Valve clearances

Spark · Post by **Spark** » Wed Dec 24, 2014 12:34 pm

Hello
Refurbishing cylinder head on series 1 2+2
Rebuilding using existing valves, springs etc, head has been vapour blasted to bring back to new finish. Prior owner had spent money refurbish also so have checked springs etc
When I refit crankshafts I have the following clearances
Inlet spread across 012" to 014"
Exhaust 012" to 013" one rouge valve measures at 018"(can fit larger pad)

My question is the manual states inlet 004" and exhaust 006"

The engine ran very well before break down, is the head off another car as its doesn't have a serial number just a stamp at end with B804

Any help please

Post by **mgcjag** » Wed Dec 24, 2014 2:33 pm

Hi not sure re the head but have a look here at the different camshaft options and gaps....

http://www.georgiajag.com/Documents/Camshafts.html

ALAN COCHRANE · Post by **ALAN COCHRANE** » Wed Dec 24, 2014 2:53 pm

Hi Spark

The valve clearances for a standard S1 3.8 are as the manual states. I recently cured my engines annoying tappety noise by re-shimming the valves. My initial clearances varied from 0.04 to 0.09 thou and they were noisy. believe me. It's difficult to comment on your engine without knowing what other mods have been done to your engine. Despite that the clearances seem excessively large and are more like those for a highly tuned race engine.
One thing I did discover is that it's vitally important to use a quality micrometer when measuring the shims. I ended up buying a Mitutoyo vernier micrometer. This will prevent you from ending up ordering shims of the wrong thickness. If you do need new shims I have a fair old selection for some unknown reason.

Cheers

Alan

Spark · Post by **Spark** » Wed Dec 24, 2014 3:48 pm

Guys
Thanks
Looks like I have the newer camshafts with the 4 bolts hence the valve clearance shown
Can someone please confirm what the clearance should be link mentions 12 to 14 thou
Any other feedback would be welcome on head and camshafts

Thanks
Phil

PeterCrespin · Post by **PeterCrespin** » Wed Dec 24, 2014 5:52 pm

Shim the 18 thou one and the rest are fine. 12-14 is the target range, not 12 inlet 14 exhaust.

Is your head unpolished at the front? Does it have 1.875" inlet valves?

abowie · Post by **abowie** » Thu Dec 25, 2014 1:25 am

It's hard to tell absolutely from the pictures but the cam lobes do look like the later profile and as Peter says 12 - 14 thou is the correct gap.

If you had the earlier profile and gaps set as you say your tappets would be very noisy.

PeterCrespin · Post by **PeterCrespin** » Thu Dec 25, 2014 2:01 am

abowie wrote:It's hard to tell absolutely from the pictures but the cam lobes do look like the later profile.

They are 4-hole cams. Parabolic 12-14 is a given.

abowie · Post by **abowie** » Thu Dec 25, 2014 4:27 am

PeterCrespin wrote:
abowie wrote:It's hard to tell absolutely from the pictures but the cam lobes do look like the later profile.
They are 4-hole cams. Parabolic 12-14 is a given.

Yes I agree that is most likely, but cams do get reground occasionally.

Spark · Post by **Spark** » Fri Dec 26, 2014 1:04 pm

Thanks for the feedback
Have attached some pics of the head as this may clear things up
The front is not polished and wasn't painted
Valves all now set at 12-14tho
Any further comments welcome

Thanks
Phil

PeterCrespin · Post by **PeterCrespin** » Fri Dec 26, 2014 2:28 pm

The polishing and valve size was to see if it was a Series 3 XJ head. Unpolished unumbered could just be regular S2E. There are water passage differences too but valve/port size is all that matters for performance.
Just curious.

Spark · Post by **Spark** » Sun Dec 28, 2014 3:03 pm

Hi
See pictures
The inlet valve measures 1.745" exhaust 1.625"
Does this help clear the head model
Thanks
Phil

PeterCrespin · Post by **PeterCrespin** » Sun Dec 28, 2014 6:14 pm

Yes, normal straight port head. Long stud engine. Assuming uour block has matching water passages at the back, a big-valve S3 XJ 4.2 head would go straight on. OTOH there's no point now you've got a refurbished standard one.

Pete

Dave K · Post by **Dave K** » Sun Dec 28, 2014 9:59 pm

My car has a big valve head and reprofiled cams and I have the valve clearances at 12 and 14 thou.
Standard engine should be 4 and 6 thou.

Dave

christopher storey · Post by **christopher storey** » Sun Dec 28, 2014 10:51 pm

Dave: that is not, I'm afraid, quite correct. The parabolic cams were introduced in 1968/69 I think , and it was those which governed the change in valve clearances, not the introduction of the big valve head with the S3 XJ6 . Therefore, if your engine has parabolic cams, the larger clearances apply

Post by **mgcjag** » Mon Dec 29, 2014 9:19 am

Hi all.......a friend has a 69 car and has a non parabolic on the inlet side and a parabloic on the exhaust side......the engine has been re built but no attention was drawn to this and the gaps all set at 12-14......it does sounda bit rattaly so we took the covers off and found the different cams........whats your opinion......swap for a cams or use the correct setting per type of cam.....Steve

christopher storey · Post by **christopher storey** » Mon Dec 29, 2014 9:26 am

If you change the inlet cam for a parabolic, you will still have to reshim that side for the particular cam you use, so it is easier just to reshim to the 4 thou nominal clearance . At least, using that cam, all you have to do is an arithmetic exercise from identification of the shims already present, which will enable you to order the new shims immediately

Post by **mgcjag** » Mon Dec 29, 2014 10:07 am

Thanks for the quick reply are we saying that its ok to have a mix to cams so long as the gaps are set for that particular type of cam.....Steve

christopher storey · Post by **christopher storey** » Mon Dec 29, 2014 3:56 pm

I don't see why not. Bearing in mind that the object of the parabolic cam was to cut down noise by altering the ramp acceleration of the cam, it is probably a little noisier to retain the earlier cam on the inlet side, but I can't see any harm other than that

EDIT : since writing that, Steve, I have been wondering. The later parabolic cams IIRC , fitted eg to the S3 XJ6, were timed slightly later than the earlier ones - 4 degrees comes to mind - for emission control purposes. The relative timings were still the same, so that instead of 57/15/15/57 it became 53/19/19/53 , but the timing notches on parabolic cams may be 4 degrees out from the E type timing . It probably doesn't matter a great deal which you use as long as you are consistent i.e. both inlet and exhausts are set to the same set of timing figures

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