Block history..

[pdq67]

Why did Chevy go with 5 head-bolts around each cylinder instead of four??

And heck, at one time the old Olds had 22 around its cylinders so why?

pdq67

[swampbuggy]

Less distance between head bolts (or) studs means LESS chance of having head gasket failure, especially with forced induction which sends cylinder pressures way high. I remember when the B & S lawn mower engine blew a head gasket, i went to get a new one and the guy said yea they blow in the same place every time. I said you know why ? he said no, i said there is a lot more distance between the two bolts on each side of the failed area. I then said GM had the same problem with their B.B.C. engines when they were pushed hard (increased cyl. pressures). Mark H.

[user-23911]

Same reason a typical 4 cylinder petrol engine has 10 head bolts but a typical 4 cylinder diesel has 18.
The extra 8 bolts sit mid way between the original 10.


It's the one thing that makes a SBC better than a SBF.

[Geoff2]

And a BB Chrysler & 426 Hemi.....

[BigBlockMopar]

I've always wondered why Chevy-guys get all giggly and almost wet their pant(ie)s when they find an engine block that needs 4 bolts to secure a main cap.
Doesn't that say the original block had some design-issues on the lower end too?

[tenxal]

I've always wondered why Chevy-guys get all giggly and almost wet their pant(ie)s when they find an engine block that needs 4 bolts to secure a main cap.

Knowledgeable ones don't.

[plovett]

Having 4 bolts securing a main cap doesn't seem like a bad idea to me.

Having an odd number of irregularly spaced small head bolts does seem suboptimal to me.

JMO,

paulie

[jeff swisher]

Uncle ran Mopar in Nascar years ago small blocks and 4 head bolts around the cylinder and his fix for blown head gaskets was to take a center punch and dink up the area holding the gasket basically making a raised area to hold gasket better.. they lived longer for him.

4 bolts on the mains..would be nice if the 2 outer bolts went into some meat.. but the way GM did the SBC with that thin crack prone area.Never liked the idea.

[Newold1]

I think that early in V-8 designs, the placement of intake and exhaust ports determined how many and where head bolts ended up being located. That sixth bolt on Chevy was a "not now moment" with those engineers. When compression ratios got up over 12-13 to one it necessitated better head bolts, better head gaskets, and some additional secondary bolts to keep'um sealed up. Even 4 bolt evenly spaced around the cylinders today do a better job of even clamping force and sealing than some of the older uneven spacing designs.

As for main caps and bolt quantity it's pretty much a matter of strength. As forces go up the depending on the block design and strengths, the main caps strengths and locating means have to get stronger. Then generally the bolt numbers and configurations have to get stronger or that crank is going to try and exit that block . Think about angled main bolt, side bolt caps (427 Ford side oiler) and many of todays deep skirt engine main cap configurations (LS engine) it's all done to keep that crazy spinning crank nicely in place. JMO

[Schurkey]

The LS uses six bolts to hold each main cap. I always figured they were using the strength of the main cap to stabilize the block, not the other way around.

[pdq67]

I asked somebody to post up pictures of the Olds 18 and 22 head-bolt pattern head gaskets and somebody did.

Thanks, but I couldn't tell which holes were head-bolt holes so got lost looking at them.

pdq67

[Truckedup]

Why did Chevy go with 5 head-bolts around each cylinder instead of four??

And heck, at one time the old Olds had 22 around its cylinders so why?

pdq67

I think you meant why did chevy go from 5 bolts to 4, I guess you where not thinking the now engine is the LS. It is called engineering regression and build it cheap attitude for 1. I would like to know when the Chevrolet engine design team lost the engineers that worked on the SBC and the W engine?

Those engineers got old and left.....How do you explain how the LS engine offers more performance with a longer lasting engine? There's documented stock junkyard truck LS's having turbochargers bolted on with enough boost to make close to 1000 HP...A stock SBC would blow right up...
It's got nothing to do with head bolts, it'sthe complete engine design...

[pdq67]

OK, let's do this again!

Why did some of the '50's V-8 engines use 4 head-bolts and the small block Chevy went with 5?

It sure wasn't a compression deal???

pdq67

[Truckedup]

OK, let's do this again!

Why did some of the '50's V-8 engines use 4 head-bolts and the small block Chevy went with 5?

It sure wasn't a compression deal???

pdq67

Perhaps lighter weigh head and block needs more fasteners....Perhaps better engineering....From what I have read, Pontiac engineers had a part in designing the early SBC. But the Pontiac has 10 head bolts? I always read the SBC was designed as an inexpensive engine , the simple sheet metal timing cover and no valley pan being a good example...The Mopar B block came out in 1958 and has 17 head bolts I believe

[PackardV8]

Don't get limited in thinking only about the head bolt count or main cap bolt count.

It's also how much iron/aluminum in the heads and block, the iron and the coolant between the cylinder bores, the diameter of the head bolts, et al.

FWIW, the 1951 Studebaker V8, with eighteen head bolts and only 3.375" bore, is one of the strongest blocks ever in a OHV8. The back story is one of the design engineers had heard Charles Wilson, president and chief executive officer of General Motors, make a prediction that 120 octane aviation gas would become standard at the pumps and 12:1 compression ratios would be the norm. Studebaker designed their V8 to handle those rigors which never came to be.