Hard to kick, too much vacuum

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cant-drive-55
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Re: Hard to kick, too much vacuum

#16

Post by cant-drive-55 » Wed Oct 11, 2017 2:58 pm

Not sure what compression ratio is. Bought it a few months back. Have a '76 I did a full topend over the winter. 9.0 ratio pistons. Not an issue kicking through.

Have to see what changed. I see the rods moving fully, so the hydraulic lifters are working. I'm going to remove primary cover to inspect. It has a belt. Not a big fan of belts, but that's a separate issue for later.

Thanks for all your help. I know it's probably something simple I'm looking over.



Mark44
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Re: Hard to kick, too much vacuum

#17

Post by Mark44 » Wed Oct 11, 2017 3:51 pm

cant-drive-55 wrote:
Wed Oct 11, 2017 2:58 pm
Have to see what changed. I see the rods moving fully, so the hydraulic lifters are working.
Not necessarily. As nmaineron suggested several posts back, the oil could have drained out of your hydraulic lifters in the time since you last started the engine. It's not a question of whether the push rods go up and down -- it's how far up and down they go. Without being fully extended they would cause the valves to open later than normal and close earlier than normal.

cant-drive-55
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Re: Hard to kick, too much vacuum

#18

Post by cant-drive-55 » Wed Oct 11, 2017 4:28 pm

Thanks. I'll measure the rod travel. Offhand, it looks like about the distance between head fins. I think a pan valve lift is .470. I'm not sure without looking at manual what rocker ratio is. It may be the valves are opening 1/2 way.
Hydraulic lifters passed test, but not by much. Needed a good cleaning.

Andygears
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Re: Hard to kick, too much vacuum

#19

Post by Andygears » Thu Oct 12, 2017 9:52 pm

How bout a compression gauge reading? Screw it in, give it a kick, get a number.
One more clue

Andygears

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Re: Hard to kick, too much vacuum

#20

Post by RUBONE » Thu Oct 12, 2017 11:47 pm

Rockers are roughly 1-1/2 to 1. An FLH cam is about .412 lift an FL about .370. That is at the valve including the ratio. Pushrods do not move very much, just a little over 1/4 of an inch. It doesn't matter if the lifters are flat, that isn't your problem.

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