since 1983....complete front suspension upgrade/rebuild over the years, new engine in 2014, new clutch kit in 2014, rear suspension component rebuild/upgrade over the years, new interior, etc. And recently, while test fitting the headers I looked into a rear end wiggle under hard acceleration with some front wheel turning. Both rear wheels have some serious movement rocking the tires. The TA, U joints, and Diff are original from the factory. After the headers are in and have been out for a ride, I need to remove the TA to bring to Gary Ramadei, GTR 1999, for a complete rebuild (he lives 2 hours from my house). I spoke to Gary and my 78 diff is well known for the soft metal used on the yokes and the C clip falling off in the diff so I need to see if the diff needs to be rebuilt by Gary as well. I would have him do the half shaft u-joints as well at the same time. In short, no 1/4 mile/ dyno runs in the cars future now or imminently...until everything is fixed. The only thing left on the car for me to rebuild if all these 3 items need to be rebuilt will by the Super T-10 4 speed...ugh!