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To check pushrod length, color the valve tip with perm. marker. Install the length checker with it adjusted as close in length to your existing pushrod as possible. Turn the engine over a few times then remove the rocker. It will have worn a line across the valve tip going front to rear. Determine whether the line is centered on the tip or not. If it needs to move towards the intake, shorten the length checker. It if needs to move out towards the exhaust, lengthen the checker.
FWIW, I've never seen a pushrod that was 'close' cause low compression numbers. It'll just cause an undesireable wear pattern.
As far as low compression numbers, knowing that the cylinders have been washed, just put some oil in the cylinders. You have not fucked the engine yet, the cylinders are just dry. Put some a little oil in there and re check the compression.
The same thing happens when a motor sits for a long time. If the cylinders are dry you will not get compression readings.
FWIW, I've never seen a pushrod that was 'close' cause low compression numbers. It'll just cause an undesireable wear pattern.
As far as low compression numbers, knowing that the cylinders have been washed, just put some oil in the cylinders. You have not fucked the engine yet, the cylinders are just dry. Put some a little oil in there and re check the compression.
The same thing happens when a motor sits for a long time. If the cylinders are dry you will not get compression readings.
He would be seeing something on the gauge, even if the cylinders were "dry" as you put it. Something is physically causing all the compression to escape. Not just a little past the rings. As stated earlier, pull the pushrods, and re check, Did you have the heads disassembled and cleaned after the last engine blew? If not, you may have debris in there. I have seen dirt/carbon hold valves open enough to give false compression readings.
Teching In
Joined: May 2006
Posts: 1
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I had simmilar problem on a SBC, no compression. I just loosend the rocker arms 1/4 and it fired right up. So small things can **** up really bad!
But thats a niice setup you have, looking forward to videos
And im norwegian so there might be some bad language
But thats a niice setup you have, looking forward to videos
And im norwegian so there might be some bad language
If the valves will stay open if you over torquethe rockers, that's my problem. I torqued them to 38ft/lbs instead of 22ft/lbs. So my pushrods might be ok but I got the checker to make sure.
How do I oil the cylinders and how much? After I check the pushrod length I need, retorque the rocker arms and get some oil in the cylinders hopefully it will build some compression. That's tomorrows project.
Today I decided to get away from the problems/frustration and work on something else that will get me back to a more possitive attitude. It worked, I finished my cog set-up and I'm pretty impressed with it. Belt slip is a thing of the past:
How do I oil the cylinders and how much? After I check the pushrod length I need, retorque the rocker arms and get some oil in the cylinders hopefully it will build some compression. That's tomorrows project.
Today I decided to get away from the problems/frustration and work on something else that will get me back to a more possitive attitude. It worked, I finished my cog set-up and I'm pretty impressed with it. Belt slip is a thing of the past:
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Verdad Gallardo He would be seeing something on the gauge, even if the cylinders were "dry" as you put it. Something is physically causing all the compression to escape. Not just a little past the rings. As stated earlier, pull the pushrods, and re check, Did you have the heads disassembled and cleaned after the last engine blew? If not, you may have debris in there. I have seen dirt/carbon hold valves open enough to give false compression readings.
I need to get a nice set of 6 bolt heads anyway but I wanted to at least get it up and running this year. I don't have the money for new heads yet. Where, through the spark plug hole? Then do I need to just spin it over a few times by hand? Can I do this before the rockers go back on and see if it starts to build compression so at least I know the valves are sealing or will it creat to much pressure for me to turn over with all the valves closed?
yes, in the spark plug hole. you can turn it over with the starter just don't shoot more fuel in there while doing it. Also, you can pull a plug and put your thumb over the spark plug hole and have someone turn it over just to see if there is any compression at all and verify your guage is good. There should be something there. Check your preload on the lifters, it may not tell you if your valvetrain geometry is right but will tell if your valves are holding open. 7.400 PR's just don't seem like they would be to long by looking at your specs but everything is suspect at this point. This is why i went with adjustables this time around. Come to think of it, with the rockers I used, my PR's were really short, like 7.250 i believe.
Dan
Dan
I just measured with the push rod tool, 7.275 with zero back lash added in. What do I add to that, .075? That would mean I need a 7.35 pushrod. Here's the thing, is that even enough difference to keep the valves open? I would think the 7.4 would still work, may not be perfect but not enough to open the valves. What do you guys think, is that enough to cause my valves to stay open? I'm going to do the compression test without the rockers on tomorrow to make sure the valves are sealing.
I see stock style rockers.. Torque them to whatever you want because the stud has a 'shoulder' that the rocker pinion sits on. I do believe that .05 extra is not going to hurt anything as the hydraulic lifters will take that and then some. But I just realized I forgot to mention something about doing the pushrod length check... You should remove the rockers and spark plug from the current cylinder, and crank the motor over untill you see oil coming out the top of the lifter or pushrod. This ensures the lifter are pumped up. Then install the length checker and rocker. Sorry about missing that detail man, my bad.
After you put oil in the cylinders (i'd prob. use a straight 30wt dino oil), unplug the injectors to be sure that you dont squirt any fuel in and start turning the motor over by the starter while holding the throttle wide open... Watch the gauge after a few revolutions and you should start seeing pressure build.
If not, its time for a leakdown test. Which you can do poor man style by adapting your compressor line to the line that comes with the compression gauge (most have the same quick connect).
Poor man's leakdown test Bring a cylinder to TDC, then fill the cylinder with about 10-15psi of regulated air pressure and listen for where it's leaking out. You will hear some gettng by the ring gap though the oil fill cap. A little there is normal. You dont want to hear it hissing out the intake or exhaust when both valves are closed on that cylinder. That means you either have hanging valves or bad seats. You should be able to tell this just by the volume of air coming out though.
