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998 Re-Bored


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#1 Syma

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Posted 19 February 2018 - 01:12 AM

Let me start off by saying that I would love love love to replace my 998 with a 1275 but being in Canada they are hard to come by and the ones I have found will cost me well over $2500.

With that said I have to stick with my trusty 998 but it needs to be rebored. I was thinking about having it bored to +60 so I can fit http://www.minispare.../P22463-60.aspx flat top pistons from mini spares. I understand that I will have higher compression but what I would like to know is there anything else I need to do? I don't want to spend too much more money on this engine as I hope one day to be able to afford a 1275.

thanks

 



#2 ACDodd

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Posted 19 February 2018 - 07:52 AM

Can you get hold of a 1098 crank?

Ac

#3 mikal

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Posted 19 February 2018 - 08:23 AM

Hi AC,

 

Pardon my ignorance but out of curiosity can you please elaborate on the 1098 crank for a 998 engine? How does it work/ what are the benefits? Is it to do with the longer stroke therefore more cc's?

 

Thanks

 

Mikal



#4 Spider

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Posted 19 February 2018 - 10:33 AM

Hi AC,

 

Pardon my ignorance but out of curiosity can you please elaborate on the 1098 crank for a 998 engine? How does it work/ what are the benefits? Is it to do with the longer stroke therefore more cc's?

 

Thanks

 

Mikal

 

The 998 and 1100 engines are all the same, except for the crank, pistons and head.

 

So, if you can get your hands on an 1100 crank, it will fit right in to your 998 block. As you'd be boring it anyway, but 1100 pistons and you're 3/4's the way there ;D



#5 ACDodd

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Posted 19 February 2018 - 01:18 PM

Yes you increase the stroke from 3" to 3.3". Boring the block to +0.060" with the longer stroke crank will give you 1150cc. This makes a cracking base for a road engine giving around 72bhp/72lbft, with a smooth idle, given all the right bits. It will perform very much like the larger 1275 engine, and still need to turn less than 6krpm to achieve it.

Ac

Edited by ACDodd, 19 February 2018 - 01:19 PM.


#6 mikal

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Posted 19 February 2018 - 10:36 PM

Thank you both for the explanations.

 

Cheers

 

Mikal



#7 Cooperman

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Posted 19 February 2018 - 10:41 PM

If you can still get them the +0.080" Hastings flat-top pistons for the 998 are very good. That gives 1060 cc.

 

What flat-tops in oversizes for 1098 engines I'm not sure, but the 1098 is excellent for producing good torque and for running up to around 6000 rpm.

 

In about 1968 my wife had a 1963 850 Mini into which I put an MG 1100 engine with a 731 cam, twin HS2's, Cooper manifolds, etc. She used it as her going-to-work and general running around car and it was very nice to drive. It didn't stop too well with single-leading-shoe brakes, but it was better with Cooper 7" discs. It had 10" wheels and Goodyear G800 145/80 x 10 tyres (anyone remember them?).



#8 Retroman

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Posted 19 February 2018 - 11:40 PM

I can sometimes have stock of +.080" and .100" and 68mm (plus .120 ?) flat tops which takes the 998 to 1107 cc  and 1098 to 1217.

Just building a 1217 at the moment with a 12g295 head, vizarded HS4 and a Cooper S type cam should make a really well mannered useful road engine.

  As Ac says the 1098 crank is a good way to go for a nice road engine. It could be cheap cc's and torque.

I would consider a head and cam change at the same time.

Value for money wise on a 998 or 1098 the head and cam should be a priority.

A 12g295 head and a 255 / 266 degree duration cam would make good improvements.

My daughter was on Vancouver Island for a wedding last year, it looks fantastic.



#9 Spider

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Posted 20 February 2018 - 02:10 AM

If you can still get them the +0.080" Hastings flat-top pistons for the 998 are very good. That gives 1060 cc.

 

They also come in +0.100" and +0.120" for both 998 and 1098, but these all need off set boring.



#10 hhhh

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Posted 20 February 2018 - 03:24 AM

If you're going to run a low lift cam, there's a good chance you can use a 1275 head (bigger valves and ports and open chambers) without having to pocket the block since 12G295s are hard to find.



#11 Syma

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Posted 20 February 2018 - 04:19 PM

Thank you everyone for the awesome information. I'm going to take a look to see if I can get a 1098 crank somewhat locally.

Thanks



#12 hhhh

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Posted 20 February 2018 - 04:29 PM

The obvious source for a 1098 crank is the (formerly) ubiquitous Austin 1100s of which many were imported to Vancouver Island. I used to buy them for $100 and run the crap out of them back in the 80s. You don't see them so much anymore. I'll check my crank stash and see if I have a 1098 crank. I know I have 12G1316 heads which are the same casting as the 12G940 1275 head if one of those interests you. 



#13 Syma

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Posted 20 February 2018 - 04:37 PM

I just had my head ground and rebuilt but I would be interested in a crank. Are you on Vancouver island as well?



#14 DomCr250

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Posted 20 February 2018 - 04:38 PM

Yes you increase the stroke from 3" to 3.3". Boring the block to +0.060" with the longer stroke crank will give you 1150cc. This makes a cracking base for a road engine giving around 72bhp/72lbft, with a smooth idle, given all the right bits. It will perform very much like the larger 1275 engine, and still need to turn less than 6krpm to achieve it.
Ac


This was one of the best A series setup I ever had, I had a 12g295 on it, mild cam, 1.5" SU and a three branch, got similar figures to above once it was setup on Redlines rolling road in Iver.

#15 hhhh

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Posted 20 February 2018 - 05:12 PM

I just had my head ground and rebuilt but I would be interested in a crank. Are you on Vancouver island as well?

Yes, I'm in Victoria.






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