valve clearance
#1 valve clearance
Hi all,
I want to check and if necessary adjust the valve clearance on a 4.2 engine from a late 420G (1970). Engine number is 7D60135-8. Both cams are the later 4bolt and have the code P31818A cast in. Actual clearance measured on a few valves showed 009 on inlet and exhaust. Afaik the cam profile was generally changed around 1968 enabling bigger valve clearance. But the original chassis plate on this 420G shows 004 / 006 in/ex clearance. Is this a stamping error? What is the correct clearance for this engine?
Thank you
I want to check and if necessary adjust the valve clearance on a 4.2 engine from a late 420G (1970). Engine number is 7D60135-8. Both cams are the later 4bolt and have the code P31818A cast in. Actual clearance measured on a few valves showed 009 on inlet and exhaust. Afaik the cam profile was generally changed around 1968 enabling bigger valve clearance. But the original chassis plate on this 420G shows 004 / 006 in/ex clearance. Is this a stamping error? What is the correct clearance for this engine?
Thank you
Last edited by MarkRado on Thu Mar 28, 2019 4:47 am, edited 1 time in total.
Mark
1963 OTS 880436
1963 OTS 880436
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#2 Re: valve clearance
The Jaguar manual says clearances of 4/6 thou for the 420G, but I think that the P31818A cam is the C35556 cam for the S2 E type and also used in the XJ6. So your cams have either been changed at some stage or Jaguar fitted the quieter cams to later 420s.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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#3 Re: valve clearance
Hi Mark...does this help...it shows how to identify camshafts......Steve http://www.georgiajag.com/Documents/Camshafts.html
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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#4 Re: valve clearance
AFAIK all the cams were changed to the parabolic type in c 1968. This is why the earlier 420G information ( which dated from late 1966 ) referred to by Andrew is for the old cams. If you have 4 bolt cams, then they are definitely parabolic and require the .012" - .014" clearances
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#5 Re: valve clearance
Andrew, Steve and Christopher,
thank you vey much for your input.
I was puzzled, because a) the comissioning plate says 004 / 006 rather than 012-014 and b) the interim parts list of 1969 still only lists the early camshafts. So either it is a very late engine and nobody bothered using the appropriate comissioning plate, or the camshafts were changed during its life (although unlikely- a car with 30 kmiles, current owner since 1974).
Anyway. I'll adjust the clearance to 012-014 inlet and exhaust.
Thank you
thank you vey much for your input.
I was puzzled, because a) the comissioning plate says 004 / 006 rather than 012-014 and b) the interim parts list of 1969 still only lists the early camshafts. So either it is a very late engine and nobody bothered using the appropriate comissioning plate, or the camshafts were changed during its life (although unlikely- a car with 30 kmiles, current owner since 1974).
Anyway. I'll adjust the clearance to 012-014 inlet and exhaust.
Thank you
Mark
1963 OTS 880436
1963 OTS 880436
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#6 Re: valve clearance
Mark : something which might interest you ( particularly when it comes to a bottom end overhaul ) is that there were some intriguing differences between the Mark 10 / 420G engines and any other XK engine . This resulted from the fact that the bodyshell was found to have a resonant frequency close to and/or the same frequency as that of the engine, and Jaguar went to a lot of trouble to deal with the resultant Noise/Vibration issues . IIRC the fix which they eventually used was to grind the crank journals with a predetermined degree of ovality which altered the resonant frequency . Thus measuring a mark 10 /420G crank can produce interesting results !
The ovality is not required if the engine is now used in an E type
The ovality is not required if the engine is now used in an E type
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#7 Re: valve clearance
Christopher, FYI for E Type engines (don't know about the 420) Clausager shows the change to the parabolic 12/14 thou camshafts was in November 1969, engine numbers from 7R8688/7R38855
Regards
Geoff
Regards
Geoff
S2 FHC Light Blue
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#8 Re: valve clearance
Wow, thats really some special information. The indepth knowledge of this forum is impressive and invaluable, thank you very much
Mark
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#9 Re: valve clearance
Just remember to go by the cams and forget everything else when it comes to setting clearances. Cams are easily changed between engines - sometimes in the mistaken belief that ‘E-type cams’ are better. All 4-bolt clearances should be in the 12–14 thou range on every valve.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas
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#10 Re: valve clearance
My August '69 car has 2 bolt cams and 4/6 thou clearances.
John
1969 Series 2 FHC
1969 Series 2 FHC
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#11 Re: valve clearance
Just be aware that the 2 hole camshaft with the grove around the front flange is also 12-14 gap....as in the link i posted above....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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#12 Re: valve clearance
Steve (mgcjag) did a post from you in this thread get deleted? I thought one or two posts on this and elsewhere I had read now don’t seem to be showing?
Geoff
Geoff
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#13 Re: valve clearance
Hi Geoff...yes i deleted a post that i posted here in error.....only others iv delete recently were spam....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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