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Mac 351w longtube headers hit floor board

6319 Views 32 Replies 7 Participants Last post by  408foureye
I mocked up my drivetrain and found the pass side collector hitting the floor board. Driver side looks fine. When I measure the collector height from the ground, the pass side sits up 1" higher, which is causing the floor board interference. The headers are 1 3/4 Mac longtubes on a 351w with convertible mounts. I also bolted up the headers with the engine block and heads on the stand - the collectors are still uneven by the same amount. Anyone else have this issue?
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That's what I was thinking. It's only been about 2 weeks since they were supposed to send me a call tag to return them for comparison with their assembly jig - lol. Just a little frustrating...
Update - it's been over 2 weeks since Mac promised to send me a call tag for my headers. Every time I talk to them, they say it will be taken care of the same day... wtf!
Send them back COD.
Believe me, I'm tempted... just after I chop them up into a bunch of little pieces.
is the motor level in the car ? the only other thing I can think of is would lower motor mounts give you the clearance you need ? might be easier than send the headers back... If I recall you can get 3/4 of a inch with drop mounts..
Everything sits level. The K-member is straight. If I bolt them up to the block sitting on the stand, they are just as uneven. I'm already running convertible mounts - don't want to use solid drop mounts.
They are just collecting dust now along with the matching Prochamber.

Good luck to you.
Can you do me a favor and post a picture of the passenger side header? I would like to compare it to mine.
Just got the email for my call tag. Hopefully it will be taken care of.
I'll get you a pic later today along with a height measurement from flange to collector.
Thank you!
My BBK 351w swap long tubes hit the floor by the firewall on the passenger side, but the driver side is fine. I wonder why it seems that most 351w swap long tubes do this?
It makes no sense to me why they would design them that way. If you look at the trans crossmember, the notch for the exhaust tubing is higher on the passenger side than on the other - maybe that has something to do with it. If so, the collectors still won't sit level and that's not a good thing for making a prefab h-pipe of any brand bolt up properly. Why can't this stuff just fit right to begin with? It's not like we're dealing with thousandths of an inch here. It's sad the mac longtubes are the only swap headers which will clear a t sump pan, otherwise I would have bought a set from hooker.
Here is the pic. I get about 12 1/4 inches drop from the flange to the top of the collector (meaning the 2 bolt flange). Hope this helps.

Hmmm... my pass side one looks totally different! What part number are those?

This is what mine looks like -


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TF 2016. Just a thought here, would it help if the collector flange was turned 90* and then reattached? I would figure the flange is what you're having the clearance problem with due to that being the highest point there. How much drop do you measure?
The flange isn't welded in place. It just slides over the collector piping. The collector itself hits the floor board.
You could always do a floorboard massage. I recall having to do a little beating.
I'd rather dent the collector than beat on the chassis. To me it's more of an issue having the collectors uneven, turning x-pipe fitment into a difficult hack job,
Did you get a drop measurement? Are yours 1 3/4? Mine are 1 5/8 which may make for different routing of the primaries than yours.
Didn't get a measurement yet. They are in the box on the way to mac.

Yes, 1 3/4 primaries. That would explain the difference. Thanks again for the research!
Update -

It's been over a month since I sent back the headers and I haven't heard anything from them. I emailed and left phone messages. Now I'm pi$$ed.

These guys are total flakes to deal with. I had to wait over 2 weeks just for a call tag. Now over a month after they received them, I'm $350 out of pocket and don't even have scrap metal to show for it. WTF... this sucks!

MAC will never get another dime of my business and I'll make sure other people will be sufficiently warned.
This is pretty much the same experience I had with them. I went to BBB and did a terrible review and they tried to defend themselves with the same BS they said to me in correspondence. Hope it works out better than mine did. Good luck.
That's sad to hear. At least they were talking to you.

If they don't end up making good on this, I will pay them a visit and also talk to the local police. I bought my headers directly from them and I'm in the warranty period, so they are fully obligated to make good on this.
So I finally got my headers back. Mac is telling me the headers fit perfectly on their assembly jig and they are designed to fit with the passenger side collector sitting higher up due to the taller pass side exhaust pipe notch at the crossmember.... wah wah wah...

I learned my lesson on this one. Never again would I buy another mac exhaust product. Their horrible customer service alone was enough to put me off. Buyer beware.
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