Author Topic: MAC 4-1 Exhaust fitment issues (Read 5088 times)

Jinsonphoto · « **on:** March 24, 2015, 09:07:03 PM »

So I just finally got my Mac 4-1 in from DCC. Now my engine is a 73 & I ordered the early years model exhaust. Anyways it doesn't fit. The end above the flange is too long? Am I doing something wrong? Surly I do not have to cut these to make them fit. I have attached pictures to show what I mean.

Any help would be greatly appreciated!!

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Stev-o · « **Reply #1 on:** March 24, 2015, 09:18:03 PM »

What doesn't fit? Didn't it come with bolts? You won't use the spigots. Have new gaskets?

Jinsonphoto · « **Reply #2 on:** March 24, 2015, 10:38:17 PM »

Stev-o the problem seems to be that the ends past the mounting point are too long. Look at the first picture (the side by side). Do you see the difference?

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Stev-o · « **Reply #3 on:** March 25, 2015, 04:30:10 AM »

I see the difference but don't see why that is an issue? I had a Kerker that was similar.
Did you get bolts?

ekpent · « **Reply #4 on:** March 25, 2015, 04:45:37 AM »

The ends are longer on the MAC and the collar mounter higher than the stock spigots so the bolts will draw the header down to the head for a tight fit. When mounted the collars will have a stand off gap. Don't forget to replace the crush washers (4).

70CB750 · « **Reply #5 on:** March 25, 2015, 05:12:04 AM »

Ha! I had the same problem with it.

The flanges are never suppose to touch the head, it's the way tehy are designed.

Jinsonphoto · « **Reply #6 on:** March 25, 2015, 05:16:17 AM »

Really? I figured they were supposed mount flush because I had Phillips screws not bolts on the last exhaust. There are no way this Phillips are going to work if it will not mount flush. I guess I will have to get new bolts? Also I didn't see the crush washers?

My bike was far from stock when I got it plus had an aftermarket exhaust so who knows what all the previous owner changed.

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Jinsonphoto · « **Reply #7 on:** March 25, 2015, 05:22:34 AM »

Hey 70CB750 what did you do to fix it? Longer bolts?

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70CB750 · « **Reply #8 on:** March 25, 2015, 05:24:04 AM »

I was in the same boat, I had spigots under phillips (actually JIS) bolts originally.

Your best bet is to use studs, it is safer for the head than bolts since the action is steel on steel not steel in Aluminum.

Crush gaskets are hollow copper pieces, like these on ebyea:

http://www.ebay.com/itm/HONDA-69-78-CB750-SOHC-EXHAUST-GASKETS-/191542644006?hash=item2c98d4cd26&vxp=mtr

Stev-o · « **Reply #9 on:** March 25, 2015, 05:25:57 AM »

Quote from: Jinsonphoto on March 25, 2015, 05:16:17 AM

Really? I guess I will have to get new bolts?

Hello?! Why do you think I asked twice about if you have bolts?!

Eydugstr · « **Reply #10 on:** March 25, 2015, 05:33:32 AM »

Quote from: 70CB750 on March 25, 2015, 05:24:04 AM

I was in the same boat, I had spigots under phillips (actually JIS) bolts originally.

Your best bet is to use studs, it is safer for the head than bolts since the action is steel on steel not steel in Aluminum.

Crush gaskets are hollow copper pieces, like these on ebyea:

http://www.ebay.com/itm/HONDA-69-78-CB750-SOHC-EXHAUST-GASKETS-/191542644006?hash=item2c98d4cd26&vxp=mtr

+1.

Jinsonphoto · « **Reply #11 on:** March 25, 2015, 07:03:52 AM »

You guys have to pardon my ignorance in learning as I go.. what is the difference between studs and bolts? Where can I get the studs?

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ekpent · « **Reply #12 on:** March 25, 2015, 07:28:01 AM »

A stud goes on the head mount hole first and then the header flange is is held on and tightened by a nut.

