Comp ratio 9,3 or 8,5:1

[73 tom tech]

Hi!

I am rebuilding a 3,0 sc engine and i am not shore what the compr ratio is on my engine .
My engine no Is *6403438* can someone tel me what compr ratio i have.
Ned to order a set of pistons and cylinders.

Hope of help

[ninesixfour]

Are you sure it's not 64C... instead of 640...? Also what is the car's VIN number?

[73 tom tech]

I am very shore 640 as the numbers are well stamped to the engine case.
Win no is 91a0 143383


And the haynes manual is cuite confusing on what the camtimming is to be set @
1mm or 1,55mm.

[Flat6pac]

The vin is 1980. 1980 Is a 9.3 Cr if its a US car. If its a ROW its an 8.7. On the flat below the engine number is a 930/xx number. with that number we know exactly what timing number you need.
Bruce

[73 tom tech]

Hi!
It is a US car . so then i can order the 9,3: pc kit.
On the block it is stamped 930 *07 so what is the cam timing mesure then !!!!!

[Flat6pac]

Cam timing is 0.9 to 1.1 with 1.0 being ideal
Youre buying new P&Cs? What did you have that youre replacing?
Bruce

[73 tom tech]

Originally Posted by Flat6pac

Cam timing is 0.9 to 1.1 with 1.0 being ideal
Youre buying new P&Cs? What did you have that youre replacing?
Bruce

The 911 is from california, the engine smoked very heyy, but it dident smell burnt oil it was a more light blue smoke and a lot of it, when the engine came to operating temperature, it started to smoke. the smoke started in the exhaust manifold and damper, as it was heated there, a comp test did show 150-160psi
on *3 *4 *5 *6 and 70psi on *1 and on *2 zero. Then i did a leakdown test and did find bad ring sealing on cyl 1 and 2. Pulled the cylinder of the piston and parts from the piston and rings fell on the flour. I think this came from gasolin with low octane , resulting pre ignition and high pressure on the first compr ring and frakturing the piston grooove, all the piston parts breaked off inwords to the casing.
And cam timing on *4 mesured 1,78mm with the tensioner mounted, yes it has changed to oilpressure type chain tensioners.

[Steve@Rennsport]

Broken rings and piston ring lands are not uncommon on these engines and yes, its due to detonation. Most US cars received cast pistons that didn't tolerate such operating conditions.

If you opt for the higher CR P/C's, make sure you use a fuel that will support this and confirm your ignition timing is compatible with the octane in use.

[73 tom tech]

Originally Posted by Steve@Rennsport

Broken rings and piston ring lands are not uncommon on these engines and yes, its due to detonation. Most US cars received cast pistons that didn't tolerate such operating conditions.

If you opt for the higher CR P/C's, make sure you use a fuel that will support this and confirm your ignition timing is compatible with the octane in use.

Is it best to change all p/c or just the 2 broken ones!
Here in norway you can chouse from 92 octane 95 / 98 and 99 octane.

I just want to replace p/c to std CR for the engine.

[Flat6pac]

In order to match what you have you need to find a partial set and you need to match the deck height. It is on the collar of the cylinder, there is a 0, 1, 2. These are bore sizes but right next to it is a triangle with a number inside either 5 or 6. This number needs to be matched to complete the 6.
There is a number cast inside the piston and that tells us exactly what the unit is. The number if Mahle will be like 95L58 amd if KS it will be like 95138. Then post in wanted exactly what you require such as Wanted 2 P&Cs Mahle, deck 6 piston 95L58
Bruce

[73 tom tech]

Originally Posted by Flat6pac

Cam timing is 0.9 to 1.1 with 1.0 being ideal
Youre buying new P&Cs? What did you have that your replacing?
Bruce

Hi!
Am I wright or wrong! My engine is stamped 930*07 isent cam timing then to be set @ 1,4 - 1,7 mm this is the same for 930*16 as well???

But as you mentioned, isent it for case stamping 930*04 then cam timing is to be set @ 0,9 - 1,1 mm?

[Tom F2]

You probably have better fuel in Europe, so you may not need to worry. In the States, it can be hard to get the good stuff. So, when I rebuilt my 83 US market 3.0 liter, I replaced the 9.3 KS alusils, which are in excellent shape, with a set of lightly used 8.5 CR Mahle nikasils that I had on hand. I know that it sounds a little unconventional, but I can't feel any loss of power. I wonder whether the nikasil is enough of an improvement to offset the lower CR, or perhaps the difference in CR is not enough to notice. It's an option that you may want to consider.

[73 tom tech]

Originally Posted by Tom F2

You probably have better fuel in Europe, so you may not need to worry. In the States, it can be hard to get the good stuff. So, when I rebuilt my 83 US market 3.0 liter, I replaced the 9.3 KS alusils, which are in excellent shape, with a set of lightly used 8.5 CR Mahle nikasils that I had on hand. I know that it sounds a little unconventionaly, but I can't feel any loss of power. I wonder whether the nikasil is enough of an improvement to offset the lower CR, or perhaps the difference in CR is not enough to notice. It's an option that you may want to consider.

Hi!
The fuel here in Norway is pretty good 95 octane as the worst and 99 octane as the best.
The 8,5:1 p/c kit is 1000 us dollars less than the 9,3:1 p/c kit.
I am sure to go for the 9,3:1 mahle kit. I keep thing as original as posible.

[Flat6pac]

Do the math and look at the euro Carrera 10.3 on the short 3.0 rods and you ll save money and control the compression.
Youre right on the 1.4 to 1.7 cam timing on the /07
Bruce