? would too tight of valves cause low compression?

[bigmanjbmopar]

initially we went with a full turn on the valve adjustments and got lock up, then backed off to 1/4 turn and it seems fine, then one day while checking a compression tester we saw 45-50 lbs of comp?? way low should be up to 110+ right? Seems we thing the valves are still too tight. would backing off to 1/8 of a turn or less work to bring it back up? No other real problems other than crappy eddy 800 and little tweek on the timing.

 

[Satellite65]

Yup!!!
Solid or hydraulic lifters?

 

[Meep-Meep]

If you're talking turns of +/- 1/4 then you must have a hydraulic. If the lifter plunger is in it's range cold or hot then the valve will seat just fine and your compression will be preserved. You have about .2" of window in the lifter. I run my adjustables at one turn from zero lash but also remember when you adjust the preload the lifter must be on the base circle of the cam just like if you are setting mechanical lifters. Follow the DC valve lash chart and you will be fine.

 

[bigmanjbmopar]

Yes Hydraulic roller, with the 9.108 long push rods. I'm think with the longer rods it is tight from the start when we went 1/2 turn from lash originally it locked up. I think we are at 1/4 maybe close to half now after 4 times at it. We bump the cam around to get it up but maybe it's just not at the right spot. trying to dial this stroker in is killing me I know it's got 500+ inside it just have to get it out lol

 

[67 B-body]

What's "locked up"?
If you have the rocker arm setting at the correct geometry, then the pushrod length is correct. How did you measure for pushrod length before purchasing them?
You should have equal travel across the tip of the valve from center when at max lift in one direction, and equal distance in the opposite direction from center at Zero lift.

 

[lewtot184]

If you're talking turns of +/- 1/4 then you must have a hydraulic. If the lifter plunger is in it's range cold or hot then the valve will seat just fine and your compression will be preserved. You have about .2" of window in the lifter. I run my adjustables at one turn from zero lash but also remember when you adjust the preload the lifter must be on the base circle of the cam just like if you are setting mechanical lifters. Follow the DC valve lash chart and you will be fine.

this is good advice. the truth is; if your are completely lost here, yank the intake and look at the tappet to make sure its on the heel of the cam lobe and then make adjustments. i would think that you'd want cylinder pressure at 150+psi. do some other checking. sometimes hydraulic roller tappets have some internal problems.

 

[IQ52]

How can you suggest a lifter preload if you don't know what cam and lifter part numbers are being used? What does the lifter maker recommend for pre load? The lifter MUST be on the cam base circle when setting the load. What static compression ratio? Have you done a leakdown test to determine the source of the low compression? Is it the intake valves, the exhaust valves, the rings? Do you have a faulty compression tester? I've seen compression testers way off or used incorrectly. Try another compression tester.

 

[Cranky]

Was a degree wheel used to set the cam?

 

[67 B-body]

I hope that "locked up" doesn't referance the engine not turning over! If it does mean that your engine gets stuck or "locked up" when turning the crank, you might have already caused damage to the valve. This is especialy true if you hit the starter with it this way! If this is what you're refering to, then valve replacement and seat machining will most likely be necessary.

 

[67 B-body]

Just one more thought on the subject.
If the lack of compression is due to valve lash, this would indicate that the valve is not closing all the way, right??
With that being said, it would be fair to suggest, it's probably the exhaust valve because you didn't mention any backfire through the intake or extremely poor drivability. Now with that being said, I would believe your exh valve seats, and valves themselves would have been burnt by now, since you have been running the engine this way.

A leak test will pinpoint the source of compression loss, and remove all questions involved.

 

[bigmanjbmopar]

Locked meaning valve being help open after over adjusting past lash. and no the cam was not ° only #1 to top and marks lined up on timing gear and crank gear. crank gear was installed at mark 4A. it runs fine the only time it back fired on me was when I help it WOT and started it after it died at idle. the compression tester was thought to be bad originally now my bud is telling me it was not and we need to go back to the valves and check and adjust again.

Will need to do the leak down test for sure am seriously considering taking it apart and setting the crank gear at 0 and pulling the valley pan off to make sure the lifters are on the center...lots of work but all can be done with the motor still in.

Your scaring me about the valves being burnt....the plugs look light brown on the second set, 1st set was for break in these look normal. motor turns over fine and runs good.

 

[Meep-Meep]

Having the cam 4 deg advanced or retarded does not necessarily mean you will have valves hanging open so I wouldn't bother messing with that. The only way you can loose compression pressure through a valve is have it not seat because you maxed out your lifter plunger travel and now holding it off it's seat by the push rod and adjuster, or a bent valve, a burnt valve, a false guide slipped out and is holding the valve open by the taper below the stem. Or any thing that allows air to escape through and otherwise closed valve. Longer or shorter push rods won't cause the valve to hang open so long as you are in the lifter preload range, but having the correct push rod length is very critical for other reasons.

