compression problem

**gublube** · 09-24-2010, 03:35 PM

ok all i put on new heads,got it all together.fired right up,sounded great.adjusted the rockers,took to lake ram couple easy laps and ran good, sounds good. but when i push the pedal to the floor, it doesnt have that get up and go and power it should.feel like i have an outboard on it.its a 454 bbc.i came home and did comp test.all or most are 50 lbs.ranging from 40 to 55 lbs.im puzzled.should it run as good as it does with that low compression.tested on 2 diff testers one just opened from store.doesnt smoke,it runs the same as it did when i had 3 sprk plugs wet with water and ate down to no electrode.im puzzled it.oil is still clean,no leaks of any kind.just cant figure the reason ive got no compression and still runs smooth,any and all help would be appreciated.

john

**David_396** · 09-24-2010, 03:36 PM

Sounds like the valves are too tight.

**The Doctor** · 09-24-2010, 03:58 PM

What rings did you put in it? Some ring packages need a bit of break in time to start sealing. David's also addressed the next thing I'd check is the valves. Is it a hydraulic cam? Lastly, is the oil still clean and water free or might you have pushed some head gaskets out?

**gn7** · 09-24-2010, 04:27 PM

When you performed this compression check, was the throttle wide open?

**Lucky** · 09-24-2010, 04:35 PM

Originally Posted by The Doctor

What rings did you put in it? Some ring packages need a bit of break in time to start sealing. David's also addressed the next thing I'd check is the valves. Is it a hydraulic cam? Lastly, is the oil still clean and water free or might you have pushed some head gaskets out?

Dam composite head gaskets

ps -- this guy could be my literary twin

I was thinking Valves are too tight also

**gublube** · 09-24-2010, 04:39 PM

ok,here is what we come up with,we closed the valves on piston one. so that both intake and exaust were completely closed.put compression tester in spark plug hole,hooked up air compressor with just enough pressure to see what happened,push rods were loos to spin freely so we know they were closed.and air leaks right out exaust valve.the new heads were rebuilt one i bought from reputable engine builder,he races and builds custom engines.all the exause valves leak. you can hear the air commin out the headers.could the guy have missed somethin,maybe didnt do the seats rt. these were heads he had laying around,same as ones i took off,oval port with closed chamber.im sure the guy tested and checked everything before i picked them up.and yes we had throttle wide open during comp test.we have a even reading in all cyl,between 40 to 50lbs.seems like at least one of the cyl would have compression.im sure the rings are ok,reason im saying is cause when the air builds up it blows open the intake valve and comes out the intake.what happened was it pushed the piston down and moved the valve open.so im assuming the rings didnt leak to do that.we only checked few ,as they all have same compression so were assuming they all have same problem.

john

john

**lbhsbz** · 09-24-2010, 04:47 PM

Originally Posted by gublube

he acid washed them resurfaced them cut new seats,did everything to make them new,all new valves and putting my springs back on ready to go for $450 out the door for both heads.

john

This price and the word "quality" generally don't go together very well when discussing cylinder heads.

**gublube** · 09-24-2010, 04:54 PM

Originally Posted by lbhsbz

This price and the word "quality" generally don't go together very well when discussing cylinder heads.

well i was refered to this guy by alot of race shops saying he was one of the best.i paid 85 ea head and he was to rebuild them and put in new valves that needed it,gring the seats and all the stuff a machineist does,for 450.i now it was a good deal ,but he is stil a reputable machinist in bakersfield.ive heard his name for years. i was told that he does some of the best work,so im sure he didnt screw me.ill be taking my whole boat to him to show him what is going on monday.he quated me 85 ea head,plus 140 ea head to do the work,which came to 450.which is about what every other machinist quated me,except they didnt have the heads.

john

**sunkisst** · 09-24-2010, 05:43 PM

Did you touch the cam timing? Even the gears??? This sounds like a cam timing issue to me. Really no reason for ALL cylinders to be equally low in pressures. Just my thought , from standing back looking.

**sunkisst** · 09-24-2010, 05:54 PM

Originally Posted by gublube

ok,here is what we come up with,we closed the valves on piston one. so that both intake and exaust were completely closed.put compression tester in spark plug hole,hooked up air compressor with just enough pressure to see what happened,push rods were loos to spin freely so we know they were closed.and air leaks right out exaust valve.the new heads were rebuilt one i bought from reputable engine builder,he races and builds custom engines.all the exause valves leak. you can hear the air commin out the headers.could the guy have missed somethin,maybe didnt do the seats rt. these were heads he had laying around,same as ones i took off,oval port with closed chamber.im sure the guy tested and checked everything before i picked them up.and yes we had throttle wide open during comp test.we have a even reading in all cyl,between 40 to 50lbs.seems like at least one of the cyl would have compression.im sure the rings are ok,reason im saying is cause when the air builds up it blows open the intake valve and comes out the intake.what happened was it pushed the piston down and moved the valve open.so im assuming the rings didnt leak to do that.we only checked few ,as they all have same compression so were assuming they all have same problem.

john

john

You got me...

**jetboatperformance** · 09-24-2010, 07:43 PM

John , just curious if after your last and most recent engine problem and subsequent reistallation of the repaired heads if you ran a quick compression test before you went abck to the water ? do you suppose the current low compression existant now is part of the last failure ? recommend before you go further you get hold of a cylinder leak down tester (some auto parts stores rent them) Tom

**GT Jets** · 09-24-2010, 08:35 PM

Just quickly reading the describing posts, it sure sounds like you have a valve timing issue and "touched" some valves with the pistons....I hope not, but it would effect each cylinder the same..

Good luck...

**cp562** · 09-24-2010, 09:06 PM

As stated by Tom at Jet Boat Performance, you need to do a leak down test on it. Like I said before, when you hydraulic a motor you can hurt a lot of things.

**gublube** · 09-24-2010, 11:50 PM

the previous issue was crackd heads,bot in couple places,shot valves on both heads.but boat still ran strong,just didnt have the power.one of the pistons has a indention from bad valve hitting on last heads.boat runs strong and revs up nice,just dont have the power it should.i dont beleive we messed with any timing,it starts rt up and sounds too good.gonna see about the leak down tester,remember these are completely different heads,rebuilt to new.it just puzzles me how good it runs and sounds,has power dont get me wrong,just not what i know it should have.

john

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