1960 exhaust manifold bolts, washers, french locks, etc

[Donald H.]

The TIM & JG says "The manifold bolts use tab locks on the front and rear bolts sets (not on center bolts) with thick washers under the locks."

Just to be clear, the washer goes between the french lock and the manifold and not between the bolt head and the french lock. Is this correct?

Also, I bought french locks, bolts, and washers from Paragon. The washers are stainless steel. Is stainless correct or should I just go buy some standard zinc plated grade 5 washers?

Thanks,

Don

[William C.]

Re: 1960 exhaust manifold bolts, washers, french locks, etc

Not stainless washers, actually plain steel as the temp is too high under normal use for Zinc. Yes on the location of the french locks, right under the bolt so an ear can easily be closed on one of the bolt head flats.

[Mike E.]

Re: 1960 exhaust manifold bolts, washers, french locks, etc

French locks weren't stainless, either.

[Gary B.]

Re: 1960 exhaust manifold bolts, washers, french locks, etc

Don,

According to my research here's what I believe about the washers.

For ‘55-‘63 Corvette I believe the washer was GM # 3754153, which is described in Noland Adams’ book on page 394 (albeit for a different Corvette application). The specs for that washer given in Noland’s book are: OD = 0.734” +/- 0.02”; ID = 0.401” +/- 0.005”; thickness = 0.1345 +/- 0.01”. The finish is listed as cad or zinc.

When I removed the manifolds on my '66 I found that the order of placement of the washers on the bolts was not always consistent from what is described in the '66 AIM. The first image below shows the order I found for two bolts. I know of several other people who say they've found the same order as seen in my photo.

For those with cars later than '63, the washers were different than what is shown in Noland's boot. For '64 and later the washer had a smaller OD and was not plated zinc or cad. See my second photo that compares the service replacement 3754153 with an original washer from my '66. Also, I don't believe the '64 and later production washer was ever available as a service replacement part, although I have found some non-GM washers that appear to me to be identical to the '64 and later GM production washer (3rd photo). Note that in photo #3, the washer on the right appears to be bright plated, but that was caused by the camera flash. For C1 or C2, stainless is not correct. And for '64 and later, zinc or cad plated is not correct.

Gary

Original-66_Exhaust_Order_Lo-Res.jpg

Service vs Orginal.jpg

Original vs. NOS washer.jpg