main cap fit to block

[AC sports]

I've never seen an actual interference fit spec for any car. Just wondering if any maker publishes a spec on this.
I mean, main cap to block register. Usually a light tap is all it takes but I'm doing a refresh on a friend's motor and noticed there is a little side clearance and it's got me worried.

[zums]

Dont take it as a universal spec, but all the SBC Bowties ive checked run .001- .0022, thats cap wider then register

Tom

[pamotorman]

if I found a loose one I put a mandrel in the bore, torqued the cap in place and used a blunt nose chisel to move the block metal to tighten it up

[PackardV8]

Not saying this is the correct or the only way, but we had one with a bit of play. We miked the play, added .0015", put the cap in the pin press, spread it to the dimension we wanted, nipped it back square in the cap grinder, installed it fit perfectly, line honed the block and good to go.

[machinedave]

When I am measuring my housing bores and I find a cap is a little loose in the register, I will measure at the two-Oclock and ten-O clock positions to find out wich side is above and wich side is below spec. I will do my staking to shift the cap over so the housing bore is consistent at both sides of the parting lines.

[simon010]

on (two of) new factory short engines - both were a push fit of the cap into the registers on fiat tc's.......

any sideways slop - should be fixed

rgds
simon

[modok]

usually should have been 000-.002
I'll peen to tighten if only a thou loose or two
Over .002 clearance....should be fixed properly. I usually braze

[SupStk]

In the past, billet main caps from Pro-Gram fit the factory registers very nicely so I didn't measure. Recently got a set of SBM caps from them which didn't have the caps precut. According to the instructions, they were to be fitted with .0025"- .003" interference.

[pamotorman]

if you don't want the caps to move you need to pin them. the cap register only locates the caps in the block. if you see fretting on the cap block interface the caps are moving.

[cgarb]

I was told if the caps are moving the fastener isn't up to the task. The fit and pins are for location and the fasteners keep it from moving. Wouldn't the pins and pin bores get beat up and loose just like the block for if the clamp load isn't up to snuff?

[zums]

You could weld those caps to the register, if it detonates enough its coming unglued, get in touch with the Tune
Tom

[modok]

The interference fit is mainly to located the cap, it does little to prevent movement.
I don't feel that more interference is better than enough.

Dowels ARE better, slightly, but yes the best solution usually includes more clamp load.

[pamotorman]

the downward force of the rotating assy causes the caps to have the ends pull inward because of the bending force on the caps. this happens because of the clearance around the bolt holes and the pins are a tight fit into the caps to prevent any cap movement.

[pamotorman]

the downward force of the rotating assy causes the caps to have the ends pull inward because of the bending force on the caps. this happens because of the clearance around the bolt holes and the pins are a tight fit into the caps to prevent any cap movement.

this is the reason that high dollar con rods use hollow dowel pins around the bolts to keep the cap and rod in alignment not just the clamping force of the bolts.

[77cruiser]

If the bolts/studs arnen't up to the task, what are a couple of hollow dowels or tiny pins going to do, other than initial alignment?