19.5 Compression Ratio

[afgunn]

I was just reading an ASE 8 training manual and it stated that in 1999 the compression ratio was changed to 19.5:1. I am assuming this was done with the pistons or the heads since the bore and stroke are the same as the other 6.5s. Does anyone know which it was and would 19.5 be as good/better CR to shoot for with the GM heads or pistons (which ever it was)? Which would be better the 19.5:1 or 18:1? Seems the GM parts would be less expensive than the aftermarket 18:1 pistons!? Are these GM parts hard to come by?

[AndyL]

Popular belief says the 19.5:1 engines were never installed into GM trucks.

However, I wouldn't be surprised if the new AM General engines are 19.5:1.

[DA BIG ONE]

I'm guessing only the the 1999 65 HO did come w/lower compression, however, there are those who say it never made it to production. So, is it a rumor, or?

Thinking parts manual would reveal the truth................but, I have had some bad luck with GM parts manuals too even when using vin#.

[Craig M]

Some of the parts houses, selling surplus military pistons, mention 19.5 compression ratio pistons. I question them and usually get ???

[afgunn]

Craig M,

Do you have the link or phone numbers of any of these part houses that are selling the surplus military pistons?

Also, I guess I will check on the post here at Ft Bragg on that 19.5 CR, since I live here and work on the post. Here are the GEP CURRENT Specs: http://www.amgeneral.com/vehicles_ge...ifications.php (20.2 or 18.1). Still do not know if 19.5 was made in the past and how they did it - most likely the pisons though since the heads do not have a combustion chamber except for the IDI chamber.

Thanks for that info!

[Craig M]

Go to ebay and search under "6.5 diesel" and "6.5L diesel". A couple of vendors should come up.