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Mac 351w longtube headers hit floor board

6288 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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Almost sounds like you got one 351 header and one 302 header.
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...
I had a similar issue with BBK 1-7/8 long tubes. I had to fiddle with the motor mounts on the K member to make them work. Pain in the you know what... It was the passenger side that was the problem for me too.
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.
Send them back COD.
Believe me, I'm tempted... just after I chop them up into a bunch of little pieces.
I feel for you man. I hope you have better luck with those than I did mine. I ordered some direct from Jet-Hot to fit a 302 five speed, really expensive with the ceramic coated black. They did not fit well; Rubbed the passenger side on the K-member. Would not bolt up to Mac's Prochamber with a Tremec 3550 due to the different exhaust hanger I think. Regardless, terrible fit.

Jet-Hot didn't want anything to do with it since they didn't make them. Mac wanted me to send them back; they wouldn't send me a call tag, I had to pay to have them sent back to be checked on the jig. Then they sent them back and said they fit on the jig fine so it was not their problem. After their sub-par customer service, Mac will NEVER get any more of my money. They are just collecting dust now along with the matching Prochamber.

Good luck to you.
They are just collecting dust now along with the matching Prochamber.
Wanna sell them?
Wanna sell them?
Actually, yes. I'll have to dig up my receipt, paperwork and all.
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..
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.
Can you do me a favor and post a picture of the passenger side header? I would like to compare it to mine.
I'll get you a pic later today along with a height measurement from flange to collector.
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?
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.
Can you do me a favor and post a picture of the passenger side header? I would like to compare it to mine.
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.

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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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