1981 Vanagon backfire through intake

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energyturtle
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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Wed Aug 10, 2016 7:01 pm

It lives. I had to compress the lifter, and bottom it out. I then set the lifters to .006 as if they were solid. Fired right up and ran exceptionally. Where do I go from here as far as a proper valve adjustment. The better answer would be what is happening exactly with these lifters?

Scottie

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Amskeptic
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Re: 1981 Vanagon backfire through intake

Post by Amskeptic » Wed Aug 10, 2016 11:10 pm

energyturtle wrote:It lives. I had to compress the lifter, and bottom it out. I then set the lifters to .006 as if they were solid. Fired right up and ran exceptionally. Where do I go from here as far as a proper valve adjustment. The better answer would be what is happening exactly with these lifters?

Scottie
I have seen such a flurry of lifters that will not bleed down correctly!

All over the country!

Damn things will not let go, valves remaining open, no compression, no adjustment possible, only cure is to disassemble and remove the oil, then try to get the 1 1/2 turns preload.

A warning to you, Scottie, if you let hydraulic lifters clack too much, they will spit their circlips and disassemble themselves ibnside the lifter bores.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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asiab3
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Re: 1981 Vanagon backfire through intake

Post by asiab3 » Thu Aug 11, 2016 12:05 am

I dealt with three(!) lifters in South Dakota that would not pump up after an oil change and 45 minutes of puttering around town. I found the culprits, and adjusted them to 1/8 turn preload for a few minutes of idling. Two of them responded well, though I do not know why the third one did not. I refused to run them with ANY lash, but I was really throwing spaghetti at the wall at that point. Have you REALLY ascertained that all eight are in fact hydraulic lifters? Bone head mechanics abound in this world, and a sanity check would be on my list.

I know my issue was backwards from yours, but I think running with 1/8 turn gives the plunger a new active area and can perhaps excite enough oil through the offending lifters to get them to bleed down.

So Scottie, tell us WHY you think adding lash (which should give the valves less lift and less open duration) seemed to make the engine happier?

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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energyturtle
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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Thu Aug 11, 2016 5:43 am

Maybe I'm not explaining things clearly, or I'm not understanding the pre load cycle. All lifters were dry. I could compress the plunger to bottom out with a screw driver on the bottom of each rocker. I adjusted to 1 1/2 turns past intial contact with the bottom of the pushrod in the lifter cup. This is were I got the backfires. While the engine was running I noticed the rockers on the #1 and #3 exhaust valves not moving. My theory is the exhaust valves were staying closed, the exhaust escaped out the intake when it opened causing the intake backfire. I then "pre loaded" all lifters to bottom out, with minimal clearearance achieved at the valve stem. Vroom. All was seemingly well. Tell me more about this preload. To answer Robbie's question ad to why this made the engine happy.......i'm assuming. By bottoming out the hydraulic lifters, I in turn made them effectively solid, causing the valves to open with plenty of lift, and close properly?

Scottie

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energyturtle
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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Thu Aug 11, 2016 2:33 pm

Was readjusting valves. Ran engine for 10 min. It was idling. I ran up to the cab and shut it off. Tried to turn it over. ENGINE IS LOCKED UP. I TOOK OF THE STARTER, RELEASED ALL PRESSURE FROM THE VALVETRAIN. CHECKED THE OIL, ITS FULL. OIL LIGHT NEVER FLICKERED, NO NOISES, NO NOTHING. ENGINE WAS RUNNING AT IDLE, I SHUT IT OFF, ENGINE IS LOCKED UP. WTF? I've fucking had it...........

Scottie

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Amskeptic
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Re: 1981 Vanagon backfire through intake

Post by Amskeptic » Fri Aug 12, 2016 10:37 pm

energyturtle wrote:Was readjusting valves. Ran engine for 10 min. It was idling. I ran up to the cab and shut it off. Tried to turn it over. ENGINE IS LOCKED UP. I TOOK OF THE STARTER, RELEASED ALL PRESSURE FROM THE VALVETRAIN. CHECKED THE OIL, ITS FULL. OIL LIGHT NEVER FLICKERED, NO NOISES, NO NOTHING. ENGINE WAS RUNNING AT IDLE, I SHUT IT OFF, ENGINE IS LOCKED UP. WTF? I've fucking had it...........

Scottie
Loosen all spark plugs. Try to turn engine by hand. Report back.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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energyturtle
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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Mon Aug 15, 2016 2:14 am

I did that already. Its a no go:(

Scottie

weswsimpson
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Re: 1981 Vanagon backfire through intake

Post by weswsimpson » Sun Oct 23, 2016 6:37 am

I had this same problem (back firing through intake), it was bad hydraulic lifters causing bad valve adjustment. replacing the lifters and adjusting the valves solved that problem.

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energyturtle
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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Oct 23, 2016 6:59 am

After I disassembled the engine, it was locked up on the front main bearing. It only had 2 flywheel shims in, so the end play was way off. My fault for assuming. Full build in progress, one piece at a time.

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