Original 63 hood hinge bolts

[David L.]

The 1963 Corvette used 3 GM # 3795488 and 2 GM # 3816170 bolts on each hood hinge as per the AIM.

The 1964-1967 Corvettes used 3 GM # 3846201 and 2 GM # 3847758 bolts for each hinge as per the AIM's.

Based on my research the 3846201 bolts (5/16"-18 X 5/8", blunt end) and the 3847758 bolts (5/16"-18 X 7/8", pointed end) used on 1964-1967 Corvettes were marked with the letter "E" with line segments at the 3, 6, and 9 o'clock positions along with a non-removable 3/4" O.D. washer.

Were the original 1963 hood hinge bolts the same except that the 3/4" O.D. washers had a serrated edge as shown in my photo below? If not, how did the 1963 bolts differ?

[Rich P.]

Re: Original 63 hood hinge bolts

Dave your right. 63-64ish used the serrated washers (for the most part)

Rich

[Scott S.]

Re: Original 63 hood hinge bolts

The 1963 Corvette used 3 GM # 3795488 and 2 GM # 3816170 bolts on each hood hinge as per the AIM.

The 1964-1967 Corvettes used 3 GM # 3846201 and 2 GM # 3847758 bolts for each hinge as per the AIM's.

Based on my research the 3846201 bolts (5/16"-18 X 5/8") and the 3847758 bolts (5/16"-18 X 7/8") used on 1964-1967 Corvettes were marked with the letter "E" with line segments at the 3, 6, and 9 o'clock positions along with a non-removable 3/4" O.D. washer and a pointed end.

Dave,

I have seen the 3847758 bolt referenced in the archives as being 5/16-18 x 7/8", but the examples on my car have been 5/16-18 x 1-1/16". They are black phos, indented hex with attached 3/4" conical flat washer, grade 5, all have the "E" headmark with a pinch-point tip.

This bolt is called out in the following pages of the 1967 AIM:

1Boltweld-A12 (Item 10)
The front clip is off, so I can see both of these (the two upper), Gr5 with "E" headmark, but have not removed them for measurement.

1ASM-D2 (Item 4)
This one is an anomaly. The AIM shows GM 3846202 Bolt (Item 6) being used in two places, and GM 3847758 bolt used in one place. The GM 3846202 bolt is 5/16-18 x 7/8", size confirmed by the 1970 Standard Parts Catalog (non-packaged Standard Stock, Gr. 8.900 Hexagon Head Bolts, p. 13) and the 1968 Illustrated Parts Book (see "1967-68 Corvette Steering Column and Support (Typical)" [Item 12 on the Illustrated Parts Book page, confirmed size match on my car, three "E" headmark and one "C" with 3 long lines, corresponds to 1967 AIM UPC 9-A4, Item 1, 3846202].

In the one position where they should have used the 3847758 under the dash [1ASM-D2, item 4], they used the 3846202 instead, which was called out for the other under-dash brace rods [see 1ASM-D2, item 6, two places].

The 3847758 bolt is shown on the same Illustrated Parts Book page referenced above [item 9 in the IPB and also Item 9 on 1ASM-D2 in the '67 AIM), on the engine bay side of the firewall, securing the steering column support assembly to the firewall. It is described in the Illustrated Parts Book as "9. 8.900 BOLT (5/16-18 x 1-1/16)"

1ASM-F6 (Item 5)
Convertible only

1Doors-K6 (Item 5)
Door hinge bolts, all eight of mine measure 5/16-18 x 1-1/16", grade 5, "E" headmark

9-A4 (Item 9, same drawing as shown in the 1968 Illustrated Parts Book referenced above)
Both of my originals measure 5/16-18 x 1-1/16", grade 5, "E" headmark

11-13-A2 and 11-13-A3 (Item 4)
Small splash shield bolts, all eight of mine measure 5/16-18 x 1-1/16", grade 5, "E" headmark

11-13-B6 (Item 7)
Hood hinge-to-Body bolts. All four measure 5/16-18 x 1-1/16", grade 5, "E" headmark

[David L.]

