7 replies to this topic

[Hughieboy]

I have been offered a mini engine block that the guy says is 'short stroke' and believes it is a 1.0L. Can anyone please explain to me what a 'short stroke' block is and what are the advantages/disadvantages of one. I have a stage 4 head too, would this be suitable for this block? Not being particularly mechanically adept any help and information would be very much appreciated. Thanks, JJ.

[carbon]

Would be worth asking for a bit more detail from the seller of this unit. The 998cc engine is 76mm stroke which is not particularly short. Did he possibly mean 'small bore' engine, as this is another term used to descibe the 998 engine.

 

The benefits of a Stage 4 head will depend on what you are planning to use the engine for...

[Alex_B]

Stroke is  the amount the piston travels up the cylinder, short stroke means a shorter con rod and the crank doesnt have as much offset where the conrod mounts, 

Pretty sure he means a small block engine which will be 850, 998, 1098cc as all the a-series engines are quite a long stroke. 

only way to tell is either the engine number or measuring the bore and conrods, the stage 4 head means very little as the stages arnt defined and one mans stage 4 is another mans mildly tweaked, plus we dont know what the engine is and cant say the head will fit, the 1275 head wont fit the 998 block without modifying where the exhaust valve goes (pocketing the block or sinking the valve into the head) 

Edited by Alex_B, 02 September 2013 - 08:24 PM.

[Cooperman]

Of course, the REAL 'Short Stroke' Mini engine is the ultra-rare 970 Cooper 'S' block which is classed as 1 litre, but is completely different from a 998.

The 1098 is one of the longest stroke engines and the 998 is not really short stroke as the stroke is still larger than the bore.

It depends on which block it is before one can tell if the head you have will fit at all. If it is a 970 block, the head should fit, but the compression ratio will need sorting out by skimming the head quite a lot.

there is no point in trying to engineer a really big-valve head from a 1275 engine to go onto a 998.

[Rog46]

He's not getting confused with a "short engine" i.e. less cylinder head and ancillaries etc, is he?

[jaydee]

I have been offered a mini engine block that the guy says is 'short stroke' and believes it is a 1.0L. Can anyone please explain to me what a 'short stroke' block is and what are the advantages/disadvantages of one. I have a stage 4 head too, would this be suitable for this block? Not being particularly mechanically adept any help and information would be very much appreciated. Thanks, JJ.

 

Hes referring to a 998 engine, otherwise you would have one of the rare 970 or 1070 S engines..

 

Its not unusal to consider the 998 as a short stroke and the 1098 as a long stroke of the small bore engines.

Infact both are exactly the same bore of 64.58mm, with the 998 of a 76,2mm stroke and the 1098 stroked to 83,72mm.

In terms of advantades pros and cons, the short stroke will be capable of higher revving, and will be more reliable on the long run (a 998 is capable of maintaining high rev speeds for outstanding periods), while the long stroke will develop more torque but at the expense of revving slower. Also they tend to use more oil.

 

Square and oversquare engine is another matter. The 1071 is an example of this, being 70,6 bore and 68,26 stroke.

The 1275 variety has a even longer stroke of 81,28mm.

 

Bear in mind these figures are all nominal, the real ones may slight differ as they were engineered in inches and thousands of inches plus you have to add the manifacturing tolerancies.

[Cooperman]

There are now 2 threads running in parallel on this topic. The other one has more info.

Shall we close this one?

[Tamworthbay]

Done