Ok I am a little lost here. Got the motor on the stand, starter functioning with switch. Motor is turning over VERY SLOW. (Like dead battery) volt meter is indicating they are indeed low - mid to low 12. I have tried two batteries. One is out of my truck (5.3) which starts fine. I have all the plugs out. I am only getting like 30 psi but motor is turning over so hard and slow. I have another battery on charge but guess i gotta wait... the motor feels good by hand (breaker bar on crank bolt) Kind of harder than I expected without the plugs in. Am i missing something here ???

 

I think the starter may be to blame. Starter is pretty warm along with the jumper cables I am using as leads. Cleaned up the starter terminals which helped but still not spinning fast enough for a good reading, I think.

Going to try leakdown test I guess. Will a piston stop tool work with LT1 angle plug heads?

 

Dunno. Don't think the starter really should get all that warm especially when there is next-to-no load on it w/out accessories or plugs.

 

Ok I tried again last night, battery had a little better charge, was like 12.8 when i started and 12.4 at the end.

This time I got different results. Some of my low cylinders are now high and some of the high are now low. They are all between 130 and 170 which is within spec according to the manual but maybe not according to online sources.

I also did a leak down test (used 70 psi baseline) and all were 55-65 except for hole #7 which was 45 -- hole 7 was one of my best holes the first night (170 psi) I am losing some air thru exhaust valve but also some i can hear in the crankcase.

I also know motor should be warm which it is not. I do not know how long it has sat either.

Not sure if i should pull heads? Thinking about doing rings but on a tight budget. Thoughts?

Edit. I dont know if i should pull heads. I could look at cylinder walls this way but not sure what else i would be able to tell (ring condition) i do have obvious exhaust valve leakage (slight) in some cylinders. The blowby in cyl 7 obviously isnt good but i think some sbc blowby isnt uncommon?? Once i pull heads tho i lose my ability to retest compression / leakdown. Do i run the motor or tear it down? The different results from night to night make me think it needs to be run.

 

Hrm. When doing a leakdown, there should be air escaping past the rings (within spec) and there should be no air escaping through either valve. You are absolutely sure you were at TDC for #7? Even at 70psi the crank likes to turn especially with no plugs in any of the other cylinders.

 

I tried multiple positions on the balancer so yes Im sure. Maybe i should loosen rockers and try again? Possible tapping valves with hammer? Crank did not try to turn at all

i should add that i know oil is getting to some rockers (evident by oil pooling) but not sure if all of them are squirting oil. Not sure if Lifters can lose prime from sitting and how much turning over would be required - also if that would effect compression or leakdown

 

Dunno what to tell you. If it were me I'd most likely take the heads off, have them milled and put on new head gaskets. Super easy since it's on a stand. And in doing so, pour some mineral spirits in the combustion chamber and see if it will leak past the valves. That's another shade tree way to find out if the valves aren't seating as they should.

 

Ok thanks for the help, Ill do that. Might be a few days as Im cramming for school right now. Stupid question but would bad rings be evident with heads off? Am i able to measure ring gap or anything or is it just more of a visual / condition of cylinder walls type of thing? Also what should I expect to pay to have heads milled. Honestly I was thinking more along the line of having them "checked out" by machine shop, of course he'll prob. just say that yes they need some reconditioning. I dont have an issue pulling heads but obviously I dont wanna sink money into this before I know if its a good motor or not, if that makes sense .. I would be out gaskets (and bolts?) if i button the thing back up and still have leakdown woes

 

Only way I know is a compression or leakdown. Perhaps after taking the heads off you can check the cylinder bores to see if they still have crosshatch on the cylinder walls.

 

Ok so cross hatching should still be visible? Was told motor has 97 k on it. It does look clean, plugs all looked even.

One last thing I want to touch on ... how much does a bone cold motor effect leakdown/compression results? Since I am technically within spec
even with exhaust valve not fully sealing off (speculating carbon maybe not really sure)

When checking for leakage (after removing heads) do I have to use solvent on valve seats or can i use oil?

 

Dry compression test for me are often way more erratic than wet, but many things can affect it.

On a stand I use a flywheel lock to hold the engine on tdc for each cylinder and do them in firing number order.
The lock allows me to run 100 PSI for the leakdown test..

On a motor thats been sitting for a long time,, I spray a small shot of marvel in each cylinder, I also do this to make sure the dry rings, or dry cylinder walls which might be contaminated with a micro amount of corrosion don't run against each other without lubrication.

Valve guide seals that have been sitting can "stick" the valves a bit as well, so some spray oil like a aerosol assembly lube on all the valve stems and springs can help.

