Help me... No Compression

[TireSmoke420]

Alright so my truck has been running like crap. so i took it to this guy i know and he ran a copression check on it. he found out the number 7 cylender has no compression. so i just took the drivers side head off expecting to see either a hole in the piston or a burnt out valve...i found nothing the number 7 looks perfectly fine not even any scores in the cylender wall like it would be rings. this engine only has 30,000 miles on it and its baffling me now. now the guy that check the engine out for me is a dodge mechanic, now does dodge number their cylenders differently like maybe the 7 on a dodge is the 8 on a chevy? damn i dunno i guess ill be taking other head off tomm. any one have any ideas. im kicking my ass now for mot listening to my buddys dad... he told me to pump air through the cylender then id know where its leaking. but i just figured id take head off and there it would be larger then life ya know

[87 STEPPER]

WOW!

Dude you over reacted you should of posted here first before rippin' you eng. apart.

I would have either ck it again with another comp. tester may be your bubby didn't get it tightened into the cyl head enough and it leaked instead of showing pressure. or ck it with air like your other buddys dad mentioned.

And if it showed low i would have got some marvills mistry oil and put some in that cyl. and cranked it over a few times. and then checked it again.

If your gonna take the other side off you should still do the marvills oil thing to every cyl. it will help the rings seat but they should be all ready but it cant hurt.

If that eng. only has 30k on it i doubt it's ring's or comp. it's probably more like the vavles were not adjusted right or the timing wasn't set right.

And all V8 are the same in that the pistons are numbered the same way the piston's on the left side of the eng. are #1,3,5,7 and the right is 2,4,6,8 now the firing orders may be differant from each Mfg.

Good luck

[motopatzo]

Did you have a look at number 7 valves? If you had no compression at all, it is possible that you may have a burnt valve.

[Mike 85]

ALWAYS pull the valve cover FIRST.
Look AT the rockers and SEE if any are NOT moving.
You could have a collapsed lifter,flat lobe on the cam (most likely) broken rocker,stud broke,blah,blah,blah. I'll shut up now.
Valve that won't open won't let anything IN to compress.

Even the Dodge guy should have known to do that.

[TireSmoke420]

so now ive inspected everything a lil closer. there is pitting on the edge of the #7 piston dad says thats pry where the cylender is leaking. so basicly i burnt a hole in my piston. i wanna rebuild it but the engine is a remanufacturd engine by marshall. dad seems to think if i try to rebuild it im gonna run into all kinda of problems cuz i dont know what all marshall did to this engine. he says they could have it bored out. or sumthing with the cam jornals and all this blah blah blah. what do you guys think should i buy the reuild kit or go to a junkyard get an original engine and rebuilt that?

[hiway]

To much timing is usually what gets a piston like that. You could pull your oil pan and remove that one piston and rod. Take it to machine shop and get a new piston and ring set put on the rod and replace it. Stock type cast pistons are like $13 and rings about the same. GET A BOOK! It sounds a little like you'll need it

[TireSmoke420]

ya i got a book. ive had this engine in an out about 4 times now, i could prollly have engine out and in with my eyes closed lol.

[TireSmoke420]

so i studied the engine pretty hard tonight and found that there is 040 printed on top of the pistons... is it safe to say that means the engine is bored .40 over. what else should i chekc bfore rebuilding?

[poorboy]

You need to pull a rod and main bearing to see if it's a stock crank or if it's been turned. The bearing are usually stamped. STD,.010,.020,ect.

[TireSmoke420]

so whats the difference between hyperteuctic pistons and flat top? what should i go with? i wanna ugrade to sumkinda aluminum head also when i do the rebuild.

[piecesparts]

NOW thata you are basically into the engine, you would be somewhat foolish to start sticking it back to gether in pieces and doing a shoddy rebuild. At this point, I would pull the motor, put it on an engine stand, redo the bearings, hone the cylinders, replace what is needed, replace the cam(upgrade at thiw time), refurbish the heads and bolt it up for a great number of miles.

[TireSmoke420]

thats what im planning on. i wanna redo everything this motor barely had any balls bfore all this i wanna give it a lil attitude. i got a lil farther in to tonight. i pulled pass. side header. and the 3rd cylender back had oil comming outta it. havnt pulled that head or cover yet gonna finnish pulling motor out omm night probly

[TireSmoke420]

k so i got the motor out. and got the pass. side head off and the3rd cylender back has a nice layer of oil on it. all in all like all the pistons are black exept for this one what does this indicate?