i have a 99 cobra with fully built block and heads with port polish, cams, stainless valves, and valve job. the guy that is doing all my work said compression should be about 9.5. iv had people tell me that 9.5 is low and now i have ppl telling he that 9.5 is way too high to throw a blower or a turbo on it.

 

I think your fine... your compression is actually lower than stock. stock was 9.85

and if your compression is too high..... you DONT put a blower on it.... just FYI

 

 

 

Well i just went through this last week.
according to MPH, the best CR for street driven mustangs with a blower is 9.2:1-9.5:1.

So you are actually in a good spot. 8.5:1 would be low for a street blown mustang. It would be a dog on the street without boost.
Although, these are the ratios he gave for a 2v... IDK if a 4V would be any diff... You might be able to get by with a little lower CR since you are making more hp/tq than a 2V stock.

Give them a call...

 

yeah fried of mine told me that his compression on a 03 cobra was 8.1 and he told me that i wouldnt be able to put 8 pounds of boost on it or id leave party all over the highway

 

9.5 is okay for MILD boost... On a shop car with a hellion kit, we started seeing "ping" on anything more than 13 psi on pump gas. So, if you plan on running serious boost, you should go with a lower CR, but on very mild boost, 9.5 CR is OKAY...

 

what would be good amount of boost that 9.5 is good for?

 

Around 12 lbs...