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Camshaft Interchange


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#1 Ruth's Mini

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Posted 13 September 2017 - 01:14 PM

As we make progress on our project (1961 Mini Minor with original 850 engine) I was quite surprised to discover that there is only 1 camshaft bearing. The other 2 journals are metal on metal. I know later engines had a bearing for each journal.

 

I've already looked into switching to a higher volume oil pump so think replacing the camshaft with a later one would allow me to use one with the correct drive.

 

So I'm wondering if journal size is at least as large and is lift & duration compatible with the 850 pistons?

 

thanks in advance,

Brian & Ruth


Edited by Ruth's Mini, 14 September 2017 - 12:22 AM.


#2 Cooperman

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Posted 13 September 2017 - 05:05 PM

The best thing to do is to have the block line-bored to accept camshaft bearings. Then fit a slightly better cam, maybe a Kent 256.

With the later cam you will be able to fit the later slot-drive oil pump. You do not need an uprated pump as the standard one is fine, even for a 1275.

Lightly gas-flowing the head would be an advantage together with a better exhaust manifold and exhaust system. In fact, the standard original 98 Cooper exhaust system is good on an 850, certainly no larger in diameter.

With all that an HS4 carburettor is slightly better.



#3 carbon

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Posted 13 September 2017 - 07:51 PM

As we make progress on our project (1961 Mini Minor with original 850 engine) I was quite surprised to discover that there is only 1 camshaft bearing. The other 2 journals are metal on metal. I know later engines had a bearing for each journal.

 

I've already looked into switching to a higher volume oil pump so think replacing the camshaft with a later one would allow me to use one the correct drive.

 

So I'm wondering if journal size is at least as large and is lift & duration compatible with the 850 pistons?

 

thanks in advance,

Brian & Ruth

 

 

The pin drive oil pumps currently available are likely to be higher capacity than the original. If you're not planning on a wild cam or regular use of high rpm the two bearings running on cast iron should be fine.

 

All depends on how original you want to keep it.

 

If you're looking for more power you would probably be better off fitting a 998 unit. Pretty easy to pick up second hand, not easy to tell the difference from outside, and can keep up with traffic more easily.



#4 gazza82

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Posted 14 September 2017 - 09:43 AM

 

As we make progress on our project (1961 Mini Minor with original 850 engine) I was quite surprised to discover that there is only 1 camshaft bearing. The other 2 journals are metal on metal. I know later engines had a bearing for each journal.

 

I've already looked into switching to a higher volume oil pump so think replacing the camshaft with a later one would allow me to use one the correct drive.

 

So I'm wondering if journal size is at least as large and is lift & duration compatible with the 850 pistons?

 

thanks in advance,

Brian & Ruth

 

 

 

Pretty easy to pick up second hand, not easy to tell the difference from outside, and can keep up with traffic more easily.

 

 

In Ontario Canada??



#5 Ruth's Mini

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Posted 14 September 2017 - 10:11 AM

yes, Barrie, Ontario



#6 gazza82

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Posted 14 September 2017 - 01:38 PM

To give him some slack your location doesn't appear on the mobile version of the forum only the full PC interface .. so he may not have realised! :-)

 

That 850 is like some of the smaller in-line A-series engines .. one cam bearing. Pretty much a standard recommendation to have them line bored and three cam bearings fitted .. just for longevity.



#7 carbon

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Posted 14 September 2017 - 06:39 PM

To give him some slack your location doesn't appear on the mobile version of the forum only the full PC interface .. so he may not have realised! :-)

 

That 850 is like some of the smaller in-line A-series engines .. one cam bearing. Pretty much a standard recommendation to have them line bored and three cam bearings fitted .. just for longevity.

No slack required, I should have read the OP's location...

 

I guess there are not that many cheap 998 units available in Ontario



#8 Ruth's Mini

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Posted 15 September 2017 - 01:49 PM

I can source a 998 camshaft but to be absolutely clear can the 850 block be machined to accept it AND is it going to be compatible with the 850 pistons?

thanks



#9 Cooperman

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Posted 15 September 2017 - 03:41 PM

Yes, most camshafts will fit the 850. All A-series cams have the same size journals. the difference with the 850 in the Mini compared to all the other Mini engines is the lack of camshaft bearings on all 3 journals. It is relatively easy to get the block machined to take the bearings in all journals and that is a wise thing to do.

However, if the 850 cast iron journals are OK it is possible to just fit a different cam, although the old issue with wear will not have gone away.

 

I'm just doing a very full restoration on a 1964 850 and when I do the engine I shall have the block machined and bearings fitted. As for a cam, I shall probably go for a Kent 256 and lightly gas-flow the head with a compression ratio of around 9.8:1.

 

The standard 998 can is not really any improvement on the 850 cam unless it is from a 998 Cooper.

 

I hope this helps.



#10 carbon

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Posted 15 September 2017 - 07:21 PM

I can source a 998 camshaft but to be absolutely clear can the 850 block be machined to accept it AND is it going to be compatible with the 850 pistons?

thanks

A pin-drive 998 cam will be a drop-in replacement, and should not need to have cam liners fitted to the block as it's pretty gentle profile.

 

I don't think A+ 998 cam is such an easy swap.

 

There is plenty of clearance between pistons and valves, and all of the cam profiles are compatible with 850 pistons. What you need to watch when changing heads (mainly applies to using 1275 head on small bore engine) is the exhaust valve touching the block at full lift. This should not affect your rebuild as long as you keep the standard sized 850 exhaust valve.



#11 Cooperman

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Posted 15 September 2017 - 07:34 PM

As far as I know the swap between any cam is OK so long as the oil pump bolts line up. A slot-drive cam/pump will now be best and if it is a 4-bolt pump it will need an additional 1/4" UNF hole drilled and tapped into the end of the block. I just fitted a slot drive cam into a 1969 Cooper 998 block and there were no problems with either the cam or the oil pump.

 

A 998/850 slot drive pump will fit fine once the hole positions are confirmed and drilled as necessary.

 

So long as a small-bore head is fitted there will be no valve clearance issues. The 12G940 head, as used on the 1275 engines, can have issues with the valves hitting a small-bore block deck, but I don't think the OP intends using a head from a 'big' engine.



#12 Ruth's Mini

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Posted 15 September 2017 - 08:18 PM

many thanks everyone!



#13 Ruth's Mini

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Posted 15 September 2017 - 09:04 PM

I think our last question on this topic... :-)

 

did the 850 (848) engine ever have 3 camshaft bearings?

 

thanks,

Brian & Ruth






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