Cylinder head studs

[Adder57]

Just to let members know, I recently bought some cylinder head studs from Rimmers, but forgot to order the nuts. Anyway the nuts came yesterday and when I tried them on the studs they only went on one end. I got on the phone to Rimmers and they went off to check the stock. They were the same so need remaking. So if anyone is ordering these parts there might be a wait or ask them to check the nuts fit. Regards adder.

[xvivalve]

So long as the nuts fit on the end of the stud with the slot and the thread on the other end fits the thread in the block there's no problem.

I have a used set here with the same UNC thread at both ends, but the ARP set from the quicksprint have UNF for the top thread...and I 'think' that's how OE were made too...

[Adder57]

I thought the nuts were 7/16 unc both ends . Mine are definitely unc on one end only. I will get back in touch with Rimmers to see what they say. Thanks for your feedback. Adder

[Mad Mart]

OE is definitely 7/16" UNC both ends. The UNC is needed, where it screws into the head, as it is going into Ali, which has a courser density. The other end, however, would probably be better with UNF.

[wgcjim20]

This is what Retro-Engineering's website says:

We use the standard 7/16 UNC thread into the block with a 7/16 UNF fine thread high tensile nut.
This helps to obtain a consistent clamping force when used in conjunction with a quality head gasket.

https://www.retro-engineering.co.uk/sho ... d-nut-kit/

[xvivalve]

OE is definitely 7/16" UNC both ends. The UNC is needed, where it screws into the head, as it is going into Ali, which has a courser density. The other end, however, would probably be better with UNF.

...but they don't screw into the head Mart, they screw into the block!

[Mad Mart]

OE is definitely 7/16" UNC both ends. The UNC is needed, where it screws into the head, as it is going into Ali, which has a courser density. The other end, however, would probably be better with UNF.

...but they don't screw into the head Mart, they screw into the block!

Doh! sorry, senior moment.

[marshman]

So long as the nuts fit on the end of the stud with the slot and the thread on the other end fits the thread in the block there's no problem.

BUT .... if the nut thread was originally UNC (coarse pitch) and the ARP ones are UNF (Fine pitch) then what torque figure do you use?? Everything else being equal a fine thread will give a higher clamping force than a coarse thread for the same torque figure. A second issue would be that the 5 studs (if they do indeed have the finer UNF thread at the nut end) would provide a higher clamping force (for the same torque figure) than the 5 bolts which would still have a UNC thread into the block.


Am assuming we are talking 1850/Sprint heads here!

[xvivalve]

BUT .... if the nut thread was originally UNC (coarse pitch) and the ARP ones are UNF (Fine pitch) then what torque figure do you use?? Everything else being equal a fine thread will give a higher clamping force than a coarse thread for the same torque figure. A second issue would be that the 5 studs (if they do indeed have the finer UNF thread at the nut end) would provide a higher clamping force (for the same torque figure) than the 5 bolts which would still have a UNC thread into the block.


Am assuming we are talking 1850/Sprint heads here!

Good question! To answer part of it, the ARP set has 10 studs, 5 shorter to replace the bolts. Not having considered the other part previously I have used 65 ftlbs as before which doesn't seem to have been detrimental to anything.

[marshman]

Ah didn't appreciate the ARP set replaced the bolts as well. In that case if the studs can take the strain so to speak then all it should do is squash the gasket a bit more, though I would be a little concerned about distortion of the block face around the top of the threads. It does happen with "normal" studs and bolts as I found when I recently rebuilt my Stag engine.

[new to this]

Ah didn't appreciate the ARP set replaced the bolts as well. In that case if the studs can take the strain so to speak then all it should do is squash the gasket a bit more, though I would be a little concerned about distortion of the block face around the top of the threads. It does happen with "normal" studs and bolts as I found when I recently rebuilt my Stag engine.

Hi Marsham you said the block face around the top of the threads distorted was that on the bolts or the studs ?the ford Cosworth's have this problem, they over come this by drilling the thread deeper in the block

Dave

[marshman]

it was on the rear two studs on my Stag block when I rebuilt it, As the Sprint and 1850 engines have the same arrangement I would expect to see the same issue there.

Also worth pointing out that the angled studs can distort the side of the hole as they exit the head face if the head has been skimmed. Because the studs are at an angle the distance between the black face and head face will alter the alignment. Again I saw this on my rather heavily skimmed Stag cylinder heads. If the distortion/bumps are not removed then they may prevent the gasket sealing at those points, possibly leading to an early failure of the head gasket seal.. On my heads I did relieve the stud holes to allow a bit more "freedom" to prevent it happening.

To be honest the problem should be spotted before reassembly when the surfaces are checked for flatness and burrs etc.