Rocker arm adjustment problem
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
Rocker arm adjustment problem
I am installing new 1.5 rocker arms on a 383 in my 81 vet. Engine was running great. Removed old 1.5 ratio rockers and installed new ones. Set the lash and preload per the instructions. When I went to start it the engine spins over but no compression. Everything is turning but no compression. I assume the valves are not closing. This engine is very strong and est. about 425-450 hp. But I dont have the build sheet for it. Should I just reset the valves with zero lash and no extra 1/3 turn. It ran great on the old 1.5 rockers. I replaced them because they were from mixed vendors. Any ides appreciated.
Safety Car
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From: BC
What method did you use to determine that each cylinder was at top dead center on the compression stroke and how did you rotate the engine to adjust the valves on each cylinder? Did you follow the proper firing order when turning the engine over in 90 degree increments and adjusting each cylinder after rotating the engine? 18436572
Last edited by CanadaGrant; Jun 9, 2018 at 11:46 PM.
Racer
Joined: Jan 2008
Posts: 291
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From: Virginia Beach VA
I’d recommend you watch a couple youtube videos on rocker arm adjusting - I’m betting you did it mostly right but we’re just a little off on the cam positioning. I didn’t really get it until I read the procedure a few times and then watched someone do it.
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Joined: Sep 2004
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
I would keep trying to do it right, until it works....these are hydraulic lifters correct? do you have good feeling in your hands that you can feel the push rods engage the plunger while spinning the pushrod? when you finally feel the spin going away you hit the spot where the plunger is just starting to depress
I think Lars has a paper on adjusting the valves.
mark the base of the distributor at the bottom of the spark plug towers on the cap and make sure the rotor is pointing at one of the marks and adjust that cylinder.
I think Lars has a paper on adjusting the valves.
mark the base of the distributor at the bottom of the spark plug towers on the cap and make sure the rotor is pointing at one of the marks and adjust that cylinder.
Last edited by bobs77vet; Jun 9, 2018 at 11:08 PM.
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For me it's easier to eliminate up and down movement of pushrod. And when I say that I mean VERY lightly. Lift pushrod up and down with light pressure and adjust until it JUST takes the play out. THEN adjust another 1/8-1/4 or whatever you feel like. Trying to do it with the "spin" method takes some feel...because often they will still spin with your fingers even though the lifter plunger is being depressed.
Make sure you adjust them in the correct order as mentioned.
JIM
Make sure you adjust them in the correct order as mentioned.
JIM
Safety Car
Joined: Sep 2001
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From: Glenbeulah Wi
There needs to be zero resistance on the pushrod when you set the preload. Rotate the pushrod until you feel the slightest drag and then set the 1/2:turn preload. You have yours set too tight.
Racer
Joined: Jul 2015
Posts: 396
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From: Lehigh Valley Pennsylvania
Are you sure you have hydraulic lifters? When the engine cranks you say there is no compression. It sounds to me like you have solid lifters. Solid lifter get a .010" to .015" gap depending upon the cam. If you are tightening them 1/3 turn down, you are holding the valves off the seat with a solid lifter. The engine would not have much compression.
A second question: If the rockers were from different vendors, were they different ratios?
A second question: If the rockers were from different vendors, were they different ratios?
Last edited by 2mnyvets; Jun 10, 2018 at 07:38 AM.
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do you have the right rocker arms. If you didnt buy the the right length for the size springs, they could be hitting the side of the spring and you are getting false setting when you set the lash. It will screw everything up
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
What method did you use to determine that each cylinder was at top dead center on the compression stroke and how did you rotate the engine to adjust the valves on each cylinder? Did you follow the proper firing order when turning the engine over in 90 degree increments and adjusting each cylinder after rotating the engine? 18436572
Thanks for the response
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
Are you sure you have hydraulic lifters? When the engine cranks you say there is no compression. It sounds to me like you have solid lifters. Solid lifter get a .010" to .015" gap depending upon the cam. If you are tightening them 1/3 turn down, you are holding the valves off the seat with a solid lifter. The engine would not have much compression.
A second question: If the rockers were from different vendors, were they different ratios?
A second question: If the rockers were from different vendors, were they different ratios?
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
Are you sure you have hydraulic lifters? When the engine cranks you say there is no compression. It sounds to me like you have solid lifters. Solid lifter get a .010" to .015" gap depending upon the cam. If you are tightening them 1/3 turn down, you are holding the valves off the seat with a solid lifter. The engine would not have much compression.
A second question: If the rockers were from different vendors, were they different ratios?
A second question: If the rockers were from different vendors, were they different ratios?
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
Thanks, there not hitting. I pulled them off and also pulled pushrods to check for damage. all was ok. Thanks for repsonse
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
Thread Starter
Racer
Joined: Jan 2013
Posts: 300
Likes: 10
I have done this several times on my other vet. But you are right I will look at you tube video. Thanks
Le Mans Master
Joined: Mar 2004
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From: Little Rock AR
No compression means the adjustment is too tight.
Loosen the nuts and retighten with a .002" feeler gauge. Set the nuts so they just barely drag the feeler gauge then remove the feeler and tighten a half turn more. Your car will build compression and it will run. Might need to snug them another 1/4 turn or so after that if it sounds at all like a sewing machine when it runs.
Loosen the nuts and retighten with a .002" feeler gauge. Set the nuts so they just barely drag the feeler gauge then remove the feeler and tighten a half turn more. Your car will build compression and it will run. Might need to snug them another 1/4 turn or so after that if it sounds at all like a sewing machine when it runs.