Hi all

I have been running std flat top cast pistons in my race motor for some time now (cannot afford forged ones). Just wondering what everyone out ther who run std cast pistons rev to. I rev my car to around 7000 constently in race situations. Not sure if it would hold together to 8000 but would like to know of anyone experiance.

Thanks

Ashley

You shouldn't have to worry about the pistons, I've known people who consistently take their engines to 7500+ or - without problems with standard pistons.

It's the valve springs and the rods bolts that are probably the major determining factor in how high you can rev it. I've seen more "rod ventilated" blocks, broken valve springs/keepers and rocker arms from over-revving than piston failures.

You also might not want to rev. so high especially when your horse power may peak, say 6500 or something. This is where a dyno pull print out will show your useable hp and much past that point your hp drops off and you should be in the next gear. Well unless you're like me and pegging 5th, I need rear gear swap.

True, the cam profile is going to be a factor in how high you want to rev it, but as anyone knows, there are times you rev it higher than you expect....:devious:

I should have added in my first reply, the compression ratio will be a big factor in the equation too...

Phred would be a good one to tell you about the maximums of the stock pistons better than I as he has built race engines and knows where the cut-off point should be.

IIRC at around eight you start to head for camshaft and crankshaft breakages. Cast pistons are more of a problem if you get a bit of pre-ignition, forged ones can withstand more such abuse.

Well with "Big Sam" we are using Mahle pistons and rev limit is 9200. Peak torque is between 6000 & 7500 and we have only gone over 7500 on occasional down changes in the gears.

Nick H am i to understand your the owner of the restored BIG SAM from the UK ?

I read the article on zhome.com a while back and was very interested if you have any pics of the car please share .

As the others say i don't think your cast iron pistons will be the problem in your motor. But that's from what i read not first hand experience.

Have you read the How to Modify and Race your L engine? Book?

It's possible to get a Z to make power above 6500rpm. My mates car runs to 7500rpm no worries it's the SU's that restrict him from there.

Hi Gav,

Yes I've had Sam for about 14 years now. The straightening and restoration took about 2 of those. Pic wise I have been trying to "downsize" the pixels to enable me to get them on here. (As you can see I am not much into Pixels and bytes and things!

Nick Howell