Correct letter marking on valve cover bolt-head for 72 LT1

[Fred H.]

Getting close to completing the restoration of my numbers matching 72 LT1 (convertible with factor air). Does anyone know the significance of the letter marking on the head of the valve cover bolts? I've been informed that the correct marking for my vehicle should have an R on the head of the valve cover bolts.

[Edward J.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Fred, There likely a few different head markings, RBW might be very popular for valve covers both Tin and aluminum.

[Guy F.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Does anyone know the significance of the letter marking on the head of the valve cover bolts? I've been informed that the correct marking for my vehicle should have an R on the head of the valve cover bolts.

Fred,

I do not know the significance of the letter marking on the head of the valve cover bolts.

Here are 2 pics of a bolt used to secure an aluminum valve cover with the R marking on the head. Pics are from a 1975 car.

Thank you,

[Terry M.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

The mark on the bolt head signifies the manufacturer of the fastener. Each manufacturer has their own logo. In cases where the number of fasteners ordered was in the millions, as in this case, several manufacturers might supply the fastener. Here we are talking about 8 fasteners per engine, and the number of engines made per anum in in the hundreds of thousands per engine plant. Remember the engine plant supplied engines for passenger cars and trucks. Then there were several engine plants. In some cases the fastener had several applications, in this case perhaps oil pan fasteners. Adding all this up you can easily understand that the orders for this fastener might easily exceed a million and multiple sources might bid on the contract.

[Mike E.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Aluminum valve cover bolts in the 70-72 time frame were obviously different in length from stamped steel valve covers, which makes them less plentiful, different size from any other engine bolt in that era, and in my many years of looking, with a more limited range of manufacturers. Every original I have seen has an untrimmed (dished) head, and a whole lot of those with an M logo. Yet on the same car, a one-owner low-mile 70 350/350 which had all M bolts, there was a variation in the style of M on two of them. Same manufacturer, different machine. As others have said, there is no way you (or a judge) can limit them to one manufacturer and one logo.

[Terry M.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Aluminum valve cover bolts in the 70-72 time frame were obviously different in length from stamped steel valve covers, which makes them less plentiful, different size from any other engine bolt in that era, and in my many years of looking, with a more limited range of manufacturers. Every original I have seen has an untrimmed (dished) head, and a whole lot of those with an M logo. Yet on the same car, a one-owner low-mile 70 350/350 which had all M bolts, there was a variation in the style of M on two of them. Same manufacturer, different machine. As others have said, there is no way you (or a judge) can limit them to one manufacturer and one logo.

Even if these are unique size, and limited to 8 fasteners per engine for only aluminum rocker covers -- if you say so Mike, I'll believe you since you are closer to the foot of the cross than I am , aluminum covers were used for quite a number of years, so there likely was multiple fastener orders over a broad stretch of years. I still argue for at minimum several different manufacturers.

[Mike E.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Even if these are unique size, and limited to 8 fasteners per engine for only aluminum rocker covers -- if you say so Mike, I'll believe you since you are closer to the foot of the cross than I am , aluminum covers were used for quite a number of years, so there likely was multiple fastener orders over a broad stretch of years. I still argue for at minimum several different manufacturers.

I will agree 100%.

[Ron G.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

On 70 and 71 I see that the majority are M and on some 71's and most 72's I have seen R.

[Guy F.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Fred,

I do not know the significance of the letter marking on the head of the valve cover bolts.

Fred, I should have been more precise with my answer to you. My apologies. Let me rephrase my previous statement:

"I do not know the significance of the R marking on the head of the aluminum valve cover bolts."

I do understand the concept of various bolts having various markings on them, such as letters, numbers, symbols, logos, and so on, each representing a particular manufacturer. As you know these types of markings are not limiterd to bolts, they appear a a wide variety of other components supplied to GM that are used to build the car.

Thank you

[Fred H.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

LT1 valve cover bolt.jpgHi Terry, attached photo of one of my LT1 valve cover bolts. I really appreciate your input.

[Fred H.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Hi Mike, I greatly appreciate you input. On my 72 LT1 the valve cover bolts have the letter M. I originally inquired to the discussion board because someone looking at my car thought they should have an R to be considered OEM original?LT1 valve cover bolt.jpg

[Fred H.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Hi Guy, thanks for the clarification

[Ron G.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Just an FYI. M = Midland Screw Company or could be Michigan Screw Products. R = Russell Bolt Manufacturing. There could be others, but I have a list of hardware suppliers to GM of the era. I would be happy to hare it with you. - Ron

[Fred H.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

Ron, I would appreciate the hardware suppliers information, when you have time. Fred

[Jack C.]

Re: Correct letter marking on valve cover bolt-head for 72 LT1

My late 72 LT-1 built on the last day of production (July 19, 1972 has the R on the valve cover bolts. I believe yours is a late car as well.