I bought a brand new motor, supposedly built for boost....however, the heads are 243 heads and the block is a 6.0L iron block. I pulled the heads to find flat top pistons...absolutely no dish and no valve reliefs. Are the flat tops and 243 chambers going to result in too high a compression ratio for much boost? Planning to run 7-8 pounds on the street with premium and up to 18 at the track with race fuel.

 

Don't believe what ANYONE tells you when your talking about a used motor. I have NEVER to this day recieved what I supposedly bought when it came to entire engines. Thats why I buy either 100% factory or build my own now. With that said, I'm not too familiar with 6.0's but my 5.3 had factory dished pistons so I'm taking a guess in saying those pistons are high compression. Best of luck to ya!

 

Exactly why I pulled the head before I did anything with it. It is a brand new motor, though....never fired.

 

Sounds like the compression ratio will be a little on the high side but swapping the 243s to 317s will change the CR to something more manageable but without dished pistons you will definitely need meth to run high amounts of boost, like the 18 you stated. 7-8 will work fine on pump gas though

 

If what you say is true, you should be around 10.9:1 compression. If you put on 317 heads, that should drop you down to 10:1. You should be able to run 9 to 10 pounds on pump and 12 or so with methanol. I would also check to see what type of rod bolts it has. Based on the condition of the other parts, I am guessing they are most likely stock. In that case, I would not push more than 6 to 7 pounds.

 

ls1290, that is exactly what I was thinking. Flat tops and 317s and you essentially have an LQ9.

 

Thanks guys. I will be pulling the pan to check rod bolts before adding ANY boost.

To clarify....9-10 pounds on pump gas WITH 317 heads and NOT 243's correct?

Which head studs should I use? When I pulled the bolts all the big bolts are the same size, so there are 2 sizes total. The smaller ones hidden by the intake and all the big ones are the same size. This leads me to believe I need to order the 04 and up stud kit.

 

I agree with ls1290.

The part number you want for the ARP head studs is: 234-4317.

 

Thanks! Ordered studs today!