39 replies to this topic

[cap'n crunch]

I was wondering if it was possible and how easy would be/how involved, by stroking my current 998 engine by using a 1100 crank shaft, is it possible? becuase i know they have the same bore just a different stroke length. Any help would be gratefully received!

[nomininolife]

There shouldn't be any problem with doing that, but if I am wrong hopefully someone will correct me.


David

[Dan]

You need special pistons with a reduced crown height (or the extra stroke will push them out of the block and mash them into the head), but other than that there is no difference between the two engines. It will need a rebore so you'll need to go to at least +20 (I think that's the first re-bore available on the small block now).

[Big_Adam]

With very long stroke cranks it can be necessary to grind out part of he block and parts of the gearbox housing in order to gain clearance.

2 secs.

[attachment=28318:DSCN1428.JPG]

[attachment=28317:DSCN1427.JPG]

Might not be a problem but if you have one you'll know.

Edited by Big_Adam, 02 March 2007 - 01:22 AM.

[fikus01]

think thats more for the 1430 - 1500 bracket engines but i was guna put that too, hehe, i think the 1098 rods are shorter if u have them too!! dont quote me on that

[Guess-Works.com]

or just buy a 1098..

[cap'n crunch]

You need special pistons with a reduced crown height (or the extra stroke will push them out of the block and mash them into the head), but other than that there is no difference between the two engines. It will need a rebore so you'll need to go to at least +20 (I think that's the first re-bore available on the small block now).

so i can't just use 1098 pistons? also why will i need to overbore?

or just buy a 1098..

thats is one solution.....but that would be far to easy

[sqweaka]

by stroking a 998 with a 1100 crank are you not just making a 1100?
if so whats the point why not as guessworks said get a 1100 in the first place
dont see the point, if your rebuilding the engine for more power better fitting a 1275 me thinks

[Dan]

The rods are the same, it's the pistons that are shorter.

The block and gearbox don't need relieving.

Yes you can just use 1098 pistons, if you can find a set. You need a re-bore because you are fitting new pistons which cannot be run on the surface the old pistons were run on, the rings won't seal. Also they are travelling further so the rings will hit the ridges at the top and bottom of the stroke left by the old piston's wear pattern and this will shatter them. So the ridges and the previous wear pattern must be reomoved. It might be possible to do this without going +20 but it's unlikely.

It is probably easier to get a genuine 1100 but they are getting rarer, especially if you want an A+.

Just to be sure, you know you CAN'T do this by stroking a 998 crank don't you? It seems that some people above seem to be sugesting that. You need an 1100 crank casting, a stroked 998 crank would have way undersize bearing journals and probably be quite weak. The castings are quite different.

Edited by Dan, 02 March 2007 - 09:52 AM.

[cap'n crunch]

Thanks dan that has made things a lot clearer, and yes i am aware it will need a actual 1100 crank.

I am asking this because i have a spare 998 A+ engine that i would like to do something with, and it will be cheaper to stroke the 998 than buying a 1098 engine especially as it is all but the same engine.

So it may be possible to re-bore rather than an overbore? because surely this will solve the problems you suggested about the rings not sealing.

[Guess-Works.com]

depends how much you want to pay for a 1098

and as Dan says, then ones I have are A series not A+, they are very few and far between...

Edited by GuessWorks, 02 March 2007 - 10:52 AM.

[cap'n crunch]

if it does need a overbore of +20 then where can you get suitable 1098cc or 1115cc pistons?

[Dan]

I always use Mini Spares for pistons (don't rely on the website, call them). How much boring needs doing depends on how worn the cylinders are and (almost as important) who is doing the machining and how good they are. Lining a cutter up inside an existing hole to within a thou is tricky if it's the same size as the hole already there, you can easily oval out the hole. That's why it's more common to overbore than try to stick a standard cutter down an existing bore I believe. You could get the original bore by having it linered if you wanted, Mini Spares have a small stock of small block liners left at present. It will last longer if it is linered than a bare block will.

[rozzer!]

wouldnt it be easier to rebore to say +40 thou or something, it would work out a hell of a lot cheaper than tryig to get an 1100 crank and pistons, etc.

[cap'n crunch]

if i bore my 998 out to +40 it will mean it will only be 1030cc. Also i am looking at a re-stroke to 1098 because it will be a long stoke engine and hopefully have better torque characteristics and there is not replacement for displacement.

Edited by cap'n crunch, 03 March 2007 - 02:12 PM.