How to tell if engine has been bored out.

I have very little history on what engine work was done to
to my 1975 Z1B.
So my question is how can I tell if the engine has been bored out ?
My seat o pants meter tells me that something good was done as she really Rip's.



Thanks Jim

jimstan wrote:

I have very little history on what engine work was done to
to my 1975 Z1B.
So my question is how can I tell if the engine has been bored out ?
My seat o pants meter tells me that something good was done as she really Rip's.



Thanks Jim

if it rips , ya hate to tear it open....but thats the only way i know of to measure bore......you can pull cam cover and see if the cam ends have any markings on them and measure a lobe and the base circle and the diff is the lift....see if that is bigger than stock......

Obviously one way is undesirable in that remove the head and measure the piston/cylinder bore diameters.... :blink:
Over 70mm then yup, been bored out...

1015cc = 70mm
1045cc = 71mm
1075cc = 72mm
1105cc = 73mm
1135cc = 74mm
1197cc = 76mm

Pretty much anything bigger would require big block and this would be quite noticeable...

Another less intrusive but non 100% way would be to get her on a Dyno... Pending other mods such as Keith mentioned Cams, carbs, head P&P if your up in the mid to high 90's in HP, more then likely it has had some internal work accomplished...

OMR

Put a bore scope inside the spark plug hole and see what the shape of the piston dome is.

1327 cc = 80mm bore
1393 cc = 82mm bore
1428 cc = 83 mm bore those numbers will really give you some zip.

timebomb33 wrote:

1327 cc = 80mm bore
1393 cc = 82mm bore
1428 cc = 83 mm bore those numbers will really give you some zip.

He would know if he has those sizes because he would have a big-block on the engine.

Thanks for your info,

One last quick question: Would the cylinder compression change if it was bored out ?
As well as it runs I will just enjoy it until I have to do a rebuild.

jimstan wrote:

Thanks for your info,

One last quick question: Would the cylinder compression change if it was bored out ?
As well as it runs I will just enjoy it until I have to do a rebuild.

All else being unchanged...yes it will go up some but you can't just lean on that number as gospel.

Pull a plug, bring a piston up near tdc, lookin the hole and see if it's got a real dome.

the only way it change cranking compression would be if they put higher compression pistons in it.

Increased cylinder volume squeezed into the unchanged combustion chamber size and unaltered cam timing should raise the static a hair...not a lot. You won't be able to tell from the PSI number with any certainty unless it's really up there.

How to tell if your engine is bored?

It yawns. Seems disinterested. Keeps looking at its watch.

:laugh: :silly: :blush:

Skyman wrote:

How to tell if your engine is bored?

It yawns. Seems disinterested. Keeps looking at its watch.

:laugh: :silly: :blush:

:woohoo: :woohoo: :woohoo: :woohoo: :woohoo: