54-56 intake manifold hex bolts needed

Started by 64\/54Cadillacking, September 08, 2022, 06:18:22 AM

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64\/54Cadillacking

I was hoping if someone had spare intake manifold bolts for this particular intake?

I just need 2 original 1/2 inch hex bolts that mount on the outer edges of the manifold.

So was able to acquire 6 of them after purchasing an original intake online that came with most of the original bolts, I've been using aftermarket bolts that aren't the correct size and need just 2 more that are in good shape to complete the job so the intake is mounted and torqued down correctly.

If nobody has any extras you would like to sell, can I buy the correct aftermarket bolts that will fit perfectly at say a Napa or online somewhere?

Thanks! 
1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Lexi

I am almost certain that I have those. Just to be sure what length are they (as measured from under the head to the end of the fastener)? Will have a look. What about washers? Think they were special as well. Like thick donuts. Clay/Lexi

64\/54Cadillacking

Quote from: Lexi on September 08, 2022, 09:42:09 AMI am almost certain that I have those. Just to be sure what length are they (as measured from under the head to the end of the fastener)? Will have a look. What about washers? Think they were special as well. Like thick donuts. Clay/Lexi


Hi Clay, I believe they're a 3/8 16 hex bolt. Here are some pics of the bolt.






1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Lexi

Although it is like pushing near 70 years later, (who knows what alterations have been made to our cars in the past), the bolt in your picture is different than the ones on my '56 intake. Yours looks like it has a built in "washer", (a hex flange bolt), and looks more like my exhaust manifold bolts. The intake manifold bolts on my car are not hex flange, but rely on a rather thick donut like washer to spread the force when torqued. I suppose that is what negated the need for that flange on the '56 bolts. Assume my car is correct and that is how I recall seeing others including one I stripped down for parts. Any bolts I have that look like the one in your photo, will be used exhaust manifold bolts from a 1956 parts car, as those are hex flange style. Would have to check on thread pitch, size etc. If indeed your bolts are also the same as the ones I have seen on '56 Caddy exhaust manifolds, then I got those, OR you can buy new repros from Chips Caddy's on Ebay. David King on this site may also have them. Provisionally, it looks like your intake fastener hardware differs from what I have here. If you want me to dig out some exhaust manifold bolts for an A-B comparison let me know. But based on your pictures my actual intake manifold bolts are of a different style. I will check my car later today and see if they also have that flange but I do not think they do, and if so, so neither will what is in my parts.  :-[   Clay/Lexi

64\/54Cadillacking

Thanks Clay,

These are definitely the correct size intake manifold bolts for a 54 with the small flange, reason being is that these specific bolts are used on the outer corners on the intake manifold where the donut size washers aren't used.

Any larger flange, and you wouldn't be able to get a socket to fit over the top of the head to torque them down.

The donut washers at least on the 54, are only used on the 4 longer center bolts.

My exhaust manifold bolts are a lot longer than these, although they do look pretty similar.

Worse comes to worse I can always try Napa to see if they can match the bolts close to the originals or go to the places you recommended.

Let me know what you have Clay, because I'd rather have original bolts more than anything.

I appreciate it. 🙂
1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Lexi

Checked Lexi today and her intake manifold is fastened by nuts with large donut like washers on studs in the center on each side. So the main hardware are studs with nuts. Think 4. Didn't count. Then one much smaller (I think hex flange) on each extreme end. Will have a look at my parts engines and see what is on them and also check my hardware boxes. Will update this thread probably this weekend. Clay/Lexi

64\/54Cadillacking

Ok sounds good Clay, I believe Cadillac used the same designed studs/nuts with the washers and the hex flanged bolts on many year Cadillacs from what I read. I'm going to reach out to the guy Chip on EBay like you mentioned, and see if he has any spare ones as well.

