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I received my Doug's D350 headers today. The port is out of shape. Although it will cover there's only 1/16 of a inch gasket coverage at the point where my finger is pointing to. Use them or send them back?
Use a good steel "rule" to check the flatness of the sealing areas FROM ONE END TO THE OTHER on each header.
That may give you two good reasons to send them back if the sealing surfaces have not been machined flat.
I checked for straightness as doorguner to said and they are straight. After taking a second look I do have another reason to send them back. One of the welds protrudes into the exhaust port by a 1/16 of a inch. And those are the stock heads too. I had a feeling that I wasn't going to like adding headers to my Car. Now I know. I have a few options. Being that the manifolds are already off, cut the air tubes off and weld up the holes. Have them coated too and call it a day.
Last edited by Fly skids up!; Oct 15, 2021 at 09:01 AM.
Find a gasket that covers all of the weld. The head is irrelevant.....it looks like **** but it should seal if flat. The inlet is a slight oval and those are available. Research the right gasket and bolt them on. You are using rebuilder exhaust manifold gaskets as a comparison. What gaskets did they come with?
Take a carbide burr and kiss that overlap.....easily rectified, should you have to do it, no....but it expedites things...I have heard that Doug's customer service is some of the best there is so you may want to contact them too......I would figure it out before I ever put the manifolds back on. To me....with the crap I see in the aftermarket....this is nothing.....just a little fitment.
Look at these: https://www.holley.com/products/gask...ets/parts/5917
Jebby
Last edited by Jebbysan; Oct 15, 2021 at 09:29 AM.
Jebby, I took your advice. And they're in. I'll say this about the Doug's, in spite of flange welding these headers were cake to install and fitment is real good. There's no spot where I can't get my hand around including the steering box, and the ground clearance is actually better than the stock y-pipe. Thank you, Marc.
Edit: they came with composite type oval hole gaskets
Last edited by Fly skids up!; Oct 15, 2021 at 12:58 PM.
Jebby, I took your advice. And they're in. I'll say this about the Doug's, in spite of flange welding these headers were cake to install and fitment is real good. There's no spot where I can't get my hand around including the steering box, and the ground clearance is actually better than the stock y-pipe. Thank you, Marc.
Edit: they came with composite type oval hole gaskets
Good work….beats the hell out of boxing them up, sending them back and waiting for something else…
Jebby
Last edited by Jebbysan; Oct 15, 2021 at 07:15 PM.
Collector is still well inside the engine bay. More like a mid-length header.
In all fairness, those are not the best choice of header bolts. Too big and six sided.
Highly recommend a 12 point small head, header bolts from ARP. Have built in washer, never rust and will never snap off in the head.
They come in stainless in packs of 12 from Summit.
So much easier to torque down with a box-end wrench.
Last edited by HeadsU.P.; Oct 16, 2021 at 09:48 AM.
What's with cyl number 3 tube? All ****-eyed. Collector is still well inside the engine bay. More like a mid-length header. In all fairness, those are not the best choice of header bolts. Too big and six sided.
I don't know the reason why the number 3 tube is **** like that but I'm guessing it was done for steering box clearance. None of the tubes come close to anything. The bolts are pretty good. They seem to be of a high grade. I had no trouble getting a socket or box end wench on any of the bolts. They are definitely a full length header.
Last edited by Fly skids up!; Oct 16, 2021 at 01:23 PM.
Just got the same headers you did. Mine werenT as buggered up, but The build up around the tubes looks like there gonna be a b1tch to seal. Also the boltholes so close to the port. That why I decide on Remflex gaskets. There about 1/4" think to start and compress around all the raised portions and squees down and fill the gaps. They worked for me before so I'l use them again untill they fail. What size tubes did you get> 1-5/8 or 1-3/4?
The definition of a Full Length Header means, all the primary tubes are of equal length. When the cylinder that is farthest away from the collector takes the shortest route that helps in equal length tubing. Unfortunately, the closest cylinders to the collector 5 and 7 (6 & 8) need more tubing length to be equal to the longer runs.
To do that, header manufacturers place the collector farther back, often well past the firewall and sometimes under the floorboard.
These headers pictured will work fine for street / strip but are not full length.
Last edited by HeadsU.P.; Oct 19, 2021 at 09:08 AM.
The definition of a Full Length Header means, all the primary tubes are of equal length.
These headers pictured will work fine for street / strip but are not full length.
They look equal to me, however I don't really care.
I received my Doug's D350 headers today. The port is out of shape. Although it will cover there's only 1/16 of a inch gasket coverage at the point where my finger is pointing to. Use them or send them back?
That looks like... 
Are these headers good to use?
