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New rebuild 0 compression??
https://slantsix.org/forum/viewtopic.php?t=52637		 Page 1 of 1
Author:  vanmansl6 [ Sun Jul 07, 2013 2:08 pm ]
Post subject:  New rebuild 0 compression??
Its been a while trying to get my 83 B150 back on the road but I am in the final phase before its done. I need to find TDC so I can drop the dizzy in and im finally done. Trouble is I couldnt get any compression - I put my finger over the plug hole while my son cranked the engine and nothing. I then used a compression tester on #s 1 4 and 6 and again nothing!! I dont know where to begin on this. Its an 81 engine and has been rebuilt ( not by me or anyone I know ) so im stumped. Rings and or valves seem like the only reason or am I missing something? Anyone have any ideas? :cry:
Author:  Rick Covalt [ Sun Jul 07, 2013 2:11 pm ]
Post subject: 
Does it have adjustable rocker arms? Are they to tight and holding the valves open?
Author:  Pierre [ Sun Jul 07, 2013 2:25 pm ]
Post subject: 
Or the guides sticking and not letting the valves fully close.

Leakdown test will be your friend here. Don't necessarily need the full test gauges, just the adapter hose from sparkplug to NPT thread that you can then put on your quick disconnect to air compressor. Put 30-40 psi air in it only while the cylinder is at TDC (so it doesn't force the piston back down) and see if theres any air coming out the carb or exhaust. Then gently tap the rocker with a mallet to see if air stops.

It's really unusual to have absolutely zero instead of a few psi even with a stuck valve or tight rocker. Have you watched the rockers move while cranking? Did the rebuilder forget a timing chain???
Author:  vanmansl6 [ Sun Jul 07, 2013 3:04 pm ]
Post subject: 
Rockers all move when the engine is cranked, but I did notice that the pushrods all spin while cranking. Is this normal? It baffles me that there is no compression. There are adjuster nuts on the rockers. I rolled the dice when I bought the truck for parts- 350 bucks delievered, but the engine had never been run. I will try the leakdown test next
Author:  vanmansl6 [ Sun Jul 07, 2013 3:07 pm ]
Post subject: 
Im not sure how to adjust the rockers on a hydraulic engine. Should there be any valve lash? all of the rockers are very tight
Author:  ceej [ Sun Jul 07, 2013 3:20 pm ]
Post subject: 
If there are adjusters, the top end is for use with a mechanical cam and lifters only.

If you have hydraulic lifters, they will not work with this setup. Oil is delivered to the lifters through the rocker shaft, arms, and pushrods of a hydraulic slant six. There are no oil galleys in any slant six block.

We need to know exactly which parts are in the engine.

If the lifters and cam are mechanical, then you need to read up on valve adjusting. To start, we need to know which cam is in there.
The stock cam should be lashed 0.010" intake, and 0.020" exhaust.

If you have a hydraulic cam and lifters in there, you need to take it apart and put the right parts in there. It will destroy the cam and lifters very quickly if you get it fired up.

The pushrods should spin when running. The way the lifters and cam are ground cause them to turn. If they don't, they will wear very quickly.

CJ
Author:  vanmansl6 [ Mon Jul 08, 2013 3:15 pm ]
Post subject:  81? or ??
Ok after finding a solid rocker shaft in my "alledged" 81 engine I found the head to be a 79-80 ( #4104362 ) Im having trouble finding a reference chart for the block. Stamped # on the block below #1 plug facing the sky ( as Dan says ) is O225R 4 23 E At this point im almost convinced it is a 79-80 engine, but I need to know for sure what I have here. The guy I bought it from said it was an 81 but it probably isnt. Lesson learned about taking someone's word for it.

As for the cam, I don't know how find that out, and with this head I can't remove the lifters without pulling the head-
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