Urgent help needed - tension of conrod bolts early SV

[craigb]

Hi everyone - I owe the forum some updates on the resto project but right now just trying to tighten the rod bolts - stripped the thread on one then got a replacement from another motor and snapped it. I'm trying to line up to see a mate who has a digital tool for reading tension on bolts so i can test my tension wrench but want to check the correct data. The manual i have states it as 33 lb. ft. for the 'engine APHM'. This is a early 1949 car that I think might be the 'engine USHM2' being the first one in the manual, but there are no "Torque spanner readings' under that heading and had assumed it would all be the same.

Any help greatly appreciated - I just need to do these, put sump back on and car should be on the road.

[RobThomas]

APHM is the 803 A-series so the figures are not correct. I don't have the sidevalve numbers to hand but they are very low, hence you've snapped the sidevalve ones that are made from recycled cheese.

[RobThomas]

http://www.morris8-bobbryan.co.uk/artic ... ttings.pdf

Quick google

[RobThomas]

http://www.morris8-bobbryan.co.uk/artic ... tening.pdf

http://seriesmm.mmoc.org.uk/tech.htm#torque

[craigb]

Thanks heaps Rob. I did google but obviously I am not as good at it as you are! I bought this big fat factory manual..... but no torque figures!

Its interesting though that after 45 years or so of working on cars and bikes, you get a bit of a feel for when something seems too tight for a certain size bolt and this certainly felt too tight. Same with the mains that I did at the 65 but should only be 42. I will pull them back out and check for any damage and then do them back up correctly. And head gasket........ aphm 40 but should be 44.

That might be a bit lucky though, and also this whole drama that has revealed me using wrong tension - might do that in another post and contribute to the knowledge base here..... will call it 'beware piston height on rebuilt motors on sidevalve engines'

[IslipMinor]

If there are figures available for the MM Minor, it would be worth collating them into a table similar to the one for the A-Series engined Minor, which is on the first page of 'Technical', 'Mechanical' & 'Thread Sizes'.

As a general rule for steel bolts and nuts being used to 'secure' steel components together there are typical ranges of torque settings for imperial threads. The coarse threads (BSW and UNC) will be slightly lower than fine threads (BSF and UNF). High tensile bolts, stamped 'S' or 'T' on the head will usually be towards the higher end of the scale, and pure 'mild steel' fixings at the bottom of the range.

Obviously thin steels covers, aluminium components etc. will have lower torques settings than the ranges shown below:

Typical Torque Settings.jpg (32.08 KiB) Viewed 1243 times

Out of interest, what diameter are the MM big-end and main bearing bolts, and are they bolts or nuts?

[craigb]

Late here now - will check tomorrow. Yes I am sure some of my workshop manuals have those general settings printed into them. Worst part is knowing deep down that it felt too tight and would strip - should have stopped and checked at that point. But you have that confidence from what you think must be right if you saw it printed. After reading Robs comment i also saw that just near it was something about the rocker shaft and i should have noticed that and realised quite different engines. The up side is dodging a bullet of running the car with wrong tensions.

[craigb]

sorry for slow response - rods 8mm and mains 10mm - I believe it is all metric.

And follow up - all back together and motor sounds very sweet..... but i have another problem now.... see other post!

[RobThomas]

There seems to be a stock of conrods in the UK but I always thought it would be nice to get a replacement conrod bolt from a modern vehicle. I theory there ought to be an ideal candidate out there in Metricland that would suffice.

Any suggestions where to go to find a suitable reference book?