Z454SS Posted September 7, 2010 Share Posted September 7, 2010 So my Monte Carlo has a little over 12,000 mile on the over the top built 454... While driving at about 55mph the MSD distributor rotor came apart completely killing the motor.... It is the second time this has happened.... So after I put on the new MSD distributor the motor ran like crap...so I did a compression test and it read like this...210,205,210,210,185,210,205, and 0.....,, pulled the head found no problems all roller rocker/ push rods are fine, springs are fine, even the piston seems to be working fine.... So where else could the compression be going???? Quote Link to comment Share on other sites More sharing options...
Z454SS Posted September 7, 2010 Author Share Posted September 7, 2010 The head looks fine I have looked it over and can't find any problems... It is a after market HI PERF... I don't really know a whole lot about it... But I will do the leak test like you mention just for the heck of it when I get back to the shop..The MSD distributor rotor seems to rattle off the two screws holding it on..it is a composite.. Would the CAM produce 0 on the compression test? Quote Link to comment Share on other sites More sharing options...
Z454SS Posted September 7, 2010 Author Share Posted September 7, 2010 Also on the bottom of the Head in the valve that is showing zero you can see where the head of the piston is hitting and has scraped off metal???? Quote Link to comment Share on other sites More sharing options...
ripleydale Posted September 7, 2010 Share Posted September 7, 2010 I wonder if the rocker(s) were too tight on that cylinder and not letting the valves close properly. Not a lot of places for the compression to be lost, especially when the reading is zero. That has to be a pretty big hole. Â Is the piston hitting the valve, or just part of the combustion chamber? Quote Link to comment Share on other sites More sharing options...
Z454SS Posted September 7, 2010 Author Share Posted September 7, 2010 The piston is hitting the valve there does not appear to be any marks on the chamber... When I first pulled off the valve covers and fired the motor all rockers were working fine so I figured the piston must have a hole in it pulled off the head and to my amazement the piston was working fine... Has me stumped !!!!!!! Quote Link to comment Share on other sites More sharing options...
Shadow Gray SS Posted September 7, 2010 Share Posted September 7, 2010 piston can be cracked/compromised from impacting the head/valve. Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted September 8, 2010 Share Posted September 8, 2010 Matt if the piston is hitting the valve it might be bent. If you're getting zero Allan's water test might show it but I'd pull that set of valves out anyway and check them. Do you know if the piston to valve clearance was ever checked? Pictures might help...Dave Quote Link to comment Share on other sites More sharing options...
Z454SS Posted September 8, 2010 Author Share Posted September 8, 2010 Well it sounds like I have quite a few things I can check on... Yeah I really hope it's in the head I would rather not have to pull the piston... It is the original 454 block with aftermarket heads and the pistons are 11:1... Not something I would have done had I been the original owner but hay, what's done is done right? Thanks for all your help guys I will post some pics and give an update as soon as I can. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted September 8, 2010 Share Posted September 8, 2010 MSD distributors use STAINLESS steel screws to hold the rotor on.. you MUST use locktite!! (ask me how I know) Quote Link to comment Share on other sites More sharing options...
Z454SS Posted September 12, 2010 Author Share Posted September 12, 2010 So it turns out Allan was right...Bent Valve... and I will be sure to use lock tight on the distributor screws seeing as how that made the motor misfire and over-rev. them damn screws have really cost me some bucks. thanks again for all the help. Quote Link to comment Share on other sites More sharing options...
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