If a motor has been setting for a long period of time without being rotated, valve springs can take a set and so some may not be pulling the valves shut hard enough. I've also seen most often when springs suddenly brake there is often a history of the engine sitting.. On a sprint car with really heavy valve spring pressure its standard to pull the valve covers and release the rockers so all the valves are closed.. Keeps the cylinders sealed and relieves the static pressure on the open valve springs..

I always used kerosene to check for valve leakage on a off the motor head.. Cheap and not much of a fire hazard.

 

Thanks for the info. I think ill play a little longer before i pull heads. I am not convinced just yet that pulling heads is the next step. I was worried about dry cylinders as well after the first night when i thought the motor was turning over a little stiff. Of course i didnt want to spoil my dry compression results. I did end up spraying a 1 second shot of fogging oil in each hole since that is what i had on hand. Not really sure what fogging oil is comprised of honestly. (Edit - according to google similar ingredients to MMO mostly mineral spirits) I think Ill spray a little more in each hole, and find something to douse the valve areas with. For the valves, I dont have aerosol assembly lube (as mentioned) just the regular stuff. Or would wd 40 be better around valves (has kero in it if im not mistaken) might help to clean things up?? Think Ill remove rockers and try to get the valves to seat. Possibly some light hammer taps over a pressurized cylinder, and do leakdown again, see what happens before pulling heads.

 

Think of it this way,,, when does the engine really compress on a dry cylinder..

Any lighter oil is fine, even vegetable oil in the cylinders can work in a pinch.

I use a dollar store squirt bottle to spray oil in the plug holes.. Marvel sprays well, so will 10WT machine oil. You can also put some regular motor oil in each cylinder,leave the plugs out and spin the motor over a half dozen times with the starter to slosh it around.

If your leakdown is good all but 1 cylinder,, spray some more oil in and on the valve stems , spin it a couple times, give it a wack it wont hurt.. and re-leakdown test the week cylinder. You can also just take the rockers all off so you know the valves are shut and use a wooden dowel to tell if your tdc, and leak the cylinders down. 70 is pretty low to seat the rings,, I use 100-150 so I get enough pressure on the rings and valves to get a test that closer to running engine reality.

At the end of the day pulling the heads isn't that big of a project on a stand. But I wouldn't go there unless you have 1 cylinder that just wont leak down.
if you pull the heads, its not many $$ to take them to a head shop and ask them to pressure test them, everybody has a gm head plate so it will just cost you a hour of labor..

 

Should look virtually brand new if the engine was taken care of and there is no excessive wear. There will most likely also be verticle marks on the bottom side of the cylinders, which is perfectly normal as long as you can't feel it. A catch of the fingernail is when it should be concerning.
You can do both. Only reason why I say do it dry first is to see if there are any issues right off the bat. I'd put a sprits in #7 and see if it will increase compression dramatically.

Use something that is thin instead of motor oil. Hell I've used water before in a pinch.

 

Thanks guys for all the good info. It's gonna be a few days (right out straight w school/work atm) but I will post findings ASAP.

 

ok guys help me out.

sprayed a little more fogging oil in each cylinder (good even 2 burst in each cyl) and worked the crank around for a little bit. Spins noticably better now.

then i removed rockers and hit the valve seat area with generous amounts of wd40, and some light tapping on valves. All even amounts.

On to leakdown. Rockers are still removed however i did follow tdc compression firing order for the test. (My thoughts are this will test rings and valve closure, feel free to give me thoughts)

i used 98 psi as my gauge only goes to 100 and not recommended to exceed 100. I did have some exhaust valves not seating completely, so i tapped under pressurized cylinder and a few taps got them to seat. Results below

Baseline 98 psi
1 - 90
8 - 92
4 - 92
3 - 94
6 - 96
5 - 92
7 - 92
2 - 94

Looks pretty damn good to me and proved that some exhaust valves were not fully seated.

May not nescessarially prove rings are good due to use of fogging oil (thoughts?) although motor does spin noticably easier now

Now i am wondering if i should reinstall rockers and try again? Should I let fogging oil sit in cylinders over night. Results all over the place last two nights got me somewhat unsure

EDIT ::: Put rockers back on followed adjustment procedure (except went 1/4 turn past instead of 3/4)
and proceeded with comp test

1 - 170
3 - 180
5 - 200
7 - 180
2 - 175
4 - 180
6 - 190
8 - 180

mind you this is with fogging oil in every hole so not sure if that ups the compression

 

So I know I got my numbers up but was debating a rering kit (rings, bearings, all gaskets) while the motor is out. On the same token I dont have a bottomless build fund and would really hate to rebuild a motor that doesnt need it especially when i can spend the money elsewhere on the build and plan for a rebuild later when it's really time.

So what are some things i can do to determine this? I was going to pull the heads i guess as a start and look at cylinder wall condition. I have heard of LT1s lasting a very long time. This one has under 100k and seems to be very clean. Just looking for advice to help me make a decision.