What is the compression ratio of the 2.5 Ross pistons sold by Gary?
What is the compression ratio of the 2.5 Ross pistons sold by Gary?
get a burette and measure the volume of the dish. When I do this on a piston, I put the piston head exactly .050" below the deck surface, apply some vasiline around the piston to cylinder wall to seal the install a peice of Lexan over the cylinder and measure the exact fill volume, then subtract the .050 volume (approx 8cc's but you can accurately calculate). once all done you'll have the exact dish volume then you can easily calculate your exact CR.
I really wish the head hasn't been bolt to the block, other wise I'd use your method in a heart beat.
I don't think definitive specs were ever published, Gary would probably be the only one who could answer. otherwise you would have to physically measure volume and calculate it out. the available specs would lower the ratio from stock, I would think. the dish is supposed to be slightly deeper (0.300), and the ring lands lower on the crown...also, (thought of this looking at your pic) - didn't Gary's run exclude valve reliefs?
yep the reliefs are machined per user. whoever machined mine made very deep clearances....
I sent a message to Gary D yesterday and this is what his response was:
Re: Relentless Ross piston questions
> The pistons don't have valve reliefs and I'm wondering what your reasoning was behind that.
The notches were a failure point at high power levels, too close to the ring pack.
> At what point are they necessary?
If I recall you were fine at all times up to a .460 lift cam, a .500 cam would work too but there is no leeway if a timebelt was broken.
> The pistons also have a deeper dish, do you know off hand what the resulting compression was with a stock swirl head?
should have been stock.
Posted with his permission
Martin
89 Horizon
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