Re: Original 63 hood hinge bolts

Scott,

Many years ago I went through my 1966 AIM and listed every bolt, nut, and washer to see where fasteners were used in other places. The 3847758 bolt (5/16"-18 X 7/8") is used on pages F74, F94, F210, F220, F221, and F229.

The 3846201 bolt (5/16"-18 X 5/8") was only used on pages F229 (UPC 11-13, sheet B6 - hood catch & hinge) and F434 (UPC U69, sheet A2 - radio). I have in my notes that the 3846201 bolt is 5/16"-18 X 5/8" "cup" head w/3/4" washer and blunt end, not pointed (photo below).

The 4 "E" bolts (5/16"-18 X 5/8", w/blunt end) in my photo below were removed from the hood latch on a 1966 Chevrolet. The 1966 Chev. AIM lists the 4 bolts as GM # 3846202 which are supposed to be 5/16"-18" X 7/8". I believe when the production workers ran out of bolts they made substitutions as necessary to keep things going.

Dave

[David L.]

Re: Original 63 hood hinge bolts

Scott,

It seems odd the Paragon Corvette sells repro 3847758 bolts as 5/16"-18 X 7/8" and AMK Products lists the 3847758 bolt as 5/16"-18 X 1 1/8".

Dave

[Scott S.]

Re: Original 63 hood hinge bolts

Scott,

Many years ago I went through my 1966 AIM and listed every bolt, nut, and washer to see where fasteners were used in other places. The 3847758 bolt (5/16"-18 X 7/8") is used on pages F74, F94, F210, F220, F221, and F229.

Here is the comparison between 1966 and 1967 AIMs:
1966 AIM F74 = 1ASM-D2 (same as 67 AIM, a.k.a. G80)
1966 AIM F94 = 1ASM-F6 (same as 67 AIM, a.k.a. G100)
1966 AIM F210 = 9-A4 (same as 67 AIM, G216)
1966 AIM F220 = 11-13-A2 (same as 67 AIM, G224)
1966 AIM F221 = 11-13-A3 (same as 67 AIM, G225)
1966 AIM F229 = 11-13-B6 (shown in 67 AIM on 11-13-B5 & B6, G233 & G235)

The 3846201 bolt (5/16"-18 X 5/8") was only used on pages F229 (UPC 11-13, sheet B6 - hood catch & hinge) and F434 (UPC U69, sheet A2 - radio). I have in my notes that the 3846201 bolt is 5/16"-18 X 5/8" "cup" head w/3/4" washer and blunt end, not pointed (photo below).

Dave

I have the same measurement for the 3846201:

GM 3846201
5/16-18 x 5/8", indented hex with attached 3/4" conical flat washer, Gr5, RBW, black phosphate. FLAT tip. The size is listed in the 1963, 1965 and 1973 Radio Parts Catalogs. This bolt is used in 1967 to secure the radio, hood hinges as in 1966, and underneath the parking brake cover assembly (x4). My hood hinge-to-hood bolts were replaced with generic bolts circa 1971. The bolts under the parking brake cover (between the seats) and the bolt used to secure the radio matched the characteristics above. I located a used set of five (I'm still missing one) original hood hinge-to-hood bolts that came from a 1966 Corvette, and they are identical Grade 5 indented hex "RBW" with attached 3/4" conical flat washer and flat tips.


GM 3846202
5/16-18 x 7/8", indented hex with attached 3/4" conical flat washer, Gr5, "E" headmark, black phosphate. Pinch point tip. The size is listed in the 1970 Standard Parts Catalog and the 1968 Illustrated Parts Book (referenced above).

Do these measurements and characteristics above match the bolt you have listed as 3847758?


GM 3847758
5/16-18 x 1-1/16", indented hex with attached 3/4" conical flat washer, Gr5, "E" headmark, black phosphate. Pinch point tip. The size is listed in the 1968 Illustrated Parts Book, on the 1967-68 steering column page (referenced above).

All three are 1/2" across-the-flats

If your notes show the 3847758 as 7/8" length, then could GM have changed the length to 1-1/16" beginning in 1967, without changing the part number? That seems unlikely, but it is also unlikely that all of the bolts on my car that should have been a 7/8" long bolt were all replaced with 1-1/16" bolts, otherwise identical.

