bigblock67

Why do most small block head bolt kits come with 3 length bolts when the 2 middle length bolts provided will not work on my 283s. All bolts under cover are same length. Need explanation.
Don

john neas

By memory, I believe they went from a two to a three bolt arrangement in 1959. The three bolt kit will cover the highest number of small blocks in use.
Regards

buns

My memory tells me all Gen 1 small blocks, '55 and up, used 3 lengths of head bolts. Used 2 catalogs to back up my failing memory bank.


14 at 3 3/4"
16 at 1 3/4"
4 at 3"

john neas

What parts book of that era did you use?
Regards

john neas

Per the 1961 Parts and Accessories Catalog Group 0.293
55-61 Corvette 14 at1 3/4"
55-61 Corvette A.R. 3 3/4"
59-61 Corvette 4 at 3"

They made several changes on the 59 and later heads.
Some of these were
Bolts which held valve cover became straight line.
Coolant passage in spark plug area
I believe the change which created the need for shorter headbolts was a depression on each end of the heads which aided in oil return to the sump.
Regards

bigblock67

Seems a lot of books state 3 length bolts for all 283s. I do know my original 770 heads on my original 739 block in my 58 had only 2 lengths. I am currently arguing with a head bolt seller who thinks I am crazy.
That may have some merit but with this issue I can say I am correct. He wont send me 4 long bolts to replace the 4 middle size that was sent.
Central did not know this either and told me they are going to create a new part number.
I know what I would be doing about now back in the late 60s. Crank up the Doors and partake in.....
Don

JohnZ

283's use two of the 3" (intermediate) length bolts on each head, under the valve cover, at the lower corner at each end. 1961 Passenger Car Shop Manual verifies it, and calls it out as a special note.

buns

H. Paulin (Papco), Fel-Pro and A.R.P. They all claim their bolt sets will fit all Gen 1 smallblocks.

john neas

They are wrong, assuming they are using 55-58 heads. Look at a 55,56.57or58 Chevrolet parts book. I am probably one of the few people that have used a ARP bolt set with early heads and I had to buy 4 extra of the long bolts to assemble the engine. Do us a favor and look at a 55-58 head vs a 59 and later before you confuse some body else. As I tried to say in the second post, very few engines use the 2 bolt arangement so the later catalogs are right 99+% of the time. Please do the research.
Regards

bigblock67

John, THANKS for reply. That makes 2 of us now. Can you have a copy from your book that states that. I am dealing with a PIN HEAD parts supplier who can read but has zilch common sence. I would like to educate him to get my 4 bolts and get away from a paypal dispute. He
p...ed me off with an attitude & Im not letting him off. Thanks
Don
Sending a pm

DZAUTO

Well, let me jump in here right quick
John Z REALLY shocks me on this one.

Sooooooooooooooooooo, everyone read the following carefully.
FIRST, I don't give a big flying flip what ANY book or what ANY fastener manufacturer says or states in their literature.

Here is what is fact. Period. End of discussion. Forget the book(s), GO GET THE HEADS AND CHECK IT OUT FOR YOURSELF!!!
The VERY EARLY SB heads used TWO, repeat, TWO lengths of head bolts---------------NOT THREE!!!!!!!!
I do not know the exact cutoff date, but the 55 to APPROXIMATELY 58 265 and 283 heads had ALLLLLLLLLLLLLLLLLLL the same length bolts under the valve cover, and all the bolts on the exhaust side were the short version.
APPROXIMATELY 1959 model 283s, and all subsequent SB heads thereafter used three lengths of head bolts, with the two end bolts being the middle length.
Again, some of you guys surprise me about this!

Don't sit there at the keyboard and argue about it-----------------go locate an early head and check it out!!!

bigblock67

Yeah John Z.. Whats that all about? I also am suprised.....

buns

Apparently, you know more about this than the people that manufacture head bolts. And you want me to do my research before I confuse somebody else?????
All my catalogs are crap. I threw them in the fireplace. Next time I need a part for something, I will ask your opinion first.


It seems to me that after 40 years you weren't the only one to inform these manufacturers that they were wrong. Why didn't they do anything about it?

DZAUTO

No! That's not true, but on this particular issue, the catalogs are incorrect, the early SB heads only used TWO lengths of head bolts:
18 long bolts at 3 3/4in length
16 short bolts at 1 3/4in length

AND, while we're on the subject of catalog incorrectness, the aftermarket Chevy catalogs that list the gear ratio discs for rearends (56-62 Vettes and pass cars up to 64), have the listings/illustrations for the 3.36 and 3.55 discs reversed and refuse to change them.

mashinter

I tried to use the cylinder head bolts out of my early '59 when I installed '61 fuelie heads, and had to buy the 4 short bolts. The early '59 3755550 heads use only 2 lengths

bigblock67

I have 4 middle size that will trade for 4 long bolts.

john neas

Even GM did not recognize this in their catalogs in the mid 60s. Would you or someone else give the approximate date of the change?
Thank you

I do agree that there was a mid 59 change.

john neas

This is the Chevrolet Parts and Accessories Catalog for 1957


It shows that the 1957 Corvette used only two head bolts:
16 at 1 3/4"
18 at 3 3/4"


This is what an intermediate 3" bolt looks like in a 58 3748770 head. (Typical of the 55 - early 59 heads). The bolt will not even go into the block and provide the necessary clamping force.


This is the same intermediate 3" bolt in a 64 3782461 head (typical of the late 59 and later heads). It will hold the head and head gasket to the block.


This picture shows the location of the long bolt early head (this is the same location which uses the intermediate bolt on the later heads)


This picture shows the same location on the later head which uses the intermediate bolt. The location was sunken which required the shorter bolt.

bigblock 67, hopes this helps you.

Regards.

mashinter

I'm assuming the change occurred when the cylinder head 3755550 (staggered cover bolts) was replaced by the 3767465 (straight cover bolts). NCRS Judging Guide says that occurred between May 5-19, 1959. Staggered covers may appear on cars assembled as late as July 1959.

john neas

Thanks