1966 gt350 header bolt question

[Karguy]

I recall sometime ago a discussion on the forum concerning the three types of header bolts that were seen on 66 models. I have looked and can't seem to find that discussion, maybe it's gone. I do recall one type has three spokes and a Small Center circle, another has the manufacturer's name on it and the third type has a round impression on the head of the bolt.  I think I may have lucked out and found 16 bolts That are the type with the round impression on the head. I have compared them to the aftermarket bolts that are available through a very reliable supplier. I have compared mine to the pictures of the ones available and they seem identical except the diameter of the impression seems slightly larger on the ones that I have found than the others. Here is a picture of one of mine, does it look like the correct, original type?  The impression on mine is exactly 5/16 of an inch in diameter.
Thanks as always for the help, Karl
6s281

[GT350Lad]

That's the type I have Karl and I was short 3 and bought a set of the circular round impression ones off Brant at VA. Very close. There is a full original set or the sundials ones on EBay for 1500$ but they aren't correct for our cars.
The knowlegable guys may correct me

Cheers

[Karguy]

Hey Trent,  you are one of the knowledgeable guys! I saw the set on eBay you're talking about and even made the guy a reasonable offer, he countered but we couldn't get close enough, glad now it never worked out. I thought I remember from the last discussion about these bolts on the forum that the 66s could've come with any of three types of bolts,  even a combination in some cases.  Anxious to hear what others have to say.
Cheers to you

[J_Speegle]

First a shot of well used but legible header bolt heads for comparison

[GT350Lad]

Hey Trent,  you are one of the knowledgeable guys! I saw the set on eBay you're talking about and even made the guy a reasonable offer, he countered but we couldn't get close enough, glad now it never worked out. I thought I remember from the last discussion about these bolts on the forum that the 66s could've come with any of three types of bolts,  even a combination in some cases.  Anxious to hear what others have to say.
Cheers to you

Thanks mate, I have learnt it all of guys like Jeff and Bob. I think your right and others had seen any combination of all 3.

cheers

[Karguy]

Thank you Jeff, you are an amazing resource. Looks like I have the right bolts for 281.

[Bob Gaines]

First a shot of well used legible header bolt heads for comparison

The Rockford marked bolt on the far right is the most common and on the vast majority of cars in 66 .  The middle is much earlier in production one.  You might see a combination of the middle one and first one but that is out of the ordinary. The one on the far left I have only seen on 65's. Just what I have seen over the years. Others may think differently.

[Karguy]

Thanks very much for the info Bob, always appreciated!
Karl

[427heaven]

First a shot of well used legible header bolt heads for comparison

The Rockford marked bolt on the far right is the most common and on the vast majority of cars in 66 .  The middle is much earlier in production one.  You might see a combination of the middle one and first one but that is out of the ordinary. The one on the far left I have only seen on 65's. Just what I have seen over the years. Others may think differently.

Your right BOB I have owned a set of bolts for the past 45 years off of car 6s 409, It had a combo of number 2 and 3 bolts. When I installed a Boss 302 in it in the 70s I removed these bolts and have set all this time.

[Steve McDonald Formally known as Mcdonas]

Car 1431 had a set of the ones on the left when I got in in 1971, the original owner said he never changed them.  I kept the original headers going until they died a noble death around 1980 when there was nothing left to fix. Still have about 12 of the bolts left

[Bob Gaines]

This is totally unrelated to post #9 which may be a anomaly but I thought I would mention something that can skew findings. The far left bolt is the one that has and is still reproduced by various people because it was easiest to recreate. You take most generic header bolt's and machine out the center. Those bolts have been around in reproduction for 30 years that I know of.

[Karguy]

 Bob, I certainly agree that it would be relatively easy for a good machinist to re-create the left side bolt in the picture, definitely the easy one of the three. The discussion brings me back to my original question which  had to do with the diameter of the recessed circle in the top of the bolt. I have attached a picture of the current aftermarket bolts as well as one of mine that I have located, the recessed area on the aftermarket bolts appears to be somewhat smaller.  Honestly, Maybe I'm just splitting hairs, I just keep striving to do the best I can on 281.
Thanks, Karl
281

[J_Speegle]

Since it appears that we're focusing on very early real 66 cars another data point I would offer is that 6S407 was reported have had used and have seen the middle style head design used on it

[Bob Gaines]

Bob, I certainly agree that it would be relatively easy for a good machinist to re-create the left side bolt in the picture, definitely the easy one of the three. The discussion brings me back to my original question which  had to do with the diameter of the recessed circle in the top of the bolt. I have attached a picture of the current aftermarket bolts as well as one of mine that I have located, the recessed area on the aftermarket bolts appears to be somewhat smaller.  Honestly, Maybe I'm just splitting hairs, I just keep striving to do the best I can on 281.
Thanks, Karl
281

If that is the case I would use the middle picture bolt posted in the picture of the three if it were my choice on 6S281 like Jeff reported on 6S407. But that is just me.

[J_Speegle]

Another example from the early real 66 production period 6S379

I don't know if all or just the ones in the pictures have this marking. Just offering some insight and data




6S598 Sports Car Graphic magazine  4-66



Ignore the arrow - from the pictures intended posting purpose - Just recyling it