Bristol Cars - Owners and Enthusiasts Forum  

Go Back   Bristol Cars - Owners and Enthusiasts Forum > Bristol Forums > 6 cyl Bristol cars

6 cyl Bristol cars Type 400 to Type 406

B400 - rocker adjustment

Reply
 
Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 05-06-19, 05:44 AM
Member
 
Join Date: Jun 2018
Posts: 39
Default B400 - rocker adjustment

The time will come when the rockers have to be adjusted.
The engine is equipped to my knowledge with a B 403 camshaft.
Would that make a difference?
Reply With Quote
  #2 (permalink)  
Old 05-06-19, 07:41 AM
Member
 
Join Date: Jul 2008
Location: Sydney, Australia
Posts: 294
Default

Bela ,
The standard valve clearance for
400 - 403(A engine) is .002 inch cold Inlet & Exhaust
late 403(AB2 engine) - 406 is .005 inch cold " "

But very few engines now have standard factory cams . Most have either
been re ground to another specification or the cam replaced and the clearance of these could be different from original standard cam .

Do you know the valve timing of the engine .
Inlet opening & closing , Exhaust opening and closing to try to identify which cam is fitted.

Geoff
Reply With Quote
  #3 (permalink)  
Old 05-06-19, 05:23 PM
Member
 
Join Date: Jun 2018
Posts: 39
Default

Quote:
Originally Posted by Geoff Dowdle View Post
Bela ,
The standard valve clearance for
400 - 403(A engine) is .002 inch cold Inlet & Exhaust
late 403(AB2 engine) - 406 is .005 inch cold " "

But very few engines now have standard factory cams . Most have either
been re ground to another specification or the cam replaced and the clearance of these could be different from original standard cam .

Do you know the valve timing of the engine .
Inlet opening & closing , Exhaust opening and closing to try to identify which cam is fitted.

Geoff
Thanks Geoff

I only found a notice of a PO that a 403 camshaft had been fitted. As you mentioned there are two options - early and late. I guess less clearance will
end in troubles.

I don't know the valve timing and I don't know how to generate that data. In the files there is a drawing. I will look for it.
Reply With Quote
  #4 (permalink)  
Old 06-06-19, 10:04 PM
Member
 
Join Date: Jun 2018
Posts: 39
Default

Quote:
Originally Posted by Bela View Post
In the files there is a drawing. I will look for it.
Here comes the drawing- for better reading twice. But I don't know the context of this drawing. I hope it was generated after purchasing a new camshaft.
Attached Images
File Type: jpg IMG_2383[1].jpg (132.5 KB, 10 views)
File Type: jpg IMG_2384[1].jpg (133.9 KB, 5 views)
Reply With Quote
  #5 (permalink)  
Old 07-06-19, 01:27 AM
Member
 
Join Date: Jul 2008
Location: Sydney, Australia
Posts: 294
Default

Bela ,

although the scan is quite clear to view , the information is not written in a form to express the valve timing correctly.

But after trying to sort out the information ,my comments are as follows (assuming a 403 camshaft is fitted or camshaft ground to 403 spec )

Inlet lobe lift of .180 inch (should be .205)
Exhaust lobe lift .200 (should be .205)
So possibly a worn camshaft or reground to a completely different grind.

Timing Inlet opening 34 BTDC
Inlet closing 44 ABTC
give duration 34 + 44+ 180 = 258 degrees (close to early 403 of 260 deg)

But the original standard early 403 timing is 15 BTDC - 65 ABDC ,
So it looks like if the timing is set as per those notes and the camshaft is a 403 cam or 403 grind , it is set about 19 deg too far advanced. Probably one tooth .
But these notes could have been taken during initial assembly (how accurately is unknown) & was corrected before final assembly .

Do you have a TDC mark on the front pulley or damper with a pointer ???
If so , set the number 1 inlet valve clearance at .002 cold, turn engine over until the clearance just closes (when you can no longer move the rocker sideways) and measure the distance between the pointer and TDC mark . Then calculate the approx opening of the inlet valve.
This ,although not an accurate measurement , will still show if the valve timing is set too far in advance or they adjusted it on assembly.

I hope this helps
Geoff
Reply With Quote
  #6 (permalink)  
Old 07-06-19, 05:41 AM
Member
 
Join Date: Jun 2018
Posts: 39
Default

Hello Geoff,

thanks for your comment and advice.

In the meantime I found a notice of a PO in the files that it is a late 403 camshaft. I hope I'll find more e.g. a bill.

Therefore I've to aks if I shall measure with 0,002 or 0,005 clearance or both.
Reply With Quote
  #7 (permalink)  
Old 07-06-19, 06:18 AM
Member
 
Join Date: Jul 2008
Location: Sydney, Australia
Posts: 294
Default

Bela ,
If the camshaft is a late 403/404/405 grind the advertised timing is
Inlet opening 36 BTDC
Inlet Closing 76 ABDC
Duration 292 deg (this is further away from the 258 deg of the notes.)
Lobe lift .205 inch
Recommended valve clearance .005 cold

I suggest you adjust the valve clearance firstly at .002 inch and rotate engine until you can not push the rocker sideways , as per my earlier post.
Then repeat at .005 inch clearance

--------------------------------------------------
The hand written notes could have been of the original badly worn camshaft before the engine was stripped for a rebuild.

Geoff
Reply With Quote
  #8 (permalink)  
Old 07-06-19, 06:39 AM
Member
 
Join Date: Jun 2018
Posts: 39
Default

My grandchild will spent the holidays with us so it will take time.
Reply With Quote
  #9 (permalink)  
Old 22-06-19, 07:53 PM
Member
 
Join Date: Jun 2018
Posts: 39
Default

Next week I will have a look.

In the meantime I found something in the WSM that sounds strange to me - see picture.

It is the first time I saw a cold clearance is minor than the clearance of a hot engine. How does it work? Parts expand when getting hot.
Attached Images
File Type: jpg Valve_clearance.JPG (38.3 KB, 12 views)
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


All times are GMT. The time now is 08:10 PM.


This is the live site

Search Engine Friendly URLs by vBSEO 3.6.0 PL2