Head bolts

[sandyt]

Anyone know the size of 4.6 head bolts think they are 7/16 heads size 14

 

[MrGorsky]

Are they not standard metric threads?

A 14mm bolt head would suggest an M10x1.5 thread (I think). If it is, I've got a helicoil kit you can use if you want it.

 

[sandyt]

To be honest not sure stripped thread on the block yesterday so trying to find a timesert or helicoil to suit

 

[wammers]

To be honest not sure stripped thread on the block yesterday so trying to find a timesert or helicoil to suit

Give RPI a ring, they must strip a few they won't throw a block away for one stripped thread. Head bolts should be 5/8" AF so thread will most likely be 7/16 UNC.

Just had a look 7/16 UNC til 95 then they went onto something else with no size listed maybe some sort of metric crap on later engines.

 

[sandyt]

Rpi send theirs out to an engineering firm and use helicoil difficult bit is finding the size as said some metric crap no doubt

 

[wammers]

Rpi send theirs out to an engineering firm and use helicoil difficult bit is finding the size as said some metric crap no doubt

If as you said before bolt head size is 14mm likely to be something metric near to 7/16" which would be 12 mm, but what the pitch is haven't got a clue. Do you not have a thread pitch gauge? I find it hard to believe that RPI with all their technical ramblings about how good they are, don't know the thread size and pitch. I get Helicoil kits from my local tool factors but they are bloody expensive for a one off job. Specially that size.

http://www.ebay.co.uk/itm/7-16-UNC-...t=UK_Hand_Tools_Equipment&hash=item23251218f9

 

[MrGorsky]

A thread gauge is cheap to buy. Probably about £5 from Machine Mart. You could get one of those and then we know what we're dealing with.

I suspect it'll be metric coarse thread. It's a metric bolt head (14mm) so it follows it should be a metric thread no? If you measure the diameter of the threaded part of the bolt (proper units please, non of this imperial nonsense) we'll have a pretty good idea of thread required.

Almost all applications use coarse thread which would be M10x1.5 if it's a 10mm bolt, or M12x1.75 if it's a 12mm bolt.

If it is M10x1.5 I'll lend you my kit. £35 is a lot of money for a one off job. If you can move it you could take it to a garage and have them fit the helicoil? Any garage should have the gear to do one I'd have thought.

 

[sandyt]

The engine is on the bench I. Was in the middle of rebuilding might give the guy who fitted the new liner a call and ask for a price

 

[sandyt]

A thread gauge is cheap to buy. Probably about £5 from Machine Mart. You could get one of those and then we know what we're dealing with.

I suspect it'll be metric coarse thread. It's a metric bolt head (14mm) so it follows it should be a metric thread no? If you measure the diameter of the threaded part of the bolt (proper units please, non of this imperial nonsense) we'll have a pretty good idea of thread required.

Almost all applications use coarse thread which would be M10x1.5 if it's a 10mm bolt, or M12x1.75 if it's a 12mm bolt.

If it is M10x1.5 I'll lend you my kit. £35 is a lot of money for a one off job. If you can move it you could take it to a garage and have them fit the helicoil? Any garage should have the gear to do one I'd have thought.

Looks like you are spot on the bolt is 10mm x 1.5

 

[sandyt]

THink I will buy this seems a good deal and the way this block is behaving may need more than one

Price: £16.25
Free UK Mainland Postage

(£19.50 Including VAT at 20%)

10MM X 1.5 THREAD REPAIR KIT
BOXED SET
25 X 10MM X 1.5 INSERTS
1X HSS TAP
2 X INSERT TOOLS
1/3RD NORMAL PRICE

 

[sandyt]

Still not sure ??

 

[dove]

I was under the impression the threads are all imperial.remember this is 1960s design .dont think they were changed to metric ,I would double check if I were you might b 7 ,16 ths .which is more like 11 mm, 10 x1.5 is a common size try a normal bolt in the hole first,to check

 

[Irishrover]

:behindsofa:
Looking at the LR Series website, the bolts are shown as 7/16" UNC for the V8. Part no. ERR2943 for the short ones. The 7/16 UNC thread is 14 threads per inch which roughly equates to 1.8mm pitch.
Ideally you need to use a screw pitch gauge and micrometer to determine the thread or you can get a M10X1.5P bolt and lay it on top of the head bolt thread, if the threads sit nicely together the pitches are the same. Otherwise, clean the thread of the head bolt with a wire brush and see if a M10 nut will fit-if the nut is too small, there is an almost certain chance that it's 7/16.

 

[MrGorsky]

Well Sandy, if it is M10x1.5 ((and I think it would be by 1995) and I can find it) the offer to use my kit still stands.

If it is 7/16 then I'm afraid I can't help you. But you should still get a kit and do it yourself. It's easy peasy.

If I ever took my motor apart I'd consider helicoiling the threads just to be safe anyway.