The earliest official GM reference I can find for the 3847758 is the 1968 Illustrated Parts Book (printed October 1967). It may be listed in earlier Illustrated Parts Books which I do not have, but I have not found 3847758 listed in the stand-alone 1970 Standard Parts Catalog or any of the 1960s P&As.

[Scott S.]

Re: Original 63 hood hinge bolts

Scott,

It seems odd the Paragon Corvette sells repro 3847758 bolts as 5/16"-18 X 7/8" and AMK Products lists the 3847758 bolt as 5/16"-18 X 1 1/8".

Dave

The plot sickens

[John H.]

Re: Original 63 hood hinge bolts

Scott -

I'll offer this - that style of bolt (phosphated indented 1/2" hex head, captured free-spinning conical washer, 5/16"-18 thread) were used all over the car in different lengths, with both pinch-pointed and flat ends, some with as little as 1/16" length difference. They were mis-used by the thousands, by both regular operators and repairmen, as almost all of them worked just fine for any application, regardless of length (inspectors could only see the head end, not the tip), and NOBODY paid any attention whatsoever to headmarks; they were bin-stocked by part number, not headmarks, and each part number had at least three suppliers in those days.

You're likely to find almost any length of that style of bolt almost anywhere occasionally on an original car.

[David L.]

Re: Original 63 hood hinge bolts

John,

What is the "official" name of the similar 63 hood hinge bolts with the washers with serrated edges?

Scott,

My 1966 and 1967 Illustration Parts Catalogs show 5/16"-18 X 5/8" and 5/16"-18 X 7/8" bolts for the hood hinges.

Dave

[Joe R.]

Re: Original 63 hood hinge bolts

Here's a pic of several bolts that are used on 63-67 model years. Yes, the bolts are not plated correctly as they have had a bath in the cad tank but from left to right the bolts were found on 63-67 model Corvettes.
The extreme left has what we will call the Central Foundry bolts and these two were found on a 14,XXX 63. These are the shorter version of the Central Foundry bolts and were found on the hood side of the hood hinge. The longer version were found on the fender side of the hood hinge. Why, because you needed the longer bolts for the shimming. If you used the longer bolts hood side of the hinge on the 63's and 64's you had a hole on the edge of the indented hood. Later in 63 came the "E" bolts and you will notice they had serated edges on the washer. These lasted until sometime in 65 when the RBW bolts made the scene. RBW bolts are found on most of the 65, 66 and 67 hood hinges and hood latches.
As John H. says these bolts were from several manufacturers and there was nothing special as they were used throughout the Corvettes body structure. I'm sure a mixture of these bolts found their way to many uses and mixtures as the supply from one manufacturer ran out and was replaced by another. The last bolt on the right is an "E" without the serated washer and is available from several sources today.
Enjoy the pic.

JR

[John H.]

Re: Original 63 hood hinge bolts

John,

What is the "official" name of the similar 63 hood hinge bolts with the washers with serrated edges?

Dave -

Just insert the word "serrated" between "free-spinning" and "conical"; that's how we described them back in the day. The "roll-point" bolt I developed came a little later (1969).

[Scott S.]

Re: Original 63 hood hinge bolts

John,

What is the "official" name of the similar 63 hood hinge bolts with the washers with serrated edges?

Scott,

My 1966 and 1967 Illustration Parts Catalogs show 5/16"-18 X 5/8" and 5/16"-18 X 7/8" bolts for the hood hinges.

Dave

Dave,

My late 1967 printing of the 1968 Illustrated Parts Book shows the same as your photo, however, if you zoom out, the Hood being pictured is from 1963 (with hood-grille ornaments) and the caption Title at the bottom of the page (on mine) says "1963-1966 Corvette Hood and Latch Details".

It seems to have been common practice to use early model year drawings whenever possible, and when a range of years is given, the drawing is invariably from the first year of the given range (sometimes earlier!). While GM sometimes updated the part numbers, it seems that they rarely updated the drawings or the dimensions if they were in the graphics area, as opposed to a parts listing at the bottom of the page.

