What size are the exhaust collector gaskets?

[Z51JEFF]

How hard are the collector gaskets to come by? I'm still trying to get that Hurst shifter in my car and if I drop the exhaust I'll need to replace these.

[WVZR-1]

Jeff - on your '91 there's a 3-bolt gasket on the right GM # 10147973 and the left is a ball/socket if your exhaust is stock. I have no idea if an off the shelf three bolt gasket from anyone is a match for it. I can look in the AM and see if I have a flange and measure for you to compare. I'm not near them this evening.

*** I've never compared an early "heat-riser" gasket but it might be a try. I don't recall if it was 3 equally spaced bolts or 2 + 1. There was an F-body flange that didn't have equal spacing but was 3 bolt also.

*** I've measured and it's 3 equally spaced.

[Z51JEFF]

Originally Posted by WVZR-1

Jeff - on your '91 there's a 3-bolt gasket on the right GM # 10147973 and the left is a ball/socket if your exhaust is stock. I have no idea if an off the shelf three bolt gasket from anyone is a match for it. I can look in the AM and see if I have a flange and measure for you to compare. I'm not near them this evening.

I've never compared an early "heat-riser" gasket but it might be a try. I don't recall if it was 3 equally spaced bolts or 2 + 1. There was an F-body flange that didn't have equal spacing but was 3 bolt also.

Thanks Dave. Too me it just looks like a conventional flange gaskets on the right side and a donut style gasket on the left. It seems when the exhaust is dropped for any reason that the gaskets would need to be replaced.

[Dynomite]

Originally Posted by Z51JEFF

Thanks Dave. Too me it just looks like a conventional flange gaskets on the right side and a donut style gasket on the left. It seems when the exhaust is dropped for any reason that the gaskets would need to be replaced.

The removal of the ZR-1 exhaust systems did NOT need replacing of the flange gasket. The Removal of the three bolts on each side DID require HEAT in several instances after which I replaced the three bolts each side with SS Bolts.

See Item #6 C4 Beam Plates and Installation

6. Re-Installing the Exhaust.

The Exhaust System can be re-installed after the C-Beam Plates are torqued and the front Exhaust Hanger is re-installed in the location of the Front C-Beam Plates.

The Entire Exhaust System can be reinstalled by sliding the Exhaust System under the ZR-1 and setting a rolling hydraulic jack under the rear of the center Exhaust and lifting up to within about 8 inches of the final position.

A. Lift the two rear Tail Pipes and slip the slider into position on the slip joints. Slide the Entire Exhaust System to the rear of the ZR-1 about 1 inch completely engaging the slip joints holding the Tail Pipes.
B. Raise the front of the Exhaust System with the rolling Hydraulic Jack to the final height aligning with the Catalytic Converter Connections. Slide the Entire Exhaust System Forward and install 6 NEW SS 10mm x 1.5 bolts. (10mm x 1.5 x 30mm on Passenger Side and 10mm x 1.5 x 50mm on Drivers Side). The SS Bolts shown have 17mm Hex Heads and Washers are NOT required.

SS 10mm x 1.5 x 30mm and SS 10mm x 1.5 x 50mm Bolts



C. Reinstall the two Front 13mm Head Hanger Bolts and the two Rear 13mm Head Hanger Bolts.

[mike100]

I dont know if somebody fitted a triangular flange to my car previously, but it is a universal 3" collector gasket available anywhere. That said i have been able to reuse them a couple of times if they dont tear or seperate.

[WVZR-1]

Originally Posted by mike100

I dont know if somebody fitted a triangular flange to my car previously, but it is a universal 3" collector gasket available anywhere. That said i have been able to reuse them a couple of times if they dont tear or seperate.

I measured the coupling/adapter this AM and my verniers are on loan but the 3" header collector gasket should work. I measured 3 3/8 centers for bolts and that's comparative to some/most of the advertised dimensions. Some use bolt circle for dimensions so you need to be careful. The coupling/adapter itself is actually threaded so I believe if quality penetrant was used it should be nearly effortless. Heat would certainly help.

I'm not a fan of 'thread to head' hardware so I'd buy something other than those mentioned in this thread. The 'thread to head' provides no shoulder/pilot and then of course you sacrifice the 'common automotive hex dimension'.

I used this Sanderson gasket link for comparisons:

http://www.centuryperformance.com/sa...askets-pr.html

What I did notice with the coupling/adapter that I have is that a person would have thought when the pipe was expanded to the dimension required by the flange it would have been uniform and on mine that's not the case. It's quite uneven.

[Racinfan83]

I used a new old Hooker Headers collector gasket on mine. Fit perfect. Had it hanging on the garage wall forever and finally found a use for it...

[Dynomite]

Originally Posted by WVZR-1

I'm not a fan of 'thread to head' hardware so I'd buy something other than those mentioned in this thread. The 'thread to head' provides no shoulder/pilot and then of course you sacrifice the 'common automotive hex dimension.

The thread to head of the SS Bolts makes NO difference in this application especially since they are NOT torqued to death. Further, the 10mm Head fits in perfectly with every other Metric Dimension used on the LT5 engine.

Install 6 NEW SS 10mm x 1.5 bolts. (10mm x 1.5 x 30mm on Passenger Side and 10mm x 1.5 x 50mm on Drivers Side)[/B][/COLOR]. The SS Bolts shown have 17mm Hex Heads and Washers are NOT required.

SS 10mm x 1.5 x 30mm and SS 10mm x 1.5 x 50mm Bolts


It is a very nice Installation using SS Bolts for the Exhaust Flanges something I did not think of until I broke off a Stock Exhaust Flange Bolt that had been rusted into place.

Do NOT void the main reason (corrosion) of the suggested SS Solution for two otherwise non existant reasons involving The Hex Head (17mm) and Thread Length......... Just saying