With a dry lifter you can put a dial indicator on the push rod side of the rocker and move the adjuster screw from zero preload to solid and measure the total travel, or count the turns of the screw and do the math. 3/8-24 thread = .0416" per turn. Setting the plunger in the middle should make everything happy. Sure, the lifter mfgr may have some optimum plunger preload setting but reality is hydraulic lifters have an operating range probably equivalent to a half turn of the adjuster screw. Their entire purpose is to "self adjust".

 

[67 B-body]

Having the cam 4 deg advanced or retarded does not necessarily mean you will have valves hanging open so I wouldn't bother messing with that. The only way you can loose compression pressure through a valve is have it not seat because you maxed out your lifter plunger travel and now holding it off it's seat by the push rod and adjuster, or a bent valve, a burnt valve, a false guide slipped out and is holding the valve open by the taper below the stem. Or any thing that allows air to escape through and otherwise closed valve. Longer or shorter push rods won't cause the valve to hang open so long as you are in the lifter preload range, but having the correct push rod length is very critical for other reasons.

With a dry lifter you can put a dial indicator on the push rod side of the rocker and move the adjuster screw from zero preload to solid and measure the total travel, or count the turns of the screw and do the math. 3/8-24 thread = .0416" per turn. Setting the plunger in the middle should make everything happy. Sure, the lifter mfgr may have some optimum plunger preload setting but reality is hydraulic lifters have an operating range probably equivalent to a half turn of the adjuster screw. Their entire purpose is to "self adjust".

You are sooo correct!

I used the comp tester with the quick connect end changed out to match my small air comp tank fitting. It has a regulator on it, so I had it around 40 PSI and listened for air leaks.
I found my two bent valves this way because the air was leaking out of the exh ports.... Two new valves later, I was back to running again.

 

[bigmanjbmopar]

Will check things out this Friday and post back going to start by taking all the plugs out and check compression one by one and adjusting the valves accordingly. Don't think I have put enough miles or time on the motor yet to burn up valves thinking it just a tight valve on one or two will see.

Also going to do leak down as well to see what's going on.

some **** oh and wrong distrb gear in there it has a bronze one..

 

[poly3521]

Ok, someone correct me if I'm wrong. The way I was taught to set small block chevys is to set the pushrods slightly loose, start it to let the lifters pump up with oil because they may have collapsed from being set too tight. Tighten the adjustment until you reach 0 lash i.e. just get the slop out of the rockers. From there, most times, you only need up to a 1/4 turn on the adjuster, or leave it as is if you start it and don't hear chatter. Some guys adjust them til they don't chatter, others give them an 1/8 to 1/4 turn more. Should be a good starting point. Just remember to set the 0 lash at the base of the lobe. Again, please correct me if I'm wrong, And yes I know it's not GM, but sometimes it helps.

 

[IQ52]

Well, those look like the 829-16 SOLID roller lifter!

But, if those are the Comp 8921-16 ProMagnum Hydraulic Roller lifters, they should be set at .000-.004" preload and NO MORE than 1/8 of a turn.

 

[IQ52]

Ok, someone correct me if I'm wrong. The way I was taught to set small block chevys is to set the pushrods slightly loose, start it to let the lifters pump up with oil because they may have collapsed from being set too tight. Tighten the adjustment until you reach 0 lash i.e. just get the slop out of the rockers. From there, most times, you only need up to a 1/4 turn on the adjuster, or leave it as is if you start it and don't hear chatter. Some guys adjust them til they don't chatter, others give them an 1/8 to 1/4 turn more. Should be a good starting point. Just remember to set the 0 lash at the base of the lobe. Again, please correct me if I'm wrong, And yes I know it's not GM, but sometimes it helps.

On stud mounted rockers, adjusting the rockers with the engine running is no big thing because the adjusting nut on the stud is standing still. Have you ever tried to hang on to the allen wrench and the box wrench simultaneously when the shaft mounted rocker is moving up and down? Now there's a rodeo!

 

[bigmanjbmopar]

This is what comp said to use..thought they were hyd roller

Well, those look like the 829-16 SOLID roller lifter!

But, if those are the Comp 8921-16 ProMagnum Hydraulic Roller lifters, they should be set at .000-.004" preload and NO MORE than 1/8 of a turn.

 

[bigmanjbmopar]

Cam specs

 

[poly3521]

On stud mounted rockers, adjusting the rockers with the engine running is no big thing because the adjusting nut on the stud is standing still. Have you ever tried to hang on to the allen wrench and the box wrench simultaneously when the shaft mounted rocker is moving up and down? Now there's a rodeo!

I never said about trying to set the lash with the engine running, although, that would be funny to see. Running the engine with the adjustment too tight can cause the lifters to partcially collapse. If you let them chatter, they should pump back up. Then you can set the lash with the engine not running.