The bolts referenced for the hood hinges in the picture you posted are listed this way in the 1963 AIM:

1963 AIM, Section 11-13-11
Item 22, GM 3816170 (hood hinge to Body bolts)
Item 26, GM 3795488 (hood hinge to Hood bolts)

I am fairly confident it is these two bolt part numbers for which the dimensions are given in the Illustrated Parts Book photo you posted. I can find no data on the dimensions for GM 3816170, but I suspect very much that it is 5/16-18 x 7/8", as the drawing shows, for the 1963 model year.

GM 3795488 is listed in the 1963 drawing of the Corvette dash board in the Radio Parts Catalog (same drawing is used for midyears through at least the 1973 Radio Parts Catalog). It is shown as being 5/16-18 x 5/8", same dimensions as the (soon to come) GM 3846201 used at the same location from 1964-67.


It is not until 1964 that the AIM first shows the GM 3847758 and GM 3846201 bolts at the hood hinge (and remained the same through 1967), a part number change that was made after the earlier drawing had become "the established record" in the IPB:

1964 AIM, Section 11-13-B7
Item 22, GM 3847758 (hood hinge to Body bolts)
Item 26, GM 3846201 (hood hinge to Hood bolts)

There is no revision record of the change in the 1964 AIM on the hood hinge page, but there is a revision record for a change FROM GM 3816170 TO GM 3847758 at the Door Hinge location (1964 AIM, 1Doors-6), indicating GM did make this Bolt substitution in at least two areas. I suspect they needed a little longer bolt, since the other bolt dimensions remained the same.

As before, I don't think the graphics in the Illustrated Parts Books were updated, once a picture was drawn. For example, the Corvette C60 section of the IPB still shows the 1963-only diverter duct on the 1964-1967 drawing.

Posted below is the "1967-68 Corvette Steering Column and Support (Typical")" page from the October '67 printing of the IPB. With the October 1967 printing, and the drawing being specific to the 1967 model year (new collapsible steering column), it is the most recent depiction of the 3847758 bolt in GM documents that I have found so far. The bolt in this drawing (attached below, Item 9, red arrows) corresponds exactly to Item 9 in the 1967 AIM, UPC 9-A4. It looks as though this drawing in the IPB was taken from the 1967 AIM, or vice-versa.

The second picture is UPC 9-A4 form the 1967 AIM, showing the comparison to the IPB page.

That's all I got!

[Philip C.]

Re: Original 63 hood hinge bolts

Scott -

I'll offer this - that style of bolt (phosphated indented 1/2" hex head, captured free-spinning conical washer, 5/16"-18 thread) were used all over the car in different lengths, with both pinch-pointed and flat ends, some with as little as 1/16" length difference. They were mis-used by the thousands, by both regular operators and repairmen, as almost all of them worked just fine for any application, regardless of length (inspectors could only see the head end, not the tip), and NOBODY paid any attention whatsoever to headmarks; they were bin-stocked by part number, not headmarks, and each part number had at least three suppliers in those days.

You're likely to find almost any length of that style of bolt almost anywhere occasionally on an original car.

JOHN AMEN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1 Phil 8063

[Timothy B.]

Re: Original 63 hood hinge bolts

I think the 1963 hood hinge to hood bolt 3795488 is approx 5/8" long (flat tip) with the serrated washer. I can post a picture of this bolt but it's just like the 64-67 bolt with exception of the serrated washer and head marking.

The 3816170 hood hinge to body is 7/8" pointed tip and longer for the shims just like JR states. This bolt is also used for the splash shield according to the AIM.

The other pointed tip bolt 3789670 approx 3/4" long is used for hood catch to firewall as well as some dash attachments parts and other places in the AIM. I have identified all three on my 63 so I know they are used .

[Larry M.]

Re: Original 63 hood hinge bolts

I'm re-opening this 2011 post to request some help. Above, Scott Smith points out that the 3847758 bolt is item 10 of 1boltweldA.12 for 1967. It is the same for 1964 which is the AIM I have. He said he could see the head because he had the front clip off. If I remove either the kick panel or the air vent grill can I get to these bolts to remove/replace them.

I would rob them for lower hood hinge bolts. On my car the door hinge and steering column to firewall are serrated so I'm guessing that these are also. If I could get them it would be great.