Exhaust nuts

A question on exhaust nuts/collars. Old Britts shows a large fin for the 850 which has a shorter thread than the small fin longer one for 750. I have a 71 750 with the stock small fin nuts and when tightened up there are still about a 1/4 inch of thread showing. Will the later large fin 850 collars tighten up enough to seal the joint?

Probably be too short and bind on the head before you got the pipe tight, the seal is inside anyway and not where the nut goes into the head. The 850 nuts engage too little of the thread length wise and wear it out quicker if they loosen off.

MikeG said:

A question on exhaust nuts/collars. Old Britts shows a large fin for the 850 which has a shorter thread than the small fin longer one for 750. I have a 71 750 with the stock small fin nuts and when tightened up there are still about a 1/4 inch of thread showing. Will the later large fin 850 collars tighten up enough to seal the joint?

Click to expand...

No, not with the OEM crush washers. If you double up on the crush washers or use the preferred steel Suzuki crush washers, then yes but barely. Fortunately there is another option now, as there are "long" thread 850 style nuts available. I got mine from eBay.

I bought some large fin long collars in bronze from Mick Hemmings - best of both worlds.



I'd be very apprehensive using short threaded collars except on balance-pipe headers where there's no option.

All ports are 3/4" deep.
What kind of pipes (flange thickness? ) do you have.
There are 3 different nuts ....pix here:

are-there-exhaust-nut-thread-size-variances-t23564.html?hilit=exhaust%20nuts#p309830

dynodave said:

All ports are 3/4" deep.
What kind of pipes (flange thickness? ) do you have.
There are 3 different nuts ....pix here:

are-there-exhaust-nut-thread-size-variances-t23564.html?hilit=exhaust%20nuts#p309830

Click to expand...

I have the one on the left, small fins. Not sure on pipe flange thickness...Gate City purchase so probabl;y a "universal" type thing.
Thanks

Rather than a crush washer, the later models use a reusable conical sealing washer. Although the threaded portion is somewhat shorter, they still leave about 1/8" of thread unused. Never had any stripped port threads, but I hear a lot of people do.

Danno said:

Rather than a crush washer, the later models use a reusable conical sealing washer. Although the threaded portion is somewhat shorter, they still leave about 1/8" of thread unused. Never had any stripped port threads, but I hear a lot of people do.

Click to expand...

????reusable conical sealing washer is for:
1. 1975 mkIII balanced exhaust (one year only style) pipes have flare at cone...
and
2. Aftermarket pipes with a "flare" for earlier commando or unbalanced 850

No telling from here what you bought from Gate city. Hopefully you can detect the difference between collets, flare and reusable conical sealing washer from a flat flange (plus crush washer)
I don't see a logical use for reusable conical sealing washer on 68-73 750 flat flanged or 73, 74 collet type balance pipes.
Kind of need to know what kind of pipes style and thickness to know if long or short threads are better

I'm using them on a pair of aftermarket SS pipes and they work just fine. I also used them on a BUB 2-into-one header and no issues there either. I see no reason why they can't be used with any other pipes, even those without a conical flare. If the cone fits into the pipe and the nut holds it in, what's the big deal?