1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Lexi

Have bought stuff from Chip a few times, (can't recall his real name). He was very good to deal with and I would recommend him as a vendor to trust. Clay/Lexi

fishnjim

If you have issues locating, try ARP.   They make in about any size.  The ones the rebuilder kit had where 12 pt, so I changed them back to hex like was on '58 and obtained from them.
These are flange head bolts.  I wasn't aware they were in use that early, but can't know everything.   I'll have to do a little bolt research...
ps; I (and others) don't recommend re-using fasteners that are torqued.

Lexi

Like Jim I am not a fan of re-using some fasteners as the old ones may have been stretched so their yield strength is compromised. Especially true of so-called torque to yield bolts. Clay/Lexi

64\/54Cadillacking

Ok guys, I contacted Chip and he has 4 nice ones that he sold me so my problem has been solved.

The size is a 3/8"- 16 x 1 1/8" bolt. I'm going to take a look at my 64 intake and see if the intake bolts are all the same as well. From quick memory the intakes look exactly the same. I believe Cadillac might have used the same size intake manifold for many many years although the engine block grew physically larger, the intakes didn't. I was thinking of installing a 67 intake on my 64 because it's the only year where the secondary intake ports are extremely massive compared to the previous years, so in theory you could use an even larger CFM Carb for more power, or I can grab a Rochester carb off a 67 Cadillac and install it on my 64 Cad with some linkage modifications.

But I don't want to mess with a good thing, as I already have an Eldelbrock installed on my 64 and the engine runs great.

Regarding not using old fasteners, I believe as long as they don't break or loosen up I should be fine. I'll have to keep on eye on the bolts after running the engine over many cycles, to see if they do loosen up, and if so, I'll just buy brand new repos.
1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Lexi

That is great news. Glad Chip could help. Some bolts are designed for one use only as their threads are not designed to be stretched more than once when torqued. Holding strength is compromised if re-used, at least in theory. The science behind fastener technology is quite detailed with much beyond my current scope of expertise. I bought new exhaust manifold bolts from Chip and they are nice repros. Think I had to shorten a couple of them as they were manufactured to fit a number of Cadillac years, (as Chip warned). Not sure if used for intake manifold whether their length has to be altered. If so, make sure you put a "safety" nut on the head's end. After cutting you can "fix" the last "jagged" threads where the cut was made, by turning out the nut to clean up that area. Think Chip ships from Troy Michigan. Clay/Lexi

64\/54Cadillacking

Quote from: Lexi on September 10, 2022, 12:23:38 PMThat is great news. Glad Chip could help. Some bolts are designed for one use only as their threads are not designed to be stretched more than once when torqued. Holding strength is compromised if re-used, at least in theory. The science behind fastener technology is quite detailed with much beyond my current scope of expertise. I bought new exhaust manifold bolts from Chip and they are nice repros. Think I had to shorten a couple of them as they were manufactured to fit a number of Cadillac years, (as Chip warned). Not sure if used for intake manifold whether their length has to be altered. If so, make sure you put a "safety" nut on the head's end. After cutting you can "fix" the last "jagged" threads where the cut was made, by turning out the nut to clean up that area. Think Chip ships from Troy Michigan. Clay/Lexi

Thanks Clay,

Chip seems to have a lot of these special original bolts for our cars. And he knows the dimensions really well. I'm definitely going to have to use him again in the future for just in case scenario's.
1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Lexi

Chip's inventory and service is quite good. I even bought a couple of fantastic repro oil dipstick tubes from him. He advertised that they were more robust than the originals. I did an A-B comparison; new vs old. A very nice, accurate reproduction tube in my opinion. Same with the exhaust manifold repro hex flange bolts. Stuff some don't think about when rebuilding an engine. Will your old dipstick tube to name one example, be any good to re-use? Can the old one be removed without damaging it beyond repair? So your engine is rebuilt and good to go but now you need an oil dipstick tube. "Who yeah gonna call". It is small problems like that which can delay a project. Lots of interesting stuff on his site, which I like to call "little big things". Clay/Lexi