i'm running a 416 hpd kit with a 12: 1 head on my explorer and only have 130 lbs of compression with all new parts. has anyone had similiar experiance ?

 

sorry to be off topic,but how is running the power valved 416 kit?
with only 12.1 i think it must right,seem a little low tough.
is the case welded?

 

A 12-1 head gives you about 150 psi on a reg cyl. Are you opening throttle wide open,warmed engine, crank over fast with rope(not starter), this all would give a few more psi. Try different gauge or call hpd/rick ritter ask.

 

static compession is missleading on a 2 stroke!!!

for example

a twin cylinder snowmobile running a stock head and single pipe may require 91 octane fuel
but same engine running twin pipes WILL require higher octane like 94 or better unless the pipe manufaturers lower compression head is used (although better quench design)
so static verses running compression are like apples to oranges
I would bet that the three pipes available for the 400 TORQUE. TOP END, and RACE all have different fuel requirements when run on the same engine

 

also engines with the same displacement and cylinder heads BUT different porting WILL have different compression readings

 

this isn't the power valve head. i tried 2 gauges, and yes with WOT.
with a brand new piston & rings {honed} i first read 130 lbs, i rode for 5 minutes and i'm already down to 115 lbs, i have spoke to rick and he is at a loss off words {pretty hard to trouble shoot over the phone}. i'm tearing her apart again today, i'll keep you guys posted, suggestions will be appreiciated.
by the way rick has bent over backwards to help me out i do not intead for this to turn into a bashing session i'm just looking for some helpful advice, thanx.

 

maybe a sticky ring
or overheated it a bit
sometimes hard to get all the air out of the cooling system
run her hot and cook the ring tension out of it

 

who know the normal compression reading for a hpd race kit 400. i've tried two gages last week and came up with two big differences.
the mac tools one read 200 psi but the snap on one read only 150 psi. treid them both more then once and believe that one of them must be broken but which one. what is the norm??

 

On my race modded 400 with the 14.5 head, a new piston and rings w/hone, I now have just over 160-165psi. 150 sounds about right for the 12.5 head. Which one are you running?

 

I have the 15.5 cool head dome.