Blue Motors
 

What Are Good Compresure numbers in a carb 500 Stock Blue Motor ?

Ones that match pretty close?

Pesky Varmint

I bought a 97 Fastech (200 hrs) BM HP500 carb. last summer, and my compression on pre inspection were:
1-165
2-165
3-160
4-160
5-165
6-160
7-165
8-165

Tony, you want consistancy. You want the numbers to all be within 10% of each other. For example, A decent reading would be

#1=152PSI
#2=146psi
#3=155psi
#4=149psi
#5=154psi
#6=151psi
#7=148psi
#8=150psi

Just a example. If there is a cylinder or two that is down more than 10% or more, chances are there is a leaky valve. I like a compression test to start, if all looks good im cool. If there is a low number, I like to do a leakdown test, and see where its leaking (intake or exhaust, or rings..)

Only thing to really watch for on the HP500 blue motor, is valve springs. They were notorious for needing valve springs around 200 hours, if the valve springs were originals. Valve spring job aint to bad though money wise. More time consuming than anything...:drink:

150-160 with no more than 15lbs difference between the highest and lowest number.