 

[sandyt]

Gents thank you for your assistance and yes I am going to check I have given one of the unused bolts to a friend who is an aircraft engineer with BA and he is going to take it to work and use their equipment to determine exactly what we have here at least then we will know for the future it could be an m10 but equally it could be a 7/16th I dont have the kit at home to measure it properly or as Irishrover suggests bolts to substitute so I shall report back hopefully tomorrow - if it is a 10mm I shall certainly take you up on your offer of the use of your kit MrGorsky once again thanks to all I have to say this forum is just brilliant without it I would have given up years ago but instead I am looking forward to driving the rangie again and with a bucket load of pride

 

[wammers]

Gents thank you for your assistance and yes I am going to check I have given one of the unused bolts to a friend who is an aircraft engineer with BA and he is going to take it to work and use their equipment to determine exactly what we have here at least then we will know for the future it could be an m10 but equally it could be a 7/16th I dont have the kit at home to measure it properly or as Irishrover suggests bolts to substitute so I shall report back hopefully tomorrow - if it is a 10mm I shall certainly take you up on your offer of the use of your kit MrGorsky once again thanks to all I have to say this forum is just brilliant without it I would have given up years ago but instead I am looking forward to driving the rangie again and with a bucket load of pride

With all the digging i have done today i am still of the opinion that the bolts are 7/16 UNC. I can find no reference to any metric head bolts at all. Certainly in all early engines fitted with studs the head nuts were 5/8" AF. But with the introduction of bolts the heads may have been reduced to 9/16" AF, which is very near to the 14 mm you say fits. You must have a sloppy 14 mm socket to get it on a 9/16 bolt head. When removing or tightening head bolts i would always use a hexigon headed socket NEVER a twelve point one. Specially one of the wrong size.

 

[Irishrover]

With all the digging i have done today i am still of the opinion that the bolts are 7/16 UNC. I can find no reference to any metric head bolts at all. Certainly in all early engines fitted with studs the head nuts were 5/8" AF. But with the introduction of bolts the heads may have been reduced to 9/16" AF, which is very near to the 14 mm you say fits. You must have a sloppy 14 mm socket to get it on a 9/16 bolt head. When removing or tightening head bolts i would always use a hexigon headed socket NEVER a twelve point one. Specially one of the wrong size.

:behindsofa:

Come to think about it, when I stripped the old engine out of my '96, 4.6, V8 and built up the brand new short engine-I am 99.99% certain that an "A/F" socket was used, not a Metric as the fit was not quite right. I only have Britool and Facom sockets, which are a very good fit.
The short engine was suitable for Gems & Thor so I believe the threads did not change during the P38 build.
It's most confusing that L.R. built cars with a hotch potch mix of Metric and Imperial fasteners etc. they should have gone 100% one way or the other. Luckily I have a good mix of tools, gathered over the years comprising of Metric, American and even the old Whit./BSF spanners, taps & dies, reamers etc.
A cheap 0-25 or 0-1" micrometer and set of american & Metric screw pitch gauges (Plenty on Ebay) are an essential pice of kit for anyone working on a P38/Disco. etc. which use a wide range of different thread type & size.

 

[wammers]

:behindsofa:

Come to think about it, when I stripped the old engine out of my '96, 4.6, V8 and built up the brand new short engine-I am 99.99% certain that an "A/F" socket was used, not a Metric as the fit was not quite right. I only have Britool and Facom sockets, which are a very good fit.
The short engine was suitable for Gems & Thor so I believe the threads did not change during the P38 build.
It's most confusing that L.R. built cars with a hotch potch mix of Metric and Imperial fasteners etc. they should have gone 100% one way or the other. Luckily I have a good mix of tools, gathered over the years comprising of Metric, American and even the old Whit./BSF spanners, taps & dies, reamers etc.
A cheap 0-25 or 0-1" micrometer and set of american & Metric screw pitch gauges (Plenty on Ebay) are an essential pice of kit for anyone working on a P38/Disco. etc. which use a wide range of different thread type & size.

Got to be 7/16" John. Normally they would have a 5/8" AF head. So don't know where his 14 mm comes from. 5/8 is nearer to 16 mm.

 

[kevwill]

That's right. 7/16 unc 5/8 af head. Got my ones out with a 16mm hex long socket for the back/bulk head ones and a 5/8 socket for the others. Stretch bolts so maybe timeserts would be best.

 

[wammers]

That's right. 7/16 unc 5/8 af head. Got my ones out with a 16mm hex long socket for the back/bulk head ones and a 5/8 socket for the others. Stretch bolts so maybe timeserts would be best.

Never ever use a cheap 16 mm twelve point socket on the 5/8" head bolts specially undoing them, but also angle tightening them. Rounding them off is real easy. Always use good quality 5/8" single hex sockets.