70CB750 · « **Reply #13 on:** March 25, 2015, 07:30:59 AM »

Stud is a bolt with no head, for this application it has thread on both ends:

http://www.autozone.com/gaskets-and-miscellaneous-fasteners/double-ended-stud

I know it is M8, the length not sure, 50mm maybe?

There are special tools to drive the stud in, but I always use two nuts technique. You tighten two nuts against each other and than use it as a bolt head to drive the stud in.

70CB750 · « **Reply #14 on:** March 25, 2015, 07:34:01 AM »

Also:

You can find studs in Pep Boys, Autozone or special bolt places like McMasterCarr or Bolt Depot.

I have a local HW store that has them and more.

DaveBarbier · « **Reply #15 on:** March 25, 2015, 08:38:00 AM »

Just want to add that you might have crush gaskets in the motor already. I'd look with a flashlight. Sometimes they stick and don't come out easily. I bent a strong pick trying to get the old ones out. Throw them away and get new ones. I've also heard of people using more than one.

---
1978 Honda CB550K

jamesbekman · « **Reply #16 on:** March 25, 2015, 09:32:40 AM »

This thread is scaring me... You need studs and only studs....

jamesbekman · « **Reply #17 on:** March 25, 2015, 09:35:22 AM »

If you dont know the difference, for your safety I suggest working with a friend who can teach you these things or else pay someone to do the work for you as your life is at risk.

flybox1 · « **Reply #18 on:** March 25, 2015, 09:43:33 AM »

+100 for studs! (especially if you have to remove the headers to change oil filter)
soo much easier to work with. you'll not run any risk in stripping out threads in the head.
A set of 8 studs will run you about $10.

http://www.partsnmore.com/parts/honda/cb750/?filters[category]=hardware&filters[page]=2

Exhaust Stud Pk/10
#49-0010
Exhaust Stud Pk/10 High Tensile Plated Size: 8mm x 56mm Threaded Ends: 15mm & 18mm

This stud stays in the head. You only need eight M8 nuts to draw the headers down snug.
Just remove the nuts if you need to pull the headers off. Studs stay in place.

Jinsonphoto · « **Reply #19 on:** March 25, 2015, 11:13:28 AM »

Okay I'm going to try and find the studs locally. At either the parts store or the hardware store. However 70CB750 can you explain why the studs are better? Not sure I understand the steel on steel not steel in aluminum reference.

Btw would M8 all-thread cut to size work?

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flybox1 · « **Reply #20 on:** March 25, 2015, 11:17:10 AM »

I just explained its benefit above...

A bolt, in and out of the head, will eventually ruin, or worse, strip out threads from over-tightening.
a stud stays in.

flybox1 · « **Reply #21 on:** March 25, 2015, 11:18:54 AM »

and yes, M8 threaded rod, cut to size, 60mm or so, would work fine.
Just use some anti-sieze on it.

70CB750 · « **Reply #22 on:** March 25, 2015, 11:37:27 AM »

I would dare to say that stud is made from better steel than threaded rod and that's why I would use a stud.

Besides, threaded metric rods are not easy to find in USA.

What flybox says, the head is aluminum and you could cross thread or just plan wear out the thread in it. It's just a cheap insurance for longetivity, nothing more. Bolts will work too, some people use stainless steel or just steel allen head bolts.

Before you ask

, this is allen head bolt:

evanphi · « **Reply #23 on:** March 25, 2015, 11:44:13 AM »

I personally use Stainless M8x35mm allen head bolts on my MAC header. Been thinking lately about switching to studs, though.

Jinsonphoto · « **Reply #24 on:** March 25, 2015, 01:19:45 PM »

Okay sorry guys I didn't see the 3 previous response before my last reply. Thanks for all your help guys!

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Author Topic: MAC 4-1 Exhaust fitment issues (Read 5088 times)