BTW, the cog setup looks absolutely beautiful! Good job man!
After you put oil in the cylinders (i'd prob. use a straight 30wt dino oil), unplug the injectors to be sure that you dont squirt any fuel in and start turning the motor over by the starter while holding the throttle wide open... Watch the gauge after a few revolutions and you should start seeing pressure build.
If not, its time for a leakdown test. Which you can do poor man style by adapting your compressor line to the line that comes with the compression gauge (most have the same quick connect).
Poor man's leakdown test Bring a cylinder to TDC, then fill the cylinder with about 10-15psi of regulated air pressure and listen for where it's leaking out. You will hear some gettng by the ring gap though the oil fill cap. A little there is normal. You dont want to hear it hissing out the intake or exhaust when both valves are closed on that cylinder. That means you either have hanging valves or bad seats. You should be able to tell this just by the volume of air coming out though.
BTW, the cog setup looks absolutely beautiful! Good job man!
Last edited by Fire67; Sep 14, 2008 at 12:41 AM.
I see stock style rockers.. Torque them to whatever you want because the stud has a 'shoulder' that the rocker pinion sits on. I do believe that .05 extra is not going to hurt anything as the hydraulic lifters will take that and then some. But I just realized I forgot to mention something about doing the pushrod length check... You should remove the rockers and spark plug from the current cylinder, and crank the motor over untill you see oil coming out the top of the lifter or pushrod. This ensures the lifter are pumped up. Then install the length checker and rocker. Sorry about missing that detail man, my bad.
After you put oil in the cylinders (i'd prob. use a straight 30wt dino oil), unplug the injectors to be sure that you dont squirt any fuel in and start turning the motor over by the starter while holding the throttle wide open... Watch the gauge after a few revolutions and you should start seeing pressure build.
If not, its time for a leakdown test. Which you can do poor man style by adapting your compressor line to the line that comes with the compression gauge (most have the same quick connect).
Poor man's leakdown test Bring a cylinder to TDC, then fill the cylinder with about 10-15psi of regulated air pressure and listen for where it's leaking out. You will hear some gettng by the ring gap though the oil fill cap. A little there is normal. You dont want to hear it hissing out the intake or exhaust when both valves are closed on that cylinder. That means you either have hanging valves or bad seats. You should be able to tell this just by the volume of air coming out though.
BTW, the cog setup looks absolutely beautiful! Good job man!
After you put oil in the cylinders (i'd prob. use a straight 30wt dino oil), unplug the injectors to be sure that you dont squirt any fuel in and start turning the motor over by the starter while holding the throttle wide open... Watch the gauge after a few revolutions and you should start seeing pressure build.
If not, its time for a leakdown test. Which you can do poor man style by adapting your compressor line to the line that comes with the compression gauge (most have the same quick connect).
Poor man's leakdown test Bring a cylinder to TDC, then fill the cylinder with about 10-15psi of regulated air pressure and listen for where it's leaking out. You will hear some gettng by the ring gap though the oil fill cap. A little there is normal. You dont want to hear it hissing out the intake or exhaust when both valves are closed on that cylinder. That means you either have hanging valves or bad seats. You should be able to tell this just by the volume of air coming out though.
BTW, the cog setup looks absolutely beautiful! Good job man!
One other thing you mentioned got me thinking about something completely off topic but very important. You mentioned cranking it over until the oil comes out the lifter or pushrod. At this point, I'm not getting any oil pressure? I thought that was normal though because it's just not spinning fast enough or for a long enough period of time to actually get the gauge to register any pressure. Just by letting the starter crank it over for how many seconds should I start to build oil pressure?
Maybe i am confused. If the engine is in fact cranking, shouldnt the blower impeller move at least a little bit since its connected via belt to the crank? Usually the oil pressure guage doesnt show oil pressure until a few seconds after the car fires anyway when new. At least thats been my experience
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He did not have the blower belt installed at the time of the video. On a fresh rebuild, it will take a long time to build oil pressure with the starter. Like a minute or so. You will have to do it in short bursts to keep from burning up the starter.
Well it looks like you were right, I'm not getting compression. I'm not sure I need new pushrods but I might need new heads. With the rockerarms off, I'm only getting around 30 lbs of pressure in each cylinder. I only tried two but one was 31 and the other was 34 so pretty close. Will I loose that much pressure from having dry cylinders? I still need to squirt a little oil in there but I don't have any way to get it in there, I have to go pick up one of those oil squirters to get it in there. I don't know much about how this stuff works but that seems like a lot of pressure to be loosing just because the cylinders are dry. I'm guessing the heads are bad.
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10 Second Club
Joined: Aug 2006
Posts: 287
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From: Dayton Ohio
It usely takes a couple of revolutions to get a good reading also if your not opening the intake valve you cant let in air to create any pressure.
ive never set valve lash on a ls1 but on a old small block if you over tighten the rockers you will get the same thing alot of popping and no compression. backfires through the intake. just my .02
ive never set valve lash on a ls1 but on a old small block if you over tighten the rockers you will get the same thing alot of popping and no compression. backfires through the intake. just my .02
It usely takes a couple of revolutions to get a good reading also if your not opening the intake valve you cant let in air to create any pressure.
ive never set valve lash on a ls1 but on a old small block if you over tighten the rockers you will get the same thing alot of popping and no compression. backfires through the intake. just my .02
ive never set valve lash on a ls1 but on a old small block if you over tighten the rockers you will get the same thing alot of popping and no compression. backfires through the intake. just my .02
