5 replies to this topic

[Curtis Brown]

Hello everyone,
I was wondering, what is the ideal ratio for a standard stroked 1275? I have seen 6" con-rods on the market, which I could include in my next build. With improving the ratio, would there be a noticeable improvement in power or less wear on the bores and pistons? In addition, are there any downsides to the use of the mandatory shorter pistons in a fast road motor? Any info will be much appreciated. Thanks..

Curtis

[Curtis Brown]

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[Cooperman]

I think more info on your build is necessary. What is a 'standard' stroked 1275. If it is standard then it will be standard bore & stroke.

[Curtis Brown]

By standard stroke, I mean 81.3 mm. The rest of the engine will not be though. I am planning on a SC 7 port but I have not decided on a cam yet. Although I did not think the engine spec would affect the pro's/con's of improving the stroke/rod ratio.

[ACDodd]

Increasing the rod lengh from stock on your stroke would increase the given compression reading figure due to a longer dwell around TDC. The fuel we have now is shockingly bad for the A-series. I would suggest if you try a longer rod, you will need to reduce the static compression to compensate at the fuel will detonate easier for a given compression. This ia already a problem in the A-series so I would not try to make it worse!!

see here for more info;

http://www.stahlhead..._Rod Length.htm

AC

[bmcecosse]

The longer rods will presumably also be heavier...... why do you want to make this change ? You would need special (no doubt v expensive) pistons too.....